Cranial nerves: parasympathetic function Flashcards
How can the ANS be divided?
Sympathetic System (thoracolumbar)
- Fight or flight
- Cell bodies are the lateral (intemediolateral) horn of T1-L2 spinal cord segments
Parasympathetic System (craniosacral)
- Rest and digest (Rest & respose)
- Cell bodies are at brain stem or S2-4 spinal cord segments
What pathway does the sympathetic system take?
2 neuron chain;
- Pre-synaptic neuron in the CNS synapses with the synaptic neuron in a ganglion
Sympathetic ganglia are located close to the ventral column -> short pre-synaptic fibres and long post-synaptic fibres (except splanchnic nerve)
- The sympathetic preganglionic neurons emerge from the cord
- They pass to the sympathetic trunk in white rami communicantes (WRC)
- Ascend in the chain
- After synapsing in a ganglion, the postganglionic fibres form grey ramus communicantes (GRC) that joins a spinal nerve in which it is distributed to the body wall
Where does the sympathetic system extend to ?
Each sympathetic trunk extends between the atlas and coccyx
Trunks fuse with each other in the single ganglion impar, opposite the coccyx
Sympathetic ganglia fuse in the cervical region;
- Superior (C1-4), middle (C5-6) and inferior (C7-8) cervical ganglia
- Inferior cervical + T1 -> Stellate Ganglion (cervicothoracic ganglion) (C7-T1)
What neurotransmitters are used in somatic, sympathetic and parasympathetic neurons?
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What are some key nerves that branch of the sympathetic trunk for the eye?
The sympathetic trunk synapses in the superior cervical ganglion and wraps around the internal carotid forming a plexus around it, leaving to supply the eye.
(The internal carotid makes it all the way to the foramen lacerum to give off arteries that supply the brain, finishing in cavernous sinus_
The sympathetic branches give off 2 branches to the eye - Long cilary nerve which innervates dilator pupilla
- Nasocillary nerve
- Oculomotor nerve
and also the oculomotor nerve (higher up) which innervates leaver palpebral superiors (shuts eyelid)
What is Horner’s Syndrome?
Interruption of sympathetic supply to head
You will see;
- Ptosis (drooping) of the upper eyelid
- Pupillary construction (miosis)
- Anhydrosis (lack of sweating)
- Flushing of face
What pathway does the parasympathetic system take?
2 neuron chain;
- pre-ganglionic neuron in the CNS synapses with the post-ganglionic neuron in a ganglion - parasympathetic ganglia are located close to the organ -> long pre-synaptic fibres and short post-synaptic fibres
What does the Oculomotor nerve (III) do in the parasympathetic system?
Its nucleus is the autonomic nucleus (Edinger-Westphall)
In midbrain
Afferents from cortex and pretectal nucleus bilaterally
Cavenous sinus -> Superior orbital fissure
Superior and infeiror divisions (rami) -> common tendinous ring of Zinn
What nerves come off the oculomotor nerve (III)?
- Superior ramus contains motor fibres from oculomotor nucleus + sympathetic fibres from superior cervical ganglion to levator palpebral superiors
- Inferior ramus contains parasympathetic fibres
- Parasympathetic fibres synapse in ciliary ganglion
- Postsynaptic fibres join short ciliary nerves
- Short ciliary nerves run alongside long ciliary nerves and ciliary artery and enter the eyeball to supply ciliary muscle + sphincter pupilla
What controls the light reflex?
- Optic nerve
- Optic tract
- Pretectal area:
- Pretecal nucleus
- Edinger-Westphal BILATERALLY (posteiror commissure)
- Oculomotor nerve
- Ciliary ganglion
- Short ciliary nerves
- Pupillary constrictor
When shine light in 1 eye picked up from optic nerve and cross over in optic chiasm - activated neurons in pretectal nucleus which has connections to booth autonomic motor nuclei
Both eyes will constrict, unless issue with crossing over in posterior commisure
What would you expect to see in an injury to the oculomotor nerve (III)
No parasympathetic input for pupil construction -> dilated pupil
Loss of motor innervation to elevator palpebral superioris -> Ptosis
Loss of motor innervation to extra ocular muscle except superior oblique (trochlear nerve) and lateral rectus (abduceeunt nerve) -> The eye turns downwards and outwards
What are the features of the facial nerve (VII) in the parasympathetic system?
- Superior salivatory nucleus in Pons
- Exits brainstem at Pontocerebellar angle
- Enters Internal acoustic meatus
How does the facial nerve (VII) supply the Lacrimal Gland ?
Parasympathetic are found in the Nucleus intermedius - through facial canal
Greater petrosal nerve - joins deep petrosal in foramen lacerum
Nerve of the pterygoid canal - through the pterygoid canal
synapse at Pterygopalatine ganglion which gives rise to the zygomatic nerve of the maxillary division (V2) which joins the Lacrimal branch of the ophthalmic division (V1) supply the lacrimal gland
How does the facial nerve supply the salivary glands?
Parasympathetic secretomotor supply to the submandibular and sublingual glands are in chorda tympani and they travel in the Lingual nerve synapsing at the submandibular ganglion
What are the features of the Glossopharyngeal nerve (IX) in the parasympathetic system?
The Glossopharyngeal nerve (IX) nucleus is the inferior salivatory nucleus found in the medulla
The Glossopharyngeal (IX) nerve passes through the jugular foramen together with the Vagus, accessory nerve and internal jugular vein
What does the vagus supply ?
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