Autonomic Innervation Of Head And Neck Flashcards
Name 3 structures of the head and neck that receive autonomic Innervation
- Eye (Smooth muscle associated with pupil, lens and eyelid)
- Salivary glands
- Lacrimal glands
Where does the Sympathetic outflow to the whole body arise from?
What about outflow to head and neck?
Where do Preganglionic fibres synapse ?
- Arises from Thoracolumbar portion of spinal cord (T1-L2)
- T1 and T2 segments of spinal cord
- Synapse with ganglion of sympathetic chain
Describe the path of the Sympathetic fibres to the head and neck
- Preganglionics arise from T1, T2 segments
- Ascend the sympathetic chain and synapse with the Superior and Middle Cervical Ganglia
- Postganglionics ‘hitch hike’ onto blood vessels to reach target tissues in head and neck
(E.g Follows ICA-> Ophthalmic to reach eye)
What are the 3 Upper Cervical Ganglia of the head and neck
- Superior Cervical
- Middle Cervical
- Inferior Cervical
(Sympathetic Preganglionics synapse with Superior and Middle)
What 3 things characterise Horner’s Syndrome
Interference with sympathetic innervation to head and neck
- Partial Ptosis
- Miosis
- Anhydrosis (Absence of sweat)
Compare Ptosis in Horner’s syndrome and Oculomotor Nerve lesion
Horner’s;
- Sympathetically innervated Smooth muscle component of Levator Palpaebrae Superioris not functioning
- Skeletal component innervated by CN III still functioning
- Thus, still a significant function of LPS maintained
CN III Lesion;
- Skeletal AND Smooth muscle components of LPS not functioning
- Thus weaker acting of LPS
Compare and explain the pupil size in Horner’s Syndrome and a CN III lesion
Horner’s;
- No sympathetic innervation to dilator muscle, so unopposed parasympathetic action of CN III
- Sphincter Pupillae constricts pupil
- MIOSIS
CN III Lesion;
- No parasympathetic innervation to SP, so unopposed action of dilator muscle
- Dilator muscle dilates pupil
- MYDRIASIS
What 4 cranial nerves ‘carry’ parasympathetic fibres from brainstem
- Oculomotor (III)
- Facial (VII)
- Glossopharyngeal (IX)
- Vagus (X)
Where does the Parasympathetic outflow arise from?
- Cranial region (4 Cranial nerves)
- Sacral region (S2-S4)
Known collectively as Craniosacral outflow
What does the cranial portion of craniosacral outflow provide innervation to?
- Head and neck structures
- Structures in thorax and abdomen (Via CN X)
The Parasympathetic Nuclei (Collections of cell bodies) lie in the Brainstem, close to the Nuclei of the cranial nerves
What is the significance of this?
When leaving the brainstem, the parasympathetic fibres ‘hitch hike’ onto the 4 cranial nerves
The parasympathetic outflow to the head and neck does not have a chain of ganglia like the sympathetic, but has 4 ganglia.
Name the 4 parasympathetic ganglia of the head and neck
- Ciliary (From CN III)
- Submandibular (From CN VII)
- Pterygopalatine (From CN VII)
- Otic (From CN IX)
Outline the path of the Parasympathetic fibres to Innervate their target tissues in the head and neck
- Arise from brainstem from parasympathetic nuclei
- ‘Hitch hike’ onto Cranial Nerves
- Reach and synapse with Parasympathetic ganglia
- Postganglionics ‘hitch hike’ onto branches of CN V
- Continue to reach target tissues
(CN fibres do not synapse with the ganglia, bur simply run through)
There are 4 parasympathetic nuclei in the brainstem, and each is related to 1/more cranial nerves.
Name and describe 1 of these
Edinger Westphal is associated with CN III
Name and describe the Pre and Postganglionics associated with the Ciliary ganglion
Preganglionic;
- CN III carries parasympathetic fibres from Edinger Westphal nucleus
Postganglionic;
- Parasympathetic innervation to Ciliary Muscle and Sphincter Pupillae muscles
Describe the Pupillary Light Reflex
- Optic nerve senses light and carries info to Optic Chiasm and Optic Tract
- Communication between Optic Tract-> Brainstem, where info reaches Edinger Westphal nucleus on both sides of brainstem
- On both sides, Preganglionics leave EDW with CN III fibres, and synpase with Ciliary Ganglion
- Innervation of left and right Spincter Pupillae muscles
The Pupillary Light Reflex is made up of the Direct and Consensual Light Reflexes
Compare them
Direct: Pupil constricts in eye that light is shone into
Consensual: Pupil constricts in opposite eye that light is shone into
Describe the pathway of the Parasympathetic fibres carried by the Facial Nerve through the Pterygopalatine Ganglion to their target tissues
- After branching off Geniculate Ganglion, Greater Petrosal nerve carries preganglionics to Pterygopalatine ganglion
- Postganglionics from Pterygopalatine ganglion continue to innervate Lacrimal Gland and Mucosal Glands of Nasal cavity and palate
Describe the pathway of the Parasympathetic fibres carried by the Facial Nerve through the Submandibular Ganglion to their target tissues
- In Petrous bone, Chorda Tympani carries preganglionics to Submandibular Ganglion
- Postganglionics continue to innervate Salivary Glands (Submandibular and sublingual)
Describe the pathway of the Parasympathetic fibres carried by the Glossopharyngeal Nerve to their target tissues
- Preganglionics arise from brainstem and exit with CN IX, which exits through Jugular Foramen and splits into multiple branches, one of which is the Tympanic Nerve
- Initially preganglionics run with Tympanic Nerve, then exit Middle Ear as Lesser Petrosal Nerve
- Preganglionics synapse with Otic Ganglion in Infratemporal Fossa, and postganglionics ’hitch hike’ onto Auriculotemporal branch of Vc
- Continue to innervate Parotid Gland
What does the Tympanic Nerve innervate?
Sensory innervation to Middle Ear
Describe the pathway of the Parasympathetic fibres carried by the Vagus Nerve to their target tissues
(Not associated with any discrete ganglia of head and neck)
- Preganglionics travel with Vagus nerve down the neck and into the thorax
- Preganglionics meet and synapse in Ganglia very close to/ within target tissues
List 3 target tissues of Vagus Nerve
- Heart
- Smooth muscle and mucosal glands of GI and Respiratory tracts
- Mucosal glands in pharynx/ larynx
