Human physiology. From cells to systems

973 Pages·2010·59.75 MB·English

by  Lauralee Sherwood

S E V E N T H E D I T I O N
Human Physiology
From Cells to Systems
Lauralee Sherwood
Department of Physiology and Pharmacology
School of Medicine
West Virginia University
Australia • Brazil • Japan • Korea • Mexico • Singapore • Spain • United Kingdom • United States
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Human Physiology: From Cells to Systems, © 2010, 2007 Brooks/Cole, Cengage Learning
Seventh Edition
ALL RIGHTS RESERVED. No part of this work covered by the copyright
Lauralee Sherwood
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With love to my family,
for all that they mean to me
and all that they have done for me:
My parents,
Larry (in memoriam) and Lee Sherwood
My husband,
Peter Marshall
My daughters,
Melinda Marple
Allison Tadros
My grandchildren,
Lindsay Marple
Emily Marple
Alexander Tadros
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Brief Contents
Chapter 1 Chapter 11
Introduction to Physiology and Homeostasis 1 The Blood 391
Chapter 2 Chapter 12
Cell Physiology 21 Body Defenses 417
Chapter 3 Chapter 13
The Plasma Membrane and Membrane Potential 53 The Respiratory System 461
Chapter 4 Chapter 14
Principles of Neural and Hormonal Communication 87 The Urinary System 511
Chapter 5 Chapter 15
The Central Nervous System 133 Fluid and Acid–Base Balance 557
Chapter 6 Chapter 16
The Peripheral Nervous System: Aff erent Division; Special The Digestive System 589
Senses 183
Chapter 17
Chapter 7 Energy Balance and Temperature Regulation 641
The Peripheral Nervous System: Eff erent Division 237
Chapter 18
Chapter 8 Principles of Endocrinology; The Central Endocrine
Muscle Physiology 257 Glands 661
Chapter 9 Chapter 19
Cardiac Physiology 303 The Peripheral Endocrine Glands 691
Chapter 10 Chapter 20
The Blood Vessels and Blood Pressure 343 The Reproductive System 741
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Contents
Preface xxi Points to Ponder 18
Clinical Consideration 19
Chapter 1
Introduction to Physiology Chapter 2
and Homeostasis 1 Cell Physiology 21
Introduction to Physiology 1 Cell Theory 21
Physiology focuses on mechanisms of action. 1 Observations of Cells 21
Structure and function are inseparable. 1
An Overview of Cell Structure 22
Levels of Organization in the Body 2
Concepts, Challenges, and Controversies:
The chemical level: Various atoms and molecules make up the HeLa Cells: Problems in a “Growing” Industry 23
body. 2
The plasma membrane bounds the cell. 23
The cellular level: Cells are the basic units of life. 2
The nucleus contains the DNA. 23
The tissue level: Tissues are groups of cells of similar
The cytoplasm consists of various organelles, the cytoskeleton,
specialization. 4
and cytosol. 24
The organ level: An organ is a unit made up of several tissue
types. 5 Endoplasmic Reticulum and Segregated Synthesis 24
The body system level: A body system is a collection of related The rough endoplasmic reticulum synthesizes proteins for
organs. 5 secretion and membrane construction. 24
The organism level: The body systems are packaged together The smooth endoplasmic reticulum packages new proteins in
into a functional whole body. 6 transport vesicles. 26
Concept of Homeostasis 6 Golgi Complex and Exocytosis 27
Body cells are in contact with a privately maintained internal Transport vesicles carry their cargo to the Golgi complex for
environment. 7 further processing. 27
The Golgi complex packages secretory vesicles for release by
Concepts, Challenges, and Controversies:
exocytosis. 27
Stem-Cell Science and Tissue Engineering: The Quest to Make
Defective Body Parts Like New Again 8 Lysosomes and Endocytosis 28
Lysosomes digest extracellular material brought into the cell by
Body systems maintain homeostasis, a dynamic steady state in
phagocytosis. 29
the internal environment. 10
Lysosomes remove worn out organelles. 31
A Closer Look at Exercise Physiology:
Peroxisomes and Detoxifi cation 31
What Is Exercise Physiology? 11
Peroxisomes house oxidative enzymes that detoxify various
Homeostatic Control Systems 14
wastes. 31
Homeostatic control systems may operate locally or
Mitochondria and ATP Production 31
bodywide. 14
Negative feedback opposes an initial change and is widely used Mitochondria are enclosed by two membranes. 32
to maintain homeostasis. 15 Mitochondria play a major role in generating ATP. 32
Positive feedback amplifi es an initial change. 15 The cell generates more energy in aerobic than in anaerobic
