ANATOMY

Detailed explanation-1: -The parasympathetic nervous system (PNS) releases the hormone acetylcholine to slow the heart rate.

Detailed explanation-2: -The sympathetic nervous system releases norepinephrine (NE) while the parasympathetic nervous system releases acetylcholine (ACh). Sympathetic stimulation increases heart rate and myocardial contractility.

Detailed explanation-3: -Targeted activation of the beta-1 receptor in the heart increases sinoatrial (SA) nodal, atrioventricular (AV) nodal, and ventricular muscular firing, thus increasing heart rate and contractility.

Detailed explanation-4: -The sympathetic side increases alertness, energy, blood pressure, heart rate, and breathing rate. The parasympathetic side, which the vagus nerve is heavily involved in, decreases alertness, blood pressure, and heart rate, and helps with calmness, relaxation, and digestion.