Cerebellum

Question 1

Function(s) of the Cerebellum

Answer 1

1. Coordinate movements
2. Maintain posture
3. Motor learning (procedural memory)

receives a lot of sensory input, but does not interpret it
lesions do not cause lasting motor paralysis - it causes motor DYSFUNCTION

Question 2

Organization of Gray Matter in the Cerebellum

Answer 2

1. Molecular Layer - next to pial surface; few neurons; cell bodies of basket and stellate cells
2. Purkinje Layer - Purkinje cell bodies
3. Granular Layer - deepest layer; granule cells and a few Golgi cells
4. White Matter - neuronal axons

be familiar with histological images

Question 3

Purkinje Cells

Answer 3

EFFERENTS
output cells from the cerebellar cortex
- inhibits cerebellar nuclei and the vestibular nuclei (GABA)
highly differentiated, many dendrites

Question 4

Granule Cells

Answer 4

Smallest neurons, only excitatory neurons, NT is glutamate

Question 5

Stellate Cells

Answer 5

axons synapse with Purkinje cells and inhibit them; star-shaped dendrites

Question 6

Golgi Cells

Answer 6

Inhibitory; NT is GABA, large/scattered neurons with short axons

Question 7

Basket Cells

Answer 7

axons synapse with Purkinje cells and inhibit them; NT is GABA

Question 8

Name the two types of afferent fibers

Answer 8

1: Climbing Fibers
2: Mossy Fibers

Both are excitatory fibers; send collaterals to the deep cerebellar nuclei in addition to their respective synapses

Question 9

Name the deep cerebellar nuclei

Answer 9

1. emboliform nucleus
2. dentate nucleus
3. globose nucleus
4. fastigial nucleus

Question 10

Climbing Fibers

Answer 10

• Afferent fibers
• From the inferior olive in the medulla
• Myelinated, excitatory influence on Purkinje cells
• Convey info about movement errors to the cerebellum

Question 11

Mossy Fibers

Answer 11

• Afferent fibers
• From SC, reticular formation, vestibular system, and pontine nucleir (everywhere but inferior olive)
• Synapse w/ granulocytes in granular layer
• Somatosensory, arousal, equilibrium, and cerebral cortex motor info to cerebellum

Question 12

Vestibulocerebellum

Answer 12

• Functional name for flocculonodular lobe
• Receives info from vestibular receptors (CN VIII and vestibular nuclei), also from visual areas
• Send output to vestibular nuclei
• FXN: influence eye movements and postural muscles of the head and body

Question 13

Spinocerebellum

Answer 13

• Functional name for vermis and paravermal region
• Somatosensory info, internal feedback from spinal interneurons and sensorimotor cortex
• FXN: control ongoing movement via brainstem descending tracts
• Vermis control postural muscles
• Paravermis controls UMNs (move limbs, gait and station)

Question 14

Ponto/Cerebrocerebellum

Answer 14

• Input from cerebral cortex via the pontine nuclei
• FXN: coordination of voluntary movements, planning of movements, and timing
• coordinates fine movements for fractionation*

Question 15

From where does the cerebrocerebellum receive afferent fibers?

Answer 15

From the cerebral cortex:

• Mossy fibers from the cortico-pontocerebellar and cortico-reticulocerebeller
• Climbing fibers from the cortico-olivocerebellar

Question 16

From where does the spinocerebellum receive afferent fibers?

Answer 16

From the spinal cord:

-Mossy fibers form the anterior/posterior spinocerebellar tracts and the cuneocerebellar tract

Question 17

From where does the vestibulocerebellum receive afferent fibers?

Answer 17

From the vestibular system:

-Mossy fibers from the vestibular nuclei and CN VIII

Question 18

What information is carried by the afferent fiber pathways?

Answer 18

unconcsious proprioception about limb movement

Question 19

Describe the posterior spinocerebellar tract

Answer 19

SC afferent fiber pathway

• axons carrying unconscious proprioception from lower limb
• 1st order neuron enters via the dorsal root ganglion
• ascends in gracile fasiculus
• synapse in nucleus dorsalis of Clark (gray matter from C8-L2)
• 2nd order neuron ascends in dorsolateral funiculus
• enters the cerebellum bia the inferior cerebellar peduncle

Question 20

Describe the cuneocerebellar tract

Answer 20

SC afferent fiber pathway

• axons carrying unconscious proprioception from upper limb
• 1st order neuron enters via the dorsal root ganglion
• ascends in the cuneate fasiculus
• synapses in accessory/lateral/external cuneate nucleus in the lower medulla
• 2nd order neuron from the accessory cuneate nuscleus ascends to the cerebellum
• enters via the inferior cerebellar nucleus

Question 21

Big picture information about the anterior spinocerebellar tract

Answer 21

• carries unconscious proprioception from the lower extremity; also Pacinian/Meissner/Meckel corpuscle
• CROSSES 2X (in the anterior white commissure and after entering the superior cerebellar peduncle)

