Week 6.6 Flashcards
What is the role of the cerebellum?
fine-tune reflexes and voluntary movements
What are the three parts of the cerebellum?
- cerebrocerebellum
- spinocerebellum
- vestibulocerebellum
What are the functions of the cerebrocerebellum, spinocerebellum, and vestibulocerebellum?
- cerebro: initiation and programming of movement
- spino: ongoing correction of movement errors
- vestibule: control of vestibular reflexes
Output from the cerebellar cortex is primarily mediated by what cell type?
purkinje cells
Describe the output of purkinje cells?
they project to deep cerebellar nuclei and have an inhibitory effect
Purkinje cells use what neurotransmitter?
GABA
Granule cells form what connections within the cerebellum?
they form parallel fibers and form many excitatory synapses with purkinje cells
What are the two inputs of the cerebellum?
climbing fibers and mossy fibers
What are cerebellar climbing fibers?
fibers that originate from the inferior olivary nucleus and synapse directly onto purkinje cells
What are mossy fibers?
fibers from the pontine nuclei and spinocerebellar tracts the form synapses on granule cells and modify their output onto purkinje cells
Cells in the deep cerebellar nuclei project to what structure?
the contralateral thalamus and red nucleus
How does climbing fiber input differ from mossy fiber input onto purkinje cells?
climbing fibers lead to an obligatory AP and elicit a complex spiking pattern while mossy fibers elicit a simple and graded response
Cerebellar efferents travel to the thalamus via what structure?
the superior cerebellar peduncle
Describe the pathway between the motor cortex and cerebellum.
- motor cortex
- pontine nucleus
- middle peduncle
- cerebellar cortex
- deep nuclei
- thalamus
- motor cortex
What is the pontine nucleus?
a relay station for information going from the cortex to the cerebellum, letting it know what the intended movement is
The cerebellum projects directly to the spinal cord via what midbrain structure?
the red nucleus
The output of the vestibulocerebellum primarily goes to what other systems?
- vestibulospinal tract
- reticulospinal tract
Why would the vestibulocerebellum want to suppress the VOR?
so that we can tract an object by moving our head
If someone has ataxia but is able to perform the Romberg test, it means what?
that the ataxia is not sensory but rather is cerebellar in nature
How is a lesion of the vestibulocerebellum likely to present?
with nystagmus and dysequilibrium or wavering, ataxic gait
How is a lesion of the cerebrocerebellum likely to present?
- hypotonia
- ataxia
- intention tremor
- dysdiadochokinesis
- decomposition of movement
What is dysdiadochokinesis?
the inability to make rapid, alternating movements and a sign of cerebrocerebellar lesion
What is decomposition of movement?
comple movements involving multiple joints are not made with continuous smooth trajectories, a sign of cerebrocerebellar lesion
Do cerebellar lesions affect contralateral or ipsilateral limbs?
ipsilateral
What is the primary function of the basal ganglia?
- to select which movements form the cortex actually get performed
- disinhibit CNS structures to allow for the initiation of voluntary movements
What is the steady state activity of the basal ganglia?
it has a high tonic inhibitory firing rate that is decreased when it decides to allow a movement
Which basal ganglia component is the receiving part?
the striatum
What is the output nucleus of the basal ganglia?
the globus pallidus
What are the four components of the basal ganglia?
- striatum
- globus pallidus
- sub thalamic nuclei
- substantia nigra
Which basal ganglia neurons are dopaminergic?
those in the substantia nigra pars compacta (SNc)
Which neurons are targeted by Parkinson’s disease?
dopaminergic neurons in the substantia nigra pars compacta
How does Parkinson’s disease lead to bradykinesia?
- loss of substantia nigra pars compacta input on the putamen
- creates an imbalance in the basal ganglia that favors the indirect pathway
- the thalamus is inhibited and the cortex can’t initiate movement
What is hemiballismus?
a movement disorder characterized by high velocity, large amplitude involuntary flinging movements, usually involving the arms
What neuron population is targeted by Huntington’s chorea?
GABAergic neurons from the putamen to the GPe
Hemiballismus is associated with what lesion?
lesions of the sub thalamic nucleus
Overactivity of the direct pathway within the basal ganglia will cause what sort of movement disorders?
hyperkinetic disorders
