Hef - Cerebellum, basal ganglia, cortical function Flashcards
cerebellum functions
- sequence of motor activities and corrects movements (corrective action)
- predictive action
- compare efferent motor from cerebral cortex and spinal cord info. to afferent proprioceptor info.
- planning movements - learns from mistakes
what does cerebellum receive inputs from?
- efferent copy neurons from motor cortex or interneurons in spinal cord
- reafferent info. from muscle spindles, Golgi tendons, and proprioceptors
Purkinje fibers
- ALWAYS inhibitory to DCN by releasing GABA
- stops the signal or prevents overshooting or oscillation
- ataxia with DCN lesion
climbing fibers
- supply low # of Purkinje fibers
- communicate with DCN and higher centers
- direct action Purkinje cells, DCN, and accessory cells
- COMPLEX spikes
- comparing and building memory - TEACHERS
mossy fibers
- supply high # of Purkinje cells
- communicate with granule cells –> signal to Purkinje cells
- SINGLE spikes
other inhibitory cells of cerebellum
- basket, stellate, Golgi
- can participate in lateral inhibition –> sharpen signal
- always inhibitory
vestibulocerebellum
predictive calculations to make anticipatory corrections to prevent one from losing balance
- direct projections to vestibular nuclei to provide sense of movements
- able to override the VOR when necessary
spinocerebellum
receive info. from spinal cord - feedback control of distal limb movements
-receive copy efferent and reafferent info. then signal to DCN –> cerebral cortex and red nucleus
cerebellum dampening functions
- prevent overshooting –> ataxia leads to loss of coordination, hypotonicity, and jerky movement
- prevent back and forth oscillation –> lesion lead to end tremors
- facilitate rapid alternating movements –> lesion lead to dysdiadochokinesia
cerebrocerebellum
- communicate with primary, supplementary, and premotor cortex
- damage lateral zones –> lose coordination
- planning and timing of sequential movements
Purkinje fiber affecting movement
fire Purkinje –> release GABA –> inhibit DCN –> inhibit motor neuron
-fire motor neuron when Purkinje stops signaling
static vs. dynamic balance
static = balance and posture when not moving
dynamic = balance and posture with extreme movement
function of the basal ganglia
- select important moves
- operational learning
- default –> suppress all movements (damage leads to rigidity and tremors)
- multitasking –> chunking (piece together info.)
basal ganglia inputs
- input from cerebral cortex to striatum releasing GABA
- substantia nigra –> dopamine
- thalamus –> glutamate to signal cerebral cortex
- STN –> nucleus
- raphe nucleus –> serotonin
output/intercommunication
- medium spiny neurons –> GABA
- interneurons –> ACh (inhibited in parkinsons)
basal ganglia outputs
SNr and GPi –> always inhibitory
-signal to thalamus, pontomedullary reticular formation, and superior colliculus
role of dopamine
found in substantia nigra (compact) –> Parkinson’s with damage
- tonic release –> steady state
- phasic release –> exaggerate signal –> punding
- amphetamine, cocaines, and antagonists increase dopamine levels –> movement
hyperdirect pathway
use myelinated axons –> stop all actions (INHIBITORY)
- fastest response
- cerebral cortex sends a copy signal to subthalamic nucleus –> + GPi –> release GABA inhibiting thalamus –> no feedback to cortex –> shut down muscles
