Cerebellum Flashcards
Brain weight cerebellum carries
10%
Develops from?
Metencephalon
Location
Posterior cranial fossa
Seperated from cerebral lobes by
Tentorium cerebelli
Median portion Seperated from pons and medulla by
Fourth ventricle
How many cerebellar hemispheres?
2
Cerebellar hemispheres united by
Vermis
Connected to midbrain via
Superior cerebellar peduncle
Connected to pons via
Middle cerebellar peduncles
Connected to medulla via
Inferior cerebellar peduncles
Fine slit indentions on surface of cerebellum
Sulci
In between sulci
Folia
Type of brain matter present
Grey - located on surface,forms cerebellar cortex
white— located under cerebral cortex
In white matter of cerebellum
4 cerebellar nuclei
Dentate
Emboliform
Globose
Fastigial
Inputs into cerebellar cortex
Mossy fibres
Climbing fibers from imferior olive
Outputs of cerebellar cortex
Purkinje neurones
Interneurones of cerebellar cortex
Granule neurones
Stellate
Basket
Golgi
fissures present in cerebellum
3
primary fissure
horizontal fissure
posterior fissure
What does horizontal fissure do
a posterolateral groove that divides cerebellum into superior and posterior halves
what does primary fissure do
a groove that divides superior half of cerebellum into a small anterior lobe and a large posterior lobe
inferior vermis made up of
nodule
pyramid
tuber vermis
uvala
Nodule at the roof of 4th ventricle
flocculus.
it projects white matter laterally
with a bulbous extremity capped with grey matter
2 flocculi and nodules form
floculonodular lobe
how many divisions is cerebellum divided functionally
3.
a. Vestibulocerebellum
b. spinocerebellum
c. cerebrocerebellum
vestibulocerebellum made up of?
the floculonodular lobe
spinocerebellum made up of
vermis and intermediate zone
the cerebrocerebellum made of
the lateral zones of cerebellar hemisphere
function of vestibulocerebellum
balance and eye movements ie fixation on a target
function of spinocerebellum
Motor execution via descending medial and lateral systems
propioception
function of cerebrocerebellum
motor planning- plans movement and motor learning
coordination of muscle movement
aids visually guided movement
largest division
cerebrocerebellum
inputs into cerebrocerebral cortex
pontine nuclei
cerebral cortex
output from cerebrocerebellum to
thallamus
red nucleus
input into vestibulocerebellum
vestibular system
output of vestibulocerebellum
vestibular nuclei
Role of vestibulocerebellum in maintaining equilibrium when balance is disturbed
when balance is disturbed->vestibular receptors send signals to the vestibulocerebellum->initiation of corrective signals sent to->vestibular nuclei and reticular formation-> toning and contraction of limb and axial muscles to maintain equilibrium during exposure to acceleration- The superior colliculus and medial geniculate body are also stimulated->
co cordinate eye movements with head movements during exposure to acceleration to maintain clear vision which is important for this.
pricipal region concerned with postural adjustment
vermis
vermis recieves input from
muscles and joint propioceptors especially axial concerning position of the body
vermis sends output to
vestibulospinal
reticulospinal tracts
mechanism of co ordination of movement
cerebral cortex->motor signals to muscles to move->efferent copy of signals sent to spinocerebellum via the cortico-ponto-cerebellar pathway and ventral spinocerebellar pathway.
as movement is ongoing, propioceptive fibres are sent to spinocerebellum via dorsal spinocerebellum
mechanism of co ordination of movement
cerebral cortex->motor signals to muscles to move->efferent copy of signals sent to spinocerebellum via the cortico-ponto-cerebellar pathway and ventral spinocerebellar pathway.
as movement is ongoing, propioceptive fibres are sent to spinocerebellum via dorsal spinocerebellum
role of intermediate zone of spinocerebellum
compares motor action of the muscles with the motor intention of the higher centres.
in case they do no match, the intermediate zone + interposed nucleus send corrective signals back to areas cortex and red nucleus that innervate the distal limb muscles.
predicting how to stop movement by cerebellum
i.e in running in a race,
the cerebellum recieves information about the velocity and direction of the movement-> giving it the ability to determine how far the body will move in a given time-> this helps it know the precise time to stop the movement-> it sends this decision to the motor cortex to stop ongoing movement exactly at intended position.
how does sequence and planning of movement occur
cortex+basal ganglia->signals to cerebrocerebellum-> planning of sequence of contraction and coordination of muscles involved to achieve intended goal of movement
This information or plan is sent to the motor cortex->to form adjusted motor command->discharge to lower motor centers
cerebellum role in motor learning
when one does a new complex activity->cerebellum makes mistakes in coordinating successive muscle movement, when it begins and ends->neuronal circuits learn to make more accurate movement after practicing-> becomes more precise.->storage of the learned processes.
ballistic movements
walking running typing writing talking
why are ballistic movements not controlled.
because these movements are so rapid that you cannot depend on sensory feedback information from periphery to control them because movement will be over before information reaches cerebellum and cortex
blood supply to cerebellum
3 paired arteries
superior cerebellar artery
anterior inferior cerebellar artery
posterior inferior cerebellar artery
damage to flocculonodular region
unsteady gait
swaying
damage to vermis
faluire to maintain upright standing position due to inability to adjust tone of antigravity muscles
damage to cerebrocerebellum and spinocerebellum
problems in planning and effecting motor action manifested as
hypotonia- loss of muscle tone and reflex i.e pendular knee jerk
asthenia- loss of muscle strength
ataxia- loss of muscle coordination
manifestations of ataxia
dysmetria intention tremors decomposition of complex movements rebound phenomenon dysdiadokinesia nystagmus dysarthria unsteady gait
dysmetria
error in comparator and damping motion.
i.e
there is error in direction and timing of movement.
asking someone with cerebellar lesion to use their finger to touch your hand, they will they might go in a different direction way past your hand (hypermetria) or it might not get there(hypometria)
what are intention tremors
tremors when one is actively trying to do something
rebound phenomenon
patient cannot stop ongoing rapid movement due to inability to provide damping and predictive responses
dysdiadokinesia
inability to perform repeated alternating actions. i.e cannot flex and pronate forearm rapidly due to inability to time properly the onset and termination of action
nystagmus
tremor of eyeball
decomposition of complex movement
motor action carried out in lots of steps rather than one like it usually done. i.e robotic movement
dysarrthria
slow speech, words fragmented into syllables. due to loss of precise timing of contraction of muscles of speech
unsteady gait
due to dysmetria and kinetic tremors of lower limb muscles
