Cerebellum

Question 1

which cerebellar aa. supply the cerebellum?

Answer 1

SCA: covers superior, some of vermis, lateral hemispheres

AICA: cerebellar peduncles

PICA: lower portions of nodulus

Question 2

what do inferior cerebellar peduncles receive?

Answer 2

inferior cerebellar peduncles mostly receive cerebellar input from:

• spinocerebellar tracts
• vesbtibular input from olive
• small portion of output to vestibular system

Question 3

what does middle cerebellar input receive?

Answer 3

all input: mostly from pontocerebellar fibers

Question 4

what does superior cerebellar conduct?

Answer 4

cerebellar output

Question 5

arbor vitae

Answer 5

white matter tracts head to center, and gray is on the surface of the cerebellum

Question 6

what are the layers of the cerebellar cortex?

Answer 6

outer layer of cortex:

1. molecular layer (parallel fibers)
2. purkinge cell layer
3. granule cell layer

Question 7

what is the basic circuitry pattern of cerebellum?

Answer 7

• affarent information is taken in mostly via mossy fibers. Cell bodies are located in SC, vestibular nuclei and pontine nuclei.
• Mossy Fibers are cholinergic and synapse (ACh) and stimulate granule cells.
• Granule cells move towards cortex and make many synapses on purkinge cells of cerebellar cortex. Granule cells release glutamate.
• Purkinge cells of cerebellar cx. project into deep cerebellar nucleus, and are inhibitory Gabanergic.
• Deep Cerebellar nucleus influences UMN tracts.

Question 8

what are three important facts of the cerebellum?

Answer 8

• Cerebellar cortex does NOT contribute to conscious awareness.
• Cerebellar hemispheres control ipsilateral body
  BA 4= primary motor cx
  BA 6 = supplementary cx
  BA 8 = premotor cx

Question 9

What are three FUNCTIONAL divisions of cerebellum?

Answer 9

1. Vestibulocerebellum
2. Cerebrocerebellum
3. Spinocerebellum
   * they are named according to source of affarents *

Question 10

where is vestibulocerebellum located?

Answer 10

flocculonodular lobe

• made up of: floculi and nodules
• named from primary affarents coming from vestibular nuclei and primary affarent from vestibular apparatus.

Question 11

what is fn. of vestibulocerebellum?

Answer 11

coordinates proximal mm, maintains body posture/balance, coordinates eye movements.

Question 12

memorize vestibulocerebellar pathway

Answer 12

Input: Vestibular nuclei (1° afferents & from nuclei)

Cerebellar Nucleus: Fastigial nucleus

Targets: Lateral Vestibular & Reticular Nuclei

Question 13

fn of cerebrocerebellum

Answer 13

• located in lateral hemispheres

- fn: assists in planning, timing and initiation of complex mvmts.

Question 14

memorize cerbrocerebellum pathway

Answer 14

Input: Area’s 4 and 6 (via pontine nuclei) (+ many other cortical regions)

Cerebellar Nucleus: Dentate

Targets: Area’s 4 and 6 via thalamus (also red nucleus)

Question 15

where is spinocerebellum located?

Answer 15

vermis and paravermal regions

Question 16

function of spinocerebellum?

Answer 16

Smoothness, accuracy, & coordination of voluntary movements
Modulation of Ongoing Motor Activity:Rate, Range, & Force of Voluntary Movements
COMPARATOR

Question 17

primary affarents of spinocerebellum? what are the tracts?

Answer 17

• bring proprioception to the spinocerebellum via primary affarents that are the same as the DCML. (unconscious proprio)
• 4 tracts, but we will only focus on two:
  1. cuneocerebellar tract
  2. posterior spinocerebellar tract

Question 18

unconscious proprio from lower limb? below L2

Answer 18

below L2- primary affarent will cell body in dorsal root ganglion, enters into dorsal horn and ascends ipsilaterally in the dorsal column.

• In T1-L2, it synapses on the ipsilateral dorsal nucleus of clarke.
• The second order neuron then travels in the Dorsal Spinocerebellar Tract (DSCT) ipsilaterally, and projects through the inferior cerebellar peduncle to the ipsilateral cerebellum

Question 19

unconscious proprioception from trunk? T1-L2

Answer 19

• primary affarent with cell body in dorsal root ganglia enters in through the dorsal horn and synapses on second order neurons in the ipsilateral nucleus of clark
• It then ascends in the DSCT to the inferior cerebellar peduncle and to ipsilateral cerebellum

Question 20

unconscious proprioception from arms? cervical branches

Answer 20

• primary affarent with cell body in dorsal root ganglia enters into dorsal horn and travels in the ipsilateral cuneiocerebellar tract (most lateral portion of dorsal column).
• It will synapse on second order neuron in the medulla in the accessory nucleus cuneatus.
• The second order neuron will then travel ipsilaterally to the cerebellum via the inferior cerebellar peduncle.

Question 21

what upper motor systems do the spinocerebellar tracts influence?

