Chapter 13 review questions

Question 1

All neural reflexes begin with a(n) that activates a receptor.

Answer 1

stimulus

Question 2

Somatic reflexes involve __________ muscles; __________ (or visceral) reflexes are controlled by autonomic neurons.

Answer 2

skeletal, autonomic

Question 3

The pathway pattern that brings information from many neurons into a smaller number of neurons is known as .

Answer 3

convergence

Question 4

When the axon terminal of a modulatory neuron (cell M) terminates close to the axon terminal of a presynaptic cell (cell P) and decreases the amount of neurotransmitter released by cell P, the resulting type of modulation is called __________. [Hint: See p. 289.]

Answer 4

presynaptic inhibition

Question 5

Autonomic reflexes are also called __________ reflexes. Why?

Answer 5

visceral reflexes because many of them involve internal organs (the viscera)

Question 6

Some autonomic reflexes are spinal reflexes; others are integrated in the brain. List some examples of each.

Answer 6

Spinal reflexes: urination and defecation. Cranial reflexes: control of
heart rate, blood pressure, and body temperature.

Question 7

Which part of the brain transforms emotions into somatic sensation and visceral function? List three autonomic reflexes that are linked to emotions.

Answer 7

Limbic system. Emotional reflexes: blushing, heart rate, gastrointestinal function

Question 8

How many synapses occur in the simplest autonomic reflexes? Where do the synapses occur?

Answer 8

Two neuron-neuron synapses in the spinal cord and the autonomic ganglion, and one neuron-target synapse.

Question 9

List the three types of sensory receptors that convey information for muscle reflexes.

Answer 9

Golgi tendon organ, the muscle spindle, and joint capsule mechanoreceptors

Question 10

Because of tonic activity in neurons, a resting muscle maintains a low level of tension known as __________.

Answer 10

tone

Question 11

Stretching a skeletal muscle causes sensory neurons to (increase/ decrease) their rate of firing, causing the muscle to contract, thereby relieving the stretch. Why is this a useful reflex?

Answer 11

increase. This reflex prevents damage from overstretching.

Question 12

Match the structure to all correct statements about it.
(a) muscle spindle
(b) Golgi tendon organ
(c) joint capsule mechanoreceptor

1. is strictly a sensory receptor
2. has sensory neurons that send information to the CNS
3. is associated with two types of motor neurons
4. conveys information about the relative positioning of bones
5. is innervated by gamma motor neurons
6. modulates activity in alpha motor neurons

Answer 12

(a)2,3,5,6;
(b)1,2,6;
(c)1,2,4

Question 13

The Golgi tendon organ responds primarily to muscle __________.

Answer 13

stretch, contraction, contraction, decreases, alpha motor neuron

Question 14

The simplest reflex requires a minimum of how many neurons? How many synapses? Give an example.

Answer 14

Two neurons and one synapse between them (monosynaptic). The
knee jerk (patellar tendon) reflex is an example.

Question 15

List and differentiate the three categories of movement. Give an example of each

Answer 15

Reflex movements, such as the knee jerk, can be integrated in the
spinal cord. Voluntary movements, such as playing the piano, and rhythmic movements, such as walking, must involve the brain. Reflex movements are involuntary; the initiation, modulation, and termination of rhythmic movements are voluntary.

Question 16

What is the purpose of alpha-gamma coactivation? Explain how it occurs

Answer 16

Alpha-gamma coactivation allows muscle spindles to continue functioning when the muscle contracts. When the muscle contracts, the ends of the spindles also contract to maintain stretch on the central portion of the spindle.

Question 17

Modulatory neuron M synapses on the axon terminal of neuron P, just before P synapses with the effector organ. If M is an inhibitory neuron, what happens to neurotransmitter release by P? What effect does M’s neurotransmitter have on the postsynaptic membrane potential of P? (Hint: Draw this pathway.)

Answer 17

Neurotransmitter release will decrease when M’s neurotransmitter hyperpolarizes P.

Question 18

At your last physical, your physician checked your patellar tendon reflex by tapping just below your knee while you sat quietly on the edge of the table. (a) What was she checking when she did this test? (b) What would happen if you were worried about falling off the table and were very tense? Where does this additional input to the efferent motor neurons originate? Are these modulatory neurons causing EPSPs or IPSPs [p. 261] at the spinal motor neuron? (c)Your physician notices that you are tense and asks you to count backward from 100 by 3’s while she repeats the test. Why would carrying out this counting task enhance your reflex?

Answer 18

(a) Assessing the components that regulate limb movement, including quadriceps muscle, the nerves that control it, and the area of the spinal cord where the reflex integrates. (b) The reflex would probably be less apparent. The origin of this inhibition is the primary motor cortex. The inhibitory cells will produce IPSPs in the spinal motor neuron. (c) If the brain is distracted by some other task, the inhibitory signals will presumably stop.

Question 19

There are several theories about how presynaptic inhibition works at the cellular level. Use what you have learned about membrane potentials and synaptic transmission to explain how each of the following mechanisms would result in presynaptic inhibition:

(a) Voltage-gated Ca2* channels in axon terminal are inhibited.
(b) Cl+ channels in axon terminal open.
(c) K* channels in axon terminal open.

Answer 19

(a) Prevents Ca2+-activated transmitter release.

(b) Cell hyperpolarizes and voltage-gated Ca2+ channels in terminal will not open.

(c) Same as (b).

Question 20

Andy is working on improving his golf swing. He must watch the ball, swing the club back and then forward, twist his hips, straighten his left arm, then complete the follow-through, where the club arcs in front of him. Which parts of the brain are involved in adjusting how hard he hits the ball, keeping all his body parts moving correctly, watching the ball, and then repeating these actions once he has verified that this swing is successful?

Answer 20

Parts of the brain include the brain stem, cerebellum, basal ganglia, thalamus, cerebral cortex (visual cortex, association areas, motor cortex).

Question 21

It’s Halloween, and you are walking through the scariest haunted house around. As you turn a corner and enter the dungeon, a skeleton reaches out and grabs your arm. You let out a scream. Your heart rate quickens, and you feel the hairs on your arm stand on end. (a) What has just happened to you? (b) Where in the brain is fear processed? What are the functions of this part of the brain? Which branch (somatic or autonomic) of the motor output does it control? What are the target organs for this response? (c) How is it possible for your hair to stand on end when hair is made of proteins that do not contract? [Hint: See p. 86.] Given that the autonomic nervous system is mediating this reflex response, which type of tissue do you expect to find attached to hair follicles?