Question 22

Superior Cerebellar Peduncle

Answer 22

• major efferent for globose, emboliform, and dentate nuclei

- afferent fibers from the ventral spinocerebellar tract

Question 23

Middle Cerebellar Peduncle

Answer 23

• largest peduncle
• in the area of the pons
• relays afferent fibers from pontine nuclei to cortex

Question 24

Inferior Cerebellar Peduncle

Answer 24

Main afferent pathway from SC

Question 25

Function of Vestibulocerebellum

Answer 25

Eye movements and neck/trunk movements

Question 26

Function of Spinocerebellum

Answer 26

axial/lower extremity movements, gait, station

Question 27

Function of Cerebrocerebellum

Answer 27

precise/coordinated movements of extremities (mainly the upper extremity)

Question 28

Cerebrocerebellum transmits to:

Answer 28

- Dentate nucleus | - Some globose/emboliform (interposed) nuclei

Question 29

Spinocerebellum transmits to:

Answer 29

- Globose/Emboliform (interposed) nuclei (paravermal region sends info here) - Fastigial nucleus (info from the vermis) - Dentate nucleus

Question 30

Vestibulocerebellum transmits to:

Answer 30

- Vestibular nucleus (bypasses the deep cerebellar peduncle; takes the inferior cerebellar peduncle and leaves via the juxtarestiform body) - Some fastigial nucleus

Question 31

Dentate Nucleus targets:

Answer 31

red nucleus, thalamus, VL of thalamus

Question 32

Interposed nuclei targets:

Answer 32

red nucleus, thalamus, VL of thalamus

Question 33

Fastigial nucleus targets:

Answer 33

reticular formation and vestibular nucleus

Question 34

Describe the effect of unilateral cerebellar lesions, and explain the mechanism of the effect

Answer 34

Unilateral lesions affect the ipsilateral side | -crosses to the opposite red nucleus, but crosses again when going back down

Question 35

Common sign of cerebellar lesions

Answer 35

Ataxia - voluntary, normal strength, jerky, and inaccurate movements - not associated with hyperstiffness - wide base gait, stumble - when damage is unilateral, fall to side of lesion

Question 36

Describe lesions of vestibulocerebellum

Answer 36

- between vestibular system and flocculonodular lobe - nystagmus* - truncal ataxia - truncle instability (titubation)

Question 37

What is truncal ataxia?

Answer 37

difficulty maintaining sitting and standing balance

Question 38

What is truncal instability/titubation?

Answer 38

Anterior-posterior tremor, can't tandem walk (sobriety test)

Question 39

Describe lesions of spinocerebellum

Answer 39

- between cutaneous/proprioceptive info from SC to the vermis/paravermal regions - gait and truncal ataxia (wide, staggering base)

Question 40

Describe midline ataxia

Answer 40

Caused by vestibulocerebellar and spinocerebellar disease - truncal instability (titubation and gait ataxia) - equilibratory (gait) ataxias

Question 41

What is gait ataxia?

Answer 41

wide based, irregular steps with lateral veering (toward side of lesion)

Question 42

What is dysarthria?

Answer 42

slurred, poorly articulated speech -scanning speech: spoken words are broken up into separate syllables, often separated by a notable pause, spoken w/ varying force

Question 43

What is movement decomposition?

Answer 43

movements are broken up into their individual compents

Question 44

Describe dysdiadochokinesia?

Answer 44

inability to rapidly alternate your movements

Question 45

Describe dysmetria?

Answer 45

inability to accurately move an intended distance

Question 46

Describe action tremors/intention tremors

Answer 46

- shaking of limb during voluntary movement | - tremor worsens as a patient tries to touch their target (worse at the end of the movement)

Question 47

Describe cerebroserebellum lesions

Answer 47

- lateral hemispheres of the cerebellum | - dysarthria, ataxic gait, decomposition of movements, limb ataxia (dysdiadochokinesia, dysmetria, action tremors)

Question 48

Describe appendicular ataxia

Answer 48

- dysfunction of the cerebellar hemispheres that results in ataxia of the extremities - also ataxia of speech (scanning dysarthria) - hypotonia, decomposition of movement, dysmetria, dysdiadochokinesia

Question 49

How can you differentiate between cerebellar ataxia and sensory ataxia?

Answer 49

Cerebellar ataxia: normal vibratory sense, proprioception, and ankle reflexes Sensory ataxia: abnormal vibratory sense, proprioception, and ankle reflexes; can stand with feet together when eyes are open

Question 50

Describe cerebellar ataxia

Answer 50

Positive Romberg test (unable to stand with their feet together), normal vibratory sense/proprioception/ankle reflexes

Question 51

Describe sensory ataxia

Answer 51

Positive Romberg test when eyes are closed (can stand with feet together when eyes are open), abnormal vibratory sense/proprioception/ankle reflexeS

Question 52

Tests to run to examine the cerebellum

Answer 52

Vestibulocerebellum and Spinocerebellm: - station - walking - tandem gait Cerebrocerebellum: - rapid alternating movements - finger-to-nose/toe-to-finger - heel-to-shin - rebound and check reflex - speech