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Animal Physiology From Genes to Organisms (with InfoTrac)

by: Sherwood, Lauralee; Klandorf, Hillar; Yancey, Paul

Animal Physiology From Genes to Organisms (with InfoTrac)

by: Sherwood, Lauralee; Klandorf, Hillar; Yancey, Paul

ISBN 13:
9780534554040
ISBN 10:
0534554040
Format: Hardcover
Copyright: 09/15/2004
Publisher: Brooks Cole
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Summary

Keep up with today?s rapid advances in the biological sciences with ANIMAL PHYSIOLOGY: FROM GENES TO ORGANISMS with InfoTrac?! With coverage of animal species that will be relevant to your animal-related career, this biology text provides you with the tools you need to succeed. Boxes found throughout the text such as Molecular Biology and Genomics, Beyond the Basics, Challenges and Controversies, Unanswered Questions, and A Closer Look at Adaptation give you examples of cutting-edge research and help you see how what you are learning applies to the real world. Each chapter contains a list of Suggested Readings, a list of websites, and free articles through InfoTrac? College Edition.

SECTION I: FOUNDATIONS

Homeostasis and Integration: The Foundations of Physiology

(22)

Introduction

(2)

Physiological processes arise through evolution

Physiology is an integrative discipline

Physiology includes comparative as well as integrative approaches

Methods in Physiology

(2)

The hypotheticodeductive method is the most widely accepted version of ``the scientific method.''

Levels of Organization in Organisms

(3)

Cells are progressively organized into tissues, organs, systems, and finally the whole body

Size and scale Among Organisms

(1)

The larger the organism, the smaller the surface-area-to-volume ratio

Homeostasis: Basic Mechanisms and Enhancements

(7)

Body cells are in contact with a privately maintained internal environment instead of with the external environment that surrounds organisms

Homeostasis is essential for proper cell function, and each cell, as part of an organized system, contributes to homeostasis. Negative feedback is the main regulatory mechanism for homeostasis

Challenges and Controversies: Can a Planet Have Physiology?

(4)

Feedback effectors can be antagonistic and can include behaviors as well as internal organs

Inadequacies in negative feedback systems can be improved by anticipation and acclimatization

Regulated Change

(1)

Some internal processes are not always homeostatic but may be changed by reset and positive feedback systems

Disruptions in regulation can lead to illness and death

Organization of Regulatory and Organ Systems

(3)

Homeostasis (and other regulation) is hierarchically distributed

Organ systems can be grouped according to whole-body contributions

Chapter in Perspective: Homeostasis and Integration

(1)

Review Questions

(1)

Suggested Readings and Internet Sites

(1)

Cellular and Molecular Physiology

(45)

Introduction

(5)

Water, other inorganic chemicals, and four types of organic molecules are the universal components of cells

Many macromolecular structures need to be flexible to function and to be regulated, and protecting those structures is the basis for many forms of homeostasis

Prokaryotic cells have a simpler organization than eukaryotes

Eukaryotic cells are subdivided into the plasma membrane, nucleus, and cytoplasm

Nucleus, Chromosomes, and Genes

(3)

DNA contains codes in the form of genes for making proteins through the processes of transcription and translation

Different genes are expressed in different tissues and organs

Telomeres protect chromosome ends, and their loss is associated with aging

Methodology

(4)

Molecular Biology and Genomics: Genomics and Evolution

(4)

Ribosomes

(1)

Endoplasmic Reticulum

(2)

The rough endoplasmic reticulum synthesizes proteins for secretion and membrane construction

The smooth endoplasmic reticulum packages new proteins in transport vesicles

Golgi Complex

(4)

Transport vesicles carry their cargo to the Golgi complex for further processing

The Golgi complex packages secretory vesicles for release of exocytosis

Lysosome and Proteasomes

(3)

Extracellular material is brought into the cell by endocytosis for attack by lysosomal enzymes

Lysosomes remove useless but not useful parts of the cell

Proteasomes destroy internal proteins

Peroxisomes

(1)

Mitochondria and Energy Metabolism

(12)

Mitochondria are the energy organelles

Aerobic metabolism relies on oxygen to convert energy in food into ATP

Mitochondrial metabolism can create oxidative stress

Mitochondrial densities vary among tissue and organ types such as muscles

Phosphogens provide a rapid source for ATP production

Oxygen deficiency forces cells to rely on glycolysis and other anaerobic reactions, producing lactic acid, propionic acid, octopine, or other end product

Tolerance of oxygen deficiency varies widely among organisms

The energy stored within ATP is used for synthesis, transport, mechanical work, and light and heat production

Vaults

(1)

Cytosol

(1)

The cytosol is important in intermediary metabolism, ribosomal protein synthesis, and storage of fat and glycogen

Cytoskeleton

(6)

Microtubules are essential for maintaining asymmetric cell shapes and are important in complex cell movements

Microfilaments are important to cellular contractile systems and as mechanical stiffeners

Intermediate filaments are important in regions of the cell subject to mechanical stress

The cytoskeleton functions as an integrated whole and links other parts of the cell together

The cytoskeleton, along with other cellular macromolecules, creates a very crowded environment that alters reaction and diffusion rates

Cell to Cell Adhesions

(2)

The extracellular matrix serves as the biological ``glue.''

Some cells are directly linked together by specialized cell junctions

Chapter in Perspective: Homeostasis and Integration

(1)

Review Questions

(2)

Suggested Readings and Internet Sites

(1)

Membrane Physiology

(35)

Membrane Structure and Composition

(4)

The plasma membrane is a fluid lipid bilayer embedded with proteins

The mosaic model and membrane-skeleton fence model describes membrane structure and function

The lipid bilayer forms the basic structural barrier that encloses the cell

The membrane proteins perform a variety of specific membrane functions

The membrane carbohydrates serve as self-identity markers

Membrane Transport

(13)

Lipid-soluble substances and small polar molecules can passively diffuse through the plasma membrane down their electrochemical gradient

Diffusion follows a concentration gradient

Osmosis is the net movement of water through a membrane

Special mechanisms are used to transport selected molecules unable to cross the plasma membrane on their own

Carrier-mediated transport is generally accomplished by a membrane protein changing its shape

Carrier-mediated transport may be passive or active

With vesicular transport, material is moved into or out to the cell wrapped in membrane

Caveolae may play roles in membrane transport and signal transduction

Intercellular Communication and Signal Transduction

(10)

Communication between cells is largely orchestrated by extracellular chemical messengers

Chemical messengers can have multiple, unrelated effects because of the ``same key, different locks'' principle

Extracellular chemical messengers bring about cell responses primarily by signal transduction

Some first messengers activate a phosphorylating enzyme in the membrane

Some first messengers open chemically gated channels

A Closer Look at Adaptation: Lighting Up the Night

(6)

Many first messengers activate second-messenger pathways

Signal transduction may trigger a normal cell function or death

Internal receptors bind hydrophobic first messengers entering the cell

Pharmacological agents and toxins are often agonists or antagonists affecting communication mechanisms

Membrane Potential

(6)

Membrane potential is a separation of opposite charges across the plasma membrane

Membrane potential is primarily due to differences in the distribution and permeability of key ions

Chapter in Perspective: Homeostasis and Integration

101

(1)

Review Questions

101

(1)

Suggested Readings and Internet Sites

102

(1)

Neuronal Physiology

103

(37)

Introduction

103

(2)

Neurons and muscles are excitable tissues

Electrical signals are produced by changes in ion movement through ion channels across the plasma membrane

Graded Potentials

105

(2)

