Chapter at a Glance

Neurons and Supporting Cells 152

Neurons 152

Classification of Neurons and Nerves 154 Supporting Cells 154 Neurilemma and Myelin Sheath 156 Myelin Sheath in PNS 157 Myelin Sheath in CNS 157 Regeneration of a Cut Axon 157 Neurotrophins 158 Functions of Astrocytes 159 Blood-Brain Barrier 159

Electrical Activity in Axons 160

Ion Gating in Axons 161 Action Potentials 161 All-or-None Law 163 Coding for Stimulus Intensity 164 Refractory Periods 164 Cable Properties of Neurons 164 Conduction of Nerve Impulses 165

Conduction in an Unmyelinated Axon 166 Conduction in a Myelinated Axon 166

The Synapse 167

Electrical Synapses: Gap Junctions 167 Chemical Synapses 168

Acetylcholine as a Neurotransmitter 170

Chemically Regulated Channels 171 Ligand-Operated Channels 171 G-Protein-Operated Channels 172 Acetylcholinesterase (AChE) 173 Acetylcholine in the PNS 174 Acetylcholine in the CNS 175

\ Refresh Your Memory

Before you begin this chapter, you may want to review the following concepts from previous chapters:

■ Diffusion Through the Plasma Membrane 128

. ■ Carrier-Mediated Transport 134

. ■ The Membrane Potential 140

Monoamines as Neurotransmitters 176

Serotonin as a Neurotransmitter 177 Dopamine as a Neurotransmitter 178 Nigrostriatal Dopamine System 178 Mesolimbic Dopamine System 178 Norepinephrine as a Neurotransmitter

Other Neurotransmitters 179

Amino Acids as Neurotransmitters 179 Excitatory Neurotransmitters 179 Inhibitory Neurotransmitters 179 Polypeptides as Neurotransmitters 179 Synaptic Plasticity 180 Endogenous Opioids 180 Neuropeptide Y 180 Endocannabinoids as Neurotransmitters Nitric Oxide and Carbon Monoxide as Neurotransmitters 181

Synaptic Integration 182

Long-Term Potentiation 182 Synaptic Inhibition 182

Summary 184 Review Activities 185 Related Websites 187

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Visit the Online Learning Center for these additional study resources.

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Mcgraw Hill Human Vein Model

Fox: Human Physiology, I 7. The Nervous System: I Text I I © The McGraw-Hill

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Clinical Investigation

Sandra, whose clinical depression was causing her grades to fall, decides to treat herself to dinner at a seafood restaurant.After eating a meal of mussels and clams, which were gathered from the local shore, she falls to the floor. Paramedics quickly arrive at the scene and notice that she has flaccid paralysis of her muscles and is having difficulty breathing. Fortunately, their emergency care saves her life. While the emergency care is being administered, a prescription bottle containing a monoamine oxidase (MAO) inhibitor is found in her purse.

Laboratory tests later reveal that her blood contained amounts of the MAO inhibitor that were consistent with its therapeutic use.What might have caused Sandra's medical emergency?

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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