Quantitative Human Physiology

Preface

Acknowledgments

UNIT 1. Physical and Chemical Foundations of Physiology

1.1. The Core Principles of Physiology

Human Physiology Is the Integrated Study of the Normal Function of the Human Body

Cells Are the Organizational Unit of Life

The Concept of Homeostasis Is a Central Theme of Physiology

The Body Consists of Causal Mechanisms That Obey the Laws of Physics and Chemistry

Evolution Is an Efficient Cause of the Human Body Working Over Long Time Scales

Living Beings Transform Energy and Matter

Function Follows Form

Coordinated Command and Control Requires Signaling at All Levels of Organization

Physiology Is a Quantitative Science

Summary

Review Questions

1.2. Physical Foundations of Physiology I

Forces Produce Flows

Conservation of Matter or Energy Leads to the Continuity Equation

Steady-State Flows Require Linear Gradients

Heat, Charge, Solute, and Volume Can Be Stored: Analogues of Capacitance

Pressure Drives Fluid Flow

Poiseuille’s Law Governs Steady-State Laminar Flow in Narrow Tubes

The Law of LaPlace Relates Pressure to Tension in Hollow Organs

Summary

Review Questions

Appendix 1.2.A1 Derivation of Poiseuille’s Law

1.3. Physical Foundations of Physiology II

Coulomb’s Law Describes Electrical Forces

The Electric Potential Is the Work per Unit Charge

The Idea of Potential Is Limited to Conservative Forces

Potential Difference Depends Only on the Initial and Final States

The Electric Field Is the Negative Gradient of the Potential

Force and Energy Are Simple Consequences of Potential

Gauss’s Law Is a Consequence of Coulomb’s Law

The Capacitance of a Parallel Plate Capacitor Depends on its Area and Plate Separation

Biological Membranes Are Electrical Capacitors

Electric Charges Move in Response to Electric Forces

Movement of Ions in Response to Electrical Forces Make a Current and a Solute Flux

The Relation Between J and C Defines an Average Velocity

Summary

Review Questions

Problem Set 1.1. Physical Foundations

1.4. Chemical Foundations of Physiology I

Atoms Contain Distributed Electrical Charges

Electron Orbitals Have Specific, Quantized Energies

Human Life Requires Relatively Few of the Chemical Elements

Atomic Orbitals Explain the Periodicity of Chemical Reactivities

Atoms Bind Together in Definite Proportions to Form Molecules

Compounds Have Characteristic Geometries and Surfaces

Single CC Bonds Can Freely Rotate

Double CC Bonds Prohibit Free Rotation

Chemical Bonds Have Bond Energies, Bond Lengths, and Bond Angles

Bond Energy Is Expressed as Enthalpy Changes

The Multiplicity of CX Bonds Produces Isomerism

Unequal Sharing Makes Polar Covalent Bonds

Water Provides an Example of a Polar Bond

Intermolecular Forces Arise from Electrostatic Interactions

Atoms Within Molecules Wiggle and Jiggle and Bonds Stretch and Bend

Summary

Review Questions

Appendix 1.4.A1 Dipole Moment

1.5. Chemical Foundations of Physiology II

Avogadro’s number Counts the Particles in a Mole

Concentration is the Amount per unit Volume

Scientific Prefixes Indicate Order of Magnitude

Dilution of Solutions Is Calculated Using Conservation of Solute

Calculation of Fluid Volumes By the Fick Dilution Principle

Chemical Reactions Have Forward and Reverse Rate Constants

The Michaelis–Menten Formulation of Enzyme Kinetics

Summary

Review Questions

Appendix 1.5.A1 Transition State Theory Explains Reaction Rates in Terms of An Activation Energy

The Activation Energy Depends on the Path

1.6. Diffusion

Fick’s First Law of Diffusion Was Proposed in Analogy to Fourier’s Law of Heat Transfer

Fick’s Second Law of Diffusion Follows from the Continuity Equation and Fick’s First Law

