Lecture 17 – Autonomic Nervous System

A comprehensive set of flashcards covering the key concepts and details from Lecture 17 on the Autonomic Nervous System.

What does the ANS regulate?

Involuntary functions such as heart rate, blood pressure, digestion, respiration, and glandular activity.

What are the two main divisions of the ANS?

Sympathetic and Parasympathetic.

What general effect does the sympathetic system have?

Fight or flight.

What general effect does the parasympathetic system have?

Rest and digest.

What types of tissues does the ANS control?

Smooth muscle, cardiac muscle, and glands.

What system controls skeletal muscle?

The somatic nervous system.

What does dual innervation mean?

Most organs receive both sympathetic and parasympathetic inputs.

Do sympathetic and parasympathetic inputs usually have opposite effects?

Yes, they counterbalance each other.

How many neurons are in an autonomic motor pathway?

Two neurons: preganglionic and postganglionic.

Where is the preganglionic neuron located?

In the CNS.

Where is the postganglionic neuron located?

In an autonomic ganglion.

What is the neurotransmitter used by ALL preganglionic fibers?

Acetylcholine (ACh).

Where do sympathetic preganglionic neurons originate?

Lateral horns of spinal cord levels T1–L2.

What is the sympathetic chain (paravertebral ganglia)?

A chain of connected ganglia running parallel to the spinal cord.

What happens to preganglionic sympathetic axons after exiting the spinal cord?

They enter the sympathetic chain via the ventral root.

What can sympathetic preganglionic axons do in the chain?

1. Synapse at the same level 2. Travel up or down chain before synapsing (divergence) 3. Pass through chain and synapse at collateral ganglia.

What neurotransmitter do sympathetic POSTganglionic neurons usually release?

Norepinephrine (NE).

Where do parasympathetic preganglionic neurons originate?

Brainstem (cranial nerves III, VII, IX, X) and Sacral spinal cord (S2–S4).

What are terminal ganglia?

Parasympathetic ganglia located near or within the target organ.

What is the length of parasympathetic preganglionic fibers?

Long.

What is the length of parasympathetic postganglionic fibers?

Short.

What neurotransmitter is used by parasympathetic postganglionic neurons?

Acetylcholine (ACh).

Which division has long preganglionic and short postganglionic neurons?

Parasympathetic.

Which division has short preganglionic and long postganglionic neurons?

Sympathetic.

Which division has chain ganglia?

Sympathetic.

Which division has terminal ganglia?

Parasympathetic.

Which division shows high divergence (broad activation)?

Sympathetic.

What happens to the pupils during sympathetic activation?

Dilate.

What happens to heart rate during sympathetic activation?

Increases.

What happens to breathing during sympathetic activation?

Respiratory passages dilate.

What happens to digestive function during sympathetic activation?

Slows down.

What happens to blood flow during sympathetic activation?

Increases to skeletal muscle; decreases to digestive organs.

What metabolic effect occurs during sympathetic activation?

Glycogen → glucose (energy mobilization).

What happens to heart rate during parasympathetic activation?

Decreases.

What happens to digestion during parasympathetic activation?

Stimulated → increased motility and secretion.

What happens to pupils during parasympathetic activation?

Constrict.

What is orthostatic hypotension?

A drop in blood pressure when standing due to failure of autonomic feedback.

What causes orthostatic hypotension?

Inadequate reflexive sympathetic activation upon standing.

What symptoms occur with orthostatic hypotension?

Dizziness, fainting.

What triggers neurocardiogenic syncope (fainting)?

A sympathetic surge followed by excessive parasympathetic drop.

What does the parasympathetic overreaction do in neurocardiogenic syncope?

Decreases heart rate and BP → decreased cerebral blood flow → fainting.

What type of neuron directly innervates the adrenal medulla?

Sympathetic PREganglionic neuron.

What does the adrenal medulla release?

Epinephrine and norepinephrine into bloodstream.

What effect does this create?

Prolonged sympathetic response.

How many neurons does the somatic pathway have?

One (CNS → skeletal muscle).

How many neurons does the autonomic pathway have?

Two (preganglionic + postganglionic).

Which pathway controls voluntary movement?

Somatic.

Which pathway controls involuntary organs?

Autonomic.

What does the ANS maintain?

Homeostasis.

Does the ANS operate consciously or unconsciously?

Unconsciously.