Answer 21

• Lateral: LCST and Rubrospinal tract

- Medial: Vestibulospinal and reticulospinal tracts

Question 22

what would damage to paravermal region look like?

Answer 22

• deficits in distal limb musculature, lack of rate/range/force of distal limb mm.

Question 23

what would damage to vermis look like?

Answer 23

• defitis in axial limb mm, huge deficit in coordination, balance and postural mm. widebased stance

Question 24

know spinocerebellar tract, influencing axial/proximal limb mm.

Answer 24

• modulation of ongoing motor activity
• neck,trunk and proximal limb proprioceptive fibers travel in Dorsalspinocerebellar tract to inferior cerebellar peduncle and into the cortex of the vermis.
• Purkinje fibers from vermis project and synapse onto fastigial nucleus.
• Fastigial nucleus synapses in vestibular nuclei and reticular nuclei and modulates MVST, LVST, MRST, LRST to influence axial proximal limb mm.

Question 25

know spinocerebellar tracts for distal limb mm.

Answer 25

- modulates ongoing coordination/comparator of distal limb musculature (and flexors) - distal limb proprioceptive information is sent to ipsilateraly paravermal cerebellum via the DSCT and cuneiocerebellar tract - Paravermal projects via purkinje neurons to the ipsilateral interposed nuclei. - interposed nuclei decussate at superior cerebellar peduncle to thalamus and mangocellular red nucleus. 1. Thalamus projects to BA 4 which decussates in pyramids and descends in LCST to influence distal limb mm. 2. mangocellular red nucleus decussates immediately and runs in rubrospinal tract to influence distal limb mm.

Question 26

where will cerebellar lesions present?

Answer 26

``` ipsilateral defecits in unilateral lesion. coordination will be ipsilateral to the lesion - see motor ataxia ipsilateral to lesion - dysrythmia dysmetria - intention tremor - dysdiadochokinsia ```

Question 26

where will cerebellar lesions present?

Answer 26

``` ipsilateral defecits in unilateral lesion. coordination will be ipsilateral to the lesion - see motor ataxia ipsilateral to lesion - dysrythmia dysmetria - intention tremor - dysdiadochokinsia ```

Question 27

intention tremor

Answer 27

- cerebellum called upon more when trying to get closer to the target. - intention tremor (seen when patient is trying to accomplish a task) is opposite of Parkinson's tremor - seen ipsilateral to cerebellar lesion

Question 27

intention tremor

Answer 27

- cerebellum called upon more when trying to get closer to the target. - intention tremor (seen when patient is trying to accomplish a task) is opposite of Parkinson's tremor - seen ipsilateral to cerebellar lesion

Question 28

motor ataxia

Answer 28

- uncoordinated movements ipsilaterally to the lesion.

Question 28

motor ataxia

Answer 28

- uncoordinated movements ipsilaterally to the lesion.

Question 29

Dysrythmia

Answer 29

abnormal timing, seen ipsilateral to cerebellar lesion

Question 29

Dysrythmia

Answer 29

abnormal timing, seen ipsilateral to cerebellar lesion

Question 30

dysmetria

Answer 30

abnormal trajectory, (i.e. past pointing) - seen ipsilateral to cerebellar lesion

Question 30

dysmetria

Answer 30

abnormal trajectory, (i.e. past pointing) - seen ipsilateral to cerebellar lesion

Question 31

dysdiadochokinesia

Answer 31

inability to rapidly alter movement - seen ipsilateral to cerebellar lesion.

Question 31

dysdiadochokinesia

Answer 31

inability to rapidly alter movement - seen ipsilateral to cerebellar lesion.

Question 32

Midline lesion effects?

Answer 32

"Vermal Lesion" - results in unsteady gait and truncal sway - wide based stance - uncoordinated eye movments

Question 33

Lateral lesion effects?

Answer 33

"Paravermal lesion" - results in ataxia of limbs (appendicular ataxia) - past pointing - dysdiadochokinsia

Question 34

sensory ataxia?

Answer 34

- loss of DCML - lose conscious proprioception - signs and symptoms are very similar of cerebellar ataxia, except for the presence of near-normal coordination when the movement is visually observed by the patient, but marked worsening of coordination when the eyes are shut. - Sensory ataxia also lacks the associated features of cerebellar ataxia such as pendular tendon reflexes, scanning dysarthria, nystagmus and broken pursuit eye movements. - Patients with sensory ataxia often demonstrate pseudoathetosis and Romberg's sign. They usually complain of loss of balance in the dark

Question 35

Romberg's Sign

Answer 35

- In the Romberg test, the standing patient is asked to close his or her eyes. A loss of balance is interpreted as a positive Romberg's test. - A positive Romberg test suggests that the ataxia is sensory in nature, that is, depending on loss of proprioception. If a patient is ataxic and Romberg's test is not positive, it suggests that ataxia is cerebellar in nature, that is, depending on localized cerebellar dysfunction instead.