cranial nerves Flashcards
what are cranial nerves 3-12 part of?
PNS but emerge in the brainste,
where do CNI and II come from?
higher up in the brain - they are extensions of the CNS
what does a cross section of the midbrain resemble?
upside down minnie mouse
what is at the back of the brain stem?
the colliculi
what are the peduncles?
they are white matter tracts made of motor fibres
what is the cerebral aqueduct contained in?
the central canal
what is a nucleus in the CNS?
a collection of cell bodies
what is the correlation of fibres and nuclei?
for each type of fibre within a cranial nerve there is a corresponding nucleus in the brain stem
how many nuclei does CNIII have and why?
CNIII carries somatic motor fibres for the extraoccular muscles which come from the extraocular nucleus. It also carries visceral autonomic control for the intraocular muscles which are the sphincter pupillae and the ciliary muscles and these come from the Edinger-Westphal nucleus
where does CNII exit from?
the interpeduncular fossa
what happens with injury to CNIII?
can injure both or just one function
where does the olfactory tract/ bulb come from?
the telencephalon
where are cranial nuclei found?
the are found spanning the length of the brainstem - there are many nuclei different fibre types that are in the medulla or midbrain.
where are sensory and motor nuclei found?
sensory more laterally and motor more medially within the brainstem - in tegmentum
what can be seen in the rostral medulla?
the fourth ventricle
for the head and neck what is found medially and laterally?
parasympathetic, motor and somatic motor are found medially and sensory laterally . They either carry sensory afferent or motor efferent fibres
what comprises somatic motor?
touch and temperature
what comprises special sensory?
smell, taste, hearing balance
what does visceral mean?
maintaining and monitoring the internal state of an organ
where are the cranial nuclei in relation to the ventricular system?
they are anterior to the ventricular system
where in relation to each other are each type of nucleus found?
most medially and ventrally there is the somatic motor, then slightly lateral is the parasympathetic motor and then dorsal to this is the head and neck motor. The visceral sensory is lateral, then more lateral to this is special sensory and then dorsal to these are somatic sensory
what is CNI?
olfactory nerve
what is the course of CNI?
it has receptors in the nasal cavity and sends fibres into the skull through the cribriform plate of the ethmoid bone. It synapses at the olfactory bulb and travels to the cortex through the olfactory which is an extension of the telencephalon.
what types of fibres are CNI?
special sensory for smell
how do you test CNI?
close one or the other nostril and smell
where do all sensory modalities go before the cortex?
EXCEPT SMELL all sensory modalities will go to the thalamus before the cortex
what is CNII?
optic nerve
what is the course of the optic nerve?
it is an extension of the diencephalon and enters the skull through the optic canal after emerging from the retina. Two optic nerves travel in the ventral view of the brain and meet at the chiasma, information sent by both eyes is sent to both areas of the brain. After information is merged with chiasma it is sent to the thalamus via the optic tract and then to the cortex
how many nerves carry motor only?
5 purely motor, 3 purely sensory and rest are mixed
what is the definition of a sensory and motor nuclei?
sensory - receive information from fibres entering the brainstem in cranial nerves which synapse here and then nuclei send fibres to appropriate higher centre
motor - will receive information from higher centre which synapse in nuclei and then give rise to motor fibres which leave brainstem in cranial nerves
where are CNI and II derived from?
forebrain
what is the function of CNII?
special sensory for vision - various visual tests
what do CNIII, IV and VI innervate?
all the muscles that move the eyeball - the extraocular - seen when eyeball removed
what foramen do CNIII, IV and VI leave the skull from?
the superior orbital fissure to the eyeball
what tests can be done for CNIII, IV and VI?
follow finger
what muscle elevates the eyelid?
the LPS (levator palpebrae superioris)
what innervates SR, IR, IO and MR and LPS?
CNIII
where is CNIII found?
pontomesencephalic junction
what are the functions of III?
somatic motor- four extraoccular muscles
visceral motor - ciliary muscle and the sphincter pupillae
what is the location and function of IV?
it is found in the dorsal midbrain and is somatic motor to the superior oblique
what is VI, where is it found and what is the function?
abducens, pontomedullary junction, somatic motor to the lateral rectus
what moves the eye a) to the midline and b) laterally?
a) adduction - medial rectus - III
b) abduction - lateral rectus which comes from VI
why can injury to one muscle affect different eye movements?
other movements are a combination of muscles
what closes and opens the eye?
closes is orbicularis oculi (VII) and opposing this to open the eye is the superior tarsal (smooth sympathetic) and LPS (III)
what dilates the pupil?
the dilators of the iris (sympathetic)
what opposes dilation?
sphincter of pupil and ciliary muscles to control shape of the lens - parasympathetic visceral motor III
what moves the eyeball up and laterally?
the superior rectus to elevate and inferior oblique to move laterally
what moves the eyeballs side to side?
lateral and middle rectus
what moves the eyeball down and laterally?
the superior oblique and the inferior rectus
what are the divisions of the trigeminal nerve?
V1: opthalamic
V2: maxillary
V3: mandibular
what are the foramens CNV divisions pass through and what is the origin of the divisions?
V1: superior orbital fissure
V2: foramen rotundum
V3: foramen ovale
they originate from the trigeminal ganglion
