Synaptic Transmission in the Central Nervous System 130

Excitatory and Inhibitory Synapses 130 Excitatory Synaptic Transmission Between Neurons 131 Temporal and Spatial Summation of Synaptic Potentials 131 Some Possible Excitatory Neurotransmitters 133 Conductance-decrease Excitatory Postsynaptic Potentials 136 Inhibitory Synaptic Transmission 137

The Synapse between Sensory Neurons and Antagonist Motor

Neurons in the Patellar Reflex 137 Characteristics of Inhibitory Synaptic Transmission 138 Mechanism of Inhibition in the Postsynaptic Membrane 139 Some Possible Inhibitory Neurotransmitters 141 The Family of Neurotransmitter-gated Ion Channels 143 Neuronal Integration 144 Indirect Actions of Neurotransmitters 146 Presynaptic Inhibition and Facilitation 149 Synaptic Plasticity 152

Short-term Changes in Synaptic Strength 152 Long-term Changes in Synaptic Strength 154 Summary 158

Part III: Cellular Physiology of Muscle Cells 161

10 Excitation—Contraction Coupling in Skeletal Muscle 163

The Three Types ofMuscle 163 Structure of Skeletal Muscle 165

Changes in Striation Pattern on Contraction 165 Molecular Composition of Filaments 167 Interaction between Myosin and Actin 169 Regulation of Contraction 172 The Sarcoplasmic Reticulum 173 The Transverse Tubule System 174 Summary 176

11 Neural Control ofMuscle Contraction 177

The Motor Unit 177

The Mechanics of Contraction 178

The Relationship Between Isometric Tension and Muscle Length 180 Control of Muscle Tension by the Nervous System 182 Recruitment ofMotor Neurons 182 Fast and Slow Muscle Fibers 184

Temporal Summation of Contractions Within a Single Motor Unit 184

Asynchronous Activation ofMotor Units During Maintained Contraction 185 Summary 187

12 Cardiac Muscle: The Autonomic Nervous System 188

Autonomic Control of the Heart 191 The Pattern of Cardiac Contraction 191 Coordination of Contraction Across Cardiac Muscle Fibers 193 Generation of Rhythmic Contractions 196 The Cardiac Action Potential 196 The Pacemaker Potential 199 Actions of Acetylcholine and Norepinephrine on Cardiac Muscle Cells 201 Summary 206

Appendix A: Derivation ofthe Nernst Equation 208 Appendix B: Derivation ofthe Goldman Equation 212 Appendix C: Electrical Properties of Cells 216 Suggested Readings 225

Index 230

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