The stronger a triggering event, the larger the resultant graded potential

Graded potentials die out over short distances

Action Potentials

107

(15)

During an action potential, the membrane potential rapidly and transiently reverses

Marked changes in membrane permeability and ion movement lead to an action potential

The Na+--K+ ATPase pump gradually restores the concentration gradients disrupted by action potentials

Action potentials are propagated from the axon hillock to the axon terminals

Molecular Biology and Genomics:Neurotoxins in War and Peace

114

(8)

Once initiated, action potentials are conducted over the surface of an axon

The refractory period ensures unidirectional propagation of the action potential and limits the frequency of action potentials

The refractory period also limits the frequency of action potentials

Action potentials occur in all-or-none fashion

The strength of a stimulus is coded by the frequency of action potentials

Myelination increases the speed of conduction of action potentials and conserves energy in the process

Fiber diameter also influences the velocity of action potential propagation

Electrical and Chemical Synapses

122

(1)

Electrical synapses transfer action potential waveforms through gap junctions

Chemical synapses convert action potentials into organic chemical messengers that are exocytosed into the synaptic gap

Neuron-to-Neuron Synapses

123

(4)

A neurotransmitter carries the signal across a fast synapse and opens a chemically gated channel

Some neurotransmitters excite the postsynaptic neuron, whereas others inhibit the postsynaptic neuron

Each fast synapse is either always excitatory or always inhibitory

Neurotransmitters are quickly removed from the synaptic cleft

Neurotransmitters in slow synapses function through intracellular second-messenger systems

Neuromuscular Synapses

127

(2)

Acetylcholine, a fast excitatory neurotransmitter, links electrical signals in motor neurons with electrical signals in skeletal muscle cells

Acetylcholinesterase terminates acetylcholine activity at the neuromuscular junction

Synapse and Integration

129

(5)

The grand postsynaptic potential depends on the sum of the activities of all presynaptic inputs

Action potentials are initiated at the axon hillock because it has the lowest threshold

Neuropeptides act primarily as neuromodulators

Presynaptic inhibition or facilitation can selectively alter the effectiveness of a given presynaptic input

Retrograde messengers travel ``backward'' and also modulate synaptic function

Neurons are linked to each other through convergence and divergence to form complex nerve pathways

Neural Transmission and External Agents

134

(3)

Drugs, disease toxins, and pollutants can modify synaptic transmission between neurons

Challenges and Controversies: Synaptic Solutions to Pet Problems

135

(2)

The neuromuscular junction is vulnerable to several chemical agents and diseases

Temperature and pressure also influence the propagation of action potentials

Chapter in Perspective: Homeostasis and Integration

137

(1)

Review Questions

137

(1)

Suggested Readings and Internet Sites

138

(2)

SECTION II: WHOLE-BODY REGULATION AND INTEGRATION

Nervous Systems

140

(56)

Evolutionary Considerations and Invertebrate Nervous Systems

140

(7)

Nervous systems evolved from simple reflex arcs to centralized brains with distributed, hierarchical regulation

Sponges have no nerves but can respond to stimuli using electrical signals

Nerve nets are the simplest nervous systems and are found in most animals

Simple ganglia and nerve rings evolved for more complex behavior

A true CNS first evolved with bilateral symmetry

True brains evolved at the anterior end of advanced animals

Cephalopod brains have complex structures supporting complex behaviors

Vertebrate brain size varies up to 30-fold for a given body size

Relative brain size may be explained by the expensive-tissue hypothesis

Nervous systems can exhibit plasticity

The Vertebrate Nervous System

147

(2)

The three classes of neurons are afferent neurons, efferent neurons, and interneurons

The Efferent Division of the Peripheral Nervous System

149

(1)

Vertebrate Autonomic Nervous System

149

(7)

The sympathetic and parasympathetic nervous systems both innervate most visceral organs

The sympathetic system dominates in times of ``fight or flight.''

The parasympathetic system dominates in times of ``rest and digest.''

Dual innervation gives precise, antagonistic control

An autonomic nerve pathway consists of a two-neuron chain

Parasympathetic postganglionic fibers release acetylcholine; sympathetic ones release norepinephrine

The adrenal medulla, an endocrine gland, is a modified part of the sympathetic nervous system

Several different receptor types are available for each autonomic neurotransmitter

Many regions of the central nervous system are involved in the control of autonomic activities

Vertebrate Somatic Nervous System

156

(1)

Motor neurons are the final common pathway

Vertebrate Central Nervous System

157

(6)

Glial cells support the interneurons physically, metabolically, and functionally

The delicate central nervous tissue is well protected

The brain floats in its own special cerebrospinal fluid

A highly selective blood-brain barrier carefully regulates exchanges between the blood and brain

The brain depends on delivery of oxygen and glucose by the blood

Brains of virtually all vertebrates display a degree of plasticity

Mammalian neural tissue is susceptible to neurodegenerative disorders

Challenges and Controversies: Neural Plasticity: A Song for All Seasons

162

(1)

Brain Evolution in Vertebrates

163

(2)

Newer, more sophisticated regions of the vertebrate brain are piled on top of older, more primitive regions

Mammalian Cerebral Cortex

165

(6)

The cerebral cortex is an outer shell of gray matter covering an inner core of white matter

The cerebral cortex is organized into layers and functional columns

The four pairs of lobes in the cerebral cortex are specialized for different activities

The parietal lobes are responsible for somatosensory processing

The primary motor cortex is located in the frontal lobes

Other regions of the nervous system besides the primary motor cortex are important in motor control

The cerebral hemispheres have some degree of specialization

Subcortical Structures and Their Relationship with the Cortex in Higher Brain Functions

171

(4)

The basal nuclei play an important inhibitory role in motor control

The thalamus is a sensory relay station and is important in motor control

The hypothalamus regulates many homeostatic functions

The limbic system plays a key role in animal motivation

The amygdala processes inputs that give rise to the sensation of fear

The limbic system and higher cortex participate in the control of basic behavioral patterns

Motivated behaviors are goal directed

Norepinephrine, dopamine, and serotonin are neurotransmitters in pathways for emotion and behavior

Cerebellum, Brain, and Spinal Cord

175

(11)

The cerebellum is important in balance as well as in planning and execution of voluntary movement

The brain stem is a critical connecting link between the remainder of the brain and the spinal cord

The spinal cord retains an inherent segmental organization characteristic of invertebrates

The white matter of the spinal cord is organized into tracts

Each horn of the spinal cord gray matter houses a different type ofneuronal cell body

Spinal nerves contain both afferent and efferent fibers

Many reflex responses and patterned movements in vertebrates are integrated in the spinal cord

Activity of command fibers elicits a fixed action pattern

Memory and Learning

186

(7)

Memory comes in two forms---declarative and procedural---and is laid down in stages

Memory traces are present in multiple regions of the brain

Short-term and long-term memory involve different molecular mechanisms

Short-term memory involves transient changes in synaptic activity

Long-term memory involves formation of new, permanent synaptic connections

Molecular Biology and Genomics: A Smarter Rodent

192

(1)

Complex memories and learning may reside in neuronal networks

The term consciousness refers to a subjective awareness of the world and self

Chapter in Perspective: Homeostasis and Integration

193

(1)

Review Questions

194

(1)

Suggested Readings and Internet Sites

195

(1)

Sensory Physiology

196

(54)

Introduction

196

(2)

Sensory cells have ion channels and receptors that respond to cues in the environment

Sensing in animals can be classified into three roles: sensing the external environment, the internal environment, and body motion and position

