Autonomic Nervous System: Structure, Function, and Neurotransmitters

What is the primary physiological role of the autonomic nervous system?

Homeostasis: regulating pupillary dilation, accommodation for near vision, blood vessel dilation/constriction, heart rate, and GI tract movements.

What are the three main components of the autonomic nervous system?

SNS, PNS, ENS

What is the function of the sympathetic nervous system?

It prepares the body for 'fight or flight' responses, innervating various tissues and providing diffuse innervation.

Where are the preganglionic neurons of the sympathetic nervous system located?

midbrain, medulla, or lateral horn of the spinal cord.

What is the function of the parasympathetic nervous system?

promotes 'rest and digest' activities, providing discrete innervation to target tissues.

Where are the preganglionic neurons of the parasympathetic nervous system located?

In the medulla or sacral segment of the spinal cord.

What is the role of the enteric nervous system?

regulates GIT activity and operates independently of the central nervous system.

What distinguishes the sympathetic nervous system's nerve structure?

It has a short preganglionic nerve and a long postganglionic nerve.

What distinguishes the parasympathetic nervous system's nerve structure?

It has a long preganglionic nerve and a short postganglionic nerve.

What are receptor agonists?

Drugs that mimic the effects of neurotransmitters.

What are receptor antagonists?

Drugs that block the effects of neurotransmitters.

Which brain structures are involved in the central control of the autonomic nervous system?

The amygdala, hypothalamus, and reticular formation.

How do postganglionic neurons in the sympathetic nervous system typically transmit signals?

release noradrenaline, acting on alpha or beta-adrenoceptors.

What neurotransmitter is involved in excitatory transmission at autonomic ganglia?

ACh acting on nicotinic acetylcholine receptors (NAChR).

What is unique about the adrenal gland's connection to the sympathetic nervous system?

Preganglionic neurons synapse directly on the adrenal gland, releasing ACh and activating nicotinic receptors, leading to the release of epinephrine into the bloodstream.

What neurotransmitter is typically involved in postganglionic parasympathetic transmission?

ACh acting on muscarinic receptors

What is the role of chromaffin cells in the adrenal medulla?

They act as postganglionic cells that release adrenaline and noradrenaline directly into the bloodstream.

What is the primary neurotransmitter for sympathetic postganglionic synapses?

Noradrenaline.

What is the primary neurotransmitter for parasympathetic postganglionic synapses?

ACh

What type of receptors do sympathetic postganglionic neurons act on?

Alpha and beta-adrenoceptors.