Notes to Instructors
Chapter 49 Nervous Systems
What is the focus of these activities?
Maintaining homeostasis is central to maintaining life. Control of homeostasis is the
system).
What is this activity designed to do?
This activity allows students to sort out and organize the functions of the peripheral
Activity 49.1 How is our nervous system organized?
Neurons are single cells composed of processes called dendrites, which carry information
1. Responding to stimuli requires at a minimum:
a. reception of a stimulus which triggers
b. an action potential in a sensory neuron which synapses with
c. a motor neuron which causes a response in
d. a muscle or gland
To coordinate activity an interneuron is often found between the sensory and motor
Notes to Instructors 327
In the space below, draw this minimum system. Be sure to name each neuron and label
each of its parts.
328 Activity 49.1
Sensory neuron
axon
synapse
cell
body
dendrite
2. The blink response is one type of simple reflex response that occurs, for example, in
response to water splashing up out of the sink or to a snowball aimed at your face. When
these events happen, you blink and only afterwards do you “realize” why you blinked.
a. What would you have to add to your diagram above to allow you to “realize”
why you blinked?
You would need to add an interneuron or another synapse to the sensory axon
b. Why does it take you longer to “realize” why you blinked than it takes for the
blink reaction to occur?
The simple reflex (sensory to motor neuron) cuts out the “middle man,” the
3. What composes the central nervous system (CNS) and how does the CNS differ in
general form and function from the peripheral nervous system (PNS)?
The CNS is the integration and processing center. As such, it contains large
4. The peripheral nervous system is subdivided into the somatic, autonomic and enteric
nervous systems.
a. What is the general function of each?
Activity 49.1 329
PNS subdivision: General function:
Somatic nervous system
Carries signals to and from skeletal muscles,
primarily in response to external stimuli.
b. The autonomic system is again further subdivided into the sympathetic and
parasympathetic systems. How do the general functions of each of these divisions
interact to maintain homeostasis?
Autonomic nervous
system divisions:
Functions: See Figure 49.8 also.
Responses by the sympathetic nervous system are often
called “fight or flight” responses. These tend to up-regulate
Fibromyalgia affects about 2% of the U.S. population. Its primary symptoms are chronic
pain, difficulty sleeping and fatigue that is not relieved by sleep. Other reported
symptoms include: jaw clenching at night, dryness of mouth and eyes, an increased
need to urinate, irritable bowels, muscle numbness and tingling, and headaches.
1. Several researchers have proposed that fibromyalgia results from failed regulation of
part of the autonomic nervous system. If this is true, failed regulation of which
division of the autonomic nervous system could account for these symptoms?
Explain your reasoning.
The sympathetic system is responsible for arousal and energy generation while the
2. To test their ideas, the researchers recorded heart rate of both controls and
individuals with fibromyalgia for 24-hour periods of normal activity. They ob-
served that patients with fibromyalgia showed greatly elevated heart rates both while
active and asleep. Does the addition of this information change or support the
hypothesis you developed in 1 above?
Given this information, the primary symptoms appear to be the result of
330 Activity 49.1
49.1 Test Your Understanding