Autonomic Nervous System (ANS)

What is the function of the ANS?

Controls involuntary activities: smooth muscle, cardiac muscle, glands.

Name the two divisions of the ANS.

Sympathetic: "Fight or flight"

Parasympathetic: "Rest and digest"

Where do sympathetic and parasympathetic neurons originate?

Sympathetic: Thoracolumbar (T1–L2)

Parasympathetic: Craniosacral (Brainstem and S2–S4)

Compare neuron pathways in the ANS.

Preganglionic → Postganglionic neuron

Sympathetic: Short pre-, long post-

Parasympathetic: Long pre-, short post-

What neurotransmitters are used?

All preganglionic: Acetylcholine (ACh)

Parasympathetic postganglionic: ACh

Sympathetic postganglionic: Norepinephrine (NE)

Types of receptors in the ANS?

• Cholinergic (bind ACh): Nicotinic (always excitatory), Muscarinic (can be either)

• Adrenergic (bind NE/E): Alpha and Beta types

What is the adrenal medulla's role?

Releases epinephrine and norepinephrine into the blood (acts like a sympathetic ganglion).

What is dual innervation?\

Most organs are controlled by both sympathetic and parasympathetic fibers.

Key sympathetic effects?

• ↑ Heart rate

• ↑ Blood pressure

• Bronchodilation

• ↓ Digestion

Key parasympathetic effects?

• ↓ Heart rate

• ↑ Digestion

• Constricted pupils

• Increased gland secretions