Receptor Physiology

198

(4)

Receptors have differential sensitivities to various stimuli

A stimulus alters the receptor's permeability, leading to a graded receptor potential

Receptor potentials may initiate action potentials in the afferent neuron

Receptors may adapt slowly or rapidly to sustained stimulation

Receptors vary according to their speed of adaptation

Each somatosensory pathway is ``labeled'' according to modality and location

Acuity is influenced by receptive field size and lateral inhibition

Photoreception: Eyes and Vision

202

(19)

Light detection in dedicated organs uses photopigments in eyespots or eyes

The vertebrate eye is a fluid-filled sphere enclosed by three specialized tissue layers

The amount of light entering the eye is controlled by the iris

The eye refracts the entering light to focus the image on the retina

Accommodation increases the strength of the lens for near vision

Light must pass through several retinal layers in vertebrates before reaching the photoreceptors

Phototransduction by retinal cells converts light stimuli into neural signals

Synaptic ribbons are found in sensory neurons that are involved in sustained activity

Rods provide indistinct gray vision at night, whereas cones provide sharp color vision during the day

The sensitivity of eyes can vary markedly through dark and light adaptation

Color vision depends on the ratios of stimulation of the various cone types

Visual information is separated and modified within the visual pathway before it is integrated into a perceptual image of the visual field by the cortex

The thalamus and visual cortices elaborate the visual message

Visual input goes to other areas of the vertebrate brain not involved in vision perception

Cephalopod camera eyes have light-sensing cells on top of neural cells

Compound eyes found in some invertebrates consist of multiple image-forming units

Phototransduction in compound eyes differs from that in vertebrate eyes

Mechanoreception: Touch and Pressure

221

(1)

Mechanically gated channels transduce touch and pressure into electrical signals

Proprioception: The Mechanoreception of Motion and Position

222

(5)

The statocyst is the simplest organ that can monitor an animal's position in space

The lateral line system of amphibians and fish detects motion in the surrounding water

The vestibular apparatus of vertebrates detects position and motion of the head and is important for equilibrium and coordination of head, eye, and body movements

Proprioceptors in the muscles, tendons, and joints give information on limb position and motion

Ears, Hearing, and the Mechanoreception of Sound Waves

227

(8)

Sound waves consist of alternate regions of compression and rarefaction of air molecules

The external ear and middle ear convert airborne sound waves into fluid vibrations in the inner ear

The tympanic membrane vibrates in unison with sound waves in the external ear

The middle ear bones convert tympanic membrane vibrations into fluid movements in the inner ear

The cochlea contains the organ of Corti, the sense organ for hearing

Hair cells in the organ of Corti transduce fluid movements into neural signals

The inner hair cells convert sound waves into electrical impulses

The outer hair cells are thought to enhance sound discrimination

Pitch discrimination depends on the region of the basilar membrane that vibrates

Loudness discrimination depends on the amplitude of vibration

The auditory cortex is mapped according to tone

Insect ears are derived from the respiratory tracheal system

Chemoreception: Taste and Smell

235

(6)

Molecular Biology and Genomics: The Smell and Taste of Evolution

236

(5)

Taste sensation is coded by patterns of activity in various taste receptors

The olfactory receptors in the nose are specialized endings of renewable afferent neurons

The axons of the receptor cells collectively form the olfactory nerve

Various parts of an odor are detected by different olfactory receptors and sorted into ``smell files.''

Odor discrimination is coded by patterns of activity in the olfactory bulb glomeruli

The olfactory system adapts quickly, and odorants are rapidly cleared

The vomeronasal organ detects pheromones

Thermoreception

241

(1)

Warmth and cold thermoreceptors give information about the temperature of the environment near the body

Infrared thermoreceptors give pit vipers the ability to detect prey and desirable thermal habitats

Nociception: Pain

242

(3)

Stimulation of nociceptors elicits the perception of pain plus motivational responses

The vertebrate brain has a built-in analgesic system

Electroreception and Magnetoreception

245

(2)

Electroreception can be passive or active, and can be used for navigation, prey detection, and communication

Electric organs use specialized electrocytes to generate signals

Some animals can detect magnetic fields for long-range navigation

Chapter in Perspective: Homeostasis and Integration

247

(1)

Review Questions

247

(2)

Suggested Readings and Internet Sites

249

(1)

Endocrine Systems

250

(64)

Introduction: Principles of Endocrinology

250

(11)

Hormones exert a variety of regulatory effects throughout the body

Hormones are chemically classified into three categories: peptides and proteins, amines, steroids

The mechanisms of hormone synthesis, storage, and secretion vary according to the class of hormone

Water-soluble hormones are transported dissolved in the plasma, whereas lipid-soluble hormones are almost always transported bound to plasma proteins

Endocrine-disrupting chemicals can mimic the effects of native hormones

Hormones produce their effects by altering intracellular proteins through ion fluxes, second messengers, and transcription factors

By stimulating genes, lipophilic hormones promote synthesis of new hormones

Hormone actions are greatly amplified at the target cell

The effective plasma concentration of a hormone is normally regulated by changes in its rate of secretion

The effective plasma concentration of a hormone can be influenced by the hormone's transport, metabolism, and excretion

The responsiveness of a target cell to its hormone can be varied by regulating the number of its hormone-specific receptors

Endocrine disorders are attributable to hormonal excess, hormonal deficiency, or decreased responsiveness of the target cells

Invertebrate Endocrinology

261

(2)

Molting is the process of replacing one exoskeleton with another

The quantity of JH released determines the quality of the molt

Pheromones are used in mating and colonial interactions

Vertebrate Endocrinology: An Overview

263

(1)

Biological Clocks: The Role of the Suprachiasmatic Nuclei and the Pineal Gland

263

(1)

The biological clock must be synchronized with environmental cues

The pineal gland produces melatonin for circadian regulation, keeping the body's circadian rhythms in time with the light--dark cycle

Molecular Biology and Genomics: Clocks and Genes

264

(1)

The Vertebrate Hypothalamus and Pituitary

264

(7)

The pituitary gland consists of anterior and posterior lobes

The hypothalamus and posterior pituitary form a neurosecretory system that secretes vasopressin and oxytocin

The anterior pituitary secretes six established hormones, many of which are tropic

Hypothalamic releasing and inhibiting hormones are delivered to the anterior pituitary by the hypothalamic-hypophyseal portal system to control anterior pituitary hormone secretion

Target gland hormones inhibit hypothalamic and anterior pituitary hormone secretion via negative feedback

Hypothalamic hormones are produced in other body regions, where they have unrelated function including learning and pair-bonding

Endocrine Control of Growth in Vertebrates

271

(6)

Growth depends on growth hormone but is influenced by other factors as well

Growth hormone is essential for growth, but it also exerts metabolic effects not related to growth

Growth hormone exerts its growth-promoting effects indirectly by stimulating somatomedins

Growth hormone secretion is regulated by two hypophysiotropic hormones and influenced by a variety of other factors

Prolactin has a wide range of effects, including lactogenesis, reproductive behaviors, and water regulation

Vertebrate Thyroid Gland

277

(6)

A Closer Look at Adaption: Brood Patch Development: Some Have It, Others Don't

277

(6)

The major thyroid hormone secretory cells are organized into colloid-filled spheres

Thyroid hormone synthesis and storage occur on the thyroglobulin molecule

To secrete thyroid hormone, the follicular cells phagocytize thyroglobulin-laden colloid

For the most part, both T4 and T3 are transported bound to specific plasma proteins

