Autonomic Nervous System

Question 1

Topography of the NS

Answer 1

• split into CNS and PNS
• CNS- brain and spinal cord
• divided into afferents(sensory) and efferents(motor)
• PNS- everything else i.e. spinal nerves and cranial nerves
• Split into somatic and autonomuc NS
• Somatic- innervate skeletal muscle and skin
• Efferents (sensory in) and afferents (motor out)
• Autonomic- innervates glands, sm muscle etc
• Visceral afferents (sensory of organs)
• Visceral efferents (sympathetic and parasympathetic)

Question 2

efferent neurones in the ANS are either

Answer 2

sympathetic or parasympathetic

Question 3

which nerves are thoracolumbar

Answer 3

sympathetic neurones (T1-L2)

Question 4

which nerves are parasympathetic

Answer 4

craniosacral; CN III, VII, IX and X + S2-4

Question 5

There are multiple neurones travelling in a single nerve

what do all spinal nerves carry?

Answer 5

sympathetic fibre

Question 6

typical spinal nerve

Answer 6

Question 7

what structure do autonomic nerves pass through

Answer 7

the sympathetic chain

Question 8

the autonomic motor pathway is comprised of what 2 fibres?

Answer 8

pre and postganglionic

Question 9

what does the ANS do for structures like cardiac muscle, sm muscle and glands?

Answer 9

detects changes

interprets change

organises response (secretion, contraction)

Question 10

what structure in thr brain primarily co-ordinates hormonal and neural outputs to maintain homeostasis

Answer 10

hypothalamus

Question 11

classical actions of the sympathetic NS fight or flight response

Answer 11

pupils dilate

sweating increases]decrease salivation

HR and BP increase

peripheral arteries constrict

airways dilate

stomach secretions decrease

parasympathetic is opposite

Question 12

where do preganglionic sympathetic fibres originate from?

Answer 12

lateral horn of the spinal cord grey matter (T1-L2)

Question 13

where do postganglionic fibres arise from

Answer 13

2 possible locations:

1) paravertebral ganglia (sympathetic chain)
2) prevertebral chain (surrounding the abdominal aorta) e.g., coeliac ganglia, SM ganglia

Question 14

Where are the cell bodies of preganglionic fibres found?

Answer 14

in the lateral horn of the grey matter

Question 15

how do preganglionic fibres leace the grey matter

Answer 15

ventral root

Question 16

how do preganglionic fibres enter the sympathetic chain?

Answer 16

via the white ramus communicans

Question 17

what are the 3 possible pathways for a pregamglionic fibre after entyering the sympathetic chain

Answer 17

1) can synapse immediately within the sympathetic chain at the same vertebral level
2) preganglionic fibres can ascend/ descend before synapsing in the symp chain
3) fibres can pass through the chain and synapse after

Question 18

what do visceral afferents do?

Answer 18

transmit sensations of visceral pain and stretch/ fullness back to the CNS.

their ganglia are in the dorsal root ganglia

Question 19

summary of the splanchnic nerves

Answer 19

Greater- splanchnic- T5-9 travels to the coeliac ganglion

Lesser splanchnic- T9/10 to 10/11 travels to the aorticorenal

least when present travels to the renal plexus

2-4 lumbar splanchnic travels to the superior hypogastric plexus

sacracl splanchnic travels to the inferior hypogastric plexus

Question 20

autonomic innervation of the heart

Answer 20

preganglionic fibres do not synapse on a blood vessel but insteaf directly on the heart

spinal cord nerves from T1-4

Question 21

suprarenal glands

Answer 21

innervated directly by preganglionic neurones

no postganglionic neurone

no parasympathetic innervation

Question 22

sympathetic nerves of the head

Answer 22

symp nerves yravel with spinal nerves on the surface of the arteries

reach the head via the internal carotid plexus

Question 23

horner’s syndrome

Answer 23

internal carotid- – opthalmic artery— eye

dirsuption of sympathetic on one side leads to unilateral symptoms of the eye

typical symptoms:

miosis- persistently small pupils

ptosis- drooping of upper eyelid (paralysis of superior tarsal muscle)

sunken appearance of eye

dry on the affected side of face

Question 24

which 2 muscles open the eyelid?

Answer 24

levator palpebrae superioris

superior tarsal muscle CN III

Question 25

which 2 locations do preganglionic parasympathetic neurones in the head arise

Answer 25

1) brain stem
2) S2-4 spinal as pelvic splanchnic nerves S2-4

Question 26

as which cranial nerves do the parasympathetic fibres leave the head as

Answer 26

3 (occulomotor) 7 (facial) 9 (glossopharyngeal). 10(vagus)

Question 27

CN preganglionic parasympathetic firbes 3,7 and 9 originate from which cranial nerve ganglia

Answer 27

• ciliary
• Pterygopalatine
• Submandibular
• Otic

vagus does no synpase in a ganglia but insetad on the wall of the heart

Question 28

vagus nerve

Answer 28

CN X

contains parasympathetic fibres

preganglionic; dorsal vagal motor nucleus

postganglionic; within walls of the viscera e.g., enteric NS

Target; thoracic and abdominal viscera (up to splenic flexure)

function; rest and digest

Question 29

oculomotor nerve

Answer 29

CN III

pregangkionic fibres; midbrain

postganglionic neurones; ciliary region

targets: ciliary muscle (accomodation of the lens) and sphincter pupillae

finction; accomodation of the lens, constriction of the pupil

Question 30

facial nerve

Answer 30

CN VII

contains parasympathetic fibres

preganglionic neurones; pons

postganglionic neurones; pterygopalatine & submandibular ganglia

targets; lacrimal glands, submandibular glands, sublingual glands

function; increased secretion (tears and/or saliva)

Question 31

glossopharyngeal nerve

Answer 31

(CN VIX)

contains parasympathetic firbes

preganglionic fibres: pons

postganglionic neurones; otic ganglion

target; parotid gland

function: increased secretion

Question 32

pelvic splanchnic nerves

Answer 32

S2-4

Preganglionic neurones: S2-4 (red) forms inferior hypogastric plexus

Postganglionic neurones: within walls of viscera

Target: Hindgut and pelvic viscera

Function: peristalsis, glandular secretion, engorgement of erectile bodies, urination

Question 33

visceral afferents

Answer 33

bring information back to ther CNS about the viscera- relexive and nociceptive

visceral reflexes do not reach consciousness

update the hypothalamus on visceral function

travel within parasympathetic nerves

Question 34

pelvic pain line

Answer 34

When reached at a conscious level, information from visceral afferents is perceived as porrly localised pain, or felt as cramps that convey hunger, fullness, or nausea.

Pain from viscera “above or in contact with the inferior layer of peritoneum (purple line) travels via the sympathetic splanchnic nerves T10-L1.

pain via sub-peritoneal organs is conveyed via parasympathetic nerves S2-4

Question 35

referred pain

Answer 35

visceral pain results from:

excessive stretch, violent contractions or ischaemia

pain is vague and often referred to cutaneous regions

when spread to a somatic structure it is often sharper and easily identified

convergence of afferent information of the visceral organs and those of somatic origin on the same segment