Question

1. The myocardium is nourished by blood flow through the coronary arteries. the majority of blood flowing into the myocardium through the coronary arteries does so:

A)Between systole and diastole

B)Continuously

C)During diastole

D)During systole

2.parasympathetic stimulation of the heart via the vagus nerve:

A)increases the influx of potassium ions from the cells of the SA node

B)None of the answers are correct

C)Increases the influx of sodium ions into the cells of the SA node

D)decreases the influx of potassium ions from the cells of the SA node

Answer 1

1. C) during diastole.

During systole the heart muscles contract constricting the coronary heart vessels, this is due to strong contraction particularly from left ventricles, which compresses the intramuscular vessel, in contrast during diastole the cardiac muscle are relaxed enabling blood flow through capillaries with no obstruction, so in diastole blood flow is rapid through capillaries.

2.B) none of the answers are correct.

Parasympathetic stimulation of the heart via the vagus nerve results in slower heart rate and AV conduction, vagus stimulation of SA node acts by inhibiting the Beeta 1 receptors directly, so parasympathetic stimulation by vagus nerve is acetyl choline mediated, it acts without electrical stimulation.