Chapter 06

Instructions

Choose your answers from a-d by clicking the radio button next to each choice and then press 'Submit' to get your score.

In the central nervous system (CNS):

a) white matter contains many nerve cell bodies.

b) the myelin sheaths are formed by Schwann cells.

c) the neurons are protected from changes in plasma composition.

d) the cerebrospinal fluid (csf) is an ultrafiltrate of plasma.

The action potential of a nerve cell:

a) results from a large increase in the membrane permeability to sodium ions.

b) can summate one with another.

c) may vary considerably in amplitude.

d) becomes larger as stimulus strength increases.

The velocity of action potential propagation:

a) is independent of an axon"s diameter.

b) depends on the thickness of the myelin around the axon.

c) will be unaffected if the axon becomes demyelinated.

d) is fastest in unmyelinated axons.

If a motor nerve has a conduction velocity of 70 m s^-1 how long will it take an action potential to reach a muscle 0.75 m from the spinal cord?

a) 10.7 ms

b) 1.07 ms

c) 14 ms

d) 1.4 ms

During synaptic excitation:

a) the membrane potential of the post-synaptic cell hyperpolarizes.

b) the epsps are all or none in nature.

c) the epsps can summate.

d) after an epsp the postsynaptic cell passes through a refractory period.

At the neuromuscular junction:

a) the muscle membrane possesses muscarinic receptors.

b) the motor nerve endings secrete norepinephrine.

c) curare leads to prolongation of neuromuscular transmission.

d) the motor nerve endings secrete acetylcholine.