Chapter 15 motor system: cerebellum Flashcards
Cerebellum
Coordinates movement and postural control.
- Compares intended to actual movement.
- Makes corrections if necessary.
Pontocerebellar
Straight back from the pons to the cerebellum
-What we intended to do
Spinocerebellar
From the spinal cord to the cerebellum
-What I am really doing
Corrections from cerebellum
Corrections from cerebellum to the brainstem and motor cortex.
-out of the top of the cerebellum.
Cerebellum informs both the cortical and brainstem UMN about needed corrections-both gross postural and fine distal.
gray matter of cerebellum
of outside the cerebellum is packed with cell bodies- responsible with comparing what I meant to do with what I really did and make corrections.
-Cells get input from a number of sources that tell cerebellum what is happening.
Spinal cord (spinocerebellar)- discriminative touch and nonconscious proprioception coming to the cerebellum (what I am really doing)
Reticular formation- What is the level of arousal of the system (what is the urgency of movement.
Vestibular system- from our inner ears. Keep us up and in equilibrium (it knows head movement and the pull of gravity and how we are oriented in it.)
Pontine Nuclei- Xerox copy- from cerebral cortex down to the pons into the cerebellum. (what I meant to do)
Cerebellum comes up with movement correction.
Purkinje cell
takes results of the processing and takes them down to the base of the cerebellum, at the base of the cerebellum the Purkinje cell hands off to the deep cerebellar nuclei.
Deep cerebellar nuclei- Take message to brainstem UMN and to cortical UMN (take it to gross motor and fine motor UMN)
Vertical divisions of cerebellum
Midline vermis- midline anatomical piece- controls the midline of us (the axial skeleton)
Paravermal hemispheres- Those are going to especially control our most proximal joints (shoulders and hips)
Lateral Hemispheres- Those control our distal muscles.
Flocculonodular lobe- (handle bar mustache of cerebellum)- helps us to maintain our equilibrium overall. (not a vertical division)
cerebellar peduncles
(fiber bundles)- a bundle of axons, there are 3 of them in the cerebellum
Inferior peduncles
The most inferior fiber bundle, the closest to the spinal cord, brings input from the spinal cord and the brainstem- brings the message of what I am really doing.
Middle Peduncles
the big one- brings input from the pontine nuclei- the Xerox copy- the message of what I meant to do.
Superior Peduncles
Out to the brainstem and cerebral cortex.
-takes messages up to make corrections if necessary.
Classes of human movement
- Equilibrium- Keep upright against gravity, on balance while doing something with arm (cerebellum- knows that center of mass will go forward and it adjusts to keep us in balance)
- Gross movements of the limbs- forward flex of the shoulder (is what puts arm in position for function)
- Fine, distal, voluntary movements- (form hand to the shape of the cup, open it up to grab and then close it so it doesn’t slip out of hand.)
Functional divisions of the cerebellum
- Vestibulocerebellum
- Spinocerebellum
- Cerebrocerebellum
Vestibulocerebellum
Flocculonodular lobe (handle bar mustache)- Has a real tight connection to the inner ear. (balance and equilibrium)
Input- vestibular receptors
Output- from the cerebellum through vestibular nuclei then to the eye muscles and postural muscles
*a steady gaze is critical to equilibrium so that we stay balanced.
influences the vestibulospinal tract
Spinocerebellum
(central cerebellum- vermis and paravermis) tight connection to the brainstem UMN (core and proximal function)
Input- Spinocerebellar tracts (discriminative touch and nonconscious proprioception) and sensorimotor cortex (what I meant to do).
Output- Medial division UMN- cerebral cortex (medial corticospinal neurons (voluntary control), and brainstem- medial and lateral vestibulospinal (medial- keeps head upright against gravity, lateral- keep lower body upright against gravity) and reticulospinal.
Function- control of core and proximal movements
Synapse occurs in a bundle of cell bodies (thalamus) anything that goes to the cortex.
Cerebrocerebellum
(lateral hemisphere and cortex)- lateral corticospinal- strong connection between the cerebellar hemispheres (fine motor control)
Input- cerebral cortex (especially cerebropontocerebellar, from the head to the pons to the cerebellum, Xerox copy machine (sends planning messages back).
Output- Lateral division UMN and cerebral cortex.
