MICROANATOMY

Detailed explanation-1: -Sympathetic nervous system activation will stimulate the SA and AV nodes to increase the heart rate, which will increase cardiac output. Parasympathetic nervous system activation will conversely act on the SA and AV nodes to decrease the heart rate, which will decrease cardiac output.

Detailed explanation-2: -Coronary Physiology and Pathophysiology This sympathetic stimulation also produces increases in heart rate and myocardial work, increasing myocardial oxygen demand, which leads to the dominating effect of coronary vasodilation through increased metabolic demand.

Detailed explanation-3: -The sympathetic nervous system (SNS) releases the hormones (catecholamines-epinephrine and norepinephrine) to accelerate the heart rate. The parasympathetic nervous system (PNS) releases the hormone acetylcholine to slow the heart rate.

Detailed explanation-4: -The SNS is activated when baroreceptors, specialised stretch receptors located within thin areas of blood vessels and heart chambers, sense changes in pressure [20]. When arterial pressure drops, the SNS is immediately activated resulting in increased cardiac output and vasoconstriction of peripheral vessels (Fig.