MUSCLE PHYSIOLOGY

Detailed explanation-1: -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-2: -Coronary artery flow depends on the autonomic nervous system. The sympathetic nervous system activation will increase the effects of catecholamines, which will induce vasoconstriction and further decrease the blood flow. It is thought that coronary artery spasm can develop if there is unopposed alpha constriction.

Detailed explanation-3: -The sympathetic receptors seem to cause coronary dilation, and there are receptors that can also lead to coronary dilation through muscarinic pathways. Parasympathetic stimulation via the coronary circulation can lead to bradycardia and hypotension (i.e., the Bezold-Jarisch reflex).

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.