Fick’s Second Law Can Be Derived from the One-Dimensional Random Walk

The Time for One-Dimensional Diffusion Increases with the Square of Distance

Diffusion Coefficients in Cells Are Less than the Free Diffusion Coefficient in Water

External Forces Can Move Particles and Alter the Diffusive Flux

The Stokes–Einstein Equation Relates the Diffusion Coefficient to Molecular Size

Summary

Review Questions

1.7. Electrochemical Potential and Free Energy

Diffusive and Electrical Forces Can Be Unified in the Electrochemical Potential

The Overall Force That Drives Flux Is the Negative Gradient of the Electrochemical Potential

The Electrochemical Potential Is the Gibbs Free Energy Per Mole

The Sign of ΔG Determines the Direction of a Reaction

Processes with ΔG>0 Can Proceed Only by Linking Them with Another Process with ΔG<0

The Large Negative Free Energy of ATP Hydrolysis Powers Many Biological Processes

Measurement of the Equilibrium Concentrations of ADP, ATP, and Pi Allows Us to Calculate ΔG0

Summary

Review Questions

Problem Set 1.2. Kinetics and Diffusion

UNIT 2. Membranes, Transport, and Metabolism

2.1. Cell Structure

For Cells, Form Follows Function

Organelles Make Up the Cell Like the Organs Make Up the Body

The Cell Membrane Marks the Limits of the Cell

The Cytosol Provides a Medium for Dissolution and Transport of Materials

The Cytoskeleton Supports the Cell and Forms a Network for Vesicular Transport

The Nucleus Is the Command Center of the Cell

Ribosomes Are the Site of Protein Synthesis

The ER Is the Site of Protein and Lipid Synthesis and Processing

The Golgi Apparatus Packages Secretory Materials

The Mitochondrion Is the Powerhouse of the Cell

Lysosomes and Peroxisomes Are Bags of Enzymes

Proteasomes Degrade Marked Proteins

Cells Attach to Each Other Through a Variety of Junctions

Summary

Review Questions

Appendix 2.1.A1 Some Methods for Studying Cell Structure and Function

2.2. DNA and Protein Synthesis

DNA Makes Up the Genome

DNA Consists of Two Intertwined Sequences of Nucleotides

RNA Is Closely Related to DNA

Messenger RNA Carries the Instructions for Making Proteins

Ribosomal RNA Is Assembled in the Nucleolus from a DNA Template

Transfer RNA Covalently Binds Amino Acids and Recognizes Specific Regions of mRNA

The Genetic Code Is a System Property

Regulation of DNA Transcription Defines the Cell Type

The Histone Code Provides Another Level of Regulation of Gene Transcription

Summary

Review Questions

2.3. Protein Structure

Amino Acids Make Up Proteins

Hydrophobic Interactions Can Be Assessed from the Partition Coefficient

Peptide Bonds Link Amino Acids Together in Proteins

Protein Function Centers on Their Ability to Form Reactive Surfaces

There Are Four Levels of Description for Protein Structure

Posttranslational Modification Regulates and Refines Protein Structure and Function

Protein Activity Is Regulated by the Number of Molecules or by Reversible Activation/Inactivation

Summary

Review Questions

2.4. Biological Membranes

Biological Membranes Surround Most Intracellular Organelles

Biological Membranes Consist of a Lipid Bilayer Core with Embedded Proteins and Carbohydrate Coats

Organic Solvents Can Extract Lipids from Membranes

Biological Membranes Contain Mostly Phospholipids

Phospholipids Contain Fatty Acyl Chains, Glycerol, Phosphate, and a Hydrophilic Group

Other Lipid Components of Membranes Include Cardiolipin, Sphingolipids, and Cholesterol

Phospholipids in Water Self-Organize into Layered Structures

Surface Tension of Water Results from Asymmetric Forces at the Interface

Amphipathic Molecules Spread Over a Water Surface, Reduce Surface Tension, and Produce an Apparent Surface Pressure

