Cranial Nerves CN VIII- CNXII Flashcards
what is the cranial nerve CN VIII
VESTIBULOCOCHLEAR NERVE
what are the two divisions of vestibulocochler nerve
the cochlear division
the vestibular division
what does the cochlear division do
The cochlear division of this nerve carries sound information from the organ of Corti in the cochlea
What does the vestibular division do
The vestibular division transfers information about balance and posture from the vestibular organ (the semicircular canals, the utricle and the saccule)
- it is functional associated with the cerebellum and oculomotor nuclei
what is the main functions of the vestibular systems on the vestibule nerve
- maintaining balance
- stablising the eye
what are the two components of monitoring motion
- must be able to detect rotation
- must also be able to detection motion along a line
what is the vestibular system divided into in order to monitor motion
- it is divided into two receptor organs
1. The semicircular canals detect angular acceleration/deceleration of the head.
2.The utricle and saccule detect linear acceleration and the pull of gravity.
how do you monitor eye movements
- there is complex connections between the 3 vestibular nuclei and the cranial nerve nuclei that control eye movement by a pathway called the medial longitudinal fasculus
what 2 reflexes does the vesitbular nerve participate in
the oculocephalic reflex (dolls eye manouvre) and the oculovestibular (caloric) reflex.
what are the clinical test that you can use in order to assess the vesicular never function
Doll’s eye reflex:This involves conjugate eye movements in response to head movement. This is performed with the patient lying down and the normal response is for the patients eyes to deviate in the opposite direction to head turning i.e. if the head is briskly extended, the eyes go downwards and if to the right, the eyes move to the left.
Caloric reflex:The caloric test involves irrigation of the ears with cold or warm water that set up convection currents in the semicircular canals and induce nystagmus of the eyes. The normal response to irrigation with cool water is for the nystagmus to develop towards the contralateral side and towards the irrigated ear if warm water is used.
Gait and station:Various patterns of gait abnormalities occur with different disorders. The test of gait is probably the most useful motor system test and should be observed in all patients.
- Gait: The patient walks normally back & forth at a moderate rate; he/she then walks on their heels and toes and tandem along a straight line, touching heel to toe; the patient then hops on each leg.
- Station - Romberg’s test: Ask the patient to stand with their feet together, initially with their eyes open and then with them shut. There should be little or no sway. Where there is proprioceptive or vestibular damage, balance is impaired only when the eyes are shut and the patient may fall over.
what are the similarities between the glossopharyngeal nerves and vagus nerves
- they are mixed nerves that convey somatic and visceral information to and from various brainstem nucleic
- they both contain parasympathetic fibres that innervate the parotid gland (CNIX) and viscera of the neck, thorax and abdomen (CNX)
what nerve is CNIX
glossopharyngeal
What nerve is CN X
vagus nerve
what does CN IX do
- primarily a sensory nerve that mediates taste, salivation and swallowing (together with CN X).
- CN IX also monitors blood pressure and blood CO2/O2 levels (from the carotid sinus and body respectively).
what does the CN X do
- they vagus alone innervates the larynx and is primarily involved in phonation
where does the sensory input from the posterior pharynx, external ear skin, dura (posterior fossa) and the tympanic membrane terminate in
spinal trigeminal nucleus (CN V)
what projection to the solitary nucleus
Taste bud (visceral) fibres of the tongue (CN IX) and epiglottis (CN X) and carotid afferents (CN IX) project to separate regions of the solitary nucleus.
where do motor fibres from CN IX and X originate from
nucleus ambiguous
what do the motor fibres of CN IX and X supply
- brachial arch muscles that control movements of the soft palate, pharynx and larynx
what reflexes are CN IX and X involved in
The gag reflex - constriction and elevation of the pharynx and palate in response to tactile stimulation of the posterior oropharynx and tonsils.
Oculocardiac reflex - pressure on the eyes slows the heart rate.
Carotid reflex - masssaging the neck over the carotid bifurcation causes heart rate to slow.
how do you test the glossopharyngeal and vagus nerve
- Ask Patient to Swallow tests integrity of pharyngeal muscles
- Ask Patient to Say “Ah” and watch the movements of the soft palate and the pharynx. The ulvula and palate usually lift centrally; unilateral damage causes uvula deviation to the good side and bilateral lesion means no lifting.
- Test Gag Reflex
Stimulate the back of the throat on each side. It is normal to gag after each stimulus. Absence of a gag reflex could mean damage to the CN IX nerve (afferent limb loss of sensation) or efferent limb (CN X) to the pharyngeal muscles.
- Assess laryngeal function by asking patient to speak and cough. Is it hoarse or nasal? Is the cough weak?
- Ask patient to puff out cheeeks – to do this the palate must elevate to close off the nasopharynx. If movement is weak, air will audibly escape through the nose
what is cranial nerve CN XI
accessory
what type of nerve is the accessory nerve
motor
where does the cell bodies of the accessory nerve lie
- lie in the ventral horn C1-C5
