Autonomic Nervous System Flashcards
Topography of the NS
- 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)
efferent neurones in the ANS are either
sympathetic or parasympathetic
which nerves are thoracolumbar
sympathetic neurones (T1-L2)
which nerves are parasympathetic
craniosacral; CN III, VII, IX and X + S2-4
There are multiple neurones travelling in a single nerve
what do all spinal nerves carry?
sympathetic fibre
typical spinal nerve
what structure do autonomic nerves pass through
the sympathetic chain
the autonomic motor pathway is comprised of what 2 fibres?
pre and postganglionic
what does the ANS do for structures like cardiac muscle, sm muscle and glands?
detects changes
interprets change
organises response (secretion, contraction)
what structure in thr brain primarily co-ordinates hormonal and neural outputs to maintain homeostasis
hypothalamus
classical actions of the sympathetic NS fight or flight response
pupils dilate
sweating increases]decrease salivation
HR and BP increase
peripheral arteries constrict
airways dilate
stomach secretions decrease
parasympathetic is opposite
where do preganglionic sympathetic fibres originate from?
lateral horn of the spinal cord grey matter (T1-L2)
where do postganglionic fibres arise from
2 possible locations:
1) paravertebral ganglia (sympathetic chain)
2) prevertebral chain (surrounding the abdominal aorta) e.g., coeliac ganglia, SM ganglia
Where are the cell bodies of preganglionic fibres found?
in the lateral horn of the grey matter
how do preganglionic fibres leace the grey matter
ventral root
how do preganglionic fibres enter the sympathetic chain?
via the white ramus communicans
what are the 3 possible pathways for a pregamglionic fibre after entyering the sympathetic chain
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
what do visceral afferents do?
transmit sensations of visceral pain and stretch/ fullness back to the CNS.
their ganglia are in the dorsal root ganglia
summary of the splanchnic nerves
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
autonomic innervation of the heart
preganglionic fibres do not synapse on a blood vessel but insteaf directly on the heart
spinal cord nerves from T1-4
suprarenal glands
innervated directly by preganglionic neurones
no postganglionic neurone
no parasympathetic innervation
sympathetic nerves of the head
symp nerves yravel with spinal nerves on the surface of the arteries
reach the head via the internal carotid plexus
horner’s syndrome
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
which 2 muscles open the eyelid?
levator palpebrae superioris
superior tarsal muscle CN III
which 2 locations do preganglionic parasympathetic neurones in the head arise
1) brain stem
2) S2-4 spinal as pelvic splanchnic nerves S2-4
as which cranial nerves do the parasympathetic fibres leave the head as
3 (occulomotor) 7 (facial) 9 (glossopharyngeal). 10(vagus)
CN preganglionic parasympathetic firbes 3,7 and 9 originate from which cranial nerve ganglia
- ciliary
- Pterygopalatine
- Submandibular
- Otic
vagus does no synpase in a ganglia but insetad on the wall of the heart
vagus nerve
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
oculomotor nerve
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
facial nerve
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)
glossopharyngeal nerve
(CN VIX)
contains parasympathetic firbes
preganglionic fibres: pons
postganglionic neurones; otic ganglion
target; parotid gland
function: increased secretion
pelvic splanchnic nerves
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
visceral afferents
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
pelvic pain line
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
referred pain
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