Phospholipids Form Bilayer Membranes Between Two Aqueous Compartments

Lipid Bilayers Can Also Form Liposomes

Lipids Maintain Dynamic Motion within the Bilayer

Lipid Rafts Are Special Areas of Lipid and Protein Composition

Membrane Proteins Bind to Membranes with Varying Affinity

Secreted Proteins Have Special Mechanisms for Getting Inside the Endoplasmic Reticulum

Summary

Review Questions

Problem Set 2.1. Surface Tension, Membrane Structure, Microscopic Resolution, and Cell Fractionation

2.5. Passive Transport and Facilitated Diffusion

Membranes Possess a Variety of Transport Mechanisms

A Microporous Membrane Is One Model of a Passive Transport Mechanism

Dissolution in the Lipid Bilayer Is Another Model for Passive Transport

Facilitated Diffusion Uses a Membrane-Bound Carrier

Facilitated Diffusion Saturates with Increasing Solute Concentrations

Facilitated Diffusion Shows Specificity

Facilitated Diffusion Shows Competitive Inhibition

Passive Transport Occurs Spontaneously Without Input of Energy

Ions Can be Passively Transported Across Membranes by Ionophores or by Channels

Water Moves Passively Through Aquaporins

Summary

Review Questions

2.6. Active Transport

The Electrochemical Potential Difference Measures the Energetics of Ion Permeation

Active Transport Mechanisms Link Metabolic Energy to Transport of Materials

Na,K-ATPase is an Example of Primary Active Transport

Na,K-ATPase forms a Phosphorylated Intermediate

There Are Many Different Primary Active Transport Pumps

The Na–Ca Exchanger as an Example of Secondary Active Transport

Secondary Active Transport Mechanisms Are Symports or Antiports

Summary

Review Questions

2.7. Osmosis and Osmotic Pressure

The Model for Water Transport Is a Microporous Membrane

Case A: The Solute Is Very Small Compared to the Pore

Case B: The Solute Is Larger than the Pore: Osmosis

The van’t Hoff Equation Relates Osmotic Pressure to Concentration

The Osmotic Coefficient Corrects for NonIdeal Behavior of Solutions

Osmosis in a Microporous Membrane Is Caused by a Momentum Deficit within the Pores

The Flow across a Membrane Responds to the Net Hydrostatic and Osmotic Pressure

Case C: The Solute is Smaller than the Pore but is not Tiny Compared to the Pore

Solutions May Be Hypertonic or Hypotonic

Osmosis, Osmotic Pressure, and Tonicity Are Related but Distinct Concepts

Osmotic Pressure Is a Property of Solutions Related to Other Colligative Properties

Cells Behave Like Osmometers

Cells Actively Regulate their Volume through RVDs and RVIs

Summary

Review Questions

Appendix 2.7.A.1 Thermodynamic Derivation of van’t Hoff’s Law

Appendix 2.7.A2 Mechanism of Osmosis across a Microporous Membrane

Problem Set 2.2. Membrane Transport

2.8. Cell Signaling

Signaling transduces One Event into Another

Cell-to-Cell Communication Can Also Use Direct Mechanical, Electrical, or Chemical Signals

Signals Elicit a Variety of Classes of Cellular Responses

Electrical Signals and Neurotransmitters Are Fastest; Endocrine Signals Are Slowest

Voltage-Gated Ion Channels Convey Electrical Signals

Voltage-Gated Ca2+ Channels Transduce an Electrical Signal to an Intracellular Ca2+ Signal

Ligand-Gated Ion Channels Open with Chemical Signals

Heterotrimeric G-Protein-Coupled Receptors (GPCRs) Are Versatile

There Are Four Classes of G-Proteins: Gαs, Gαi/Gαo, Gαq, and Gα12/Gα13

The Response of a Cell to a Chemical Signal Depends on the Receptor and Its Effectors

