organisation of the brainstem and the cranial nerves Flashcards
define the brainstem
the part of the CNS, exculsive of the cerebellum, that lies between the cerebrum and the spinal cord
major divisions of the brainstem *
medulla oblongata
pons
midbrain
where does the brainstem sit *
in the posterior cranial fossa
list and describe the features at visible from the posterior of the brainstem *
pineal gland - not bilateral, in control of circadian rhythms (light/dark) trained by eyes, control day night release of cortisol
superior colliculus - cause coordinated neck and eye movements, bump on back of brainstem
inferior colliculus - basic survival function - auditory reflex, look towards sound
dorsal columns - in medulla, touch and proprioception - damage cause loss - medial info from leg (gracile), lateral from upper half (cuneate)
4th ventricle - floor of 4th ventricle is in the pons, diamond space
trochlear nerve - CN4, small, supply superior oblique muscle of the eye
in imaging what is the roof of the midbrain referred to as
the tectum
which nerves don’t arise from in the brainstem *
CN1 and CN 2
features that you can see from the anterior of the brainstem *
optic chiasm pituitary stalk mammillary body cerebral peduncle oculomotor nerve trigeminal nerve abducens, fascial and vestibulocochlear nerves pyramids glossopharyngeal, vagus and accessory nerves hypoglossal nerves pyramidal decussation
describe the location of CN 1 - olfactory nerve *
top of nose
project through skull through Cribiform plate in ethmoid bone - to the olfactory bulb
describe path of the optic nerve CN2*
half nerves come from retina, cross over, to back of brain - occipital lobe
what is the optic chiasm *
where the cranial nerves cross over
where is the pituitary stalk in the brainstem *
in the midline
directly behind the optic chiasm
also called the infundibulum
location of the mamillary body *
bilaterally
base of the hypothalamus
describe the oculomotor nerve *
CN3
emerge at midline level, just below mamillary body
control eye movement
describe the cerebral peduncle *
they are motor fibres - come down from the motor cortex and into the spinal cord - forms part of the cortical spinal tract
describe the trigeminal nerve *
only cranial nerve that emerges only from the pons
sensory nerve of the head and neck - 3 divisions - small root next to larger root -some motor functions eg chewing
nuclei is all the way through the brainstem
general somatic afferent
describe the abducens, facial and vestibulocochlear nerve *
they emerge at the pontomedullary junction
medially to laterally
abducens - lateral rectus muscle - move eye laterally
fascial - fascial expression
vestibulocochlear - involved in balance and hearing - goes into the inner ear where there is the cochlear and vestibule - special somatic afferent
why is the pons called the pons
normally info is all transmitted up amnd down in brain - the pons goes across like a bridge between 2 halves of cerebellum
what is bell’s palsy
musculature has lost innervation from the facial nerve usually post infection
where do the glossopharyngeal, vagus and accessory nerve originate from and their functions *
the medulla
glossopharyngeal - tongue/pharynx - swallowing and breaking up food
vagus - PNS to whole body
accessory - supply muscle of shoulder and sternocleidomastoid muscle
where does the hypoglossal nerve come from and what does it do *
more medially than CN 9, 10, 11 in medulla
supply all muscle under tongue
describe the pyramids *
corticospinal tract in medulla
if there is a motor function to do with the corticospinal tract it is called pyramidal symptoms
what and where is the pyramidal decussation*
at the base of the medulla
where 95% of the motor fibres cross over - meaning motor function is contralateral
