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.
Answer is: A) A slow depolarization occurs when Na+ is transported out of the cell and K+ moves back in, resulting in resting membrane potential.
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.
You might also like to view...
When the nurse is told that a patient has a compound comminuted fracture, the nurse is concerned because this type of fracture is one in which the bone is:
1. bent but not completely broken, and the bent piece protrudes through the skin. 2. compressed, and bone pieces protrude through the skin. 3. twisted, and the fragments are separated. 4. broken into two or more pieces, and bone fragments protrude through the skin.
A nurse manager discovers that the readmission rate of hospitalized patients is very high on the hospital unit. The nurse manager desires improved coordination of care and accountability for cost-effective quality care
Which nursing care delivery model is best suited for these needs? a. Team nursing b. Total patient care c. Primary nursing d. Case management
When teaching a postpartum female patient about using a perineal pad, you should teach her to
A) discard the pad in a biohazard container. B) fold the soiled pad inward when removing it. C) wear gloves when handling the soiled pad. D) hold the clean pad in the middle while applying it.
All of the following may be factors in plaque formation except:
a. chronic irritation to interior arterial walls. b. lack of immune system response. c. unrelenting infection in the body. d. bacterial antigens.