Chemical Signals Can Bind to and Directly Activate Membrane-Bound Enzymes

Many Signals Alter Gene Expression

Nuclear Receptors Alter Gene Transcription

Nuclear Receptors Recruit Histone Acetylase to Unwrap the DNA from the Histones

Nuclear Receptors Recruit Transcription Factors

Other Signaling Pathways Also Regulate Gene Expression

Summary of Signaling Mechanisms

Summary

Review Questions

2.9. ATP Production I

Take a Global View of Metabolism

Energy Production and use in the Cell is Analogous to Societal Production and use of Electrical Power

Energy Production Occurs in Three Stages: Breakdown into Units, Formation of Acetyl CoA and Complete Oxidation of Acetyl CoA

Fuel Reserves are Stored in the Body Primarily in Fat Depots and Glycogen

Glucose is a Readily Available Source of Energy

Glucose Release by the Liver is Controlled by Hormones through a Second Messenger System

The Liver Exports Glucose into the Blood Because it can Dephosphorylate Glucose-1-P

A Specific Glucose Carrier Takes Glucose up into Cells

Glycolysis is a Series of Biochemical Transformations Leading from Glucose to Pyruvate

Glycolysis Generates ATP Quickly in the Absence of Oxygen

Glycolysis Requires NAD+

Gluconeogenesis Requires Reversal of Glycolysis

Summary

Review Questions

2.10. ATP Production II

Oxidation of Pyruvate Occurs in the Mitochondria via the TCA Cycle

Pyruvate Enters the Mitochondria and Is Converted to Acetyl CoA

Pyruvate Dehydrogenase Releases CO2 and Makes NADH

The TCA Cycle Is a Catalytic Cycle

The ETC Links Chemical Energy to H+ Pumping Out of the Mitochondria

Oxygen Accepts Electrons at the End of the ETC

Proton Pumping and Electron Transport Are Tightly Coupled

Oxidative Phosphorylation Couples Inward H+ Flux to ATP Synthesis

The Proton Electrochemical Gradient Provides the Energy for ATP Synthesis

NADH Forms 3 ATP Molecules; FADH2 Forms 2 ATP Molecules

ATP Can Be Produced From Cytosolic NADH

Most of the ATP Produced During Complete Glucose Oxidation Comes from Oxidative Phosphorylation

Mitochondria Have Specific Transport Mechanisms

Summary

Review Questions

2.11. ATP Production III

Fats and Proteins Contribute 60% of the Energy Content of Many Diets

Depot Fat Is Stored as Triglycerides and Broken Down to Glycerol and Fatty Acids for Energy

Glycerol Is Converted to an Intermediate of Glycolysis

Fatty Acids Are Metabolized in the Mitochondria and Peroxisomes

Beta Oxidation Cleaves Two-Carbon Pieces off Fatty Acids

The Liver Packages Substrates for Energy Production by Other Tissues

Amino Acids Can Be Used to Generate ATP

Amino Acids Are Deaminated to Enable Oxidation

Urea Is Produced During Deamination and Is Eliminated as a Waste Product

Summary

Review Questions

UNIT 3. Physiology of Excitable Cells

3.1. The Origin of the Resting Membrane Potential

Introduction

The Equilibrium Potential Arises from the Balance Between Electrical Force and Diffusion

The Equilibrium Potential for K+ Is Negative

Integration of the Nernst–Planck Electrodiffusion Equation Gives the Goldman–Hodgkin–Katz Equation

Slope Conductance and Chord Conductance Relate Ion Flows to the Net Driving Force

The Chord Conductance Equation Relates Membrane Potential to All Ion Flows

The Current Convention Is that an Outward Current Is Positive

Summary

Review Questions

Appendix 3.1.A1 Derivation of the GHK Equation

3.2. The Action Potential

Cells Use Action Potentials as Fast Signals

The Motor Neuron Has Dendrites, a Cell Body, and an Axon

Passing a Current Across the Membrane Changes the Membrane Potential

An Outward Current Hyperpolarizes the Membrane Potential

The Result of Depolarizing Stimulus of Adequate Size Is a New Phenomenon—the Action Potential

