the cerebellum Flashcards
what brain structure contains more neurons than the rest of the nervous system combined?
the cerebellum
what are the 3 zones of the cerebellum?
spinocerebellum (vermis) , vestibulocerebellum ( nodulus and flocculus), cerebrocerebellum( hemispheres)
what are the 3 basic elements of the cerebellum?
cerebellar cortex, deep cerebellar nuclei, large white matter tracts
what are the 6 main types of neurons identified in the cerebellar cortex?
the main 3 we need to know: granule, golgi, purkinje
and stellate, lugaro, basket
what are the 2 main neurons in the deep cerebellar nuclei?
projection neurons and local interneurons
how is the shape of a purkinje fiber different than other neuron?
it is a huge dentritic tree structure
where do climbing fibers come from?
the inferior olive
what cell in particular accounts for the abundance of neurons in the cerebellum?
the abundance of granule cells
are purkinje cells out put or input?
they are output
are purkinje cells inhibitory or excitatory?
inhibitory, GABA is the marker for these cells
are golgi cells inhibitory or excitatory?
inhibitory, GABA is the marker for these cells
are granule cells inhibitory or excitatory?
excitatory, both GABA and glutamate are markers
what are the purkinje cells inhibitory to?
the deep nuclei
does the cerebellum just do balance/ coordination?
no it is involved in a lot of functions (some propose: sesnory processing, classical conditioning, associative learning, memory retrieval, language,etc. )
purkinje cells are unique in that they produce 2 types of action potentials, what are those 2 types of action potentials?
simple and complex spikes
describe a simple spike
a simple spike is a typical neuronal action potential produced by mossy fiber activation of granule cells which in turn leads to parallel activation of purkinje cells , they occur in predictable fashion and are related moment to moment changes in behavior e/g an eye movement, or joint rotation
during what type pf behavior is complex spiking usually seen?
during unexpected signals or error signal ( e.g. when tipping annette back)
where do complex spikes originate from?
the inferior olives and climbing fibers
when can a complex spike be reliably ( more than once or twice in per second) produced?
if there is an application of a stimulus on a distinct patch of skin
complex spikes occur in a ______ to _______ relationship with arrival of action potentials on climbing fibers
1:1 relationship
complex spikes are typical or atyipcal?
atypical i.e. membrane voltage increases rapidly but then stays elevated for a period of 20 ms or more
describe the membrane voltage change in a simple spike
it increase from -50 mv to 50 mv and then returns to resting potential all within less than 3 miliseconds
what is the basis for cerebellar learning?
long term depression: during or after a complex spike the purkinje cell is refractory to parallel fiber activation ( think of annette being tipped back and then being better able to stabilize herself over multiple trials because of rapid cerebellar learning )
what are some symptoms of cerebellar lesions?
asthenia ( loss of muscle strength ), atonia ( loss of tone) ( mostly in the arms but also in the legs), ataxia ( disorder of coordinating movement, rebound disorder, postural disorders, scanning speech, dysmetria, dysdiadochokinesia, nystagmus
patients with cerebellar lesions may exhibit asynergia, what is that?
asynergia is difficulty coordinating muscular actions
what type of tremor is seen in cerebellar lesion?
intentional tremor
there is a fractured somatotopy in the cerebellum, so how are the same parts of the body connected if they are represented in different areas of the cerebellum?
via parallel fibers
what does cutting the lateral rectus in one eye and immediately patching it then patching the opposite eye for a few ays show?
that the damaged eye can fix the error over time ( this is due to the cerebellum adaptively modifying the commands for movement to optimize outcomes ( see pg. 897)
what is an essential tremor?
it is a resting tremor often mistaken for parkinsons but it can be treated with alcohol or deep brain stimulation
what does an essential tremor result from>
over activity in the olive and deep nuclei not the sub thalamic nuclei
how does ethanol help an essential tremor?
it acts as a glutamate antagonist and a GABA agonist which eliminates the cerebellar modifications of motor commands which cause the tremor (see figure on pg 903)