Function- coordinate voluntary movement (plan movements and timing)
Down from cortex- cortical cells send axons down gets to the pons and it splits, one part of split goes down to spinal cord (message to actually move) and the other split goes to the pons where it synapses and sends neuron straight back to the cerebellum (what I meant to do message).
green message says to do it and the red tells us here is what I am doing.
Spinocerebellar pathways
Nonconscious
- 2 high-fidelity pathways (body mapping), each pathway has 2 neurons (1 peripheral and 1 central)
- somatosensory input from body (discriminative touch and nonconscious proprioception)
- project to cerebellum ipsilaterally, (take sensory info from one side of the body to the cerebellum on the same side of the body) cerebellum in cortex takes care of the crossing.
- MESSAGE OF “WHAT I AM REALLY DOING”
collapse all of cerebellar input into name of spinocerebellar (discriminative touch and nonconscious proprioception headed to the cerebellum). grossly tells us where it comes from and where it is going.
Signs of cerebellar dysfunction
- Signs are ipsilateral to damage
- ataxia (common to all damage areas)- incoordination not due to muscle weakness.
Vestibulocerebellum (vermal and floculonodular damage)- truncal ataxia- have a hard time controlling trunk itself.
Spinocerebellar damage- gait ataxia- hard time coordinating my trunk over my hips. always chasing base of support somewhere.
Cerebrocerebellar- Hand ataxia- hard time coordinating movements of the hands.
Vestibulocerebellum damage
Truncal ataxia- have a hard time controlling trunk itself
Nystagmus- at its core- is a gaze control problem, eye movement problem. Shows up a lot in balance and incoordination issues.
Dysequilibrium- impaired equilibrium- balance deficit (truncal ataxia)
Spinocerebellar damage
Gait ataxia- hard time coordinating my trunk over my hips. always chasing my base of support in motion.
-unsteady, veering, staggering gate. (usually a compensation. problems with proximal joint control and leads to these signs we would see).
Limb ataxia-
– Dysdiadochokinesia- alternating reversing movements that have a rhythm, to switch direction.
(test it by rapidly pronate and supinate, may have trouble rapidly controlling their supination and pronation). (for legs, tapping, can you keep the rhythm up).
-Dysmetria- impaired ability to accurately hit a target
metria- ability to accurately hit a target.
-Action (intention tremor)- tremor when I move and I oscillate back and forth around a joint or a limb. (overcorrection hones in and eventually gets finger to target). Leg= put heel on knee or slide heel down your shin.
Decompose movements- have trouble controlling things (especially multiple joints at the same time) robot like in their movements= focus on one joint at a time. (treatments can be to decompose movements to focus on one joint and simplify what the brain has to control and makes us better at doing the motion/task.
*See what you are doing, simplify movements, move slower, think about what you are doing
Cerebrocerebellar damage
Hand ataxia- hard time coordinating movements of the hands.
-trouble with fine coordination- trouble manipulating and controlling buttons on remote or trouble threading a needle.
Paravermis and hemisphere damage
Dysarthria- difficulty/inability to speak (ataxic-problem with the mechanical production of speech, varies in production of loudness, pitch, volume) uneven articulation.
Cerebellar vs. Somatosensory ataxia
Cerebellar problems demonstrate ataxia- we need to tease out due to them not being able to feel where they are (what they are really doing) if they cant feel that, then we cant control it.
Is it a sensory ataxia or a cerebellar ataxia?
Sensory ataxia- will present different than those with cerebellar ataxia
Romberg test- eyes open she will be good for the most part, eyes closed and her sway will increase and she is very likely to lose balance backwards. (support at backward diagonal with arms or hip)
cerebellum broken?- all the input you can want but the cerebellum cannot process them.
may have to substitute a sense, lose coordination and have to use vision to help with coordination.
Cerebellar vs. Somatosensory ataxia.
Somatosensory- don’t get discriminative touch and don’t get proprioception to the cerebellum- doesn’t know what we are doing at the moment.
Romberg- cerebellar- doesn’t matter with eyes open or closed because the cerebellum just isn’t there to coordinate movement. sway either way.
Somatosensory- as long as they can see they are golden. Take vision away and they begin to sway. As long as they have an alternate sense. Test sensation, fail somatosensory test.