Most of the secreted T4 is converted into T3 outside the thyroid

Thyroid hormone is the primary determinant of overall metabolic rate and exerts other effects as well

Thyroid hormone is regulated by the hypothalamus--pituitary--thyroid axis

Abnormalities of thyroid function include both hypothyroidism and hyperthyroidism

Vertebrate Adrenal Glands

283

(9)

In most vertebrates the adrenal gland consists of a steroid-secreting cortex intermingled with chromaffin tissue

The adrenal cortex secretes mineralocorticoids, glucocorticoids, and sex hormones

Glucocorticoids exert metabolic effects and have an important role in adaptation to stress

Glucocorticoid secretion is directly regulated by the hypothalamic--pituitary--adrenal axis

The adrenal cortex secretes both male and female sex hormones in both sexes

The catecholamine-secreting adrenal medulla is a modified sympathetic postganglionic neuron

Epinephrine and norepinephrine vary in their affinities for the different adrenergic receptor types

Epinephrine reinforces the sympathetic nervous system in ``fight-or-flight'' short-term stress, and exerts additional metabolic effects

Sympathetic stimulation of the adrenal medulla is solely responsible for epinephrine release

The stress response is a generalized, nonspecific pattern of neural and hormonal reactions to any situation that threatens homeostasis

The multifaceted stress response is coordinated by the hypothalamus

Activation of the stress response by chronic psychosocial stressors may be harmful

Endocrine Control of Fuel in Vertebrates Metabolism

292

(11)

Fuel metabolism includes anabolism, catabolism, and interconversions among energy-rich organic molecules

Because food intake is intermittent, nutrients must be stored for use between meals, primarily as adipose tissue

Glucose is homeostatically regulated to supply the brain and to prevent damaging processes at high concentrations

Metabolic fuels are stored during the absorptive state and are mobilized during the postabsorptive state

Lesser energy sources are tapped as needed

The pancreatic hormones, insulin and glucagon, are most important in regulating fuel metabolism

Insulin lowers blood glucose, amino acid, and fatty acid levels and promotes their storage

The primary stimulus for increased insulin secretion is an increase in blood glucose concentration

Glucagon in general opposes the actions of insulin

Glucagon secretion is increased during the postabsorptive state

Insulin and glucagon work as a team to maintain blood glucose and fatty acid levels

Epinephrine, cortisol, growth hormone, and thyroid hormone also exert direct metabolic effects

Endocrine Control of Calcium Metabolism in Vertebrates

303

(9)

Plasma calcium must be closely regulated to prevent changes in neuromuscular excitability

Control of calcium metabolism includes regulation of both calcium homeostasis and calcium balance

Parathyroid hormone raises free plasma calcium levels by its effects on bone, kidneys, and intestine

Bone continuously undergoes remodeling

PTH's immediate effect is to promote the transfer of Ca++ from bone fluid into plasma

PTH's chronic effect is to promote localized dissolution of bone to release Ca++ into plasma

PTH acts on the kidneys to conserve Ca++ and to eliminate PO43-

PTH indirectly promotes absorption of Ca++ and PO43- by the intestine

The primary signal for regulating PTH secretion is the plasma concentration of free Ca++

Calcitonin lowers the plasma Ca++ concentration, but may not be essential

Vitamin D actually is a hormone that increases calcium absorption in the intestine

Phosphate metabolism is controlled by the same mechanisms that regulate Ca++ metabolism

Disorders in Ca++ metabolism may arise from abnormal levels of parathyroid hormone or vitamin D

Chapter in Perspective: Homeostasis and Integration

312

(1)

Review Questions

312

(1)

Suggested Readings and Internet Sites

313

(1)

SECTION III: SUPPORT AND MOVEMENT

Muscle Physiology

314

(45)

Introduction

314

(1)

Skeletal Muscle

315

(5)

Skeletal muscle fibers have a highly organized internal arrangement that creates a striated appearance

Skeletal muscle fibers are striated by a highly organized internal arrangement

Myosin forms the thick filaments

Actin, along with tropomyosin and troponin, forms the thin filaments

Molecular Basis of Skeletal Muscle Contraction

320

(8)

During contraction, cycles of cross-bridge binding and bending pull the thin filaments closer together between the stationary thick filaments, causing shortening of the sarcomeres

Complete shortening is accomplished by repeated cycles of cross-bridge binding and bending

Calcium is the link between excitation and contraction

Removal of calcium is the key to muscle relaxation

Beyond the Basics: Conversion of Muscle into Meat

326

(2)

Contractile activity far outlasts the electrical activity that initiated it

Skeletal Muscle Mechanics

328

(8)

Whole muscles are groups of muscle fibers bundled together by connective tissue, often attached to skeletal elements in antagonistic pairs

Contractions of a whole muscle can be of varying strength

The number of fibers contracting within vertebrate muscle depends on the extent of motor unit recruitment

The frequency of stimulation can influence the tension developed by each vertebrate skeletal muscle fiber

Twitch summation results from a sustained elevation in cytosolic calcium

Arthropod muscle tension is controlled by gradation of contraction within a motor unit

There is an optimal muscle length at which maximal tension can be developed on a subsequent contraction

Muscle tension is transmitted to skeletal elements as the contractile component tightens the series-elastic component

The two primary types of contraction are isotonic and isometric

The velocity of shortening is related to the load

Although muscles can accomplish work, much of the energy is converted to heat

Interactive units of skeletal muscles, tendons, skeletons, and joints form lever systems

Skeletal Muscle Metabolism and Fiber Types

336

(6)

Muscle fibers have alternate pathways for forming ATP

Fatigue has multiple causes

Increased oxygen consumption is necessary to recover from activity

There are three types of skeletal muscle fibers, which differ in ATP hydrolysis and synthesis

Molecular Biology and Genomics: Myosin Family Genetics

340

(2)

Muscle fibers adapt considerably in response to the demands placed on them

Adaptations for Flight: Continuous High Power at High Contraction Frequencies

342

(2)

Asynchronous muscle contractions are characterized by a nearly constant myoplasmic Ca++ concentration

Control of Motor Movement

344

(4)

Multiple motor inputs influence vertebrate motor unit output

Muscle spindles and the Golgi tendon organs provide afferent information essential for controlling skeletal muscle activity

Smooth Muscle

348

(8)

Smooth and cardiac muscle share some basic properties with skeletal muscle

Smooth muscle cells are small and unstriated

Smooth muscle cells are turned on by Ca++-dependent phosphorylation of myosin

Multiunit smooth muscle is neurogenic

Single-unit smooth muscle cells form functional syncytia

Single-unit smooth muscle is myogenic

Gradation of single-unit smooth muscle contraction differs considerably from that of skeletal muscle

Smooth muscle activity can be modified by the autonomic nervous system

Smooth muscle can still develop tension yet inherently relaxes when stretched

Smooth muscle is slow and economical, especially in latch and catch types

Cardiac Muscle

356

(1)

Chapter in Perspective: Homeostasis and Integration

356

(1)

Review Questions

356

(2)

Suggested Readings and Internet Sites

358

(1)

SECTION IV: SELF-MAINTENANCE

Circulatory Systems

359

(68)

Evolution of Circulation

359

(2)

Circulatory systems evolved to overcome the limits of diffusion

Circulatory systems have up to three distinct components: fluid, pump, and vessels

Circulatory Fluids

361

(1)

Plasma in Circulatory Fluids

361

(2)

Many of the functions of plasma are carried out by plasma proteins

Lipoprotein complexes carry energy lipids and structural lipids for biosynthesis

Respiratory pigments carry oxygen

Erythrocytes in Circulatory Fluids

363

(2)

