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CHAPTER
11
Fundamentals of the Nervous
System and Nervous Tissue
Objectives
Functions and Divisions of the Nervous System
Histology of Nervous Tissue
3. List the types of neuroglia and cite their functions.
4. Define neuron, describe its important structural components, and relate each to a
functional role.
Membrane Potentials
8. Define resting membrane potential and describe its electrochemical basis.
9. Compare and contrast graded potentials and action potentials.
The Synapse
13. Define synapse. Distinguish between electrical and chemical synapses by structure and
by the way they transmit information.
Neurotransmitters and Their Receptors
16. Define neurotransmitter and name several classes of neurotransmitters.
Basic Concepts of Neural Integration
17. Describe common patterns of neuronal organization and processing.
18. Distinguish between serial and parallel processing.
Suggested Lecture Outline
I. Functions and Divisions of the Nervous System (p. 387; Figs. 11.1–11.2)
A. The nervous system has three basic functions: gathering sensory input from sensory
receptors, processing and interpreting sensory input to decide an appropriate response
(integration), and using motor output to activate effector organs, muscles and glands, to
cause a response (p. 387; Fig. 11.1).
a. Somatic sensory fibers carry impulses from receptors in the skin, skeletal muscles,
and joints.
b. Visceral sensory fibers carry impulses from organs within the ventral body cavity.
2. The motor, or efferent, division of the peripheral nervous system carries impulses
from the central nervous system to effector organs, which are muscles and glands.
II. Histology of Nervous Tissue (pp. 387–395; Figs. 11.3–11.5; Table 11.1)
A. Neuroglia, or glial cells, are closely associated with neurons, providing a protective and
supportive network (pp. 388–390; Fig. 11.3).
1. Neuroglia of the CNS include:
a. Astrocytes regulate the chemical environment around neurons and exchange
between neurons and capillaries.
2. Neuroglia in the PNS include:
a. Satellite cells are glial cells of the PNS whose function is largely unknown. They
B. Neurons are specialized cells that conduct messages in the form of electrical impulses
throughout the body (pp. 390–395; Figs. 11.4–11.5; Table 11.1).
1. Neurons function optimally for a lifetime, are mostly amitotic and have an exception-
ally high metabolic rate requiring oxygen and glucose.
3. Neurons have armlike processes that extend from the cell body.
a. Dendrites are cell processes that are the receptive regions of the cell and provide
surface area for receiving signals from other neurons.
b. Each neuron has a single axon that arises from the axon hillock and generates and
4. There are three structural classes of neurons.
a. Multipolar neurons have three or more processes.
5. There are three functional classes of neurons.
a. Sensory, or afferent, neurons conduct impulses toward the CNS from receptors.
III. Membrane Potentials (pp. 395–407; Figs. 11.6–11.15)
A. Basic Principles of Electricity (pp. 395–397)
1. Voltage is a measure of the amount of difference in electrical charge between two
points, called the potential difference.
B. The Role of Membrane Ion Channels (pp. 396–397; Fig. 11.6)
1. The cell has many gated ion channels.
a. Chemically gated (ligand-gated) channels open when the appropriate chemical
binds.
2. When ion channels are open, ions diffuse across the membrane along their
electrochemical gradients, creating electrical currents.
C. The Resting Membrane Potential (pp. 397–398; Figs. 11.7–11.8)
1. The membrane of a resting neuron is polarized, and the potential difference of this
polarity (approximately –70 mV) is called the resting membrane potential. The resting
membrane potential exists only across the membrane and is mostly due to two factors:
D. Membrane Potentials That Act as Signals (pp. 397–405; Figs. 11.8–11.15)
1. Neurons use changes in membrane potential as communication signals and can be
brought on by changes in membrane permeability to any ion, or alteration of ion
concentrations on the two sides of the membrane.
4. Graded potentials are short-lived local changes in membrane potentials, can either be
depolarizations or hyperpolarizations, and are critical to the generation of action
potentials.
5. Action potentials, or nerve impulses, occur on axons and are the principle way neurons
communicate.
a. Generation of an action potential involves a transient increase in Na+ permeability,
6. A critical minimum, or threshold, depolarization is defined by the amount of influx
of Na+ that at least equals the amount of efflux of K+.
8. Stimulus intensity is coded in the frequency of action potentials.
9. The refractory period of an axon is related to the period of time required so that a
neuron can generate another action potential.
E. Conduction Velocity (pp. 405–407; Fig. 11.15)
IV. The Synapse (pp. 407–414; Figs. 11.16–11.19; Table 11.2)
A. A synapse is a junction that mediates information transfer between neurons or between a
neuron and an effector cell (p. 407; Fig. 11.16).
B. Neurons conducting impulses toward the synapse are presynaptic cells, and neurons
carrying impulses away from the synapse are postsynaptic cells (p. 407).
