Download Lecture Suggestions and Guidelines

CHAPTER 10
NERVOUS SYSTEM I: BASIC STRUCTURE AND
FUNCTION
LEARNING OBJECTIVE 1: Explain the general functions of the nervous system.
Lecture Suggestions and Guidelines
1. Introduce three general functions of the nervous system: a) sensory; b)
integrative; and c) motor.
2. Discuss the concept that the nervous system can detect changes in the body, make
decisions based on information received and stimulate muscles or glands to
respond.
3. Describe the nervous system’s role in maintaining homeostasis.
Application Question(s)
1. Ask students to develop an organizational flow chart which illustrates the
relationships among the central nervous system, peripheral nervous system,
sensory division, motor division, autonomic nervous system, somatic nervous
system, sympathetic division and parasympathetic division. Briefly describe the
function of each.
Answer: Flow charts will vary.
Critical Thinking Issue(s)
1. Divide the class into small groups and ask each group to define brain death.
Consider the legal, moral, ethical and medical implications as the groups prepare
their viewpoints. Discuss the groups’ findings.
Answer: Viewpoints will vary but may include criteria such as inability to
respond to stimuli, cessation of respiration, absence of reflexes, non-responsive
EEG, etc.
LEARNING OBJECTIVE 2: Describe the general structure of a neuron.
Lecture Suggestions and Guidelines
1. Illustrate the structure of a typical motor neuron. Label the major structures such
as dendrites, myelin sheath, cell body, neurilemma, Schwann cell, Nodes of
Ranvier, axon, and synapse.
2. Describe the structures of a neuron cell body, including the cytoplasm,
mitochondria, lysosomes, Golgi apparatus, microtubules, neurofibrils, and Nissl
bodies.
3. Discuss different types of neurons based on structural differences, including
bipolar neurons, unipolar neurons, and multipolar neurons.
4. Discuss different types of neurons based on functional differences, including
sensory neurons, interneurons, and motor neurons.
Application Question(s)
1. Neuron processes that generally carry impulses away from the nerve cell body are
axons and neuron processes that generally carry impulses toward the nerve cell
body are dendrites. What would one call the portion of the neuron process which
connects the dendrites to the axon?
Answer: In unipolar sensory neurons, the portion of the neuron process which
connects dendrites to axon conveys properties of both. Therefore, that portion
from dendrites to cell body, is sometimes referred to as the peripheral process,
whereas the second portion, from cell body to the CNS, is referred to as the
central process.
Critical Thinking Issue(s)
1. A 35-year-old female patient experiences occasional tingling sensations in the
extremities, numbness in the facial area, muscular weakness, loss of balance and
bladder dysfunction. The signs and symptoms are characterized by periods of
remission and exacerbation. What might be a probable diagnosis?
Answer: A chronic, progressive disease of unknown origin which affects the
central nervous system by the degeneration of the protective myelin sheath called
Multiple Sclerosis would be a possible diagnosis which should be confirmed via
MRI and other clinical testing.
LEARNING OBJECTIVE 3: Explain how neurons are classified.
Lecture Suggestions and Guidelines
1. Discuss the concept that neurons are classified according to structure and/or
function. Sensory neurons are regarded as afferent neurons, motor neurons are
considered to be efferent neurons. Association neurons, or interneurons, connect
sensory and motor neurons in neural pathways.
2. Introduce the terms cutaneous sense organs and proprioceptors.
3. Discuss the structural characteristics and location of bipolar neurons, unipolar
neurons, and multipolar neurons.
Application Question(s)
1. How might you stimulate the following types of sensory receptors: a) Meissner’s
corpuscle b) Ruffini’s corpuscle c) Pacinian corpuscle d) Golgi tendon organ e)
Krause’s end bulb.
Answer: Responses will vary. Students should provide an example of each type
of sensory receptor stimulation and define its primary function, i.e., pain receptor,
touch receptor, deep pressure receptor, proprioceptor, etc.
Critical Thinking Issue(s)
1. Based on your knowledge of the integumentary system, sensory receptors, and the
immune system, what might be considered a major threat to a victim of thirddegree burns?
Answer: a) After 24 hours, infection becomes a major concern; b) Third-degree
burns are generally not painful, initially, since the nerve endings in the burned
area are destroyed; c) Burned respiratory passageways may result in difficult
breathing or suffocation; d) Scar tissue may form; e) Skin grafting may be
necessary, since regeneration is unlikely.
LEARNING OBJECTIVE 4: Name four types of neuroglial cells and describe the
functions of each.
Lecture Suggestions and Guidelines
1. Introduce neuroglial cells as accessory cells which fill spaces, support neurons,
hold nervous tissue together, metabolize glucose, regulate potassium ions,
produce myelin and phagocytize.