The Action Potential Is All or None

The Latency Decreases with Increasing Stimulus Strength

Threshold Is the Membrane Potential at Which an Action Potential Is Elicited 50% of the Time

The Nerve Cannot Produce a Second Excitation During the Absolute Refractory Period

The Action Potential Reverses to Positive Values, Called the Overshoot

Voltage-Dependent Changes in Ion Conductance Cause the Action Potential

Conductance Depends on the Number and State of the Channels

Patch Clamp Experiments Measure Unitary Conductances

Summary

Review Questions

Appendix 3.2.A1 The Hodgkin–Huxley Model of the Action Potential

3.3. Propagation of the Action Potential

The Action Potential Moves Along the Axon

The Velocity of Nerve Conduction Varies Directly with the Axon Diameter

The Action Potential Is Propagated by Current Moving Axially Down the Axon

The Time Course and Distance of Electrotonic Spread Depend on the Cable Properties of the Nerve

Cable Properties Define a Space Constant and a Time Constant

The Cable Properties Explain the Velocity of Action Potential Conduction

Saltatory Conduction Refers to the “Jumping” of the Current from Node to Node

The Action Potential Is Spread out Over More than One Node

Summary

Review Questions

Appendix 3.3.A1 Capacitance of a Coaxial Capacitor

Problem Set 3.1. Membrane Potential, Action Potential, and Nerve Conduction

3.4. Skeletal Muscle Mechanics

Muscles Either Shorten or Produce Force

Muscles Perform Diverse Functions

Muscles Are Classified According to Fine Structure, Neural Control, and Anatomical Arrangement

Isometric Force Is Measured While Keeping Muscle Length Constant

Muscle Force Depends on the Number of Motor Units That Are Activated

The Size Principle States that Motor Units Are Recruited in the Order of Their Size

Muscle Force Can Be Graded by the Frequency of Motor Neuron Firing

Muscle Force Depends on the Length of the Muscle

Muscle Force Varies Inversely with Muscle Velocity

Muscle Power Varies with the Load and Muscle Type

Eccentric Contractions Lengthen the Muscle and Produce More Force

Concentric, Isometric, and Eccentric Contractions Serve Different Functions

Muscle Architecture Influences Force and Velocity of the Whole Muscle

Muscles Decrease Force Upon Repeated Stimulation; This Is Fatigue

Summary

Review Questions

3.5. Contractile Mechanisms in Skeletal Muscle

Introduction

Muscle Cells Have a Highly Organized Structure

The Sliding Filament Hypothesis Explains the Length–Tension Curve

Force is Produced by an Interaction Between Thick Filament Proteins and Thin Filament Proteins

Cross-Bridges from the Thick Filament Split ATP and Generate Force

Cross-Bridge Cycling Rate Explains the Fiber Type Dependence of the Force–Velocity Curve

Force Is Transmitted Outside the Cell Through the Cytoskeleton and Special Transmembrane Proteins

Summary

Review Questions

3.6. The Neuromuscular Junction and Excitation-Contraction Coupling

Motor Neurons Are the Sole Physiological Activators of Skeletal Muscles

The Motor Neuron Receives Thousands of Inputs from Other Cells

Postsynaptic Potentials Can Be Excitatory or Inhibitory

Postsynaptic Potentials Are Graded, Spread Electrotonically, and Decay with Time

Action Potentials Originate at the Initial Segment or Axon Hillock

Motor Neurons Integrate Multiple Synaptic Inputs to Initiate Action Potentials

The Action Potential Travels Down the Axon Toward the Neuromuscular Junction

Neurotransmission at the Neuromuscular Junction Is Unidirectional

Motor Neurons Release Acetylcholine to Excite Muscles

Ca2+ Efflux Mechanisms in the Presynaptic Cell Shut Off the Ca2+ Signal

Acetylcholine Is Degraded and Then Recycled

The Action Potential on the Muscle Membrane Propagates Both Ways on the Muscle

The Muscle Fiber Converts the Action Potential into an Intracellular Ca2+ Signal

The Ca2+ during E-C Coupling Originates from the Sarcoplasmic Reticulum

Ca2+ Release from the SR and Reuptake by the SR Requires Several Proteins

Reuptake of Ca2+ by the SR Ends Contraction and Initiates Relaxation

Cross-Bridge Cycling Is Controlled by Myoplasmic [Ca2+]