Feedforward mechanisms initiate responses in anticipation of a conditions. 37
change. 16 A Closer Look at Exercise Physiology:
Disruptions in homeostasis can lead to illness and death. 17 Aerobic Exercise: What For and How Much? 39
The energy stored within ATP is used for synthesis, transport,
Chapter in Perspective:
and mechanical work. 39
Focus on Homeostasis 17
Ribosomes and Protein Synthesis 39
Review Exercises 17
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Vaults as Cellular Trucks 40 Active transport is carrier-mediated transport that uses energy
Vaults may serve as cellular transport vehicles. 40 and moves a substance against its concentration
gradient. 69
Centrosome, Centrioles, and Microtubule
A Closer Look at Exercise Physiology:
Organization 41
Exercising Muscles Have a “Sweet Tooth” 70
Cytosol: Cell Gel 42
With vesicular transport, material is moved into or out of the cell
The cytosol is important in intermediary metabolism, ribosomal
wrapped in membrane. 73
protein synthesis, and nutrient storage. 42
Membrane Potential 75
Cytoskeleton: Cell “Bone and Muscle” 42
Membrane potential is a separation of opposite charges across
Microtubules help maintain asymmetric cell shapes and play a
the plasma membrane. 75
role in complex cell movements. 43
Membrane potential is due to diff erences in the concentration
Microfi laments are important to cellular contractile systems and
and permeability of key ions. 78
as mechanical stiff eners. 47
Chapter in Perspective:
Intermediate fi laments are important in cell regions subject to
mechanical stress. 49 Focus on Homeostasis 82
The cytoskeleton functions as an integrated whole and links Review Exercises 83
other parts of the cell. 49
Points to Ponder 84
Chapter in Perspective: Clinical Consideration 85
Focus on Homeostasis 49
Review Exercises 50 Chapter 4
Points to Ponder 51 Principles of Neural and Hormonal
Clinical Consideration 51 Communication 87
Chapter 3 Introduction to Neural Communication 87
Nerve and muscle are excitable tissues. 87
The Plasma Membrane and Membrane
Membrane potential becomes less negative during
Potential 53
depolarization and more negative during
hyperpolarization. 87
Membrane Structure and Functions 53
Electrical signals are produced by changes in ion movement
The plasma membrane is a fl uid lipid bilayer embedded with
across the plasma membrane. 88
proteins. 53
Graded Potentials 88
The lipid bilayer forms the basic structural barrier that encloses
the cell. 55 The stronger a triggering event is, the larger the resultant graded
potential. 88
Concepts, Challenges, and Controversies:
Graded potentials spread by passive current fl ow. 89
Cystic Fibrosis: A Fatal Defect in Membrane Transport 56
Graded potentials die out over short distances. 90
The membrane proteins perform various specifi c membrane
Action Potentials 91
functions. 56
During an action potential, the membrane potential rapidly,
The membrane carbohydrates serve as self-identity markers. 57
transiently reverses. 91
Cell-to-Cell Adhesions 57
Marked changes in membrane permeability and ion movement
The extracellular matrix serves as the biological “glue.” 58
lead to an action potential. 91
Some cells are directly linked by specialized cell junctions. 58 The Na(cid:2)–K(cid:2) pump gradually restores the concentration
Overview of Membrane Transport 60 gradients disrupted by action potentials. 93
Unassisted Membrane Transport 60 Action potentials are propagated from the axon hillock to the
axon terminals. 94
Particles that can permeate the membrane diff use passively
down their concentration gradient. 60 Once initiated, action potentials are conducted throughout a
nerve fi ber. 96
Ions that can permeate the membrane also move passively along
their electrical gradient. 63 The refractory period ensures one-way propagation of action
potentials and limits their frequency. 96
Osmosis is the net diff usion of water down its own concentration
gradient. 63 Action potentials occur in all-or-none fashion. 99
Tonicity refers to the eff ect the concentration of nonpenetrating The strength of a stimulus is coded by the frequency of action
solutes in a solution has on cell volume. 66 potentials. 99
Myelination increases the speed of conduction of action
Assisted Membrane Transport 67
potentials. 100
Carrier-mediated transport is accomplished by a membrane
carrier changing its shape. 67 Concepts, Challenges, and Controversies:
Multiple Sclerosis: Myelin—Going, Going, Gone 102
Facilitated diff usion is passive carrier-mediated transport. 69
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Fiber diameter also infl uences the velocity of action potential The nervous and endocrine systems have their own realms of
propagation. 102 authority but interact functionally. 128
Concepts, Challenges, and Controversies: Chapter in Perspective:
Best Bets for Regenerating Nerve Fibers 103 Focus on Homeostasis 129
Synapses and Neuronal Integration 104 Review Exercises 129
Synapses are typically junctions between presynaptic and
Points to Ponder 131
postsynaptic neurons. 104
Clinical Consideration 131
A neurotransmitter carries the signal across a synapse. 105
Each neurotransmitter–receptor combination always produces
Chapter 5
the same response. 107
Neurotransmitters are quickly removed from the synaptic The Central Nervous System 133
cleft. 107
Organization and Cells of the Nervous System 133
The grand postsynaptic potential depends on the sum of the
activities of all presynaptic inputs. 107 The nervous system is organized into the central nervous system
Action potentials are initiated at the axon hillock because it has and the peripheral nervous system. 133
the lowest threshold. 109 The three functional classes of neurons are aff erent neurons,
Neuropeptides act primarily as neuromodulators. 110 eff erent neurons, and interneurons. 135
Presynaptic inhibition or facilitation can selectively alter the Glial cells support the interneurons physically, metabolically, and
eff ectiveness of a presynaptic input. 111 functionally. 135
Drugs and diseases can modify synaptic transmission. 112 Protection and Nourishment of the Brain 139
Neurons are linked through complex converging and diverging Three meningeal membranes wrap, protect, and nourish the
pathways. 112 central nervous system. 139
Intercellular Communication and Signal The brain fl oats in its own special cerebrospinal fl uid. 139
Transduction 113 A highly selective blood–brain barrier regulates exchanges
between the blood and brain. 141
Communication between cells is largely orchestrated by
extracellular chemical messengers. 113 The brain depends on constant delivery of oxygen and glucose by
the blood. 141
Extracellular chemical messengers bring about cell responses
primarily by signal transduction. 115 Overview of the Central Nervous System 141
Some extracellular chemical messengers open chemically gated Concepts, Challenges, and Controversies:
receptor-channels. 115 Strokes: A Deadly Domino Eff ect 142
Some extracellular chemical messengers activate receptor-
Cerebral Cortex 143
enzymes via the tyrosine kinase pathway. 115
The cerebral cortex is an outer shell of gray matter covering an
Most extracellular chemical messengers activate second-
inner core of white matter. 143
messenger pathways via G-protein-coupled receptors. 117
The cerebral cortex is organized into layers and functional
Introduction to Hormonal Communication 117
columns. 143
Hormones are classifi ed chemically as hydrophilic or
The four pairs of lobes in the cerebral cortex are specialized for
lipophilic. 118
diff erent activities. 143
The mechanisms of synthesis, storage, and secretion of
The parietal lobes accomplish somatosensory processing. 144
hormones vary according to their chemical diff erences. 119
The primary motor cortex located in the frontal lobes controls
Hydrophilic hormones dissolve in the plasma; lipophilic
the skeletal muscles. 145
hormones are transported by plasma proteins. 120
The higher motor areas are also important in motor
Hormones generally produce their eff ect by altering intracellular
control. 145
proteins. 120
Somatotopic maps vary slightly between individuals and are
Hydrophilic hormones alter preexisting proteins via second-
dynamic, not static. 149
messenger systems. 120
Because of its plasticity, the brain can be remodeled in response
Concepts, Challenges, and Controversies: to varying demands. 149
Programmed Cell Suicide: A Surprising Example of a Signal
Diff erent regions of the cortex control diff erent aspects of
Transduction Pathway 124 language. 150
By stimulating genes, lipophilic hormones promote synthesis of The association areas of the cortex are involved in many higher
new proteins. 125 functions. 150
Comparison of the Nervous and Endocrine Systems 126 The cerebral hemispheres have some degree of
The nervous system is “wired,” and the endocrine system is specialization. 152
