8. Cerebellum

Question 1

cerebellum: functions

Answer 1

• regulation of upper motor neuron activity
• coordinating movement
• matching actual movement w/ intended movement (by detecting and reducing motor error)

Question 2

motor learning: define

Answer 2

the process of improving motor skills through practice, with long-lasting changes in the capability for responding.

key players: cerebellum and basal nuclei play a major role in such coordination.

Question 3

where in the hierarchy of volitional motor control does the cerebellum fall?

Answer 3

affects upper motor neurons of the brainstem centers (basic movements and postural control)

Question 4

cerebellum: location

Answer 4

posteriorly in the brain

inferior to the occipital lobe

dorsal to pons and medulla

Question 5

what are the 2 components to the cerebellum?

Answer 5

1. cerebellar CORTEX
2. deep cerebellar nuclei

Question 6

general organization of the cerebellum: (rule of 3s)

Answer 6

• 3 anatomic subdivisions of cerebellar cortex (sagittal plane)
• 3 anatomic lobes of cerebellar cortex in horizontal plane
• 3 functional subdivisions of the cerebellar corted
• 3 deep cerebellar nuclei
• 3 main fiber tracts (peduncles) for inputs/outputs
• 3 major clinical syndromes

Question 7

3 anatomic divisions of cerebellar cortex in sagittal plane

Answer 7

1. Midline: Vermis and nodulus
2. Intermediate: Paravermal region of cerebellar hemisphere
3. Lateral: Lateral region of cerebellar hemisphere & flocculus

Question 8

which anatomic region of the cerebellum contains the NODULUS?

Answer 8

MIDLINE

(part of the vestibulocerebellum)

Question 9

which anatomic region of the cerebellum contains the VERMIS?

Answer 9

Midline

(part of spinocerebellum)

Question 10

which anatomic region of the cerebellum contains the FLOCCULUS?

Answer 10

intermediate

(vestibulocerebellum)

Question 11

locate the VERMIS, NODULUS, and FLOCCULUS in the view from the 4th ventricle

Answer 11

vermis and nodulus: on midline

flocculus laterally

Question 12

3 anatomic lobes of the cerebellum & locations

Answer 12

1. floccolondular: anterior to posterolateral fissue on inferior surface
2. anterior lobe: anterior to primary fissue
3. posterior: between primary fissue and posterolateral fissure

Question 13

which fissure separates the 2 anatomic lobes:

anterior lobe and posterior lobe

Answer 13

primary fissure

Question 14

which fissure separates the following 2 anatomic lobes?

flocculonodular lobe & posterior lobe

Answer 14

posterolateral fissure

Question 15

3 functional subdivisions of cerebellar cortex

Answer 15

1. CEREBROcerebellum
2. SPINOcerebellum
3. VESTIBULOcerebellum

Question 16

VESTIBULOcerebellum: structures

Answer 16

flocculolondular lobe (connects w/ vestibular system)

this includes both the flocculus and the nodulus

Question 17

SPINOcerebellum: structures

Answer 17

vermis and intermediate zone (particularly in anterior lobe), which connects w/ the spinal cord

Question 18

CEREBROcerebellum

Answer 18

lateral part of cerebellar hemispheres; (particularly in the posterior lobe) which connects w/ the cerebral cortex

Question 19

function of the subdivision:

VESTIBULOcerebellum

Answer 19

regulates movements to control posture and balance, gaze, and VOR (vestibulo-ocular reflex)

Question 20

function of the subdivision:

SPINOcerebellum

Answer 20

regulates gross limb movements & gait

Question 21

function of the subdivision:

CEREBROcerebellum

Answer 21

regulates highly skilled movements, complex spatial and temporal sequences of movement (incl. speech, visually guided coordination of ongoing movement, motor planning)

Question 22

3 deep cerebellar nuclei (DCN)

Answer 22

1. dentate nucleus (laterally)
2. interposed nuclei between
3. fastigial nucleus (medially)

(DIF)

Question 23

deep cerebellar nuclei: function

Answer 23

these nuclei are main source of outputs from the cerebellum;

receieve information/input from the cerebellar cortex

Question 24

where is the dentate nucleus visible in anatomic sections?

Answer 24

located w/in white matter, deep to cerebellar cortex

Question 25

3 main fiber tracts (**PEDUNCLES**) for inputs/outputs and their **location**

Answer 25

1. superior 2. middle 3. inferior Found in lateral boundaries of the FOURTH VENTRICLE

Question 26

fourth ventricle in relation to peduncles, pons, medulla

Answer 26

floor of 4th ventricle is diamond shaped depression - found on dorsal surface of pons and medulla - bordered by superior, middle, and inferior cerebellar peduncles (which form the roof of the 4th ventricle)

Question 27

main function of the: **superior** cerebellar peduncle

Answer 27

* connects cerebellum to **midbrain** * contains mainly **OUTPUT** fibers

Question 28

main function of the: **middle** cerebellar peduncle

Answer 28

* connects cerebellum to **pons** * contains only **input** fibers

Question 29

main function of the: **inferior** cerebellar peduncle

Answer 29

* connects cerebellum to **spinal cord** * contains **BOTH input/output** fibers

Question 30

inputs and input routes | (w/ middle cerebellar peduncle)

Answer 30

**cerebral cortical areas** project to **pontine nuclei** --\> pontine nuclei axons _cross the midline_ and ( via the middle cerebellar peduncle) enter the **cerebellum**

Question 31

input route w/ inferior cerebellar peduncle

Answer 31

inferior cerebral peduncle contains \*MAINLY axons from the: 1. **_contralateral_ inferior olive**, and 2. **_ipsilateral_ spinal cord** 3. **_ipsilateral_ vestibular nuclei**:

Question 32

cell types in the cerebellar cortex and function

Answer 32

1. **granule** *(only excitatory cells in cerebellar cortex)* 2. **purkinje** *(inhibitory; ONLY output cells of cerebellum)*

Question 33

2 types of input to PURKINJE cells

Answer 33

1. *(direct input)* climbing fibers from **inferior olive** 2. *(indirect input via granule cell parallel fibers*), mossy fibers from **pontine nuclei, spinal cord, vestibular nuclei**

Question 34

describe direct input to PURKINJE cells

Answer 34

(climbing fiber input to purkinje cells) 1. single climbing fiber enwraps Purkinje cell dendrites 2. makes multiple excitatory synapses 3. generates powerful purkinje cell activation --\> evoking atypical action potential (complex spike)

Question 35

describe **indirect** input to purkinje cells

Answer 35

(granule cells input to purkinje cells) 1. granule cell axons ascend and bifurcate into parallel fibers 2. each parallel fiber synapses only once on a purkinje cell 3. synchronous firing of many parallel fibers are needed toa ctivate purkinje cell --\> generating typical action potential

Question 36

neuronal activity w/in cerebellar cortex: **simple spike activity** (describe)

Answer 36

* high at rest * incresaes w/ SENSORY INPUT and MOVEMENT * signals info about sensory stimuli/movements * INHIBITED during acquistion of new movements

Question 37

neuronal activity w/in cerebellar cortex: **complex spike activity** (describe)

Answer 37

* low at rest * influences responsiveness of Purkinje cell to parallel fiber input * appears to signal movement error * increases during acquisition of new movements * returns to low levels when new movement becomes coordinated

Question 38

inputs of deep cerebellar nuclei (DCN)

Answer 38

1. excitatory input from **collateral branches of climbing and mossy fibers** 2. inhibitory input from **Purkinje cells in cerebellar cortex**

Question 39

outputs of deep cerebellar nuclei (DCN)

Answer 39

DCN are the main source of outputs from the cerebellum to upper motor neurons in brainstem centers (reticular formation, superior colliculus) and in the motor cortex via the thalamus

Question 40

targets of cerebellar output | (controversial)

Answer 40

Question 41

match cerebellar cortex w/ deep cerebellar nuclei: ## Footnote **cerebrocerebellum**

Answer 41

dentate nucleus | (premotor cortex/ motor planning)

Question 42

match cerebellar cortex w/ deep cerebellar nuclei: ## Footnote **SPINOcerebellum**

Answer 42

interposed and fastigial nuclei (**motor** **execution**; motor cortex/brainstem)

Question 43

match cerebellar cortex w/ deep cerebellar nuclei: ## Footnote **VESTIBULOcerebellum**

Answer 43

vestibular nuclei (balance and vestibuloocular regulation/ lower motor neurons in spinal cord and brainstem)

Question 44

all pathways leaving cerebellum project to... where?

Answer 44

upper motor neurons

Question 45

which lobe is responsible for the following functions: * learning and coordination of complex, skilled movements * extensive reciprocal connections w/ cerebral cortex

Answer 45

posterior lobe

Question 46

input/output, and path of posterior lobe

Answer 46

* INPUTS: corticopontine input to cerebellum from MIDDLE CEREBRAL PEDUNCLE * OUTPUT: projects to **dentate nucleus**, whose axons exit cerebellum via **superior peduncle** to **motor thalamus** --\> motor thalamus projects to **motor cortex** (mainly to premotor cortex for control of _motor planning_)

Question 47

which lobe has the following functions? * coordination of limb movements (particularly of lower extremity) * extensive reciprocal connections w/ spinal cord

Answer 47

anterior lobe

Question 48

inputs/output pathway of anterior lobe

Answer 48

* INPUTS: from mechanoreceptors and proprioceptors * OUTPUTS: projects to **fastigial and interposed** nuclei --\> whose axons exit cerebellum via **SUPERIOR** and **INFERIOR** cerebellar peduncles --\> project to **motor thalamus** --\> projects to **motor cortex** (mainly to motor cortex for control of motor execution)

Question 49

**CC: posterior lobe syndrome**

Answer 49

* ATAXIA - *loos of coordination of voluntary movements* * HYPOTONIA - *dec muscle tone* * DYSMETRIA - *inability to control ROM* * DYSDIADOCHOKINESIA - *inability to perform rapid alternating movements* * TREMOR - intension tremor from disruption of normal agonist/antagonist contractions * Disrupted or explosive speech

Question 50

**CC: anterior lobe syndrome**

Answer 50

* ATAXIA - *loss of coordination of voluntary movements, mainly of lower limbs* * HYPOTONIA - *dec. muscle tone* * GAIT INSTABILITY

Question 51

Which lobe is responsible for the following functions: * coordination of axial (paraxial) muscles, movements involved in maintaining upright stance and balance, and eye movements to maintain direction of gaze * reciprocal connections w/ vestibular nuclei

Answer 51

flocculonodular lobe

Question 52

inputs/outputs of flocculonodular lobe

Answer 52

* INPUTS: direct input from **vestibular apparatus** * OUTPUTS: projects to **fastigial and vestibular nuclei** --\> vestibular axons project to **spinal cord** and to **cranial nerve nuclei** controlling extraocular muscles

Question 53

CC: Floculonodular lobe syndrome

Answer 53

* INABILITY TO MAINTAIN BALANCE * ATAXIA - *loss of coordination of movements in axial muscles (truncal ataxia)* * GAIT INSTABILITY