Lecture 14: The Cerebellar and Pyramidal Motor Systems of the Brain Flashcards
Name 3 unique things at each level of the brainstem.
Mesencephalic Tegmentum: Red nuclei
Pars Basilaris: Pontine Nuclei
Medullary Pyramids: Inferior Olives
What ist he Extrapyramidal System?
The extrapyramidal pathway or system is an important part of the motor system of the body and can also be described as the descending motor pathway, whose fibres pass through the tegmentum rather than the medullary pyramid.
The extrapyramidal pathway is actively involved in the initiation and selective activation of movements, along with their coordination.
Major contribution in the extrapyramidal motor system are the nuclei of the basal ganglia. Other structures which are involved include s_ubstantia nigr_a, red nucleus, subthalamic nucleus, mesencephalic reticular formation and the cerebellum.
What is the Pyramidal System?
Corticospinal tract (from Cerebrum to the lower motor neuron)
What is the Vestibulo spinal system involved in?
The vestibulospinal tract is a component of the extrapyramidal system and is classified as a component of the medial pathway.
Like other descending motor pathways, the vestibulospinal fibers of the tract relay information from nuclei to motor neurons.[1] The vestibular nuclei receive information through the vestibulocochlear nerve about changes in the orientation of the head. The nuclei relay motor commands through the vestibulospinal tract.
The function of these motor commands is to alter muscle tone, extend, and change the position of the limbs and head with the goal of supporting posture and maintaining balance of the body and head.[1]
What is the difference between Corticospinal/Pyramidal and Extrapyramidal system?
The motor tracts can be functionally divided into two major groups:
Pyramidal tracts – These tracts originate in the cerebral cortex, carrying motor fibres to the spinal cord and brain stem. They are responsible for the voluntary control of the musculature of the body and face.
Extrapyramidal tracts – These tracts originate in the brain stem, carrying motor fibres to the spinal cord. They are responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion
What is the Reticulospinal system?
System helps us on our feet (oppose gravity)
Also system that helps our body and cells ready to go (not sleeping)
= both involved in consciousness
What is the Rubrospinal System?
Doesn’t do a lot for humans
Allow us to engage with automated movements (e.g. moving our arms when you walk or action of crawling)
You don’t think about it, but highly co-ordinated movement
What do the Vestibulospinal, Reticulospinal and Ruberoscpinal system all have in common?
Brainstem nuclei that have input into lower motor nuerons to help us coordinate movement, stay upright and how we do movements when the cerebral cortex is not necessarily hugely involved.
Where is the Reticular Formation in the brain?
Not 1 structure, formed by dozens of structures/nuclei in the brain
Name the Subdivisions of the Cerebellum (Anatomical)
1) Anterior lobe
2) Posterior lobe
3) Flucculonodular lobe
4) Vermis
Name the Subdivisions of the Cerebellum/Fibre connections (Functional)
1) neocerebellum (area of cerebellum that developed last)
- involved in fine motor control
- puts input into the thalamus
1a) Pontocerebellar fibres (fibres from pons into the cerebellum)
2) paleocerebellum
- involved in proprioception
2a) Spinocerebellar fibres (Spinal cord to cerebellum for proprioception)
3) archicerebellum
- In the flocculonodular lobe
3a) Vestibulocerebllar fibres (vestibular fibres are having input in the flocculonodular lobe and assist in movement)
What is the Inferior Cerebellar Peduncle responsible for?
Spinocerebellar tract goes up the Spinal Cord and goes into the cerebellum via the Inferior Cerebellar Peduncles
The Inferior Cerebellar peduncle is also responsible for taking the Vestibulo-cerebellar fibres into the cerebellum.
The inferior olive also has input in the inferior cerebellar peduncle
Inputs into the Cerebellum are through the ___________
Middle and Inferior Cerebellar Peduncles
What is the Middle Cerebellar Peduncle responsible for?
Input from the Ponto-cerebellar fibres
What is the Superior Cerebellar Peduncles responsible for?
Output from the cerebellum
Efferents to:
1) Thalamus
2) Red nucleus
3) Vestibular Nucleus
Where do the ponto-cerebellar fibres feed into?
Neocerebellum of the cerebellum
(involved in fine motor co-ordination)
Where do the spino-cerebellar fibres feed into?
paleocerebellum (Proprioception)
Where do the vestibulocerebellar fibres feed into?
Archicerebellum
Name the 3 deep cerebellar nuclei
1) Fastigial
2) Interpositus(2 nuclei)
3) Dentate
These are distributed around the deep cerebellum
What is the Role of the Fastigial Nucleus of the Cerebellum?
Send output from the Vermis and the Flocculonodular lobe out towards the lateral vestibular nucleus
(this is a feedback loop).
It also feeds into the reticular formation (olivary complex) and this info goes to the lower motor neuron pool (to decide how we keep our core muscles aligned so we can balance)
Describe the function of the Red Nucleus
Send fibres to the Red nucleus which feeds the rubro-spinal tract
Describe the function of the Dentate nucleus
Feeds into the Red nucleus, which feeds into the Thalamus which informs the Upper motor neuron area via the planning area on what should go on with fine movement control.
Draw the inputs and outputs of the cerebellum
The interpositus nucleus will be closely related to the _________pathway
Reticulo-spinal
The dentate nucleus will be closely related to the _________pathway
Ruberospinal pathway
What happens if the vestibular cerebellar pathway or the flocculonodular lobe goes wrong?
Problems with general balance and unusual eye movements (cacadic movements).
If someone comes in with problems with general balance and unusual eye movements (cacadic movements), what area(s) may be damaged?
Vestibulo cerebellar fibres or the flocculonodular lobe
What happens when the spino-cerebellar fibres become damaged?
Postural instability (like if they’re drunk)
What happens if the neocerebellum is damaged?
Causes difficulty in c_o-ordinating fine movement_ (e.g. intension tremor- cannot coordinate movements in a smooth way, or under/over-shooting).
Rebound reflex (grab someone’s arm, pull it down, and tell them they’re going to let go, and if they end up hitting themselves- it means that they do not have any stopping ability of their movements)
Neocerebellum makes a map of the mvoement you anticipate doing. If someone/thing interupts the plan, the neocerebellum will correct that.