“wireless.” 127 An electroencephalogram is a record of postsynaptic activity in
Neural specifi city is due to anatomic proximity; and endocrine cortical neurons. 152
specifi city, to receptor specialization. 127 Neurons in diff erent regions of the cerebral cortex may fi re in
rhythmic synchrony. 153
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Basal Nuclei, Thalamus, and Hypothalamus 153 Chapter 6
The basal nuclei play an important inhibitory role in motor
The Peripheral Nervous System: Aff erent
control. 153
Division; Special Senses 183
The thalamus is a sensory relay station and is important in motor
control. 154
Receptor Physiology 183
The hypothalamus regulates many homeostatic functions. 155
Receptors have diff erential sensitivities to various stimuli. 183
Emotion, Behavior, and Motivation 155
A stimulus alters the receptor’s permeability, leading to a graded
The limbic system plays a key role in emotion. 156 receptor potential. 185
The limbic system and higher cortex participate in controlling Receptor potentials may initiate action potentials in the aff erent
basic behavioral patterns. 156 neuron. 185
Motivated behaviors are goal directed. 157 Receptors may adapt slowly or rapidly to sustained
Norepinephrine, dopamine, and serotonin are neurotransmitters stimulation. 186
in pathways for emotions and behavior. 157 Visceral aff erents carry subconscious input whereas sensory
Learning and Memory 157 aff erents carry conscious input. 187
Learning is the acquisition of knowledge as a result of A Closer Look at Exercise Physiology:
experiences. 157 Back Swings and Prejump Crouches: What Do They Share in
Memory is laid down in stages. 158 Common? 188
Short-term memory and long-term memory involve diff erent Each somatosensory pathway is “labeled” according to modality
molecular mechanisms. 159 and location. 188
Short-term memory involves transient changes in synaptic Acuity is infl uenced by receptive fi eld size and lateral
activity. 159 inhibition. 189
Long-term memory involves formation of new, permanent Perception is the conscious awareness of surroundings derived
synaptic connections. 162 from interpretation of sensory input. 190
Memory traces are present in multiple regions of the brain. 163 Pain 191
Concepts, Challenges, and Controversies: Stimulation of nociceptors elicits the perception of pain plus
Alzheimer’s Disease: A Tale of Beta Amyloid Plaques, Tau Tangles, motivational and emotional responses. 191
and Dementia 164 The brain has a built-in analgesic system. 192
Cerebellum 166 Concepts, Challenges, and Controversies:
Acupuncture: Is It for Real? 194
The cerebellum is important in balance and in planning and
executing voluntary movement. 166 Eye: Vision 195
Brain Stem 167 Protective mechanisms help prevent eye injuries. 195
The brain stem is a vital link between the spinal cord and higher The eye is a fl uid-fi lled sphere enclosed by three specialized
brain regions. 167 tissue layers. 195
Sleep is an active process consisting of alternating periods of The amount of light entering the eye is controlled by the
slow-wave and paradoxical sleep. 167 iris. 196
The sleep–wake cycle is controlled by interactions among three The eye refracts the entering light to focus the image on the
neural systems. 170 retina. 197
The function of sleep is unclear. 171 Accommodation increases the strength of the lens for near
vision. 200
Spinal Cord 172
Light must pass through several retinal layers before reaching
The spinal cord extends through the vertebral canal and is
the photoreceptors. 201
connected to the spinal nerves. 172
Phototransduction by retinal cells converts light stimuli into
The white matter of the spinal cord is organized into tracts. 172
neural signals. 201
Each horn of the spinal cord gray matter houses a diff erent type
Rods provide indistinct gray vision at night, whereas cones
of neuronal cell body. 174
provide sharp color vision during the day. 207
Spinal nerves carry both aff erent and eff erent fi bers. 175
Color vision depends on the ratios of stimulation of the three
The spinal cord is responsible for the integration of many basic
cone types. 208
refl exes. 176
The sensitivity of the eyes can vary markedly through dark and
A Closer Look at Exercise Physiology: light adaptation. 209
Swan Dive or Belly Flop: It’s a Matter of CNS Control 177
Visual information is modifi ed and separated before reaching the
Chapter in Perspective: visual cortex. 209
