these questions are hard!!
cant find source where these questions could have possibly been originated from.
please help if you can answer, I'd appreciate it.
the action potential of a neuron:
a) is initiated by efflux of Na+
b) is terminated by efflux of K+
c) declines in aimplitude as it moves along the axon
d) results in a transient reversal of the concentration gradient of Na+ across the cell membrane
e) is not associated with any net movement of Na+ of K+ across the cell membrane
If the Ek+ is -90 mV, the Ena+ is 60 mV, and the Emeasured is -65 mV, which ion is more permeable?
a) neither, they are the same
b) Na+
c) K+
d) insufficient data to tell
At threshold:
a) the influx Na+ current exceeds the efflux of the K+ current
b) the influx Na+ current is less than the efflux K+ current
c) not all the Na+ channels have opened
d) all the K+ channels have opened
e) A and C
Which of the following is true for an action potential ?
a) the K+ permeability increases more than the Na+ permeability during the rising phase
b) Ca2+ permeability increases more than Na+ permeability
c)at the peak Na+ permeability is greater than K+ permeability
d)the Na+ permeability increases before K+ permeability
e) C and D
f) all the above
The rate of conduction in small, unmyleinated neurons is ________the rate of conduction in large, myelinated neurons.
a) greater than
b) the same as
c) less than
The membrane of all cells are polarized. The degree of polarization, however, varies widely from -20 mV to -200 mV. When a cell becomes depolarized, the________
a) inside of the cell becomes more negative
b) outside of the cell becomes more positive
c) inside of the cell becomes less negative
d) outside of the cell becomes less negative
e) none of the above
During the relative refractory period
a) the cell is positive inside
b) the threshold is lower than when at rest
c)the membrane is more permeable to K+ than at rest
d) membrane permeability to Na+ is higher than for K+
An action potential may be characterized by which of the following?
a) self-propagating
b) all-or-none
c) decremental conduction
d) all the above
e) A and B
f) none of the above
The effect a presynaptic neuron has on a postsynaptic neuron may be enhanced (facilitated) or diminished (inhibited) by exerting a positive or negative effect, respectively, on the presynaptic neuron. WHich of the following combinations is/are true?
facilitation/inhibitiona) closing K+ channels/opening K+ channels
b) opening K+ channels/closing K+ channels
c) opening Cl- channels/closing Cl- channels
d) closing Na+ channels/opening Na+ channels
e) A and D
Repolarization is accomplished by
a) a decrease in membrane permeability to Na+
b) an increase in membrane premeability to K+
c) a decrease in membrane permeability to Ca2+
d) all the above
e) A and B
Release of neurotransmitter from synaptic vesicles
a) is independent of intracellular Ca2+ concentrations
b) is directly dependent on intracellular Ca2+ concentrations
c) is directly dependent on intracellular K+ concentrations
d) is directly dependent on the Na+ concentrations
In posttetanic potentiation
a) presynaptic neurons contain more Na+ than usual
b) presynaptic neuron terminals have higher concentrations of Ca2+
c) slight inhibition of the postsynaptic neuron results
d)larger than normal postsynaptic potentials are produced
e) B and D
f) A and D
Direct-acting neurotransmitters
a) require cAMP
b) mediate very slow responses
c) open ion channels to provoke rapid responses
d) act through second messengers
The total duration of a compound action potential of a mixed nerve recorded 50 mm from the stimulating electrode is _________the total duration of an action potential of a mixed nerve recorded 5 mm from the stimulating electrode.
a) greater than
b) the same as
c) less than
d none of the above
Action potentials is a sensory nerve fiber:
a) result from the activation of Na+ channels by a local generator potential
b) generally occur at a higher frequency the larger the generator potential
c) can be blocked without affecting the generator potential
d) will not occur if the receptor is phasic
e) all the above
f) A, B, and C
Neurons whose axons exit the spinal cord through the ventral root may be classified as:
a) sensory neurons
b) part of the PNS
c) motor neurons
d) all the above
e) B and C
Which of the following is not a function of the autonomic nervous system?
a) innervation of smooth muscle of the digestive tract
b) innervation of cardiac muscle
c) innervation of glands
d) innervation of skeletal muscle
In contrast to the somatic nervous system, the autonomic nervous system
a) has two afferent neurons
b) has two efferent neurons
c) has both afferent and efferent neurons
d) stimulates its effector cells
Preparing the body for the "fight-or-flight" response is the role of the
a) sympathetic nervous system
b) somatic nervous system
c) parasympathetic nervous system
d) none of the above
The adrenal medulla gland is innervated by
a) the sympathetic nervous system only
b) the parasympathetic nervous system only
c) the somatic nervous system only
d) all the above
e) A and B
All preganglionic axons of the autonomic nervous system release
a) dopamine
b) serotonin
c) the same transmitter as the one released by the sympathetic postganglionic axons
d) the same transmitter as the one released by the parasympathetic postganglionic axons
If Na+ channels are inactivated more slowly than normal, the resulting action potential would be
a) abolished
b) inverted in polarity
c) increased in amplitude
d) prolonged in duration
e) C and D
please, please help!
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