Sequential SR Release and Summation of Myoplasmic [Ca2+] Explains Summation and Tetany

The Elastic Properties of the Muscle Are Responsible for the Waveform of the Twitch

Repetitive Stimulation Causes Repetitive Ca2+ Release from the SR and Wave Summation

Summary

Review Questions

3.7. Muscle Energetics, Fatigue, and Training

Muscular Activity Consumes ATP at High Rates

The Aggregate Rate and Amount of ATP Consumption Varies with the Intensity and Duration of Exercise

In Repetitive Exercise, Intensity Increases Frequency and Reduces Rest Time

In Maximum Effort, There Is No Rest Phase

Metabolic Pathways Regenerate ATP on Different Timescales and with Different Capacities

The Metabolic Pathways Used by Muscle Varies with Intensity and Duration of Exercise

At High Intensity of Exercise, Glucose and Glycogen Is the Preferred Fuel for Muscle

Muscle Fibers Differ in Their Metabolic Properties

Blood Lactate Levels Rise Progressively with Increases in Exercise Intensity

Mitochondria Import Lactic Acid, Then Metabolize it; This Forms a Carrier System for NADH Oxidation

Lactate Shuttles to the Mitochondria, Oxidative Fibers, or Liver

The “Anaerobic Threshold” Results from a Mismatch of Lactic Acid Production and Oxidation

Exercise Increases Glucose Transporters in the Muscle Sarcolemma

Fatigue Is a Transient Loss of Work Capacity Resulting from Preceding Work

Early and Rapid Strength Gains Comes from Training the Brain

Strength Training Induces Muscle Hypertrophy

Hormones Influence Muscle Size (=Strength)

Myostatin Is a Negative Regulator of the Muscle Mass

Endurance Training Uses Repetitive Movements to Tune Muscle Metabolism

Our Ability to Switch Muscle Fiber Types Is Limited

Summary

Review Questions

Problem Set 3.2. Neuromuscular Transmission, Muscle Force, and Energetics

3.8. Smooth Muscle

Smooth Muscles Show No Cross-Striations

Smooth Muscle Develops Tension More Slowly But Can Maintain Tension for a Long Time

Smooth Muscle Can Contract Tonically or Phasically

Smooth Muscles Exhibit a Variety of Electrical Activities that May or May Not Be Coupled to Force Development

Contractile Filaments in Smooth Muscle Cells Form a Lattice that Attaches to the Cell Membrane

Adjacent Smooth Muscle Cells Are Mechanically Coupled and May Be Electrically Coupled

Smooth Muscle Is Controlled by Intrinsic Activity, Nerves, and Hormones

Nerves Release Neurotransmitters Diffusely onto Smooth Muscle

Contraction in Smooth Muscle Cells Is Initiated by Increasing Intracellular [Ca2+]

Smooth Muscle Cytosolic [Ca2+] Is Heterogeneous and Controlled by Multiple Mechanisms

Smooth Muscle [Ca2+] Can Be Regulated by Chemical Signals

Force in Smooth Muscle Arises from Actin–Myosin Interaction

Myosin Light Chain Phosphorylation Regulates Smooth Muscle Force

Myosin Light Chain Phosphatase Dephosphorylates the RLC

Ca2+ Sensitization Produces Force at Lower [Ca2+] Levels

Nitric Oxide Induces Smooth Muscle Relaxation by Stimulating Guanylate Cyclase

Activation of Beta2 Receptors on Smooth Muscle Causes Relaxation by Removing Cytosolic [Ca2+]

