Autonomic Nervous System

Question 1

what nervous system is the autonomic nervous system part of?

Answer 1

Peripheral nervous system

Question 2

What does the autonomic nervous system do?

Answer 2

Controls body functions but not under conscious control.

It maintains and fine tunes internal environment.

Question 3

How is the ANS arranged?

Answer 3

Two neurone arrangement and an associated ganglion.

Question 4

What are the target tissues for the ANS?

Answer 4

Smooth muscle (cardiac muscle in thorax) and glands (lacrimal and salivary)

Question 5

Where do the preganglionic nerves of sympathetic ANS leave the spinal cord?

Answer 5

T1-L2

It has a ‘thoracolumbar outflow’

The cell bodies within lateral horn of grey matter of spinal cord.

Question 6

Where do the preganglionic nerves of parasympathetic ANS leave the spinal cord?

Answer 6

Craniosacral outflow.

Cranial (4 cranial nerves)

Sacral (S2-4) - pelvic splanchnics.

Question 7

What do sympathetics do?

Answer 7

Smooth muscle of blood vessles, eye lid (tarsal muscle) and iris (dilator pupillae)

Sweat glands

Arrector pili muscles (hair follicles)

It decreases secretions from salivary and lacrimal glands (smaller volume but higher protein - more viscous)

Question 8

What do the parasympathetics do?

Answer 8

Smooth muscle of iris

Lacrimal glands (tears)

Salivary and mucosal glands

Smooth muscle of the respiratory and GI tract

Question 9

How do sympathetics get to the eye?

Answer 9

Via blood vessels - Follow the internal carotid then ophthalmic.
They then follow one of the cranial nerves to get into the eye.

Question 10

How do sympathetics get to the skin?

Answer 10

Follow the external carotid artery

Question 11

How is the rule of 4s helpful?

Answer 11

4 parasympathetic nuclei - Edinger Westphal, superior salivary, inferior salivary, dorsal motor
4 CNs - III, VI, IX, X
4 Ganglia - Ciliary, Submandibular, Pterygopalatine, Otic

Question 12

What is the route of the oculomotor parasympathetics?

Answer 12

Brainstem - Edinger Westphal Nucleus

Parasympathetic fibres emerge with CN III fibres

Ciliary ganglion

(Hitch hikes on small branches from CN Va)

Eye - ciliary body: lense, constrictor of the pupil

Question 13

Why is the route of oculomotor parasympathetics important?

Answer 13

Can test it to see if pathology is happening.

Question 14

Wh do both pupils constrict if shine a light in one?

Answer 14

Light in left pupil

Sensory afferent from left retina (CN II)

Some branches leave CN II to enter midbrain

Connection with EDW nuclei (left and right)

Parasympathetic fibres from EDW leave brainstem with CN III (left and right)

Pass via ciliary ganglion

Reach sphincter pupilae

Direct light reflex to left and consensual light reflex to right

Question 15

How do VII parasympathetics reach the target tissue?

Answer 15

Parasympathetic pre-ganglionic nerves exit brainstem with the motor and sensory axons forming the facial nerve.

Parasympathetics reach target tissues via two main branches of the facial nerve that arise in petrous bone.

• Greater petrosal nerve
• Chordates tympani nerve

Question 16

What are the parasympathetic ganglia of VII?

Answer 16

There are two associated parasympathetic ganglia

• Pterygopalatine ganglion
• Submandibular ganglion

These ganglia are cell bodies of post-ganglionic parasympathetic nerves.

Question 17

Where do the Glossopharyngeal parasympathetics arise from?

Answer 17

Brainstem with CN IX. It then exits through the jugular foramen then splits into a number of branches.

Question 18

Branches of parasympathetic CN IX?

Answer 18

Sensory - oropharynx 
Taste and general sensory to back 1/3 of tongue 
Carotid sinus 
Stylophangeus 
Tympanic nerve

Question 19

What is the route of CN IX parasympathetics?

Answer 19

Initially run with the tympanic nerve
Then, they exit middle ear as lesser petrosal nerve
Synapse in otic ganglion then hitch hike on branch of CM Vc
Parotid gland

Question 20

What is the route of the parasympathetic CN X?

Answer 20

Brainstem (medulla)

Run with CN X and branches

Meet ganglion at or in target tissue.

Then glands, heart and smooth muscle

Question 21

Wha do vagus parasympathetics do?

Answer 21

Glands - laryngopharynx, larynx, glands and smooth muscle of oesophagus and trachea
GI and resp smooth muscle
Heart