G. Postsynaptic Potentials and Synaptic Integration (pp. 410–414; Figs. 11.18–11.19;
Table 11.2)
1. Neurotransmitters mediate graded potentials on the postsynaptic cell that may be
excitatory or inhibitory.
a. Excitatory potentials on the postsynaptic cell occur when there is a net influx
of Na+ into the cell, and are called excitatory postsynaptic potentials (EPSPs).
b. Inhibitory potentials on the postsynaptic cell occur when there is an increase in
permeability to either K+ or Cl- and are called inhibitory postsynaptic potentials
(IPSPs).
4. Presynaptic inhibition results when another neuron inhibits the release of an excitatory
neurotransmitter from a presynaptic cell.
5. Neuromodulation occurs when a neurotransmitter acts via slow changes in target cell
metabolism or when chemicals other than neurotransmitters modify neuronal activity.
V. Neurotransmitters and Their Receptors (pp. 414–421; Figs. 11.20–11.21;
Table 11.3)
A. Neurotransmitters fall into several chemical classes: acetylcholine, the biogenic amines,
amino acid derived, peptides, purines, and gases and lipids. (For a more complete listing
of neurotransmitters within a given chemical class, refer to pp. 415–416; Table 11.3.)
VI. Basic Concepts of Neural Integration (pp. 421–423; Figs. 11.22–11.24)
A. Organization of Neurons: Neuronal Pools (p. 421; Fig. 11.22)
1. Neuronal pools are functional groups of neurons that integrate incoming information
from receptors or other neuronal pools and relay the information to other areas.
B. Types of Circuits (p. 421; Fig. 11.23)
1. Diverging, or amplifying, circuits are common in sensory and motor pathways. They
are characterized by an incoming fiber that triggers responses in ever-increasing
numbers of fibers along the circuit.
neuron.
C. Patterns of Neural Processing (pp. 421–423; Fig. 11.24)
1. Serial processing is exemplified by spinal reflexes and involves sequential stimulation
of the neurons in a circuit.
2. Parallel processing results in inputs stimulating many pathways simultaneously and is
vital to higher-level mental functioning.
VII. Developmental Aspects of Neurons (pp. 423–424; Fig. 11.25)
A. The nervous system originates from a dorsal neural tube and neural crest, which begin as
Cross References
Additional information on topics covered in Chapter 11 can be found in the chapters listed below.
1. Chapter 2: Enzymes and enzyme function
5. Chapter 13: Membrane potentials; neural integration
6. Chapter 14: Cholinergic and adrenergic receptors and other neurotransmitter effects;
autonomic synapses
7. Chapter 15: Receptors for the special senses; synapses involved in the special senses;
neurotransmitters in the special senses
8. Chapter 16: Nervous system modulation of endocrine function
Lecture Hints
1. By this time, the class has been exposed to only a few systems (integumentary, skeletal,
and muscular), but enough information has been given so that students can understand
the basics of nervous system function from the beginning of this section. Ask students
questions such as: When you touch something hot, how does your body know how to
react? Do you have to consciously think about pulling your hand away? The idea for the-
2. Emphasize strongly the three basic functions of the nervous system: sensory, integration,
3. Stress that although we discuss the nervous system in segments, it is actually tightly
integrated.
4. Present a general introduction of the entire nervous system near the beginning of nervous
5. Point out the similarities between skeletal muscle cells and neurons. It is also possible to
introduce the electrical characteristics of cardiac pacemaker cells (modified muscle cells)
7. Many students have difficulty understanding the difference between the myelin sheath
and the cell membrane. Use a diagram to point out that both are parts of the same cell.
9. Many students have trouble relating ion movements with electrical current. One way to
approach neurophysiology is to (loosely) compare a 1.5-V battery to the cell membrane.
10. Clearly distinguish the difference between graded potentials and action potentials. It
11. Most introductory physiology students will experience difficulty with the idea of
12. Present a diagram of a synapse, then use root word dissection to emphasize the distinc-
13. Use absolute numbers as an introductory example for summation. For example: If three
presynaptic neurons each simultaneously deliver a one-third threshold stimulus, will the
postsynaptic neuron fire? Use several examples to emphasize the difference between
spatial and temporal summation.
Activities/Demonstrations
1. Audiovisual materials are listed in the Multimedia in the Classroom and Lab section of
this Instructor Guide (p. 387).
3. Obtain an oscilloscope and a neurophysiology kit to illustrate how an action potential can
be registered.
Critical Thinking/Discussion Topics
1. How can drugs, such as novocaine, effectively block the transmission of pain impulses?
Why don’t they block motor impulses—or do they?
2. What effect does alcohol have on the transmission of electrical impulses?
Library Research Topics
1. Of what value is the development of recombinant DNA technology to our study of
protein-based neurotransmitters?
2. What is the status of research on the repair and/or regeneration of nervous tissue of the
CNS?