Synopsis of Mechanisms Promoting Contraction or Relaxation of Smooth Muscle

Summary

Review Questions

UNIT 4. The Nervous System

4.1. Organization of the Nervous System

The Neuroendocrine System Controls Physiological Systems

A Central Tenet of Physiological Psychology Is That Neural Processes Completely Explain All Behavior

The New Mind–Body Problem Is How Consciousness Arises from a Material Brain

External Behavioral Responses Require Sensors, Internal Processes, and Motor Response

The Nervous System Is Divided into the Central and Peripheral Nervous System

The Brain Has Readily Identifiable Surface Features

CSF Fills the Ventricles and Cushions the Brain

The Blood-Brain Barrier Protects the Brain

Cross Sections of the Brain and Staining Reveal Internal Structures

Gray Matter Is Organized into Layers

Overall Function of the Nervous System Derives from its Component Cells

Overview of the Functions of Some Major Areas of the CNS

Summary

Review Questions

4.2. Cells, Synapses, and Neurotransmitters

Nervous System Behavior Derives from Cell Behavior

Nervous Tissue Is Composed of Neurons and Supporting Cells

Glial Cells Protect and Serve

Neurons Differ in Shapes and Size

Input Information Typically Converges on the Cell and Output Information Diverges

Chemical Synapses Are Overwhelmingly More Common

Ca2+ Signals Initiate Chemical Neurotransmission

Vesicle Fusion Uses the Same Molecular Machinery That Regulates Other Vesicle Traffic

Ca2+ Efflux Mechanisms in the Pre-Synaptic Cell Shut Off the Ca2+ Signal

Removal or Destruction of the Neurotransmitter Shuts Off the Neurotransmitter Signal

The Pre-Synaptic Terminal Recycles Neurotransmitter Vesicles

Ionotropic Receptors Are Ligand-Gated Channels; Metabotropic Receptors Are GPCR

Acetylcholine Binds to Nicotinic Receptors or Muscarinic Receptors

Catecholamines: Dopamine, Norepinephrine, and Epinephrine Derive from Tyrosine

Dopamine Couples to Gs and Gi-Coupled Receptors through D1 and D2 Receptors

Adrenergic Receptors Are Classified According to Their Pharmacology

Glutamate and Aspartate Are Excitatory Neurotransmitters

GABA Inhibits Neurons

Serotonin Exerts Multiple Effects in the PNS and CNS

Neuropeptides Are Synthesized in the Soma and Transported via Axonal Transport

Summary

Review Questions

4.3. Cutaneous Sensory Systems

Sensors Provide a Window onto Our World

Exteroreceptors Include the Five Classical Senses and the Cutaneous Senses

Interoreceptors Report on the Chemical and Physical State of the Interior of the Body

Sensory Systems Consist of the Sense Organ, the Sensory Receptors, and the Pathways to the CNS

Perception Refers to Our Awareness of a Stimulus

Long and Short Receptors Differ in Their Production of Action Potentials

Anatomical Connection Determines the Quality of a Sensory Stimulus

The Intensity of Sensory Stimuli Is Encoded by the Frequency of Sensory Receptor Firing and the Population of Active Receptors

Frequency Coding is the Basis of the Weber–Fechner Law of Psychology

Adaptation to a Stimulus Allows Sensory Neurons to Signal Position, Velocity, and Acceleration

Receptive Fields Refer to the Physical Areas at Which a Stimulus Will Excite a Receptor

Cutaneous Receptors Include Mechanoreceptors, Thermoreceptors, and Nociceptors

Somatosensory Information Is Transmitted to the Brain through the Dorsal Column Pathway

The Cutaneous Senses Map onto the Sensory Cortex

Pain and Temperature Information Travel in the Anterolateral Tract

Disorders of Sensation Can Pinpoint Damage

Pain Sensation Can Be Reduced by Somatosensory Input

The Receptive Field of Somatosensory Cortical Neurons is Often On-Center, Off-Surround