2. Describe four major types of neuroglial cells, including characteristics and
functions of each. Discussion should include astrocytes, oligodendrocytes,
microglia, and ependymal cells.
Application Question(s)
1. Ask students to develop a table which summarizes four major types of neuroglial
cells, including name, characteristics, and functions. Sketch and label each type.
Answer: The table should include astrocytes, oligodendrocytes, microglia, and
ependymal cells.
Critical Thinking Issue(s)
1. In what ways might implanted neuroglia (provided perhaps from fetal tissue), help
victims suffering from Alzheimer’s disease or AIDS?
Answer: By replacing needed neurotransmitters, repairing damaged spinal cords,
or alleviating harmful side effects of chemotherapy.
LEARNING OBJECTIVE 5: Explain how an injured nerve fiber may regenerate.
Lecture Suggestions and Guidelines
1. Lecture should include a discussion of the concept that the proximal portion of a
peripheral nerve fiber may regenerate if severed.
2. Discuss regeneration of axons within the central nervous system.
Application Question(s)
1. Are neurons likely to be a site for tumorigenesis in adults?
Answer: Supporting cells, such as neuroglia and Schwann cells, all of which are
mitotically active, are more likely sites for the development of a tumor. Fully
mature neurons, as well as some precursor cells, are not capable of mitosis.
Critical Thinking Issue(s)
1. Discuss redundancy of the brain following a CVA. What actually happens in the
brain? Does redundancy occur in all patients following a CVA?
Answer: Redundancy occurs in the brain by establishing new pathways, i.e.,
utilizing previously little used neurons to carry impulses. Recovery from a CVA
is dependent upon the site and extent of damage. However, for many patients,
timely rehabilitation and phenomenon such as redundancy greatly increase the
chances for effective recovery.
LEARNING OBJECTIVE 6: Explain how a membrane becomes polarized.
Lecture Suggestions and Guidelines
1. Introduce two major functional properties of neurons: a) irritability; and b)
conductivity.
2. Briefly describe polarization during the resting potential. Discussion should
include a description of the major extracellular and intracellular ions.
3. Describe the exodus of positive ions leaving the cell to create a positive charge on
the outside of the cell membrane with respect to the inside.
Application Question(s)
1. Explain what happens when your arm “falls asleep” after awkwardly lying on it
for an extended period of time.
Answer: The pressure exerted on your arm by your body weight has caused a
decrease in supply of oxygen and nutrients to the neurons. When the pressure is
alleviated, you feel a tingling in your arm due to the return of nerve impulse
transmission.
Critical Thinking Issue(s)
1. Compare the events leading to the generation of a nerve impulse to the events
leading to an impulse within muscle tissue.
Answer: The events are very similar in terms of polarization, depolarization and
repolarization. Ask students to review information from Chapter 9—Muscular
System, as necessary.
LEARNING OBJECTIVE 7: Describe the events that lead to the conduction of a nerve
impulse.
Lecture Suggestions and Guidelines
1. Discussion should include a description of local potential changes, action
potentials, the refractory period, the all-or-none response, and impulse
conduction.
2. Summarize the events of the generation of a nerve impulse in terms of
polarization, depolarization, development of an action potential, and
repolarization.
3. Introduce the concept that nerve impulse transmission is both electrical and
chemical in nature.
Application Question(s)
1. What factors can affect nerve impulse conduction?
Answer: The textbook mentions calcium deficiency, increases and decreases in
extracellular potassium, and anesthetics. Ask students to make a list of other
factors which may effect conduction such as alcohol, sedatives, cold, and
pressure, and give a brief explanation of how conduction is impaired, e.g.,
decreased membrane permeability to sodium ions, decreased circulation, etc.
Critical Thinking Issue(s)
1. Ask students to write a brief report on the dangers associated with cocaine use and
the mechanism by which it produces its effect.
Answer: Points of interest will vary from student to student, but each report
should contain a statement regarding cocaine’s ability to block the reabsorption of
the neurotransmitters dopamine and norepinephrine.
LEARNING OBJECTIVE 8: Explain how a nerve impulse is transmitted from one
neuron to another.
Lecture Suggestions and Guidelines
1. Lecture should include a discussion of synaptic transmission, neurotransmitters,
and neuropeptides.
2. Discuss factors which may affect impulse conduction.
3. Introduce the terms presynaptic neuron and postsynaptic neuron.
4. Discuss the release of neurotransmitters by exocytosis as a result of increased
calcium concentration inside the cell.
Application Question(s)
1. Ask students to devise a set of six index cards, each card describing one major
event leading to neurotransmitter release. Shuffle the index cards and ask students
to rearrange them in the correct sequence.
Answer: The major events leading to neurotransmitter release are summarized in
Table 10.6.
