Unformatted text preview: 97. Award: 1.00 point Problems? Adjust credit for all students. Click and drag the terms on the left to accurately complete the sentences on the right. Then click and drag the sentences to arrange them
in order to accurately describe the process. ECF
stimulated A muscle cell is stimulated by a neurotransmitter from a
Ion channels open in the plasma membrane and sodium
ions diﬀuse into the ICF.
The membrane depolarizes, or becomes less negative.
Sodium ion channels close, but potassium ion channels
remain open, and loss of that ion repolarizes the
The process just described is called a(n) action potential. Explanation:
When a nerve or muscle cell is stimulated, ion channels in the plasma membrane open and Na+ instantly diffuses down its concentration
gradient into the cell. These cations override the negative charges in the ICF, so the inside of the plasma membrane briefly becomes positive. This change is called depolarization of
the membrane. Immediately, Na+ channels close and K+ channels open. K+ rushes out of the cell, partly because it is repelled by the
positive sodium charge and partly because it is more concentrated in the ICF than in the ECF, so it diffuses down its concentration
gradient when it has the opportunity. The loss of positive potassium ions from the cell turns the inside of the membrane negative again
(repolarization). This quick upanddown voltage shift, from the negative RMP to a positive value and then back to a negative value
again, is called an action potential. The RMP is a stable voltage seen in a “waiting” cell, whereas the action potential is a quickly
fluctuating voltage seen in an active, stimulated cell. References Composition eBook & Resources Section: 11.03 ...
View Full Document
- One '14
- Sodium, ICF