MICROANATOMY

Detailed explanation-1: -Sympathetic stimulation increases heart rate and myocardial contractility. During exercise, emotional excitement, or under various pathological conditions (e.g., heart failure)[5], the sympathetic nervous system is activated.

Detailed explanation-2: -The sympathetic nervous system (SNS) has a wide variety of cardiovascular effects, including heart-rate acceleration, increased cardiac contractility, reduced venous capacitance, and peripheral vasoconstriction.

Detailed explanation-3: -Cardiac sympathetic innervation of the heart includes innervation of the sinoatrial (SA) node, which allows sympathetic nerves to increase heart rate by increasing the slope of diastolic depolarization during the spontaneous SA node action potential.

Detailed explanation-4: -The sympathetic nervous system increases heart rate, whereas the parasympathetic nervous system suppresses it. Heart rate variability (HRV) can be analyzed using electrocardiography (ECG) to assess the activity of the autonomic nervous system (Kimura et al., 1996).