During the relative refractory period, an initial threshold-level depolarization is usually not sufficient to trigger an action potential. Why?
A) Some Na+ channels have returned to their resting position and K+ channels are still open, so Na+ entry is offset by K+ loss.
B) Only some Na+ channels have returned to their resting position.
C) Only K+ channels are still open, so Na+ entry is offset by K+ loss.
D) The statement is incorrect; a threshold-level depolarization always triggers an action potential.
E) Only a few K+ channels have returned to their resting position.
A) Some Na+ channels have returned to their resting position and K+ channels are still open, so Na+ entry is offset by K+ loss.
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Which of the following is the major positive ion outside cells?
A) nitrogen B) hydrogen C) potassium D) sodium
The refractory period:
1.prevents the retrograde propagation of Action Potentials along the neuronal membrane 2.prevents the retrograde propagation of Graded Potentials along the neuronal membrane 3.results from actions of the Na+/K+ pump 4.Both 1 and 3 are correct. 5.All of these are correct.
During an action potential ________.
A. K+ influx causes after-hyperpolarization B. Na+ influx causes depolarization C. Na+ efflux causes depolarization D. K+ influx causes repolarization
Match the enzyme or hormone with the organ that produces it.A. Salivary glandsB. StomachC. LiverD. Small intestineE. PancreasCarboxypeptidase
Fill in the blank(s) with the appropriate word(s).