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
why is there functional classification of the CN
because they have some specific functions different to other nerves
describe general somatic afferent CN *
this type of nerve is all over body, they are related to the body, they arrive at the CNS - for CN they receive sensation from the skin and mucous membranes in mouth
describe general visceral afferent CN *
they receive innervation from the GI, heart, vessels and lungs going to the brain
describe general somatic efferent CN *
muscles for eye and tongue movement
describe general visceral efferent *
preganglionic PNS - vagus - modulate gut movements
describe special somatic afferent *
doesn’t apply to whole body
vision, hearing, equilibrium
describe special visceral afferent *
smell and taste
describe special visceral efferent *
muscles involved in chewing facial expression, swallowing, vocal sounds and turning head - CN11
describe the sulcus limitans *
differentiates between the ventral motor and the dorsal sensory
rombencephalon *
hind brain
summarise where the motor and sensory nuclei are in the brainstem *
motor - medial
sensory - lateral
[image]
where are the different classifications of motor CN nuclei in the brainstem from medial to lateral *
GSE
SVE
GVE
where are the different classifications of sensory CN nuclei in brainstem from medial to lateral
GVA/SVA
GSA
SSA
how is the midbrain recognisable on a transverse image*
general shape - micky mouse - ears are the cerebral peduncles
cerebral aqueduct - only in the midbrain
substantia nigra - black substance, neuromelanin in dopinergic cells project to basal ganglia, if not present it is responsible for the motor symptoms of Parkinsons
inferior colliculus - the roof of the midbrain
[image]
how is the pons recognisable on a transverse image *
4th ventricle
middle cerebral peduncle - where the fibres join to the cerebellum
transverse fibres
how is the medulla recognisable on a transverse image *
4th ventricle
inferior olivary nucleus - high in medulla
pyramids
how is the LOWER medulla recognisable in a transverse image *
dorsal columns
central canal for the spinal cord
pyramidal decussation
describe lateral medullary syndrome
thrombosis of vertebral artery/posterior inferior cerebella artery - blood clot stop flow into the area
vertigo - because vestibular nerve is affected therefore lose balance perception
loss of balance because of inferior cerebral peduncle - fibre from spinal cord
ipsilateral cerebral ataxia - unsteady on feet
hoarseness/difficulty in swallowing - loss innervation to throat because N ambiguous affected
ipsilateral loss of pain/thermal sense - face because of spinal nuclei of the peduncle
contralateral loss of pain/thermal sense - spinothalamic tract affected
horner’s syndrome - loss of SNS innervation because sympathetic tract is affected - pinpoint pupil, reduced sweating
where are the nuclei for the oculomotor CN *
medial midbrain
motor
GSE
where are the nuclei for the trochlear CN *
medial midbrain
lower than oculomotor
GSE
where is the nuclei for the trigeminal motor nerve *
pons
SVE
where is the nuclei for the facial nerve *
pons
lower than trigeminal m
SVE
where is the nuclei for the abducens *
completely in pons
GSE
where is the nuclei for the salivatory *
pons and medulla
GVE
what makes up the salivatory nuclei *
glossopharyngeal and motor nerve cell bodies
where is the nuclei for the vagus nerve *
medulla
GVE
where is the ambiguus nuceli *
medulla
SVE
what is the ambiguus nuclei *
innervate muscle of pharynx and output of many cranial nerves
where is the nuclei for the hypoglossal nerve *
medulla
GSE
where is the nuclei for the accessory nerve *
cervical spinal cord
SVE
where is the trigeminal nucleus *
GSA
all the way down brain stem
where is the vestibulocochlear nucleus *
pons and medulla
SSA
where is the solitaries nucleus *
for taste
pons and medulla
GVA/SVA
what is the Edinger Westphal nucleus *
nuclei for PNS innervation of the eye
in midbrain
GVE
