Ch 6

Question 1

Which of the following electrophysiologic events is correctly paired with the change in ionic currents causing the event?

A. Fast inhibitory postsynaptic potentials (IPSPs) and closing of Cl– channels
B. Fast excitatory postsynaptic potentials (EPSPs) and an increase in Ca2+ conductance
C. Endplate potential and an increase in Na+ conductance
D. Presynaptic inhibition and closure of voltage-gated K+ channels
E. Slow EPSPs and an increase in K+ conductance

Answer 1

C. Endplate potential and an increase in Na+ conductance

Question 2

Which of the following physiologic processes is NOT correctly paired with a structure?

A. Electrical transmission : gap junction
B. Negative feedback inhibition : Renshaw cell
C. Synaptic vesicle docking and fusion : presynaptic nerve terminal
D. Endplate potential : muscarinic cholinergic receptor
E. Action potential generation : initial segment

Answer 2

D. Endplate potential : muscarinic cholinergic receptor

Question 3

Initiation of an action potential in skeletal muscle
A. requires spatial facilitation.
B. requires temporal facilitation.
C. is inhibited by a high concentration of Ca2+ at the
neuromuscular junction.
D. requires the release of norepinephrine.
E. requires the release of acetylcholine.

Answer 3

E. requires the release of acetylcholine.

Question 4

A 35-year-old woman sees her physician to report muscle weakness in the extraocular eye muscles and muscles of the extremities. She states that she feels fine when she gets up in the morning, but the weakness begins soon after she becomes active. The weakness is improved by rest. Sensation appears normal. The physician treats her with an anticholinesterase inhibitor, and she notes immediate return of muscle strength. Her physician diagnoses her with
A. Lambert–Eaton syndrome.
B. myasthenia gravis.
C. multiple sclerosis.
D. Parkinson disease.
E. muscular dystrophy.

Answer 4

B. myasthenia gravis.

Question 5

A 55-year-old woman had an autonomic neuropathy that disrupted the sympathetic nerve supply to the pupillary dilator muscle of her right eye. While having her eyes examined, the ophthalmologist placed phenylephrine in her eyes. The right eye became much more dilated than the left eye. This suggests that

A. the sympathetic nerve to the right eye had regenerated.
B. the parasympathetic nerve supply to the right eye remained intact and compensated for the loss of the sympathetic
nerve.
C. phenylephrine blocked the pupillary constrictor muscle of the right eye.
D. denervation supersensitivity had developed.
E. the left eye also had nerve damage and so was not responding as expected.

Answer 5

D. denervation supersensitivity had developed.

Question 6

A 47-year-old woman was admitted to the hospital after experiencing nausea and vomiting for about 2 days followed by severe muscle weakness and neurologic symptoms, including ptosis and dysphagia. She indicated she had eaten at a restaurant the evening before the symptoms began. Laboratory tests were positive for Clostridium botulinum. Neurotoxins
A. block the reuptake of neurotransmitters into presynaptic terminals.
B. such as tetanus toxin bind reversibly to the presynaptic membrane at the neuromuscular junction.
C. reach the cell body of the motor neuron by diffusion into the spinal cord.
D. exert all of their adverse effects by acting centrally rather than peripherally.
E. such as botulinum toxin prevent the release of acetylcholine from motor neurons due to cleavage of either synaptosome- associated proteins or vesicle-associated membrane proteins.

Answer 6

E. such as botulinum toxin prevent the release of acetylcholine from motor neurons due to cleavage of either synaptosome- associated proteins or vesicle-associated membrane proteins.