Week 8b - cerebellum - finished Flashcards
Does the cerebellum have many neurons?
It has as many neurons as the rest of the CNS combined
What does cerebellar damage lead to?
Equilibrium and postural abnormalities and the incoordination of voluntary movements.
On the superior surface of the cerebellum, what lobes can we see?
The anterior and middle lobes
What are folia?
Small indentations or cortical ridges which cover the entire cerebellar surface
What does the primary fissure divide the cerebellum into?
Anterior and posterior lobes
What does the posterolateral fissure separate within the cerebellum?
Separates the flocculonodular lobe from the much larger body of the cerebellum and is so deep that the flocculus is almost pinched off from the rest of the cerebellum
What are the general functions of the cerebellum?
The cerebellum receives corollary discharge from brain structures functional in motor programming & execution
motor plans & the sensory information they were based on
It receives inputs from descending motor pathways to monitor descending control signals
It receives peripheral sensory feedback during the movement
In the cerebellar cortex this information is compared
When the motor plan fails to match the current sensory feedback, error signals are sent via a set of deep cerebellar nuclei, to the many areas involved in planning & execution
Cerebellar projections target the descending motor pathways to superimpose control and correct any discrepancy between the intention and the actual
Cerebellar projections also feed back to the cerebral cortical areas functional in the planning and execution of movements to realign any upcoming motor plans with the events that are actually taking place
Although the cerebellum is involved in extensive sensory processing, it is considered part of the motor system.
Cerebellar damage typically results in dysfunction of posture & balance and poor coordination of voluntary movement.
It does not generally produce sensory symptoms.
What are the 3 functional regions of the cerebellum?
vestibulocerebellum
cerebrocerebellum
spinocerebellum
- vermis (central region)
- intermediate zone (lateral portions)
What is the function of the vestibulocerebellum?
Where does it receive input from?
Where does it output to?
The vestibulocerebellum acts in the control of balance and eye movements and as such lesions in this portion of the cerebellum give rise to nystagmus and ataxia with a wide based stance.
The vestibulocerebellar cortex receives input from the vestibulocerebellar tract and outputs to the vestibular nuclei (primarily the lateral vestibular nucleus), as with all other regions the information for comparison comes from the inferior olivary nucleus of the medulla.
What is the function of the spinocerebellum?
What do the different regions of the spinocerebellar do? What do lesions in this region result in?
Where does it receive input from and where does it output to?
The spinocerebellum adjusts on going movements and regulates muscle tone via gamma motor neuron output to muscle spindles. As the spinocerebellum functions in muscle tone, lesions in this portion of the cerebellum lead to hypotonia.
The vermis acts to regulate axial and proximal limb musculature by superimposing control over the medial descending motor pathways. Lesions of the vermis give rise to ataxic gait, disturbances in truncal control and difficulty with articulation.
The intermediate zone regulates distal limb musculature by superimposing control over the lateral descending motor pathways. Lesions of the intermediate zone give ipsilateral limb ataxia and action tremor.
The spinocerebellum receives inputs from the spinocerebellar tracts and outputs to the descending motor pathways of the spinal cord via the deep cerebellar nuclei, the vermis functions via the fastigial nucleus while the intermediate zone functions via the interposed (globose and emboliform) nuclei.
What is the function of the cerebrocerebellum?
What do lesions in this region result in?
Where does it receive input from and where does it output to?
The cerebrocerebellum plays a role in the co-ordination of motor planning, rapid movements and fine dexterity; this includes the trajectory, speed and force of movements. Rather than directly altering the motor commands of the descending pathways by superimposing control over them, the cerebrocerebellum influences motor commands primarily via its action over the areas of the cerebral cortex which give rise to these descending pathways.
Lesions of this region give rise to:
initiation and termination delays
termination tremor
spatial inco-ordination of hand and finger movements
disorders of temporal or time related coordination of movements
The cerebrocerebellum receives its input from the cerebropontinecerebellar and oliverocerebellar tracts and outputs to the cerebral cortex via the dentate nucleus and VLo of the thalamus.
What is the inferior olivary nucleus? Where is it located?
A large convoluted nucleus located in the anterolateral medulla. It gives a basis for comparison.
Where does the inferior olivary nucleus receive input from?
Receives input from primary motor & somatosensory cortex, red nucleus, spinocerebellar tracts and visual cortex
Where does the inferior olivary nucleus output to?
The entire cerebellar cortex
What are the 2 different zones of the spinocerebellum
The vermis and the intermediate zone
