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Animal Physiology From Genes to Organisms (with InfoTrac)

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Cengage Learning
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  • Animal Physiology : From Genes to Organisms
    Animal Physiology : From Genes to Organisms


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.

Table of Contents

Homeostasis and Integration: The Foundations of Physiology
Physiological processes arise through evolution
Physiology is an integrative discipline
Physiology includes comparative as well as integrative approaches
Methods in Physiology
The hypotheticodeductive method is the most widely accepted version of ``the scientific method.''
Levels of Organization in Organisms
Cells are progressively organized into tissues, organs, systems, and finally the whole body
Size and scale Among Organisms
The larger the organism, the smaller the surface-area-to-volume ratio
Homeostasis: Basic Mechanisms and Enhancements
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?
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
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
Homeostasis (and other regulation) is hierarchically distributed
Organ systems can be grouped according to whole-body contributions
Chapter in Perspective: Homeostasis and Integration
Review Questions
Suggested Readings and Internet Sites
Cellular and Molecular Physiology
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
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
Molecular Biology and Genomics: Genomics and Evolution
Endoplasmic Reticulum
The rough endoplasmic reticulum synthesizes proteins for secretion and membrane construction
The smooth endoplasmic reticulum packages new proteins in transport vesicles
Golgi Complex
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
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
Mitochondria and Energy Metabolism
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
The cytosol is important in intermediary metabolism, ribosomal protein synthesis, and storage of fat and glycogen
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
The extracellular matrix serves as the biological ``glue.''
Some cells are directly linked together by specialized cell junctions
Chapter in Perspective: Homeostasis and Integration
Review Questions
Suggested Readings and Internet Sites
Membrane Physiology
Membrane Structure and Composition
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
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
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
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
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
Review Questions
Suggested Readings and Internet Sites
Neuronal Physiology
Neurons and muscles are excitable tissues
Electrical signals are produced by changes in ion movement through ion channels across the plasma membrane
Graded Potentials
The stronger a triggering event, the larger the resultant graded potential
Graded potentials die out over short distances
Action Potentials
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
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
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
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
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
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
Drugs, disease toxins, and pollutants can modify synaptic transmission between neurons
Challenges and Controversies: Synaptic Solutions to Pet Problems
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
Review Questions
Suggested Readings and Internet Sites
Nervous Systems
Evolutionary Considerations and Invertebrate Nervous Systems
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
The three classes of neurons are afferent neurons, efferent neurons, and interneurons
The Efferent Division of the Peripheral Nervous System
Vertebrate Autonomic Nervous System
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
Motor neurons are the final common pathway
Vertebrate Central Nervous System
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
Brain Evolution in Vertebrates
Newer, more sophisticated regions of the vertebrate brain are piled on top of older, more primitive regions
Mammalian Cerebral Cortex
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
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
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
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
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
Review Questions
Suggested Readings and Internet Sites
Sensory Physiology
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
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
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
Mechanically gated channels transduce touch and pressure into electrical signals
Proprioception: The Mechanoreception of Motion and Position
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
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
Molecular Biology and Genomics: The Smell and Taste of Evolution
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
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
Stimulation of nociceptors elicits the perception of pain plus motivational responses
The vertebrate brain has a built-in analgesic system
Electroreception and Magnetoreception
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
Review Questions
Suggested Readings and Internet Sites
Endocrine Systems
Introduction: Principles of Endocrinology
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
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
Biological Clocks: The Role of the Suprachiasmatic Nuclei and the Pineal Gland
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
The Vertebrate Hypothalamus and Pituitary
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
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
A Closer Look at Adaption: Brood Patch Development: Some Have It, Others Don't
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
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
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
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
Review Questions
Suggested Readings and Internet Sites
Muscle Physiology
Skeletal Muscle
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
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
Contractile activity far outlasts the electrical activity that initiated it
Skeletal Muscle Mechanics
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
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
Muscle fibers adapt considerably in response to the demands placed on them
Adaptations for Flight: Continuous High Power at High Contraction Frequencies
Asynchronous muscle contractions are characterized by a nearly constant myoplasmic Ca++ concentration
Control of Motor Movement
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
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
Chapter in Perspective: Homeostasis and Integration
Review Questions
Suggested Readings and Internet Sites
Circulatory Systems
Evolution of Circulation
Circulatory systems evolved to overcome the limits of diffusion
Circulatory systems have up to three distinct components: fluid, pump, and vessels
Circulatory Fluids
Plasma in Circulatory Fluids
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
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
