Lecture 16 - Cerebellum

Question 1

What does the cerebellum do?

Answer 1

• compares motor plans with physical execution

- makes adjustments to keep movements coordinated, fluid and on target

Question 2

cerebrocerebellum

Answer 2

• lateral zone
• receives input from contralateral cerebral cortex
• regulates complex sequences of movement including speech

Question 3

spinocerebellum

Answer 3

• paramedain + median zones
• receives input from spinal cord
• somatopic organization

Question 4

vestibulocerebellum

Answer 4

• caudal + inferior lobes
• receives input from the vestibular nuclei
• regulates posture + balance including some eye movements

Question 5

Ataxia

Answer 5

reeling, wide-based gait

Question 6

Decomposition of movement

Answer 6

inability to correctly sequence fine, coordinated acts

Question 7

Dysarthria

Answer 7

• inability to articulate words correctly

- slurring + inappropriate phrasing

Question 8

Dysdiadochokinesia

Answer 8

inability to perform rapid alternating movements

Question 9

Dysmetria

Answer 9

inability to control range of movement (hypo or hypermetria)

Question 10

Hypotonia

Answer 10

decreased muscle tone

Question 11

Nystagmus

Answer 11

• involuntary, rapid oscillation of eyeballs in horizontal, vertical or rotary direction
• fast component maximal toward side of cerebellar lesion

Question 12

Tremor

Answer 12

• rhythmic, alternating, oscillatory movement of limb at it approaches target
• or of proximal musculature when fixed posture or weight bearing is attempted

Question 13

What are 3 cerebellar outputs?

Answer 13

1. Dentate
2. Interposed
3. Fastigial

Question 14

Dentate

Answer 14

Input: from cerebrocellebellar zone

Projects to: contralateral premotor cortex + association cortices of frontal lobe (planning)

Question 15

Interposed

Answer 15

Input: spinocerebellar zone

Projects to: contralateral motor cortex (executing movement)

Question 16

Fastigial

Answer 16

Input: spinocerebellar zone

Projects to: upper motor neurons in ipsilateral brainstem (executing movement)

Question 17

Where does the vestiublocerebellum project?

Answer 17

to the vestibular nuclei

Question 18

What are peduncles?

Answer 18

fiber bundles carrying inputs and outputs

Question 19

What are 3 cerebellar peduncles?

Answer 19

1. superior
2. middle
3. inferior

Question 20

What characterizes the superior peduncle?

Answer 20

• efferent pathway (mainly)

- made of fibers exiting from deep cerebellar nuclei

Question 21

What characterizes the middle peduncle?

Answer 21

• afferent pathway

- made of fibers carrying info from cortex (via pons)

Question 22

What characterizes the inferior peduncle?

Answer 22

• afferent fibers from brainstem + spinal cord

- efferent fibers from vestibulocerebellum

Question 23

What does the cerebral cortex control? What does it project?

Answer 23

• the contralateral side of the body

- projects to the ipsilateral pontine nuclei

Question 24

Where does each cerebellar hemisphere receive input from? What does it control?

Answer 24

• receives ascending input from same (ipsilateral) side of body
• controls movements on same side of body

Question 25

pathways from the cerebral cortex to the cerebellum will cross the ________ at some _____

Answer 25

midline, point

Question 26

What is the cerebrocerebellum?

Answer 26

influences premotor cortex via the dentate (motor planning)

Question 27

What is the spinocerebellum?

Answer 27

influences motor cortex via the interposed nuclei (motor execution)

Question 28

how does the spinocereellum influence brainstem structures?

Answer 28

via fastigial nucleus (motor execution)

Question 29

Where does the vistibulocerebellum project?

Answer 29

directly to the vestibular nuclei (motor adjustment, balance)

Question 30

What are the 3 layers of the cerebellar cortex?

Answer 30

1. molecular layer (ML) 2. Purkinje cell layer (PL) 3. Granule cell alyer (GL)

Question 31

what is the molecular layer made up of?

Answer 31

- mainly dendrites of Purkinje cells | - axons of granule cells (parallel fibers)

Question 32

What is the Purkinje cell layer made up of?

Answer 32

Purkinje cells and basket cells

Question 33

Where do climbing fibers convey input from?

Answer 33

inferior olive

Question 34

Where does the inferior olive receive input from?

Answer 34

- cerebral cortex - spinal cord - red nucleus

Question 35

Each purkinje cell receives input from a single _______ _____

Answer 35

climbing fiber

Question 36

What is the Purkinje cell's response to input form a climbing fiber?

Answer 36

cells fire a complex spike

Question 37

Where do mossy fibers come from?

Answer 37

the pontine nuclei

Question 38

What are the pontine nuclei?

Answer 38

relay input from the cerebral cortex, spinal cord, vestibular nuclei

Question 39

What do mossy fibers synapse with?

Answer 39

granule cells

Question 40

Each Purkinje cell receives _______ of inputs from parallel fibers

Answer 40

hundreds of thousands

Question 41

What do purkinje cells fire in response to input from parallel fibers?

Answer 41

"simple"

Question 42

motor learning means that the cerebellum can "learn" to ____ for ______

Answer 42

compensate, changes in the status quo

Question 43

What are the 2 types of cerebellar loops?

Answer 43

1. direct loop | 2. cortical inhibitory loop from mossy fibers

Question 44

What happens in a direct loop from mossy fibers

Answer 44

- afferent sensory information - from mossy fibers - to deep cerebellar nuclei - to motor system (reflex pathway)

Question 45

What happens in a cortical inhibitory loop?

Answer 45

- from mossy fibers to granule cells - via parallel fibers - to Purkinje cells - to deep cerebellar nuclei + motor system - fine-tune reflexes

Question 46

What is the cortical inhibitory loop involved in?

Answer 46

fine tuning reflexes

Question 47

What is the climbing fiber loop involved in?

Answer 47

- mediates motor learning | - involves complex spikes

Question 48

Where do climbing fibers originate?

Answer 48

-in inferior olive

Question 49

Where do mossy fibers originate?

Answer 49

pontine nuclei