the cerebellum

Question 1

what brain structure contains more neurons than the rest of the nervous system combined?

Answer 1

the cerebellum

Question 2

what are the 3 zones of the cerebellum?

Answer 2

spinocerebellum (vermis) , vestibulocerebellum ( nodulus and flocculus), cerebrocerebellum( hemispheres)

Question 3

what are the 3 basic elements of the cerebellum?

Answer 3

cerebellar cortex, deep cerebellar nuclei, large white matter tracts

Question 4

what are the 6 main types of neurons identified in the cerebellar cortex?

Answer 4

the main 3 we need to know: granule, golgi, purkinje

and stellate, lugaro, basket

Question 5

what are the 2 main neurons in the deep cerebellar nuclei?

Answer 5

projection neurons and local interneurons

Question 6

how is the shape of a purkinje fiber different than other neuron?

Answer 6

it is a huge dentritic tree structure

Question 7

where do climbing fibers come from?

Answer 7

the inferior olive

Question 8

what cell in particular accounts for the abundance of neurons in the cerebellum?

Answer 8

the abundance of granule cells

Question 9

are purkinje cells out put or input?

Answer 9

they are output

Question 10

are purkinje cells inhibitory or excitatory?

Answer 10

inhibitory, GABA is the marker for these cells

Question 11

are golgi cells inhibitory or excitatory?

Answer 11

inhibitory, GABA is the marker for these cells

Question 12

are granule cells inhibitory or excitatory?

Answer 12

excitatory, both GABA and glutamate are markers

Question 13

what are the purkinje cells inhibitory to?

Answer 13

the deep nuclei

Question 14

does the cerebellum just do balance/ coordination?

Answer 14

no it is involved in a lot of functions (some propose: sesnory processing, classical conditioning, associative learning, memory retrieval, language,etc. )

Question 15

purkinje cells are unique in that they produce 2 types of action potentials, what are those 2 types of action potentials?

Answer 15

simple and complex spikes

Question 16

describe a simple spike

Answer 16

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

Question 17

during what type pf behavior is complex spiking usually seen?

Answer 17

during unexpected signals or error signal ( e.g. when tipping annette back)

Question 18

where do complex spikes originate from?

Answer 18

the inferior olives and climbing fibers

Question 19

when can a complex spike be reliably ( more than once or twice in per second) produced?

Answer 19

if there is an application of a stimulus on a distinct patch of skin

Question 20

complex spikes occur in a ______ to _______ relationship with arrival of action potentials on climbing fibers

Answer 20

1:1 relationship

Question 21

complex spikes are typical or atyipcal?

Answer 21

atypical i.e. membrane voltage increases rapidly but then stays elevated for a period of 20 ms or more

Question 22

describe the membrane voltage change in a simple spike

Answer 22

it increase from -50 mv to 50 mv and then returns to resting potential all within less than 3 miliseconds

Question 23

what is the basis for cerebellar learning?

Answer 23

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 )

Question 24

what are some symptoms of cerebellar lesions?

Answer 24

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

Question 25

patients with cerebellar lesions may exhibit asynergia, what is that?

Answer 25

asynergia is difficulty coordinating muscular actions

Question 26

what type of tremor is seen in cerebellar lesion?

Answer 26

intentional tremor

Question 27

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?

Answer 27

via parallel fibers

Question 28

what does cutting the lateral rectus in one eye and immediately patching it then patching the opposite eye for a few ays show?

Answer 28

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)

Question 29

what is an essential tremor?

Answer 29

it is a resting tremor often mistaken for parkinsons but it can be treated with alcohol or deep brain stimulation

Question 30

what does an essential tremor result from>

Answer 30

over activity in the olive and deep nuclei not the sub thalamic nuclei

Question 31

how does ethanol help an essential tremor?

Answer 31

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)