Erythrocytes serve primarily to transport oxygen

Hemoglobin has additional transport functions

Hemopoietic tissues continuously replace worn-out erythrocytes

Erythropoiesis in mammals and probably other vertebrates is controlled by erythropoietin from the kidneys

Leukocytes in Circulatory Fluids

365

(1)

Thrombocytes and Platelets in Circulatory Fluids and the Process of Hemostasis

366

(6)

Thrombocytes and platelets function in clotting

Hemostasis prevents blood loss from damaged small vessels

Vascular spasm reduces blood flow through an injured vessel

Platelets aggregate to form a plug at a vessel defect by positive feedback

A triggered chain reaction and positive feedback involving clotting factors in the plasma results in blood coagulation

The clotting cascade may be triggered by the intrinsic pathway or the extrinsic pathway

Fibrinolytic plasmin dissolves clots and prevents inappropriate clot formation

Hemocytes and hemolymph proteins provide hemostasis in arthropods

A Closer Look at Adaptation: Vampires and Medicine

372

(1)

Circulatory Pumps

372

(1)

Pumps: Anatomic and Evolutionary Considerations

372

(11)

Many animals have primary hearts aided by auxiliary pumps

Arthropod systemic hearts are dorsally located and have many valved openings

Vertebrate systemic hearts evolved from a two-chambered to a four-chambered structure

Avian and mammalian hearts are dual pumps

Heart valves ensure that the blood flows in the proper direction through the heart

Vertebrate heart walls are composed primarily of spirally arranged cardiac muscle fibers interconnected by intercalated discs

Molecular Biology and Genomics: Zebrafish---A Hearty Physiolocigal Genomics Model

378

(5)

The sinoatrial node is the normal pacemaker of the mammalian heart

The spread of cardiac excitation is coordinated to ensure efficient pumping

The action potential of contractile cardiac muscle cells shows a characteristic plateau

Ca++ entry from the ECF induces a much larger Ca++ release from the sarcoplasmic reticulum

Tetanus of cardiac muscle is prevented by a long refractory period

Pumps: Mechanical Events of the Mammalian Cardiac Cycle

383

(3)

Hearts alternately contract to empty and relax to fill

Pumps: Cardiac Output and Its Control

386

(3)

Cardiac output depends on the heart rate and the stroke volume

Heart rate is determined primarily by antagonistic regulation of autonomic influences on the SA node

Stroke volume is determined by the extent of venous return and by sympathetic activity

Increased end-diastolic volume results in increased stroke volume

The contractility of the heart and venous return are increased by sympathetic stimulation

Pumps: Nourishing the Vertebrate Heart Muscle

389

(1)

The heart receives most of its own blood supply through coronary circulation

Circulatory Pathways and Vessels

390

(2)

Circulatory fluids are driven by pressure and can transmit useful force

Vessels: Flow Regulation and Hemodynamics

392

(2)

Blood flow through vessels depends on the pressure gradient and vascular resistance

Pathways: Open Circulation

394

(2)

Vessels: Closed Circulation

396

(3)

The vascular system evolved from one circuit to two separate circuits in vertebrates

Vessels: Arteries

399

(3)

Mean arterial pressure is the main driving force for blood flow

Vessels: Arterioles

402

(5)

Arterioles control blood distribution and are the major resistance vessels

Local (intrinsic) control of arteriolar radius is important in determining the distribution of cardiac output

Local metabolic influences on arteriolar radius help match blood flow with the tissues' needs

Local histamine release dilates arterioles in pathological conditions

Local heat or cold exposure dilates or constricts arterioles, respectively

Extrinsic sympathetic control of arteriolar radius is primarily important in the regulation of arterial blood pressure

The medullary cardiovascular control center and several hormones regulate blood pressure

Vessels: Capillaries and Lymphatics

407

(9)

Water-filled pores in the capillary wall permit passage of small, water-soluble substances that cannot cross the endothelial cells themselves

Many capillaries are not open under resting conditions

Interstitial fluid is a passive intermediary between the blood and cells

Diffusion across the capillary walls is important in solute exchange

Bulk flow across the capillary wall is important in extracellular fluid distribution

The lymphatic system is an accessory route by which interstitial fluid can be returned to the blood

Vessels: Veins

416

(2)

Veins serve as a blood reservoir as well as passageways back to the heart

Venous return is enhanced by a number of extrinsic factors

Integrated Cardiovascular Function

418

(6)

Regulation of gas transport and mean arterial blood pressure is accomplished by controlling cardiac output, total peripheral resistance, and blood volume

Gas transport and blood pressure are monitored by arterial sensors

The baroreceptor reflex is the most important mechanism for short-term regulation of blood pressure

Regulation of gas transport and blood pressure are coordinated during locomotory activity

Chapter in Perspective: Homeostasis and Integration

424

(1)

Review Questions

425

(1)

Suggested Readings and Internet Sites

426

(1)

Defense Systems

427

(35)

Evolution of Defense Systems

427

(2)

Pathogenic bacteria, viruses, and internal parasites are the major targets of the immune defense system

In most vertebrates, immune responses can be either innate or acquired

Immune responses in any organism depend on ability to distinguish ``self'' from ``non-self.''

Some animals behaviorally acquire defense components from other organisms

The Vertebrate Immune System

429

(2)

Active immune responses are regulated by feedback systems with sensors, integrators, and effectors

Innate Immunity

431

(10)

Barrier tissues are the first line of defense, using passive and active mechanisms

Inflammation, a second line of defense, is a nonspecific response to foreign invasion or tissue damage

Salicylates and glucocorticoids suppress the inflammatory response

The complement system kills microorganisms directly, both on its own and in conjunction with antibodies and also augments the inflammatory response

Interferon transiently inhibits multiplication of viruses in most cells

Natural killer cells destroy virus-infected cells and cancer cells on first exposure to them

Acquired (Adaptive) Immunity

441

(1)

Acquired immunity includes cell-mediated and antibody-mediated responses

An antigen induces an immune response against itself

B Lymphocytes: Antibody-Mediated Immunity

442

(7)

Antibodies are Y-shaped and classified according to properties of their tail portion

Antibodies largely amplify innate immune responses to promote antigen destruction

Clonal selection accounts for the specificity of antibody production

Selected clones differentiate into active plasma cells and dormant memory cells

The huge repertoire of B-cells is built by reshuffling a small set of gene fragments

Active immunity is self-generated; passive immunity is ``borrowed.''

Lymphocytes respond only to antigens presented to them by antigen-presenting cells

T Lymphocytes: Cell-Mediated Immunity

449

(7)

The two types of T-cells are cytotoxic and helper T-cells

Helper T-cells secrete chemicals that regulate other immune cells

Cytotoxic T-cells secrete chemicals that destroy target cells

The immune system is normally tolerant of self-antigens

The major histocompatibility complex is the code for self-antigens

Immune surveillance against cancer cells involves an interplay among immune cells and interferon

A regulatory loop links the immune system with the nervous and endocrine systems

Acquired Immunity in Other Vertebrates

456

(2)

Molecular Biology and Genomics: An Accidental Origin for Adaptive Immunity?