Summary

Review Questions

4.4. Spinal Reflexes

A Reflex is a Stereotyped Muscular Response to a Specific Sensory Stimulus

The Withdrawal Reflex Protects Us from Painful Stimuli

The Crossed-Extensor Reflex Usually Occurs in Association with the Withdrawal Reflex

The Myotatic Reflex Involves a Muscle Length Sensor, the Muscle Spindle

The Muscle Spindle Is a Specialized Muscle Fiber

The Myotatic Reflex Is a MonoSynaptic Reflex Between Ia Afferents and the α Motor Neuron

The Gamma Motor System Maintains Tension on the Intrafusal Fibers During Muscle Contraction

The Inverse Myotatic Reflex Involves Sensors of Muscle Force in the Tendon

The Spinal Cord Possesses Other Reflexes and Includes Locomotor Pattern Generators

The Spinal Cord Contains Descending Tracts That Control Lower Motor Neurons

All of the Inputs to the Lower Motor Neurons Form Integrated Responses

Summary

Review Questions

4.5. Balance and Control of Movement

The Nervous System Uses a Population Code and Frequency Code to Control Contractile Force

Control of Movement Entails Control of α Motoneuron Activity

The Circuitry of the Spinal Cord Provides the First Layer in a Hierarchy of Muscle Control

The Motor Nerves Are Organized by Myotomes

Spinal Reflexes Form the Basis of Motor Control

Purposeful Movements Originate in the Cerebral Cortex

The Primary Motor Cortex Has a Somatotopic Organization

Motor Activity Originates from Sensory Areas Together with Premotor Areas

Motor Control Is Hierarchical and Serial

The Basal Ganglia and Cerebellum Play Important Roles in Movement

The Substantia Nigra Sets the Balance Between the Direct and Indirect Pathways

The Cerebellum Maintains Movement Accuracy

The Sense of Balance Originates in Hair Cells in the Vestibular Apparatus

Rotation of the Head Gives Opposite Signals from the Two Vestibular Apparatuses

The Utricles and Saccules Contain Hair Cells That Respond to Static Forces of Gravity

The Afferent Sensory Neurons from the Vestibular Apparatus Project to the Vestibular Nuclei in the Medulla

Summary

Review Questions

Problem Set 4.1. Nerve Conduction

4.6. The Chemical Senses

The Chemical Senses Include Taste and Smell

Taste and Olfactory Receptors Turn Over Regularly

The Olfactory Epithelium Resides in the Roof of the Nasal Cavities

Olfactory Receptor Cells Send Axons Through the Cribriform Plate

Humans Recognize a Wide Variety of Odors but Are Often Untrained in Their Identification

The Response to Specific Odorants Is Mediated by Specific Odorant Binding Proteins

The Olfactory Receptor Cells Send Axons to Second-Order Neurons in the Olfactory Bulb

Each Glomerulus Corresponds to One Receptor That Responds to its Molecular Receptive Range

Olfactory Output Connects Directly to the Cortex in the Temporal Lobe

A Second Olfactory Output Is Through the Thalamus to the Orbitofrontal Cortex

A Third Pathway of Olfactory Sensors Is Between the Vomeronasal Organ and the Hypothalamus

The Detection Limits for Odors Can Be Low

Adaptation to Odors Involves the Central Nervous System

Some “Smells” Stimulate the Trigeminal Nerve and Not the Olfactory Nerve

Some Odorants Do Not Use Golf Linked to Odorant Binding Proteins

Humans Distinguish Among Five Primary Types of Taste Sensations

The Taste Buds Are Groups of Taste Receptors Arranged on Taste Papillae

TRCs Respond to Single Modalities

Salty Taste Has Two Mechanisms Distinguished by Their Amiloride Sensitivity

Sour Taste Depends on TRC Cytosolic pH

Sweet, Bitter, and Umami Taste Is Transduced by Three Sets of G-Protein-Coupled Receptors

The “Hot” Taste of Jalapeno Peppers Is Sensed Through Pain Receptors

Taste Receptors Project to the Cortex Through the Solitary N