Chapter 4 Workbook Questions

Question 1

An individual with a vestibular disorder has a decreased neural response to movements that formerly induced dizziness and nausea.

This is an example of what type of process?

Answer 1

Habituation

Question 2

Ability to learn an individual’s name.

This is an example of what type of process?

Answer 2

Long-term potentiation (LTP)

Question 3

After severing the median nerve, the distal segments of the severed axons degenerate.

This is an example of what type of process?

Answer 3

Wallerian degeneration

Question 4

After an injury to axons of the ulnar nerve, the associated cell bodies undergo degenerative changes.

This is an example of what type of process?

Answer 4

Central chromatolysis

Question 5

After severing the median nerve, the proximal segments of the severed axons regrow.

This is an example of what type of process?

Answer 5

Sprouting

Question 6

B.J. partially severed the median nerve in his forearm. Approximately how many days should it take for the axons to reinnervate the thenar muscles whose motor points are 18 millimeters (mm) from the injury site?

Answer 6

Peripheral nerve regeneration occurs at a rate of approximately 1 mm per day, therefore it will require approximately 18 days.

Question 7

Twenty days after the injury, B.J. returns to therapy, concerned that when he tries to move his thumb one direction the thumb actually moves in an unintended direction. What is the name of this disorder?

Answer 7

Synkinesis is a phenomenon that occurs after a peripheral nerve injury because of the axon sprouting to the inappropriate target muscle, resulting in unintended movements.

Question 8

Will B.J. need surgery to correct the movement disorder? Why or why not?

Answer 8

No, surgery is not required to reverse the synkinesis. B.J. will learn to produce the intended thumb movements by practicing the movements.

Question 9

Resolution of local edema causes synapses that were inactive because of compression of the presynaptic neuron to resume functioning.

What is the name of this synaptic change?

Answer 9

Denervation hypersensitivity

Question 10

Synapses that were inactive before a lesion become active after the lesion.

What is the name of this synaptic change?

Answer 10

Unmasking of silent synapses

Question 11

After the destruction of some axon branches of a presynaptic neuron, the remaining axon branches receive all of the neurotransmitters that were shared by more endings.

What is the name of this synaptic change?

Answer 11

Synaptic hypereffectiveness

Question 12

New receptor sites on the postsynaptic membrane develop after presynaptic terminals are destroyed.

What is the name of this synaptic change?

Answer 12

Denervation hypersensitivity

Question 13

Changes in cortical representation occur after amputation or prolonged nonuse.

What is the name of this synaptic change?

Answer 13

Functional reorganization

Question 14

Overexcitation of a neuron that leads to death of the neuron.

What is the name of this synaptic change?

Answer 14

Excitotoxicity

Question 15

Neurons that are deprived of oxygen for a prolonged period:
A. Release glycine, which inhibits the postsynaptic neurons and prevents neural function even in neurons not directly affected by the oxygen deprivation.
B. Become inactive and slowly regenerate.
C. Release glutamate, which causes overexcitation of the surrounding neurons.
D. A, B, and C
E. None of the above

Answer 15

C: When a person suffers a stroke or traumatic injury, neurons in the brain that are deprived of oxygen for a prolonged period die and do not regenerate. Oxygen-deprived neurons release large quantities of glutamate, an excitatory neurotransmitter, from their axon terminals.

Question 16

Excitotoxicity begins with:
A. Excessive production of lactic acid
B. Destruction of cellular proteins
C. Cellular edema
D. Persistent binding of glutamate to N-methyl-D-aspartate (NMDA)–type receptors in the postsynaptic cell membrane
E. Interference of mitochondria functions

Answer 16

D: First, glutamate binds persistently to the NMDA-type glutamate receptor in the cell membrane. Stimulation of this receptor results in an influx of calcium ions (Ca+2) into the cell, and indirectly facilitates the release of internal Ca+2 stores. An influx of sodium ions (Na+) into the cell results in further stimulation of NMDA receptors and an additional influx of Ca+2 into the cell. Channels that are permeable to Ca+2 open because of the injury. With the increase in Ca+2 inside the cell, more potassium ions (K+) diffuse out of the cell, requiring increased glycolysis that provides energy for the Na+/K+ pump to actively transport K+ into the cell. Together, the increased glycolysis and the increased Ca+2 lead to several destructive consequences for neurons.

Question 17

Cellular effects of excitotoxicity include:
A. Excessive production of lactic acid
B. Destruction of cellular proteins
C. Cellular edema
D. Interference of mitochondria functions
E. All of the above

Answer 17

E: Excitotoxicity causes excessive production of lactic acid, destroys cellular proteins, causes cellular edema, and interferes with the function of mitochondria.

Question 18

Which one of the following types of memory is affected by an injury to the hippocampus?
	A. Memory of how to ride a bicycle
	B. Memory of names and events
	C. Memory of how to tie shoe laces
	D. Both A and B
	E. A, B, and C

Answer 18

B: The hippocampus, located in the temporal lobe, is essential for processing memories that are easily verbalized. For example, the hippocampus is important in remembering names and events (declarative memory) but not in remembering how to perform motor acts (procedural memory). Riding a bicycle and tying shoe laces are examples of procedural memory.

Question 19

In the mature central nervous system (CNS), axonal regeneration is impeded by which of the following?
	A. Glial scar formation
	B. Absence of neural growth factor
	C. Release of growth inhibiting factors
	D. Both A and B
	E. A, B, and C

Answer 19

E: Development of glial scars, limited expression or complete absence of nerve growth factor (NGF), and growth inhibiting factors prevent functional axonal regeneration in the brain and spinal cord.

Question 20

Constraint-induced movement after a stroke requires which one of the following?
A. Immobilization of the affected upper extremity (UE) to control spasticity
B. Repetitive closed-chain resistance training
C. Aggressive range of motion and exercise within 12 hours after a stroke
D. Repetitive, task-specific functional movements of only the affected UE
E. Weight bearing and prolonged stretching of the affected UE

Answer 20

D: Constraint-induced movement is one type of task-specific training used in individuals with chronic dysfunction resulting from a stroke. In this technique, use of the unaffected UE is constrained by a sling. The patient then undergoes intense practice of functional movements with the affected UE.

Question 21

Learning an individual’s name requires:
	A. Sprouting
	B. LTP
	C. Habituation
	D. Central chromatolysis

Answer 21

B: Experience-dependent plasticity requires the synthesis of new proteins, the growth of new synapses, and the modification of existing synapses. With repetition of a specific stimulus or the paring of presynaptic and postsynaptic firing, the synthesis and activation of proteins alter the neuron’s excitability and promote or inhibit the growth of new synapses, especially at dendritic spines. Several mechanisms of experience-dependent plasticity occur, depending on the type of synapse and location involved; LTP is one of these mechanisms.