Autonomic Nervous SystemChad Byworth

Reference: Material from lecture Autonomic Nervous System, Dr R Tunstall

What is the ANS?

The autonomic nervous system allows for the self-regulation of the body viscera, it is split into the...Sympathetic Nervous System Parasympathetic Nervous System

which have these effects...

● Raises heart rate● Increases force of contraction● Constricts most blood vessels● Slows GI transit● Constricts sphincters● Bronchodilates● Increase sweating● Dilates pupil (mydriasis)● Secretion of seminal fluid/movement of sperm

● Slows heart rate ● (no effect on force)● Relaxes blood vessels● Speeds up GI transit● Relaxes sphincters● Increases salivation● Bronchoconstricts● Constricts pupil (miosis)● Erection

ANS fibres are classified as pre- and post-ganglionic

Brainstem nucleus / Cell body in lateral horn

Peripheral ganglion

Target

Preganglionic Postganglionic

Lateral hornAutonomic (only seen T1-L2 & S2-4)

What is this portion of the spinal cord?

Sympathetic Nervous System

Sympathetic supply arises from the...Sympathetic Chain

Sympathetic nerves exit the CNS at...T1 - L2

What would damage at this level result in?

Damage at the level of the L1 vertebral body and below should not affect the sympathetic supply. However parasympathetic outflow to the pelvis will be disrupted.

How are sympathetics to the head supplied?Sympathetics to the head arise from the chaincontinuing to the base of the skull.

Sympathetic Nervous System

Sympathetics to the head come from the sympathetic chain continuing up to the base of the skull. There are 3 ganglia in the neck, from here the supply continues alongside arteries and cranial nerves.

Sup.CervicalGanglia

Plexusaround ICA CN VII

Forms deep petrosal nerve which joins parasympathetic greater petrosal nerve

Run to pterygo-palatine ganglion from which they are distributed

with CN V

Patient Case

What signs can you see on this patient?What else might you expect to see?

Miosis (pupillary constriction)Partial ptosisAnhydrosis (lack of sweating)Vasodilation

What is this condition called?What has happened?

Horner’s SyndromeLoss of sympathetic supply to one side of the head

What could cause this?

Pancoast Tumour IatrogenicBase of Skull Tumour TraumaLymphadenopathy

Parasympathetic Nervous System

CN IIICN VIICN IX

CN X

Pelvic splanchnic nervesFrom S2-4 Spinal nerves

Parasympathetic supply arises from...

4 cranial nerves

3 spinal nerves

Parasympathetic Nervous System

Parasympathetic post-ganglionic fibres emerge from...

Cranial nerves III, VII, IX & X

...and travel with...

Cranial nerve V

Loss of parasympathetics to the head can lead to loss of the...

Pupillary light reflex, this is because there is unopposed sympatheticaction leading to full dilation of the affected pupil.

Neurotransmitters

What are the 2 principal neurotransmitters in the peripheral nervous system?

Acetylcholine and Noradrenaline

CNS

Somatic efferent ACh

SympatheticACh

ACh AChParasympathetic

NANicotinic

Nicotinic

Nicotinic

Muscarinic

α or β

Complete with each neurotransmitter and receptor

Spinal nerveVirginia Lam

+What are they?

• Part of peripheral nervous system• Communication between periphery and CNS

+Where are they? from?

McGraw-Hill Companies

• Arise through numerous rootlets from dorsal and ventral surface of spinal cord

• The dorsal and ventral root of spinal nerve will combine and form dorsal root ganglion, and extend to be spinal nerve

• Where do they emerge from in the vertebral column?

• Intervertebral foramen

+How they are named?

• A little tricky! Or may be not• 31 pairs of spinal nerve

8 pair of cervical 12 thoracic 5 lumbar 5 sacral1 coccyx

• Cervical spinal nerves exit …… corresponding vertebrae

• What happen in thoracic and the following?

+How spinal nerves distribute?

Dorsal and ventral rami

Plexus

+Ramus

• Branch off after dorsal root ganglion

• Both are mixed (somatic motor & sensory, visceral sensory and autonomic)

• Innervation:• Dorsal ramus: • deep muscle and skin of the

back• Ventral ramus:• muscle and structure of upper

and lower limbs, and skin of anteriolateral of the trunk

+Plexuses

Plexuses = network of axon

Principle plexus:Cervical

Brachial

Lumbar

sacral

coccygeal

+Why bother?

Lumbar puncture

AnaesthesiaEpidural

Spinal

Caudal

PathologyIV Disc prolapse

Cervical/lumbar spondylosis (osteroarthritis)

Trauma to nerve or plexuses

Herpes zoster (dermatonal distribution in thorax)

+For IV disc prolapse, the damage will be one level below