Learning Objective

Understand the primary neurotransmitters of the autonomic and somatic nervous systems and their receptor targets, including ACh, NE, dopamine, and epinephrine.

Acetylcholine (ACh)

ACh is the neurotransmitter for both nicotinic and muscarinic receptors in innervated tissues.

• All preganglionic autonomic neurons (sympathetic and parasympathetic) use ACh on nicotinic (NN) receptors.
• All somatic motor neurons use ACh on nicotinic (NM) receptors.
• Most parasympathetic postganglionic neurons also release ACh (on muscarinic receptors).

Norepinephrine (NE)

NE is the neurotransmitter released by most sympathetic postganglionic neurons, acting primarily on α- and β-adrenoceptors.
It mediates responses in cardiac muscle and most smooth muscle tissues.

Dopamine (DA)

Dopamine activates D1 receptors, producing vasodilation in the renal and mesenteric vascular beds.
This increases perfusion to these regions, especially relevant in shock states.

Epinephrine (E)

Epinephrine, released from the adrenal medulla, circulates in the blood and activates most adrenoceptors (α and β). It produces widespread sympathetic effects, including increases in heart rate, bronchodilation, and metabolic activation.

Activity

Activity