Cerebellum Flashcards
What is the role of the basal ganglia in the context of movement
- Receives input from widespread cortical areas, integrates this input and projects it back to the cortex
- Encodes the decision to move, the direction and amplitude of movement and the motor expression of emotions
What connects the cerebellum to the medulla?
Inferior peduncles
What connects the cerebellum to the pons?
Middle peduncles
What connects the cerebellum to the midbrain?
Superior peduncles
Excitatory fibres of the cerebellum
- Mossey fibres
* Climbing fibres
What are the layers of the cerebellum?
- Molecular layer - parallel fibres, axons, sensory info
- Purkinje cell - all in a straight line
- Granule cell layer: granular cells, glomeruls, Golgi cells
Inhibitory fibres of the cerebellum
- Golgi
* Purkinje
Input of the cerebellum
- Inputs from the climbing fibres come up and synapse with the parallel fibres.
- Mossey fibres brings sensory info and synapse on parallel fibres
- Purkinje and Golgi are inhibitory
- Spinocerebellar tracts
Which cell mediates learned movements
Purkinje
What sends signals to the red nucleus?
- Deep cerebellar nuclei
* via rubrospinal tract
What are the deep cerebellar nuclei?
- Dentate
- Emboliform
- Globose
- Fastigial
What makes up the interposed nucleus?
- Emboliform
* Globose
What are the roles of the cerebellum?
- Acts as a comparator
- Acts as a timing device
- Initiates and stores movements
- modulate motor output
Cerebellum as a comparator
- Compares descending supra spinal motor signals with ascending afferent feedback information
- So movement is smoothly and accurately coordinated
Cerebellum as a timing device
- Pontocerebellum - Creates a sequence for motor activation
- Vestibulocerebellum - maintains balance
- Spinocerebellum - maintains posture
Cerebellum initiating and storing movements
- Modifiable synapse (purkinje cells)
* Can store information and update it
How does the cerebellum modulate motor output?
- Activity of the pre motor and the motor areas as well as the spinal motor circuits
- Sensory feedback from the vestibular system, visual system and ascending proprioceptive information
What are the clinical features of cerebellar damage?
- Hypotonia/reduced muscle tone
- Incoordination/ataxia
- Dysarthria
- Nystagmus
- Palatal tremor/ myoclonus
Position of the macula
- Vertical in the saccule
* Horizontal in the utricle
What are otoliths?
Particles of calcium carbonate
What are the semi-circular canals sensitive to?
Angular acceleration
Describe the vestibulo-ocular reflex
- Direct stimulation of ampullarf nerves elicits specific eye movements
- Stimulation of afferents from left horizontal canal causes eye to turn right
- Specific adaptation to allow gaze to remain steady during head movement
- Lateral recti - cranial nerve VI
- medial recti - cranial nerve III
What is Menieres Disease?
• Excessive accumulation of the endolymph and damage to the hair cells
What are the symptoms of Meniere’s disease
- Vertigo
- Nausea
- Tinnitus
- Hearing loss
What is vertigo?
Sensation of turning or rotation in space in absence of actual rotation
What are the causes of vertigo?
- Debris from the otolithic membrane adhering to capital in ampulla of posterior semicircular canal
- Lesions of vestibular aspect of CNVIII or central lesions affecting brainstem vestibular nuclei
What are the clinical symptoms of vertigo?
- Nausea
- Vomiting
- Gait ataxia
What structures does the vestibular part fo the membranous labyrinth contain?
- Otolith organs - detects gravity and head tilt
* Semicircular canal - detects head rotation