457

(1)

Innate (and Acquired?) Immunity in Other Animals

458

(1)

Phagocytotic cells and an inflammation-like response are the major form of cell-mediated innate immunity in most animals

Antimicrobial peptides are common noncellular defenses in barrier tissues and immune cells of animals

Lectins and Ig-fold proteins act as opsonins in many invertebrates

The proPO system encapsulates large foreign materials in arthropods

Invertebrate immune cells communicate with cytokines such as IL-1

Some forms of acquired immunity may occur in some arthropods

Chapter in Perspective: Homeostasis and Integration

459

(1)

Review Questions

460

(1)

Suggested Readings and Internet Sites

461

(1)

Respiratory Systems

462

(59)

Evolutionary Solutions to Gas Demands

462

(1)

General Principles

462

(1)

External respiratory processes must meet the demands of size, metabolism, and habitat through diffusion and bulk transport

Evolutionary Forces

463

(3)

Breathing as a form of bulk flow can be tidal or flow-through

External respiration can involve up to four major steps

Water Respirers

466

(4)

Water is a more difficult medium than air for gas exchange

The limitations of diffusion in water are overcome with thin, high-surface-area structures and bulk transport

Breathing muscles provide consistent and often fast bulk transport

Aquatic respiratory systems can perform numerous nonrespiratory functions

Air Respirers

470

(9)

Land slugs and snails use skin, mantle tissue, or lungs

In insects, internal air-filled tubes---tracheae---supply oxygen directly to the tissues

Arachnids use book lungs or tracheae

Vertebrate air breathers use respiratory airways to conduct air between the atmosphere and the gas exchange surfaces in the lung

The first air-breathing vertebrates were bimodal

Reptiles, birds, and mammals use lungs ranging from simple sacs to elaborate folds, inflated by negative pressure

Mammalian airways terminate in alveoli

Avian airways terminate in air capillaries

Aerial respiratory systems can perform numerous nonrespiratory functions

Respiratory Mechanics

479

(1)

Principles of Airflow

480

(6)

Interrelationships among atmospheric, intra-alveolar, and intrapleural pressures are important in respiratory mechanics of mammals

The lungs are normally stretched to fill the larger thorax

Flow of air into and out of mammalian lungs occurs because of cyclical intra-alveolar pressure changes brought about indirectly by respiratory muscle activity

Respiratory diseases often increase airway resistance

Elasticity in mammalian lungs depends on connective tissue and alveolar surface tension, which is reduced by surfactant

Mechanics: Lung Volumes and Respiratory Cycles

486

(7)

The respiratory cycle of mammals is similar between species

Alveolar ventilation is less than pulmonary ventilation because of the presence of dead space

Water breathers have relatively lower dead-space volumes

Local controls act on the smooth muscle of the airways and arterioles to maximally match blood flow to airflow

Bird respiration exhibits an efficient flow-through mechanism

Mechanics: Water versus Air Respirers

493

(1)

The work of normal breathing requires as little as 2% of total energy expenditure in some mammals to as much as 50% in some fishes

Gas Exchange

493

(5)

Gases move down partial pressure gradients

In air breathers, oxygen enters and CO2 leaves the blood in the lungs passively

Flow-through breathing plus countercurrent blood flow enhances pressure gradients in fishes

Flow-through breathing plus crosscurrent blood flow enhances pressure gradients in birds

Skin breathing occurs in most vertebrates, but its contribution is variable

Factors other than the partial pressure gradient influence the rate of gas transfer

Gas exchange across the systemic capillaries also occurs down partial pressure gradients

Gas Transport

498

(12)

Most O2 in many animal circulatory systems is transported bound to respiratory pigments

A Closer Look An Adaptation: Life in the Cold: The Hemoglobinless Icefish

499

(11)

Myoglobin stores oxygen in aerobic muscle and may facilitate diffusion from the blood to the mitochondria

The PO2 is the primary factor determining the percent hemoglobin saturation

By acting as a storage depot, hemoglobin promotes the net transfer of O2 from the alveoli to the blood

Increased CO2, acidity, temperature, and organic phosphates shift the O2-Hb dissociation curve to the right, favoring unloading

Evolutionary adaptation results in different hemoglobin P50 values

Filling of the gas bladder is aided by the Root effect

Most CO2 in both vertebrates and invertebrates is transported in the blood as bicarbonate

Various respiratory states are characterized by abnormal blood-gas levels

Other unusual respiratory states are not necessarily pathological

Control of Respiration

510

(8)

A Closer Look at Adaptation: Effects of Depths

510

(2)

Respiratory centers in the vertebrate brain stem establish a rhythmic breathing pattern

Molecular Biology and Genomics: Effects of Heights

512

(6)

The magnitude of ventilation is adjusted in response to three chemical factors: PO2, PCO2, and H+

Adjustments in ventilation in response to changes in arterial H+ are important in acid--base balance

Activity profoundly increases ventilation, but the mechanisms involved are unclear

Chapter in Perspective: Homeostasis and Integration

518

(1)

Review Questions

519

(1)

Suggested Readings and Internet Sites

520

(1)

Excretory Systems

521

(51)

Introduction

521

(5)

Selective excretion is crucial to internal fluid homeostasis and involves several systems

Nitrogen metabolism creates special stresses and produces three major end products: ammonia, urea, and uric acid

Molecular Biology and Genomics: Osmolytes and Gene Regulation

525

(1)

A Closer Look at Adaptation: Avian Longevity: Unraveling the Mystery

526

(1)

Renal Excretory Organs

526

(2)

Renal tubules produce urine using the processes of filtration, secretion, reabsorption, and osmoconcentration

The Mammalian Urinary System

528

(6)

The kidneys form the urine; the remainder of the urinary system is the bladder and ductwork that carries the urine

The nephron is the functional unit of the kidney

The basic renal processes are glomerular filtration, tubular reabsorption, tubular secretion, and osmoconcentration

Glomerular Filtration

534

(6)

The glomerular membrane is more than 100 times more permeable than capillaries elsewhere

The glomerular capillary blood pressure is the major force responsible for inducing glomerular ultrafiltration

The most common factor resulting in a change in the GFR is an alteration in the glomerular capillary blood pressure

The GFR can be influenced by changes in the filtration coefficient

Tubular Reabsorption

540

(7)

Tubular reabsorption is tremendous, highly selective, and variable

Tubular reabsorption involves transepithelial transport

An energy-dependent Na+--K+ ATPase transport mechanism in the basolateral membrane is essential for Na+ reabsorption

Glucose and amino acids are reabsorbed by Na+-dependent secondary active transport

With the exception of Na+, actively reabsorbed substances exhibit a tubular maximum

Active Na+ reabsorption is responsible for the passive reabsorption of Cl-, H2O, and urea

In general, unwanted waste products except urea are not reabsorbed

The renin-angiotensin-aldosterone system stimulates Na+ reabsorption in the distal tubules, elevates blood pressure, and stimulates thirst and salt hunger

Atrial natriuretic peptide antagonizes the renin-angiotensin-aldosterone system, inhibiting Na+ reabsorption and reducing blood pressure

Tubular Secretion

547

(4)

Hydrogen ion secretion is important in acid-base balance

Potassium secretion is controlled by aldosterone

Organic anion and cation secretion helps efficiently eliminate foreign compounds from the body

Plasma clearance is the volume of plasma cleared of a particular substance per minute

Osmoconcentration

551

(11)

The ability to excrete urine of varying concentrations depends on the medullary countercurrent-multiplier system and vasopressin

Urea recycling in the renal medulla contributes to medullary hypertonicity and helps concentrate urea in the urine

The medullary vertical osmotic gradient permits excretion of urine of differing concentrations by means of vasopressin-controlled, variable, H2O reabsorption from the collecting duct

Countercurrent exchange within the vasa recta enables the medulla to be supplied with blood while conserving the medullary vertical osmotic gradient