Focus on Homeostasis 180 The thalamus and visual cortexes elaborate the visual
message. 210
Review Exercises 180
Visual input goes to other areas of the brain not involved in
Points to Ponder 181
vision perception. 213
Clinical Consideration 181
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Some sensory input may be detected by multiple sensory- The sympathetic and parasympathetic nervous systems dually
processing areas in the brain. 213 innervate most visceral organs. 240
Ear: Hearing and Equilibrium 213 The adrenal medulla is a modifi ed part of the sympathetic
nervous system. 243
Sound waves consist of alternate regions of compression and
rarefaction of air molecules. 213 Several diff erent receptor types are available for each autonomic
neurotransmitter. 243
Concepts, Challenges, and Controversies:
Many regions of the central nervous system are involved in the
“Seeing” with the Tongue 214
control of autonomic activities. 245
The external ear plays a role in sound localization. 216
Somatic Nervous System 246
The tympanic membrane vibrates in unison with sound waves in
Motor neurons supply skeletal muscle. 246
the external ear. 216
Motor neurons are the fi nal common pathway. 246
The middle ear bones convert tympanic membrane vibrations
into fl uid movements in the inner ear. 217 Neuromuscular Junction 246
The cochlea contains the organ of Corti, the sense organ for Motor neurons and skeletal muscle fi bers are chemically linked
hearing. 217 at neuromuscular junctions. 246
Hair cells in the organ of Corti transduce fl uid movements into Acetylcholine is the neuromuscular junction
neural signals. 217 neurotransmitter. 247
Pitch discrimination depends on the region of the basilar Acetylcholinesterase ends acetylcholine activity at the
membrane that vibrates. 220 neuromuscular junction. 250
Loudness discrimination depends on the amplitude of A Closer Look at Exercise Physiology:
vibration. 222 Loss of Muscle Mass: A Plight of Spacefl ight 251
The auditory cortex is mapped according to tone. 222 The neuromuscular junction is vulnerable to several chemical
Deafness is caused by defects in either conduction or neural agents and diseases. 251
processing of sound waves. 223
Concepts, Challenges, and Controversies:
The vestibular apparatus is important for equilibrium by Botulinum Toxin’s Reputation Gets a Facelift 253
detecting position and motion of the head. 224
Chapter in Perspective:
Chemical Senses: Taste and Smell 227
Focus on Homeostasis 254
Taste receptor cells are located primarily within tongue taste
buds. 229 Review Exercises 254
Taste discrimination is coded by patterns of activity in various Points to Ponder 255
taste bud receptors. 229
Clinical Consideration 255
The olfactory receptors in the nose are specialized endings of
renewable aff erent neurons. 230
Chapter 8
Various parts of an odor are detected by diff erent olfactory
receptors and sorted into “smell fi les.” 230 Muscle Physiology 257
Odor discrimination is coded by patterns of activity in the
Structure of Skeletal Muscle 257
olfactory bulb glomeruli. 232
Skeletal muscle fi bers are striated by a highly organized internal
The olfactory system adapts quickly, and odorants are rapidly
arrangement. 258
cleared. 232
Myosin forms the thick fi laments. 260
The vomeronasal organ detects pheromones. 232
Actin is the main structural component of the thin
Chapter in Perspective: fi laments. 261
Focus on Homeostasis 232
Molecular Basis of Skeletal Muscle Contraction 261
Review Exercises 233
During contraction, cycles of cross-bridge binding and bending
Points to Ponder 234 pull the thin fi laments inward. 261
Clinical Consideration 235 Calcium is the link between excitation and contraction. 264
Contractile activity far outlasts the electrical activity that
Chapter 7 initiated it. 268
Skeletal Muscle Mechanics 268
The Peripheral Nervous System: Eff erent
Whole muscles are groups of muscle fi bers bundled together and
Division 237
attached to bones. 268
Muscle tension is transmitted to bone as the contractile
Autonomic Nervous System 237
component tightens the series-elastic component. 269
An autonomic nerve pathway consists of a two-neuron
Contractions of a whole muscle can be of varying strength. 269
chain. 237
The number of fi bers contracting within a muscle depends on the
Parasympathetic postganglionic fi bers release acetylcholine;
extent of motor unit recruitment. 269
sympathetic ones release norepinephrine. 238
Contents ix
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