Author Question: Which of the following statements describes phase 4 of the action potential of cells in the ... (Read 49 times)

Tirant22 · **on:** Jun 25, 2018

Which of the following statements describes phase 4 of the action potential of cells in the sinoatrial (SA) node?

A)
A slow depolarization occurs when Na+ is transported out of the cell and K+ moves back in, resulting in resting membrane potential.
B)
The cells are capable of responding to a greater than normal stimulus before the resting membrane potential is reached.
C)
The fast sodium channels in the cellular membranes close, causing an abrupt decrease in intracellular positivity.
D)
Potassium permeability is allowing the cell membrane to remain depolarized, and Ca2+ channel opens moving Ca2+ back into the cell.

Question 2

As a result of dehydration, a client's epithelial cells are producing insufficient amounts of mucus. Consequently, the client's mucociliary blanket is compromised.

Which of the following changes would the care provider anticipate as a direct result of this change?
A)
Impaired function of the client's cilia
B)
Decreased levels of oxygen saturation
C)
Increased amounts of bacteria in the lungs
D)
Increased carbon dioxide levels

josephsuarez · **Reply #1 on:** Jun 25, 2018

Answer to Question 1

Ans:
A

Feedback:

During phase 4 in the cells of the SA node, a slow leakage of current through the slow channels of the cellular membrane leads to spontaneous depolarization; this slow response enables pacemaker function. Answer B describes the relative refractory period of the action potential curve, which occurs at the end of phase 3 in cardiac cells, and answer C describes phase 1 of the action potential, which signals the end of depolarization. The sodium-potassium pump transports sodium out of the cell and a smaller amount of potassium into it, contributing to the negative intracellular charge of the resting membrane potential in phase 4.

Answer to Question 2

Ans:
C

Feedback:

The primary role of the mucociliary blanket is to trap foreign particles and bacteria and thus prevent their entry into the lungs. Impaired ciliary function may result in an inadequate mucociliary blanket, but the opposite relationship is unlikely. Decreased oxygen and increased carbon dioxide levels may eventually result, but not as a direct or immediate consequence.