List of Figures and Tables
All of the figures in the main text are available in JPEG format, PPT, and labeled & unlabeled
format on the Instructor Resource DVD. All of the figures and tables will also be available in
Transparency Acetate format. For more information, go to www.pearsonhighered.com/educator.
Figure 11.1 The nervous system’s functions.
Figure 11.2 Levels of organization in the nervous system.
Figure 11.6 Operation of gated channels.
Figure 11.7 Measuring membrane potential in neurons.
Figure 11.8 Resting Membrane Potential.
Figure 11.9 Depolarization and hyperpolarization of the membrane.
Figure 11.10 The spread and decay of a graded potential.
Figure 11.19 Neural integration of EPSPs and IPSPs.
Figure 11.20 Direct neurotransmitter receptor mechanism: Channel-linked receptors.
Figure 11.21 Indirect neurotransmitter receptor mechanism: G protein–linked
receptors.
Answers to End-of-Chapter Questions
Multiple-Choice and Matching Question answers appear in Appendix H of the main text.
Short Answer Essay Questions
13. Anatomical divisions are defined by their location in the body, and include the CNS
(brain and spinal cord) and the PNS (nerves and ganglia outside the CNS). Functional
14. a. The cell body is the biosynthetic and metabolic center of a neuron. It contains the
usual organelles, but lacks centrioles. (p. 390)
15. a. Myelin is a whitish, fatty, phospholipid-insulating material (essentially the wrapped
plasma membranes of oligodendrocytes or Schwann cells).
392–393)
16. Multipolar neurons have many dendrites, one axon, and are found in the CNS, and motor
divisions of the PNS. Bipolar neurons have one axon and one dendrite, and are found in
17. A polarized membrane possesses a net positive charge outside, and a net negative charge
inside, with the voltage across the membrane being at –70 mV. Diffusion of Na+ and K+
18. a. The generation of an action potential involves changes in the state of ion channels in
response to changes in membrane potential, which leads to: (1) an increase in sodium
permeability and reversal of the membrane potential; (2) a decrease in sodium
19. The CNS determines a stimulus to be strong when the frequency, or rate, of action
potential generation is high. Conversely, a low frequency, or rate, of action potential
generation indicates weaker stimuli. (p. 404)
20. a. An EPSP is an excitatory (depolarizing) postsynaptic potential that increases the
chance of a depolarization event. An IPSP is an inhibitory (hyperpolarizing)
21. Each neuron’s axon hillock keeps a “running account” of all signals it receives via
temporal and spatial summation. (p. 413)
22. The effects of neurotransmitter binding are brief because the neurotransmitter is quickly
removed by enzymatic degradation or reuptake into the presynaptic axon. In the absence
23. When the professor discusses group A fibers, he is referring to fibers that have a large
diameter, thick myelin sheaths, and rapid conduction. Group B fibers are lightly myeli-
nated, have intermediate diameters, and have slower conduction velocity. (p. 406)
24. In serial processing, the pathway is constant and occurs through a definite sequence of
25. During the first developmental stage, neurons proliferate; during the second stage,
neurons migrate to proper position; during the third stage, neurons differentiate. (p. 423)
26. Development of the axon is due to the chemical signals neurotropin and NGF that inter-
act with receptors on the developing axon to support and direct its growth. (p. 423)
Critical Thinking and Clinical Application Questions
3. The bacteria remain in the wound; however, the toxin produced travels via axonal
transport to reach the cell body. (p. 392)
4. In MS, the myelin sheaths are destroyed. Loss of this insulating sheath results in a failure
5. Glycine is an inhibitory neurotransmitter that is used to modulate spinal cord transmis-
sion. Strychnine blocks glycine receptors in the spinal cord, leading to unregulated
stimulation of muscles, and spastic contraction to the point where the muscles cannot
relax. (p. 416; Table 11.3)
Suggested Readings
Aldrich, Richard W. “Fifty Years of Inactivation.” Nature 411 (6838) (June 2001): 643–644.
Barres, Ben A., and Stephen J. Smith. “Cholesterol—Making or Breaking the Synapse.”
Science 294 (5545) (Nov. 2001): 1296–1297.
Gallo, Vittoria, and Ramesh Chittajallu. “Unwrapping Glial Cells from the Synapse: What
Lies Inside?” Science 292 (5518) (May 2001): 872–873.
569–570.
Hoppe, C., and J. Stojanovic. “High-Aptitude Minds: The Neurological Roots of Genius.”
Scientific American Mind 19 (4) (Sept. 2008): 60–67.
2266–2267.
Niewiadomska, Grazyna, Anna Mietelska-Porowska, and Marcin Mazurkiewicz. “The
Cholinergic System, Nerve Growth Factor and the Cytoskeleton.” Behavioural Brain
Research 221 (2) (Aug. 2011): 515–526.