Thrombocytes and Platelets in Circulatory Fluids and the Process of Hemostasis
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
Circulatory Pumps
Pumps: Anatomic and Evolutionary Considerations
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
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
Hearts alternately contract to empty and relax to fill
Pumps: Cardiac Output and Its Control
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
The heart receives most of its own blood supply through coronary circulation
Circulatory Pathways and Vessels
Circulatory fluids are driven by pressure and can transmit useful force
Vessels: Flow Regulation and Hemodynamics
Blood flow through vessels depends on the pressure gradient and vascular resistance
Pathways: Open Circulation
Vessels: Closed Circulation
The vascular system evolved from one circuit to two separate circuits in vertebrates
Vessels: Arteries
Mean arterial pressure is the main driving force for blood flow
Vessels: Arterioles
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
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
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
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
Review Questions
Suggested Readings and Internet Sites
Defense Systems
Evolution of Defense Systems
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
Active immune responses are regulated by feedback systems with sensors, integrators, and effectors
Innate Immunity
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
Acquired immunity includes cell-mediated and antibody-mediated responses
An antigen induces an immune response against itself
B Lymphocytes: Antibody-Mediated Immunity
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
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
Molecular Biology and Genomics: An Accidental Origin for Adaptive Immunity?
Innate (and Acquired?) Immunity in Other Animals
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
Review Questions
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Respiratory Systems
Evolutionary Solutions to Gas Demands
General Principles
External respiratory processes must meet the demands of size, metabolism, and habitat through diffusion and bulk transport
Evolutionary Forces
Breathing as a form of bulk flow can be tidal or flow-through
External respiration can involve up to four major steps
Water Respirers
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
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
Principles of Airflow
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
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
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
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
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
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
A Closer Look at Adaptation: Effects of Depths
Respiratory centers in the vertebrate brain stem establish a rhythmic breathing pattern
Molecular Biology and Genomics: Effects of Heights
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
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Excretory Systems
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
A Closer Look at Adaptation: Avian Longevity: Unraveling the Mystery
Renal Excretory Organs
Renal tubules produce urine using the processes of filtration, secretion, reabsorption, and osmoconcentration
The Mammalian Urinary System
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
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
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
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
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
Urine is temporarily stored in the bladder, from which the process of micturition empties it
Renal Diseases
Renal diseases are numerous and have wide-ranging consequences
Other Vertebrate Urinary Systems and Extrarenal Organs
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
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
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Fluid and Acid-Base Balance
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
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
Several osmotic problems threaten cells and animals
Animals have evolved two strategies to cope with osmotic challenges
A Closer Look at Adaptation: Life at the Top
Osmoregulators rely on special transport mechanisms to maintain internal osmotic constancy
Osmotic and Volume Balance in Mammals
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
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
Chemical buffer systems act as the first line of defense against changes in hydrogen ion concentration
pH Regulation: Respiration
Respiratory systems regulates hydrogen ion concentration through adjustments in ventilation and (in gills) membrane transport
pH Regulation: Excretion
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
Review Questions
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Digestive Systems
Introduction: Feeding Strategies and Evolution
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
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
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
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
The gastroesophageal sphincter prevents reflux of gastric contents
Esophageal secretion is entirely protective
The crop is a modified section of the esophagus and functions mainly as a storage organ
Stomach or Midgut
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
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
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
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
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 . .
The large intestine of birds and hindgut of insects actively transports glucose and amino acids
Ruminant Digestion
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
Chapter in Perspective: Homeostasis and Integration
Review Questions
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Energy Balance and Thermal Physiology
Life follows the laws of thermodynamics
Energy Balance
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?
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
Thermal Physiology: General Principles
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
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
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 are endotherms that are not fully homeothermic
Chapter in Perspective: Homeostasis and Integration
A Closer Look at Adaptation: The Naked Mole Rat---Mammalian Hive Ectotherm
Review Questions
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Reproductive Systems
Reproductive Processes
Animals employ a variety of reproductive strategies to ensure survival of the species
Reproductive Systems and Genetics
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
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
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
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
The end is a new beginning
Chapter in Perspective: Homeostasis and Integration
Review Questions
Suggested Readings and Internet Sites
Answers to End of Chapter Review Questions
Online Chapter Summaries and Appendices A through C are located at
A. Metric System
B. Review of Chemical Principles
C. Storage, Replication and Expression of Genetic Information
Glossary 1(1)
Credits 1(1)
Index 1

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