S1: Anatomy of the Autonomic Nervous System Flashcards
How many pairs of spinal nerves do we have?
31
Where do spinal nerves exit the CNS?
Vertebral foramen
The vertebral bodies are seperated by the intervertebral discs
What are vertebral bodies seperated by?
The vertebral bodies are seperated by the intervertebral discs
How many somatic nerve fibres make contact with NMJ?
1
Ach is used at Nicotinic receptors
Explain how ANS efferent fibres are in a series
Preganglionic fibre synapses at an autonomic ganglion to (one of more) post ganglionic neurone
What outflow does sympathetic fibres exit the spinal cord at?
Thoracolumbar outflow
Where are sympathetic preganglionic cell bodies found?
In the spinal cord
The sympathetic chain runs parallel to the spinal cord
What is its function?
It enables innervation to reach the rest of the body
What outflow does sympathetic fibres exit at?
Cranio-sacral outdlow
Parasympathetic fibres leave the medulla (cranial nerves) and sacral regions
What part of the brain controls the ANS?
Hypothalamus
What vertebral level does thoracolumabar outflow have?
T1-L2/3
What is the autonomic outflow?
Sympathetic preganglionic fibres exit the CNS
Explain how sensory and motor fibres enter and exit the spinal cord
Sensory fibres enter into the posterior horn
Motor fibres exit out of the anterior horn
What is the origin of preganglionic fibres?
The intermediolateral horn in the middle of the spinal cord and it is the origin of pre-ganglionic fibres (where sympathetic cell bodies are).
These then exit via the anterior horn
What connects sympathetic chain to spinal nerve?
Grey and white communicantes which feed into the ganglion.
The white rami contain myelinated axons while the grey contain unmyelinted.
Explain the course of a sympathetic pre-ganglionic fibre exiting the CNS to ganglion
A sympathetic pre-ganglionic fibre exits the CNS down the mixed spinal nerve and enter into the autonomic ganglion through the white ramus communicans.
The pre-ganglionic fibre synapses to the post-ganglionic fibre and this then exits via the grey ramus communicans rejoining the mixed spinal nerve then travels to its target structure.
However, the preganglionic nerve doesn’t have to synapse at first ganglion
if the preganglionic fibre doesn’t synapse at the first ganglion, what are the three routes it can travel from the sympathetic chain?
It can travel up the sympathetic chain towards cervical ganglia
It can travel down towards lumbosacral ganglia
It can becomes part of the splanchic nerves that supply the gut
What are the three main ganglia in the cervical region?
Superior cervical ganglion
Middle cervical gangion
Stellate ganglion (inferior)
Describe the cervical ganglia (sympathetic supply to the head)
- Sym fibres travel in the internal carotid plexus (in the walls of arteries travelling to their target structure)
Superior cervical ganglion is the origin which innervates: dilator pupillae, superior tarsal muscle and facial sweat glands
What is Horner’s Syndrome?
Loss of sympathetic supply to the head
- Side effects: Small pupil (myosis) and loss of sweating
Explain sympathetic supply to abdominopelvic viscera
The abdominopelvic viscera (organs/tissue in this area) are supplied by the ‘splanchnic nerves’, the greater, lesser and least splanchnic nerves.
Pre-ganglionic fibres pass through the sympathetic chain (T6-T12) and terminate in the pre-aortic ganglia. These surround the major vessels (coeliac trunk, mesenteric arteries).
The post ganglionic fibres are then distributed with the arteries (they get into the wall of the arteries)
What cranial nerve are parasympathetic?
III - occulomotor
VII - facial
IX- glossopharyngeal
X- Vagus
What level is the sacral outflow?
S2 S3 S4
pelvis splanchic nerve
