Head And Neck Week 5 Flashcards
Describe some general differences between the parasympathetic and sympathetic nervous systems
Sympathetic origin - Thoracolumbar
Parasympathetic origin - Craniosacral
Sympathetic - shorter preganglionic (chain), longer postganglionic
Parasympathetic - longer preganglionic, shorter postganglionic (effector tissue)
Sympathetic - fight or flight
Parasympathetic - rest and digest
Sympathetic - chain of ganglia
Parasympathetic - number of discrete ganglia
What is the autonomic nervous system?
Component of the peripheral nervous system, controls body functions not under conscious control and plays a critical role in maintaining and regulating the body’s internal environment
Give examples of structures in the head and neck that receive autonomic supply
Smooth muscle (blood vessels, eye) Glands (sweat, salivary, lacrimal)
Where does the sympathetic outflow arise from?
T1-L2
Where does the sympathetic outflow to head and neck structures arise from?
T1/T2 spinal segments
Where do the preganglionic sympathetic fibres to head and neck structures synapse?
Upper (cervical) ganglia:
Superior and middle
How do the postganglionic sympathetic fibres reach their target tissues?
Hitch hike onto blood vessels - carotid plexus
And then Trigeminal nerve (CN V)
Which portion of the spinal cord supplies parasympathetic innervation to the head and neck (as well as thorax and abdomen) ?
Cranial portion
Where do the parasympathetic nuclei lie?
Brainstem - close proximity to cranial nerve nuclei
What do the preganglionic parasympathetic fibres do once leaving the brainstem?
Hitch hike on cranial nerves
How many parasympathetic ganglia are there in the head and neck and what are they called?
4 Ciliary Pterygopalatine Submandibular Otic
Onto which cranial nerves do preganglionic parasympathetic fibres of the head and neck hitch hike?
III, VII, IX and X
What happens to the postganglionic parasympathetic fibres after the ganglion?
Hitch hike onto branches of trigeminal nerve to reach target tissues
Where is the ganglion for parasympathetic fibres of the vagus nerve?
Do not have a discrete ganglion within the head
travel some distance with the vagus nerve down the neck, and into the thorax
remain with the vagus nerve until the autonomic fibres meet and synapse in ganglia very close to or within its target effector tissues e.g. mucous membrane glands of pharynx, larynx, thorax and abdomen and the heart.
Which head and neck structures receive sympathetic innervation?
Smooth muscle of blood vessels - vasoconstriction
Smooth muscle eyelid - tarsal muscle-assists in retracting eyelid
Smooth muscle iris - dilator pupillae-dilates pupil
Sweat glands - sweating
Arrector pili muscles - hair follicles stand on end
Salivary and lacrimal glands - decreased secretion
Describe the structures of the head and neck innervated by parasympathetic nerves?
Smooth muscle of iris (sphincter pupillae - constriction) and ciliary body (lens thickness)
Lacrimal glands
Mucosal glands
What is Horner’s syndrome?
Interruption of sympathetic nerve supply to head and neck structures
Pathology relates to anatomical relations of sympathetic nerve supply on route from spinal cord to head:
- apex of lung - pancoast tumours
- carotid artery dissection
What are the main causes of Horner’s syndrome?
Apical lung tumour (pancoast)
Carotid artery dissection
What are the classic symptoms of Horner’s syndrome?
Miosis (constriction of pupil- dilator pupillae not functioning) Partial ptosis (tarsal muscle affected - levator palpebrae superioris unaffected) Anhydrosis (sympathetic innervation of sweat glands lost)
Which parasympathetic ganglia correspond to which cranial nerves?
Ciliary - Oculomotor
Pterygopalatine - Facial
Submandibular - Facial
Otic - Glossopharyngeal
How do the parasympathetic fibres hitch hike onto trigeminal nerve branches?
A branch of the trigeminal runs through the parasympathetic ganglia and picks up postganglionic parasympathetic fibres to reach target tissues (except vagus nerve)
What is the rule of 4s concerning the parasympathetic supply to the head and neck ?
4 nuclei: Edinger Westphal Superior salivary Inferior salivary Dorsal motor 4 cranial nerves: Oculomotor Facial Glossopharyngeal Vagus 4 ganglia: Ciliary Pterygopalatine Submandibular Otic
Describe the course and functions of the parasympathetic portion of the oculomotor nerve
Brainstem –> hitch hikes on CN III –> ciliary ganglion –> hitch hikes on V1 (ophthalmic) –>eye - sphincter pupillae and ciliary body
Function : constriction of pupil, contract - thickens lens
Which part of the nervous system is responsible for the pupillary light reflex?
Parasympathetic
Describe the branches and functions of the facial nerve (including course of parasympathetics)
Brainstem –> hitchhike on CN VII
CN VII exits cranium through internal acoustic meatus into facial canal
CN VII Goes through geniculate ganglion (sensory ganglion)
CN VII divides into chorda tympani, greater petrosal, nerve to stapedius and motor branches of the facial nerve
Greater petrosal - travels through hiatus of facial canal/greater petrosal nerve
- parasympathetic travels to pterygopalatine ganglion –> lacrimal gland, nasal and oral mucosa
- sensory - soft palate - geniculate ganglion
Chorda tympani - travels through stylomastoid foramen -
carries - special sensory to anterior 2/3 of tongue (geniculate ganglion)
-parasympathetic to salivary glands –>submandibular ganglion –> salivary glands
Nerve to stapedius - supplies stapedius muscle - if muscle not functioning get hyperacusis (intolerance to sound levels that arent normally an issue)
Motor branch - travels through stylomastoid foramen - muscles of facial expression
Compare the signs and symptoms if pathology were to occur at or before the geniculate ganglion v.s. If the pathology occurred after the geniculate ganglion
At or before - All functions of the facial nerve affected
After - spares functions of greater petrosal nerve (lacrimal glands, nasal and oral mucosa, sensory soft palate) - if the lesion is after other branches - those functions will be spared also
Compare the signs and symptoms seen in Horner’s syndrome to those seen in an oculomotor nerve lesion and explain the differences
Oculomotor lesion:
Eye down and out position - superior oblique lost
Ptosis (complete) - levator palpebrae superioris lost
Mydriasis (dilated pupil) (parasympathetic lost)
Horner’ syndrome:
Anhydrosis - sweat glands of the face (sympathetic lost)
Partial ptosis - superior tarsal muscle/mullers muscle (sympathetic lost)
Miosis (contracted pupil) (sympathetic lost)
Describe the course of the parasympathetics to the head and neck (from nucleus to branch of CNV)
Edinger Westphal nucleus –> Oculomotor –> ciliary ganglion –> branches of ophthalmic (v1) - short ciliary nerves
Superior salivatory nucleus –> Greater petrosal –> pterygopalatine ganglion –> maxillary (v2)
Superior salivatory nucleus –> Chorda tympani –> submandibular ganglion –> lingual branch of mandibular nerve (v3)
Inferior salivatory nucleus –> Glossopharyngeal –> otic ganglion –> auriculotemporal branch of mandibular nerve (v3)
Describe the course and function of the parasympathetics carried by the glossopharyngeal nerve
Glossopharyngeal nerve –> jugular foramen –> tympanic nerve –> tympanic plexus –> joins lesser petrosal (which originated from geniculate ganglion and passed through foramen ovale) –> otic ganglion –> auriculotemporal nerve –> parotid gland
Innervates the parotid gland (increase secretion)
What do parasympathetics of the vagus nerve innervate?
Meets ganglion in target tissue
Glands - laryngopharynx, larynx, oesophagus and trachea
Viscera of thorax and abdomen
