Question

Select the MOST CORRECT answer. During the cardiac cycle...

		Blood flows from the right atrium, through the AV valve, and is pumped by the right ventricle into the pulmonary artery.
		The ventricular diastole occurs at the same time as atrial systole and atrial diastole.
		The second heart sound (S2, or dup) occurs just as the left ventricle reaches its highest pressure, which exceeds aortic pressure.
		Both a) and b) are correct and c) is incorrect.
		a), b) and c) are all correct.

Sympathetic and parasympathetic regulation of the heart (select the MOST CORRECT statement):

		Both the sympathetic and parasympathetic branches of the autonomic nervous system regulate heart rate by releasing neurotransmitters that activate a specific G protein-coupled receptor on the surface of sinoatrial (SA) node cells.
		The in vivo pharmacological inhibition of the muscarinic acetylcholine receptor on SA node cells would lead to an increase in heart rate.
		The pharmacological inhibition of beta-1 receptors on SA node cells and cardiomyocytes would lead to a decrease in mean arterial pressure.
		Both a) and b) are correct and c) is incorrect.
		a), b) and c) are all correct.

Answer 1

1. ANSWER: C is incorrect.

Reason: The second heart sound is heard due to the closure of semilunar valves which occurs just after ventricular systole that is it occurs after the fall from its highest pressure.

2. ANSWER: A,B,C are correct

Reason: Both sympathetic and parasympathetic system work on the heart by g protein coupled receptors. Inhibition of acetylcholine receptor would increase the heart rate and beta 1 receptor inhibition would decrease the heart beat thus decreasing the mean arterial pressure.