Cranial Nerves: Descending nerves Flashcards
What are the divisions of the nervous system?
- Sympathetic (thoracolumbar)
* Parasympathetic (craniosacral)
Where are the cell bodies of the sympathetic system located?
In the lateral horn of T1-L2 spinal cord segments
Where are the cell bodies of the parasympathetic nervous system located?
In the brain stem or s2-4 spinal cord segments
Where are the sympathetic ganglia located?
Close to the vertebral column
Describe the sympathetic neurone chain
- Short pre-synaptic fibres (pre-ganglionic) emerge from the cord and pass to the sympathetic trunk in the white rami communicantes
- Long post synaptic fibres - after synapsing in a ganglion, fibres from the grey ramus communicantes join a spinal nerve
- Then it is distributed to the body wall
Where do the sympathetic chains fuse?
At the ganglion impair, opposite the coccyx
Sympathetic ganglia
- Superior cervical ganglion: C1- C4
- Middle cervical ganglion: C5, C6
- Inferior cervical ganglion: C7,C8
- Stellate ganglion is formed from the inferior cervical ganglion and T1 (C7,8)
What are the symptoms of Horner’s syndrome?
- Ptosis
- Pupillary constriction
- Anhydrosis
- Flushing of the face
Where are the parasympathetic ganglia located?
Close to the organ
Which of the cranial nerves contain parasympathetic fibres?
- CN III oculomotor
- CN VII facial
- CN IX glossopharyngeal
- CN X Vagus
What and where is the nucleus for oculomotor?
- In the Midbrain
* Autonomic nucleus - Edinger Westphall
What are the afferents of the oculomotor nerve?
• From the cortex and pretectal nucleus bilaterally
Describe the course of oculomotor
- In the interpeduncular fossa, it runs between the superior cerebellar and inferior cerebral arteries
- Runs in the lateral wall of the cavernous sinus
- Travels through the superior orbital fissure into the orbit
Superior ramus of the oculomotor nerve
- Motor fibres to levator palpebra superioris
* Sympathetic fibres from the superior cervical ganglion to the same muscle
Inferior ramus of the oculomotor nerve
- Parasympathetic fibres which synapse in the ciliary ganglion
- Post synaptic fibres join short ciliary nerves which run alongside the long ciliary nerves and ciliary artery, enter the eyeball and supplies the ciliary muscle and sphincter pupilla
Describe the route of the impulse in the light reflex
- Optic nerve
- Optic tract
- Pretetal area: pretectal nucleus
- Edinger Westphal bilaterally
- Oculomotor nerve
- Ciliary ganglion
- Short ciliary nerves
- Pupillary constrictor
Describe the results of injury to the oculomotor nerve
- No parasympathetic input for pupillary constriction - dilated pupil
- Loss of motor innervation to levator palpebral superioris - ptosis
- Loss of motor innervation to extra ocular muscles except superior oblique and lateral rectus - eye turns down and out
Where and what is the nucleus of the facial nerve?
• Superior salivatory nucleus in the pons
Where does the facial nerve exit the brainstem?
• Pontocerebellar angle
Describe the course of the facial nerve
- Enters the internal acoustic meatus
- Parasympathetics are found in n.intermedius through the facial canal
- Greater petrosal nerve joins the deep petrosal in the foramen lacer to form the nerve of the pterygoid canal
- Synapses at the pterygopalatine ganglion
What supplies the submandibular and sublingual salivary glands?
• The lingual nerve (branch of the facial) carries parasympathetic from the facial nerve, secretomotor supply to the submandibular glands
Where and what is the nucleus of the glossopharyngeal nerve?
- Inferior salivatory nucleus
* In the medulla
Where does the glossopharyngeal nerve leave the brainstem?
Posterior to the olive
Which nerves pass through the jugular foramen (+vessel)?
• Glossopharyngeal
• Vagus
• Accessory nerve
(• Internal jugular vein)
Describe the course of the glossopharyngeal nerve
- Inferior to the jugular foramen, gives off the tympanic nerve which forms the tympanic plexus giving off the lesser petrosal , synapses in the optic ganglion
- Post synaptic fibres join the auriculotemporal nerve and it innervates the parotid gland
