Block 5 W4 Flashcards
Describe the role of cerebellum and basal ganglia in movement.
Cerebellum - coordination of ongoing movement.
Basal ganglia - selection/inhibition of voluntary movements.
Improve accuracy of movements by providing feedback loops with motor and sensory areas in cortex. Modify signals of UMNs.
What are the effects of damage to cerebellum and basal ganglia?
Cerebellum - jerky movements, uncoordinated and inaccurate.
Basal ganglia - uncontrolled movement at rest.
Describe the cerebellum.
Located in hindbrain.
Folia - folds and ridges.
50% of total neurones in CNS.
Outline the functions of cerebellum.
Coordination of planned, voluntary multi-joint movements, balance and muscle tone.
Comparator function - detects difference in ‘motor error’ between intended movement and actual movement. Correction of ongoing movement.
Motor memory - stores learnt movement e.g. riding a bike, driving.
What are the divisions of the cerebellum?
Cerebrocerebellum
Spinocerebellum
Vestibulocerebellum
Describe the cerebrocerebellum.
Large, inputs from cerebral cortex. Regulates highly skilled movements e.g. speech.
Describe the spinocerebellum.
Direct input from SC.
Lateral section - distal muscle movement.
Medial section (vermis) - proximal muscle movement.
Describe the vestibulocerebellum.
Includes nodules and flocculus. Inputs from vestibular nuclei in brainstem. Regulates movements underlying posture and balance.
What are the cerebellar peduncles?
Attaches cerebellum to brainstem.
Superior cerebellar peduncle -> efferent pathway from cerebellum.
Middle cerebellar peduncle -> afferent pathway to cerebellum via pons.
Inferior cerebellar peduncle -> afferent and efferent pathways.
What are the 3 inputs to the cerebellum?
- Motor - from cerebral cortex via relay neurones in pons cross over to opposite cerebellar hemisphere (middle cerebellar peduncle).
- Sensory inputs (muscle proprioception, vestibular, visual, auditory) on same side convey position and motion info (inferior cerebellar peduncle).
- Inferior olive - timing, learning, memory.
What are the deep cerebellar nuclei?
Major output structures.
Relay cortical cerebellar info to motor cortex and brainstem to make corrections in movement.
These exit via superior cerebellar peduncles.
What is the nuclei in vestibulocerebellum?
Fastigial nucleus or vestibular nuclei
What is the nuclei in spinocerebellum?
Interposed (+ fastigial) nuclei.
What is the nuclei in cerebrocerebellum?
Dendate nucleus
What are the input microcircuitry of the cerebellum?
Climbing fibre
Mossy fibre
What are the output microcircuitry of the cerebellum?
Purkinje cells
What are the interneurons of the cerebellum?
Granule, stellate, Golgi, basket cells.
Describe the granule cells.
Receive input from mossy fibres.
Outputs branch like a ‘T’, each branch - parallel fibres.
Describe purkinje cells.
Purkinje axons synapse onto neurones in deep cerebellar nuclei.
Use GABA (inhibitory)
Receives input from ~100,000 parallel fibres.
Describe climbing fibres.
Inputs received from inferior olive and twists around purkinje cell dendrites.
Receives input from 1 inferior olive neurone.
Carry error signals which allows for correction by altering effectiveness of the parallel inputs to purkinje cells.
Describe cerebellar damage.
Damage disrupts coordination of ongoing movements -> jerky, imprecise (cerebellar ataxia).
Movement errors always on same side as damage to cerebellum.
Describe damage to vestibulocerebellum.
Disturbances of balance and eye movements.
Describe damage to spinocerebellum.
Impaired gait
Describe damage to cerebocerebellum.
Impairments in highly skilled sequences of learned movement.
What is dyssynergia?
Loss of synergistic multi-joint movement. Patient touching nose with finger will first move shoulder joint, then elbow, then wrist - no simultaneous movement.
What is dysmetria?
Inability to judge distance - wrong location e.g. finger shoots past nose.
What is dysdiadochokinesia?
Inability to perform rapid alternating movements.
What is intention tremor and ataxic dysarthria?
Tremor when trying to move and slurred speech.
Describe cerebellar damage owing to alcohol.
Degeneration of anterior cerebellum:
- damage specifically affects movement of lower limbs (anterior spinocerebellum)
- wide and staggering gait but little impairment of arm or hand movements.
What is the basal ganglia.
Collection of functionally distinct nuclei.
Caudate nucleus + putamen = striatum (input)
Globus pallidus + substantia nigra = pars reticulata (output)