The Nervous System 203Test Your Knowledge
- The supporting cells that form myelin sheaths in the
peripheral nervous system are
a. oligodendrocytes. d. astrocytes.
b. satellite cells. e. microglia.
c. Schwann cells. - A collection of neuron cell bodies located outside the CNS is
called
a. a tract. c. a nucleus.
b. a nerve. d. a ganglion. - Which of these neurons are pseudounipolar?
a. Sensory neurons
b. Somatic motor neurons
c. Neurons in the retina
d. Autonomic motor neurons- Depolarization of an axon is produced by
a. inward diffusion of Na^1.
b. active extrusion of K^1.
c. outward diffusion of K^1.
d. inward active transport of Na^1.- Repolarization of an axon during an action potential is
produced by
a. inward diffusion of Na^1.
b. active extrusion of K^1.
c. outward diffusion of K^1.
d. inward active transport of Na^1. - As the strength of a depolarizing stimulus to an axon is
increased,
a. the amplitude of action potentials increases.
b. the duration of action potentials increases.
c. the speed with which action potentials are conducted
increases.
d. the frequency with which action potentials are produced
increases. - The conduction of action potentials in a myelinated nerve
fiber is
a. saltatory.
b. without decrement.
c. faster than in an unmyelinated fiber.
d. all of these. - Which of these is not a characteristic of synaptic potentials?
a. They are all-or-none in amplitude.
b. They decrease in amplitude with distance.
c. They are produced in dendrites and cell bodies.
d. They are graded in amplitude.
e. They are produced by chemically regulated gates.Review Activities
- Which of these is not a characteristic of action potentials?
a. They are produced by voltage-regulated gates.
b. They are conducted without decrement.
c. Na^1 and K^1 gates open at the same time.
d. The membrane potential reverses polarity during
depolarization. - A drug that inactivates acetylcholinesterase
a. inhibits the release of ACh from presynaptic endings.
b. inhibits the attachment of ACh to its receptor protein.
c. increases the ability of ACh to stimulate muscle contraction.
d. does all of these. - Postsynaptic inhibition is produced by
a. depolarization of the postsynaptic membrane.
b. hyperpolarization of the postsynaptic membrane.
c. axoaxonic synapses.
d. long-term potentiation. - Hyperpolarization of the postsynaptic membrane in response
to glycine or GABA is produced by the opening of
a. Na^1 channels. c. Ca^2 1 channels.
b. K^1 channels. d. Cl^2 channels. - The absolute refractory period of a neuron
a. is due to the high negative polarity of the inside of the neuron.
b. occurs only during the repolarization phase.
c. occurs only during the depolarization phase.
d. occurs during depolarization and the first part of the
repolarization phase. - Which of these statements about catecholamines is false?
a. They include norepinephrine, epinephrine, and dopamine.
b. Their effects are increased by action of the enzyme
catechol-O-methyltransferase.
c. They are inactivated by monoamine oxidase.
d. They are inactivated by reuptake into the presynaptic axon.
e. They may stimulate the production of cyclic AMP in the
postsynaptic axon. - The summation of EPSPs from numerous presynaptic nerve
fibers converging onto one postsynaptic neuron is called
a. spatial summation.
b. long-term potentiation.
c. temporal summation.
d. synaptic plasticity. - Which of these statements about ACh receptors is false?
a. Skeletal muscles contain nicotinic ACh receptors.
b. The heart contains muscarinic ACh receptors.
c. G-proteins are needed to open ion channels for nicotinic
receptors.
d. Stimulation of nicotinic receptors results in the
production of EPSPs.