Neuroanatomy 3 Flashcards
what is the internal capsule?
white matter area
visual, motor and many other modalities of information pass through here, therefore a stroke here can be very serious - can cause a lack of descending control of the corticospinal tract causing a spastic paralysis with hyperflexion of the upper limbs (decorticate posturing)
a lesion at the level of the midbrain causes what symptoms?
causes lack of descending cortical control of vestibulospinal tract
this leads to domination of extensor muscles and hyperextended spastic paralysis
brown sequard’s syndrome?
caused by lateral hemisection of the spinal cord
e. g lesion on right side of spinal cord
- ipsilateral paralysis as motor nerves (corticospinal tract) have already crossed over in the medulla on the way down from the brain so will be on the ipsilateral side to the muscles controlled and will be affected by the injury
- ipsilateral loss of vibratory sense and proprioception as medial lemniscus pathway doesn’t cross over until the medulla on the way up
- contralateral loss of pain and temp sensation as spinothalamic tract crosses over at the level of entry to the spinal cord
what other things feed into the primary motor cortex to determine type, strength of movement/contraction etc?
cingulate motor area
supplementary motor area
premotor area
(all can also directly project directly to the spinal cord)
function of basal ganglia and cerebellum in movement?
cerebellum receives input from sensory fibres as you are moving and relays this through the thalamus to the motor cortex to plan and execute movement
basal ganglia also feed information through thalamus to improve movement
(knows how you are moving so can coordinate how movement continues through the thalamus, then to the cortex)
lobes of the cerebellum
anterior
posterior (biggest)
flocculonodular lobe (like little ears at the base)
where does the cerebellum sit?
beneath tentorium cerebellae in the posterior cranial fossa
falx cerebelli sits behind
how does cerebellum attach to brainstem?
3 peduncles (stumps) of white matter
- superior, middle (biggest) and inferior
- all carry white matter fibres into the cerebellum
vermis of the cerebellum?
worm like middle area of cerebellum
what are gyri known as in the cerebellum?
folia
where is grey matter found in the cerebellum?
surrounding the thick white matter core (arbour vitae)
some deep grey matter areas within the white matter core (4 areas with different functions and communicate to brainstem etc)
layers of cerebellum tissue?
molecular layer (synaptic layer) purkinjie cell layer (project down to the deeper nuclei which communicate with the brainstem granular layer (filled with neurons)
how does information arrive at the cerebellum?
afferents arrive from:
- spinal cord
- cerebral cortex (relayed via the pons)
- vestibular apparatus via vestibular nuclei
enter via cerebellar peduncles and project into granule cell layer (mainly)
outputs from the cerebellum?
central stripe (veremis) involved in subconscious motor function flocularnodular lobe = receives vestibular information and feeds back to brainstem only output from all lobes is via axons of purkinjie cells which synapse on neurons of deep cerebellar nuclei, then to the thalamus which then coordinates functions of all motor tracts
how is the cerebellum different from the cerebrum?
cerebellar hemispheres are ipsilateral, not contralateral like the cerebrum
- right hemisperes coordinates movement in right side of body etc
functional divisions of the cerebellum?
vestibulocerebellum - receives vestibular input and coordinates balance and eye movement
spinocerebellum - receives proprioception information to coordinate limb movement
pontocerebellum - evaluates sensory information and plans for movement
midline cerebellum lesion?
disturbance of postural control
patient will fall over when standing or sitting but with preserved limb coordination
unilateral hemispheric lesion?
disturbance of coordination in limbs (can cause tremor, unsteady gait etc)
bilateral cerebellar lesion?
slowed, slurred speech, bilateral incoordination of the arms and staggering wide based gait(cerebellar ataxia)
alcohol and cerebellum?
alcohol temporarily causes bilateral cerebellar hemisphere dysfunction causing cerebellar ataxia
what do basal ganglia do generally?
feed back to the cortex - facilitate purposeful movement - inhibit unwanted movements - role in posture and muscle tone (should really be called nucleus as ganglia means collection of neurons outside of CNS)
what is the basal ganglia?
5 structures aggregated together to perform this function
- caudate nucleus
- putamen
- globus pallidus
- subthalmic nucleus
- substantia nigra
striatum?
caudate nucleus and putamen
lenticular nucleus?
pitamen and globus pallidus
corpus striatum?
caudate nucleus
putamen
globus pallidus
where is the caudate nucleus?
round grey matter blob under lateral ventricles
where is the putamen?
cone shaped grey matter under caudate nucleus
where is the globus pallidus?
2 striped medial to the putamen
much paler
where is the substantia nigra?
black line either side within the midbrain
how is substantia nigra involved in parkinsons?
substantia nigra produces dopamine
degenerates in parkinsons
what is the direct pathway?
series of neurones which travel through basal ganglia to enhance outflow of thalamus to enhance desired movement
indirect pathway?
inhibits outflow from thalamus to inhibit unwanted movement
what effects result from a lesion in the basal ganglia?
unilateral lesions affect contralateral side of body
do not cause paralysis, sensory loss, loss of power or ataxia
do cause
- changes in muscle tone
- dyskinesias (involuntary movement - tremor, chorea, myoclonus)
name 2 diseases associated with basal ganglia
parkinsons
huntingtons
