Sensory and Motor Supply of the Head Flashcards
What are the 12 cranial nerves?
- I = olfactory
- II = optic
- III = oculomotor
- IV = trochlear
- V = trigeminal
- VI = abducens
- VII = facial
- VIII = vestibulocochlear
- IX = glossopharyngeal
- X = vagus
- XI = accessory
- XII = hypoglossal
Describe if each cranial nerve is sensory, motor or both and also if they are afferent, efferent or both
- I = sensory, afferent
- II = sensory, afferent
- III = motor, efferent
- IV = motor, efferent
- V = both, both
- VI = motor, efferent
- VII = both, both
- VIII = sensory, afferent
- IX = both, both
- X = both, both
- XI = motor, efferent
- XII = motor, efferent
Describe the pathway of the trigeminal nerve
first branchial branch given off from the lateral side of the pons then passes to the middle cranial fossa, where it gives off 3 main branches
What are the 3 main branches of the trigeminal nerve?
- ophthalmic (V1)
- maxillary (V2)
- mandibular (V3)
What does the trigeminal nerve supply sensory function to?
everything in front of the vertex-ear-chin line
What is the only motor supply of the trigeminal nerve?
innervation of the muscles of mastication
Describe the pathway of the ophthalmic division of the trigeminal nerve
runs in the lateral wall of the the cavernous sinus then enters the orbit through the superior orbital fissure
What does the ophthalmic division supply sensory function to?
- skin of the face above the eye
- eyeball
- external nose
What part of the corneal reflex does the ophthalmic division mediate?
the afferent limb by the nasociliary branch
What does the maxillary division of the trigeminal nerve supply sensory function to?
- part of the face below the eyes
- upper lip
- palate
- paranasal sinuses
- upper teeth
Describe the pathway of the maxillary division of the trigeminal nerve
it passes along the lateral wall of the cavernous sinus then exits through the foramen rotundum to the pterygopalatine fossa
What does the mandibular division of the trigeminal nerve supply sensory function to?
- lower part of the face including lower lip, anterior ear and chin
- lower teeth
- anterior 2/3 of the tongue
What does the mandibular division supply motor function to?
- muscles of mastication for biting and clenching of the jaw
- afferent and efferent limbs of the jaw jerk reflex
What does lesion of the trigeminal nerve lead to?
- sensory loss of the face
- weakness of the muscles of mastication
What does lesion of the lingual nerve lead to?
- loss of general sensation and taste to the anterior 2/3 of the tongue
- salivary secretion from the submandibular and sublingual glands
What is trigeminal neuralgia marked by?
shock-like pain along the course of the trigeminal nerve, especially radiating to the maxillary or mandibular area
What are common causes of trigeminal neuralgia?
aberrant blood vessels or aneurysms compressing on the trigeminal nerve at the base of the brain
Describe the pathway of the facial nerve
second branchial branch that leaves the pons at the pontomedullary junction then enters the internal acoustic meatus together with the vestibulocochlear nerve VIII
What is the internal acoustic meatus?
the facial canal in the temporal bone
What are the 5 terminal branches of the facial nerve?
- temporal
- zygomatic
- buccal
- marginal mandibular
- cervical
What does the facial nerve supply motor function to?
muscles of facial expression
What are the muscles of facial expression for the upper face?
- frontalis - raises the eyebrow
- orbicularis oculi - closes the eyelids
What are the muscles of facial expression for the lower face?
- zygomaticus major and minor - smile
- levator labii superioris - smile
- orbicularis oris
What does the facial nerve do in the eye blink reflex?
mediate the efferent limb of the reflex i.e. the closure of the orbicularis oculi
Where are all the sensory bodies for the facial nerve?
the geniculate ganglion
What does the facial nerve give sensory supply to?
- taste fibres on the anterior 2/3 of the tongue
- a small number of fibres from the external acoustic meatus and the auricle
What does lesion of the facial nerve cause?
Bell’s palsy
What is Bell’s palsy characterised by?
distortion of the face e.g. no wrinkles on forehead, dropping of the eyebrow, inability to close or blink the eye, sagging corner of the mouth and inability to smile, whistle or blow
What does Bell’s palsy lead to?
- loss of taste in the anterior 2/3 of the tongue
- decreased salivary secretion and lacrimation
- painful sensitivity to sounds
Where does the lower motor neuron of the face receive commands from?
upper motor neurons from the opposite cerebral cortex
Where does the upper motor neuron of the face receive commands from?
upper motor neurons from the cerebral cortex of both sides
What does damage to the upper motor neuron cause?
paralysis of muscles in the lower face but not upper face of the contralateral side
What is the pathway of the glossopharyngeal nerve?
given off from the medulla oblongata then leaves the skull through the jugular foramen together with cranial nerves X and XI
What does the glossopharyngeal nerve supply sensory function to?
- posterior third of the tongue
- soft palate
- pharynx
- middle ear
- carotid sinus and carotid body
What does the glossopharyngeal nerve supply motor function to?
- one muscle of the pharynx
- parotid gland
What does a lesion of the glossopharyngeal nerve lead to?
- loss of motor fibres to the stylopharyngeus muscle
- loss of taste on the posterior third of the tongue and vallate papillae
- loss of the afferent limb of the gag reflex
What is pharyngitis?
a condition that can lead to glossopharyngeal neuralgia which manifests as a sore throat and severe ear pain
Describe the pathway of the Vagus nerve
it is given off from the medulla oblongata then leaves the skull through the jugular foramen
What does the Vagus nerve supply motor function to?
the muscles involved in swallowing and voice production, including most of the muscles of the soft palate and pharynx and larynx (voice box)
Which reflexes does the Vagus nerve mediate?
- efferent limb of the gag reflex
- cough reflex
- efferent limb of sneeze reflex
What smooth muscle and glands does the Vagus nerve provide parasympathetic preganglionic innervation to?
- pharynx
- oesophagus
- GI tract
What do lesions of the Vagus nerve lead to?
- loss of the gag reflex
- dysphagia (difficulty in swallowing)
- dysphonia (difficulty in speaking)
- aphonia (loss of voice)
- numbness of the lower part of the larynx
What are the 2 components of the accessory nerve and what are they given off from?
- cranial given off from medulla oblongata
- spinal given off from spinal cord
Describe the pathway of the cranial accessory nerves
leave the skull through the jugular foramen to join the Vagus nerve then are distributed as Vagus nerve branches to muscles of the pharynx and larynx
What muscles does the spinal accessory nerve supply and what do they do?
- sternocleidomastoid - turns the head
- trapezius - shrugs the shoulders
What does lesion of the spinal accessory nerve cause?
- torticollis (wry neck) because of paralysis of the sternocleidomastoid
- shoulder drop from paralysis of the trapezius
Describe the pathway of the hypoglossal nerve
it leaves the medulla oblongata and passes through the hypoglossal canal in the skull
What does the hypoglossal nerve supply motor function to?
almost all muscles of the tongue
What does lesion of the hypoglossal nerve lead to?
the tongue deviating to the injured side during protrusion
