A: elevated levels of sodium Ion increase the heart rate and contact ility

R: elevated sodium Ion level increase excitability of s a node

Asked by arushidabhade | 25th Aug, 2019, 02:57: PM

Expert Answer:

Decreased sodium lowers blood volume, causing the blood pressure to drop and the heart rate to increase. Therefore, assertion (A) is not true.

The pacemaker potential is produced by a decrease in membrane permeability to potassium, a slow inward current because of calcium influx via T-type (transient) calcium channels, and an increased sodium current because of sodium–calcium exchange. Therefore, reason (R) is true.

Answered by Sheetal Kolte | 26th Aug, 2019, 11:56: AM