MICROANATOMY

Detailed explanation-1: -The parasympathetic nerve (vagus nerve) releases the neurotransmitter acetylcholine to decrease heart rate.

Detailed explanation-2: -Dopamine can be converted into norepinephrine and thus can increase heart rate and blood pressure.

Detailed explanation-3: -tricular receptors results in a decrease in heart rate and fall in blood pressure; and stimulation of atrial receptors results in an increase in heart rate and an increase in urine flow.

Detailed explanation-4: -It was later discovered the heart contains cells that synthesize and release catecholamines (norepinephrine, epinephrine and dopamine), which are neurotransmitters once thought to be produced only by neurons in the brain and ganglia.