Critical Thinking Issue(s)
1. Compare the effects of dopamine deficiency to dopamine excess. What
pathological conditions and symptoms are likely?
Answer: Responses should include discussion of diseases such as Parkinson’s
disease (deficiency), Tardive dyskinesia (deficiency), and SIDS (excess).
LEARNING OBJECTIVE 9: Distinguish between excitatory and inhibitory
postsynaptic potentials.
Lecture Suggestions and Guidelines
1. Introduce the terms EPSP and IPSP.
2. Describe the triggering and inhibition of action potentials. Emphasize that the
effects of neurotransmitters may vary.
3. Discuss the trigger zone, the decision-making part of the neuron, where
summation of postsynaptic potentials takes place.
Application Question(s)
1. What are the major elements involved in a somatic reflex? Have students perform
a knee-jerk reflex procedure on each other and then describe the sensory receptor,
the effector organ, the afferent pathway and efferent pathway.
Answer: The sensory receptors are the Golgi tendon organs in the patellar region,
the effector organ is the quadriceps muscle, the afferent pathway sends a signal
from the sensory receptors to the gray matter ventral horn, and the efferent
pathway returns a signal from the gray matter to the effector organ.
Critical Thinking Issue(s)
1. Why does a patient often complain about pain that arises in areas of the body
quite removed from the actual origin?
Answer: This phenomenon is known as referred pain and is the result of specific
sites supplied by a single spinal nerve. These sites are known as dermatomes.
Each dermatome produces an action potential that is always delivered to a precise
spinal cord segment. For example, chest pains on the left side as a result of a heart
attack may be explained by pain information being transmitted from the heart to
the left side of the spinal cord.
LEARNING OBJECTIVE 10: Explain two ways impulses are processed in neuronal
pools.
Lecture Suggestions and Guidelines
1. Define a neuronal pool as neurons within the central nervous system which are
organized into groups.
2. Discuss facilitation, convergence, and divergence.
3. Distinguish between divergence and amplification.
4. Reiterate the concept of efferent vs. afferent pathways.
Application Question(s)
1. Apply the students’ knowledge of this Learning Objective by asking each student
to create a flow chart depicting impulse processing. Begin the flow chart with a
box labeled neuronal pools. Be creative and make the flow chart understandable
to a person with limited knowledge of impulse processing. Include any necessary
branches and descriptions but, at a minimum, include boxes labeled facilitation,
convergence, divergence, and amplification.
Answer: Flow charts will vary.
Critical Thinking Issue(s)
1. Reiterate the students’ mastery of the concepts of convergence and divergence of
nerve impulses by applying these terms to some other unrelated phenomenon,
such as convergence and divergence of vision, convergence and divergence of
two lines, or convergence and divergence of lanes of traffic.
Answer: Basically, convergence is defined as the movement of two objects
toward a common point. Divergence is defined as a separation or movement of
objects away from each other.
RELATED DISEASES OF HOMEOSTATIC INSTABILITY
1. Concussion—A transient disorder of the nervous system resulting from a violent
blow to the head. Loss of consciousness is possible. The brain is not actually
damaged. Close monitoring of the patient’s condition is important.
2. Meningitis—An acute inflammation of the first two meninges of the brain and
spinal cord (pia mater and arachnoid mater). Symptoms include high fever,
delirium, convulsions, chills, severe headache, stiff neck, nausea, and vomiting.
3. Encephalitis—An inflammation of the brain and meninges. A viral infection
possibly from wild birds and mosquitoes. It could result in persistent drowsiness,
delirium, and possible coma.
SUGGESTIONS FOR ADDITIONAL READING
Barones, Samuel H. February 25, 1994. Thinking about Prozac. Science, vol. 263. The
anti-depressant drug Prozac alters mood by preventing a receptor on a receiving nerve
cell from binding the neurotransmitter serotonin.
Bower, Bruce. December 14, 2002. Brain’s moving Experience–Motion illusion yields a
neural surprise. Science News.
Bower, Bruce. January 4, 2003. Secrets of Memory All-Stars–Brain reflects superior
recollection strategy. Science News.
Kosik, Kenneth S. May 8, 1992. Alzheimer’s disease: A cell biological perspective.
Science, vol. 256. We are beginning to understand Alzheimer’s disease at the cellular
level, with the help of families that inherit it.
Loftus, Elizabeth F. September 1997. Creating False Memories. Scientific American.
Pollen, Daniel A. 1993. Hannah’s heirs. New York: Oxford University Press. A
fascinating historical discussion of Alzheimer’s disease, first identified in 1844 in a
woman named Hannah.
Sapolsky, Robert M., and Dora Y. Ho. June 1997. Gene Therapy for the Nervous System.
Scientific American.