Different osmoconcentrating abilities among species depend on nephron anatomy and metabolic rates

Bladder Storage and Micturition

562

(1)

Urine is temporarily stored in the bladder, from which the process of micturition empties it

Renal Diseases

563

(1)

Renal diseases are numerous and have wide-ranging consequences

Other Vertebrate Urinary Systems and Extrarenal Organs

563

(4)

Freshwater bony fishes excrete water with their kidneys, and their gills excrete wastes and take up salts

Marine bony fishes use gills for most excretion and retention processes

Cartilaginous fishes retain urea and trimethylamine oxide, and use gills, kidneys and rectal glands for excretion and retention

Amphibians use kidneys and bladders for excretion and retention

Reptiles use amphibian-like kidneys, hindguts, and (in marine and desert species) salt glands for excretion and retention

Birds use mammalian-like kidneys, hindguts, and (in marine species) salt glands for excretion and retention

Insect Malpighian Tubules

567

(2)

Malpighian tubules initiate filtration by ion secretion, which causes osmosis

The tubules and hindgut modify the lumen fluid by specific secretion and reabsorption

Chapter in Perspective: Homeostasis and Integration

569

(1)

Review Questions

570

(1)

Suggested Readings and Internet Sites

571

(1)

Fluid and Acid-Base Balance

572

(40)

Introduction

572

(4)

If balance is to be maintained, input must equal output

Body water is distributed between the intracellular and extracellular fluid compartments

A Closer Look at Adaptation: The Sweet Solution to Desiccation

574

(2)

In vertebrates, the plasma and interstitial fluid are similar in composition; but the ECF and ICF are markedly different in all animals

Osmotic and Volume Balance

576

(2)

Several osmotic problems threaten cells and animals

Animals have evolved two strategies to cope with osmotic challenges

Osmoconformers

578

(7)

A Closer Look at Adaptation: Life at the Top

581

(4)

Osmoregulators

585

(3)

Osmoregulators rely on special transport mechanisms to maintain internal osmotic constancy

Osmotic and Volume Balance in Mammals

588

(7)

Osmotic balance is maintained by regulating ECF volume and ECF osmolarity

Control of ECF osmolarity prevents changes in ICF volume

Control of water balance by means of vasopressin and thirst is of primary importance in regulating ECF osmolarity

Control of ECF volume is important in the long-term regulation of blood pressure

During hemorrhagic shock, circulatory functions and fluid balance are coordinately regulated

Acid-Base Balance

595

(4)

Acids liberate free hydrogen ions, whereas bases accept them

The pH designation is used to express hydrogen ion concentration

Fluctuations in hydrogen ion concentration have profound effects on body chemistry

Hydrogen ions are continually being added to body fluids as a result of metabolic activities

pH Regulation: Buffers

599

(2)

Chemical buffer systems act as the first line of defense against changes in hydrogen ion concentration

pH Regulation: Respiration

601

(1)

Respiratory systems regulates hydrogen ion concentration through adjustments in ventilation and (in gills) membrane transport

pH Regulation: Excretion

602

(7)

Excretory systems contribute powerfully to control of acid-base balance by controlling both hydrogen ion and bicarbonate concentrations in the ECF

Acid-base imbalances can arise from either respiratory dysfunction or metabolic disturbances

Chapter in Perspective: Homeostasis and Integration

609

(1)

Review Questions

610

(1)

Suggested Readings and Internet Sites

611

(1)

Digestive Systems

612

(58)

Introduction: Feeding Strategies and Evolution

612

(8)

Animal digestion evolved from an intracellular to an extracellular process in a specialized sac or tube connected to the environment

Animals can be classified according to their primary feeding methods

Digestive systems perform four basic digestive processes

The digestive tract and accessory digestive organs make up digestive systems

Regulation of digestive function is complex and synergistic

Receptor activation alters digestive activity through neural reflexes and hormonal pathways

Mouth

620

(3)

Saliva aids in mastication but plays a more important role in lubricating food boluses before swallowing

The continuous low level of salivary secretion can be increased by simple and conditioned reflexes

Digestion in the mouth is minimal, and no absorption of nutrients occurs

Pharynx, Esophagus, and Crop

623

(1)

Swallowing in vertebrates is a sequentially programmed all-or-none reflex

During the oropharyngeal stage of swallowing, food is directed into the esophagus and prevented from entering the wrong passageways

Esophagus

624

(2)

The esophagus is a muscular tube guarded by sphincters at both ends

The pharyngoesophageal sphincter keeps air from entering the gut

Peristaltic waves push the food through the esophagus

Challenges and Controversies: Global Warming and the Rumen

625

(1)

The gastroesophageal sphincter prevents reflux of gastric contents

Esophageal secretion is entirely protective

Crop

626

(1)

The crop is a modified section of the esophagus and functions mainly as a storage organ

Stomach or Midgut

626

(12)

The midgut stores food and begins nonsalivary digestion

The stomach stores food and begins protein digestion

Gastric filling involves receptive relaxation

Gastric storage takes place in the body of the stomach

Gastric mixing takes place in the antrum of the stomach

Gastric emptying is largely controlled by factors in the duodenum

Peristaltic contractions occur in the empty stomach before the next meal

Stress can influence gastric motility

The body of the stomach does not actively participate in the act of vomiting

Gastric digestive juice is secreted by glands located at the base of gastric pits

Pepsinogen, once activated, begins protein digestion

Intrinsic factor is essential for absorption of vitamin B12

Multiple regulatory pathways influence the parietal and chief cells

Control of gastric secretion involves three phases

Gastric secretion gradually decreases as food empties from the stomach into the intestine

The stomach lining is protected from gastric secretions by the gastric mucosal barrier

Carbohydrate digestion continues in the body of the stomach, whereas protein digestion begins in the antrum

Proventriculus-gizzard processes begin the process of digestion in birds and insects

Pancreas, Liver, and Fat Body

638

(2)

The pancreas is a mixture of exocrine and endocrine tissue

The exocrine pancreas secretes digestive enzymes and an aqueous alkaline fluid

Pancreatic exocrine secretion is hormonally regulated to maintain neutrality of the duodenal contents and to optimize digestion

Liver and Gallbladder

640

(5)

The vertebrate liver performs various important functions, including bile production

The liver lobules are delineated by vascular and bile channels

Bile is continuously secreted by the vertebrate liver and is diverted to the gallbladder between meals

Bile salts are recycled through the enterohepatic circulation

Bile salts aid fat digestion and absorption through their detergent action and micellar formation, respectively

Bilirubin is a waste product excreted in the bile

Small Intestine

645

(12)

The digestive tract wall has four layers

Segmentation contractions mix and slowly propel the chyme

The migrating motility complex sweeps the intestine clean between meals

The ileocecal juncture prevents contamination of the small intestine by colonic bacteria

Small-intestine secretions in vertebrates do not contain any digestive enzymes

Small-intestine enzymes complete the process of digestion at the brush border membrane

The small intestine is highly adaptable for its primary role in absorption

The mucosal lining experiences rapid turnover

Energy-dependent Na+ absorption drives passive H2O absorption

Carbohydrate and protein are both absorbed by secondary active transport and enter the blood

Most absorbed nutrients immediately pass through the liver for processing

Extensive absorption by the small intestine keeps pace with secretion

Biochemical balance among the stomach, pancreas, and small intestine is normally maintained

Diarrhea results in loss of fluid and electrolytes

Large Intestine

657

(4)

The large intestine functions in electrolyte and fluid balance, harbors microbes for fermentation and VFA production, and serves as a temporary storage site for excreta

Diet composition governs the variation in structure of the large intestine

Haustral contractions prolong the retention of digesta

Postgastric fermentation is not as efficient as pregastric fermentation in obtaining nutrients

Mass movements propel colonic contents long distances

Feces are eliminated by the defecation reflex

Large-intestine secretion is protective in nature

The large intestine absorbs primarily salt and water, converting the luminal contents into feces

Molecular Biology and Genomics: Big Bugs Have Little Bugs . .

