21) Interneurons
A) found only in the central nervous system.
B) carry : 1200515.
21) Interneurons
A) are found only in the central nervous system.
B) carry only sensory impulses.
C) carry only motor impulses.
D) only connect motor neurons to other motor neurons.
E) are found between neurons and their effectors.
22) Most neurons lack centrioles. This observation explains
A) why neurons grow such long axons.
B) why such neurons cannot divide through mitosis.
C) the conducting ability of neurons.
D) the ability of neurons to communicate with each other.
E) the longevity of neurons.
23) The all-or-none principle states that
A) all stimuli will produce identical action potentials.
B) all stimuli great enough to bring the membrane to threshold will produce identical action potentials.
C) the greater the magnitude of the stimuli, the greater the intensity of the action potential.
D) only sensory stimuli can activate action potentials.
E) only motor stimuli can activate action potentials.
24) The resting potential of a neuron is ________.
A) 0 mV
B) +10 mV
C) -70 mV
D) -10 mV
E) + 70 mV
25) Changes in the membrane potential that cannot spread far from the site of stimulation are called ________.
A) threshold
B) graded potentials
C) refractories
D) hyperpolarizations
E) action potentials
26) Saltatory conduction
A) occurs only if the myelin sheath is continuous.
B) occurs only if nodes of Ranvier are lacking.
C) is faster than conduction on an unmyelinated axon.
D) is slower that conduction on an unmyelinated axon.
E) occurs at the synapse.
27) Opening of voltage-gated sodium channels in the membrane of a neuron results in
A) depolarization.
B) repolarization.
C) hyperpolarization.
D) increased negative charge inside the membrane.
E) myelination.
28) When a neuron is at rest, which ion passes through its membrane most easily?
A) sodium
B) chloride
C) sulfate
D) potassium
E) proteins
29) During continuous conduction,
A) action potentials move in all directions along an axon.
B) action potentials occur at successive nodes along the length of the stimulated axon.
C) local currents depolarize adjacent areas of membrane so that action potentials continue to form along the membrane.
D) action potentials produce a local current that is strong enough to spread along the length of the axon.
E) local potentials produce a continuous outward flow of potassium ions.
30) A stimulus that opens gated potassium ion channels, taking the membrane potential away from 0 mV, results in which of the following?
A) repolarization
B) hyperpolarization
C) depolarization
D) refraction
E) summation
21) Interneurons
A) found only in the central nervous system.
B) carry : 1200515