660

(1)

The large intestine of birds and hindgut of insects actively transports glucose and amino acids

Ruminant Digestion

661

(5)

The rumen is divided into separate compartments

The abomasum is similar in function to the stomachs of nonruminants

Neonatal ruminants rely only on the abomasum

Motility of the ruminant stomach is predominantly regulated by central nervous system reflex mechanisms

Rumination is the regurgitation, remastication, and reswallowing of ingesta

The environment of the rumen fosters the growth of anaerobic microbes

Nutrients for the host ruminant are generated by anaerobic microbes

Rumen microbes synthesize vitamins for their host and detoxify some ingested toxins

Some ruminants are selective in what they eat, whereas others simply graze the available forage

Overview of the Gastrointestinal Hormones

666

(2)

Chapter in Perspective: Homeostasis and Integration

668

(1)

Review Questions

668

(1)

Suggested Readings and Internet Sites

669

(1)

Energy Balance and Thermal Physiology

670

(37)

Introduction

670

(1)

Life follows the laws of thermodynamics

Energy Balance

671

(11)

Animals require food intake to compensate for entropy

Metabolic rate is scaled to body mass

Aerobic locomotory energy reflects the limits of oxygen delivery and is also scaled to body mass

Challenges and Controversies: A Universal Scale of Life?

675

(6)

Diet-induced thermogenesis occurs after eating in most animals

Energy input must equal energy output to maintain a neutral energy balance

Many mammals maintain long-term neutral energy balance

Some animals undergo periods of positive or negative energy balance

Food intake in mammals is controlled primarily by the hypothalamus in response to numerous inputs

Molecular Biology and Genomics: Discovering the Obesity Gene

681

(1)

Thermal Physiology: General Principles

682

(6)

Temperature is one of the most important habitat factors

Biomolecules can be altered to work optimally at different temperatures

The thermal adaptation strategies of animals depend on their primary source of heat

Heat exchange between the body and the environment takes place by radiation, conduction, convection, and evaporation

Heat gain versus heat loss determines core body temperature

Ectotherms

688

(4)

Body temperatures of ectotherms may follow the environment, or may be regulated by external exchanges

Some ectotherms can metabolically compensate for changes in body temperatures

Ectotherms survive extreme cold by metabolic dormancy and by either freeze avoidance or freeze tolerance

Ectotherms may survive extreme heat with the heat shock response

Endotherms

692

(9)

Birds and mammals homeostatically maintain internal core temperature, whereas other endotherms heat selected body regions

To maintain a stable core temperature, heat gain must balance heat loss

The hypothalamus integrates a multitude of thermosensory inputs from both the core and the surface of the body

To regulate core temperature homeostatically, the hypothalamus simultaneously coordinates heat---production, heat---loss, and heat conservation mechanisms

During a fever, the hypothalamic thermostat is ``reset'' to an elevated temperature

Heterotherms

701

(2)

Heterotherms are endotherms that are not fully homeothermic

Chapter in Perspective: Homeostasis and Integration

703

(1)

A Closer Look at Adaptation: The Naked Mole Rat---Mammalian Hive Ectotherm

704

(1)

Review Questions

704

(2)

Suggested Readings and Internet Sites

706

(1)

SECTION V: REPRODUCTION

Reproductive Systems

707

Introduction

707

(1)

Reproductive Processes

707

(3)

Animals employ a variety of reproductive strategies to ensure survival of the species

Reproductive Systems and Genetics

710

(8)

The reproductive system of vertebrates includes the hypothalamus, gonads, and reproductive tract

Reproduction systems in insects includes neuroendocrine organs, gonads, and reproductive tract

Gametogenesis is accomplished by meiosis

The sex of an individual is determined by the combination of sex chromosomes or by environmental stimuli

Sex differentiation in mammals depends on the presence or absence of masculinizing determinants during critical periods of embryonic development

Vertebrate Male Reproductive Physiology

718

(11)

Spermatogenesis in most mammals is temperature sensitive and cannot occur at normal body temperatures

The testicular Leydig cells secrete masculinizing testosterone during the breeding season

Spermatogenesis yields an abundance of highly specialized, mobile sperm

Throughout their development, vertebrate sperm remain intimately associated with Sertoli cells

LH and FSH from the anterior pituitary control testosterone secretion and spermatogenesis

Gonadotropin-releasing hormone activity increases at puberty

The ducts of the reproductive tract stores and concentrates sperm and increases their fertility

The accessory sex glands contribute the bulk of the semen

Prostaglandins are ubiquitous, locally acting chemical messengers

The male sex act is characterized by erection and ejaculation

Erection is accomplished by penis vasocongestion

Ejaculation includes emission and expulsion

Vertebrate Female Reproductive Physiology

729

(29)

Complex cycling characterizes female reproductive physiology in many vertebrates

The steps of gametogenesis are the same in both sexes, but the timing and outcome differ sharply

Concepts and Controversies

Environmental Estrogens: Bad News for Reproduction

731

(26)

The ovarian cycle of mammals consists of alternating follicular and luteal phases

The follicular phase is characterized by the development of maturing follicles

The luteal phase is characterized by the presence of a corpus luteum

The mammalian estrous cycle is regulated by complex hormonal interactions among the hypothalamus, anterior pituitary, and ovarian endocrine units

The uterine changes that occur during the estrous cycle reflect hormonal changes during the ovarian cycle

Fluctuating concentrations of estrogens and progesterone produce cyclic changes in cervical mucus

The reproductive cycles of nonviviparous vertebrates are fundamentally similar but have some unique differences

Sexual maturity events in mammalian females are similar to those in males

The oviduct is the site of fertilization

The mammalian blastocyst implants in the endometrium through the action of its trophoblastic enzymes

The placenta is the organ of exchange between maternal and fetal blood

Hormones secreted by the corpus luteum and placenta play a critical role in the maintenance of pregnancy

Maternal body systems respond to the increased demands of gestation

Changes during late gestation prepare for parturition

The factors that trigger the onset of parturition are only partially characterized

Parturition is accomplished by a positive-feedback cycle

Lactation requires multiple hormonal inputs

Mammary gland feeding is advantageous to both the infant and the female

Molecular Biology and Genomics: Prolactin: A Key with Many Locks

757

(1)

The end is a new beginning

Chapter in Perspective: Homeostasis and Integration

758

(1)

Review Questions

758

(1)

Suggested Readings and Internet Sites

759

Answers to End of Chapter Review Questions

(1)

Online Chapter Summaries and Appendices A through C are located at http://biology.brookscole.com/animalphys1

A. Metric System

B. Review of Chemical Principles

C. Storage, Replication and Expression of Genetic Information

Glossary

(1)

Credits

(1)

Index

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Animal Physiology From Genes to Organisms (with InfoTrac)

Animal Physiology From Genes to Organisms (with InfoTrac)

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0534554040

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Animal Physiology From Genes to Organisms (with InfoTrac)

Animal Physiology From Genes to Organisms (with InfoTrac)

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0534554040

Summary

Table of Contents

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