Cerebellum Flashcards
which cerebellar aa. supply the cerebellum?
SCA: covers superior, some of vermis, lateral hemispheres
AICA: cerebellar peduncles
PICA: lower portions of nodulus
what do inferior cerebellar peduncles receive?
inferior cerebellar peduncles mostly receive cerebellar input from:
- spinocerebellar tracts
- vesbtibular input from olive
- small portion of output to vestibular system
what does middle cerebellar input receive?
all input: mostly from pontocerebellar fibers
what does superior cerebellar conduct?
cerebellar output
arbor vitae
white matter tracts head to center, and gray is on the surface of the cerebellum
what are the layers of the cerebellar cortex?
outer layer of cortex:
- molecular layer (parallel fibers)
- purkinge cell layer
- granule cell layer
what is the basic circuitry pattern of cerebellum?
- 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.
what are three important facts of the cerebellum?
- 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
What are three FUNCTIONAL divisions of cerebellum?
- Vestibulocerebellum
- Cerebrocerebellum
- Spinocerebellum
* they are named according to source of affarents *
where is vestibulocerebellum located?
flocculonodular lobe
- made up of: floculi and nodules
- named from primary affarents coming from vestibular nuclei and primary affarent from vestibular apparatus.
what is fn. of vestibulocerebellum?
coordinates proximal mm, maintains body posture/balance, coordinates eye movements.
memorize vestibulocerebellar pathway
Input: Vestibular nuclei (1° afferents & from nuclei)
Cerebellar Nucleus: Fastigial nucleus
Targets: Lateral Vestibular & Reticular Nuclei
fn of cerebrocerebellum
- located in lateral hemispheres
- fn: assists in planning, timing and initiation of complex mvmts.
memorize cerbrocerebellum pathway
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)
where is spinocerebellum located?
vermis and paravermal regions
function of spinocerebellum?
Smoothness, accuracy, & coordination of voluntary movements
Modulation of Ongoing Motor Activity:Rate, Range, & Force of Voluntary Movements
COMPARATOR
primary affarents of spinocerebellum? what are the tracts?
- 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
unconscious proprio from lower limb? below L2
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
unconscious proprioception from trunk? T1-L2
- 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
unconscious proprioception from arms? cervical branches
- 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.
what upper motor systems do the spinocerebellar tracts influence?
- Lateral: LCST and Rubrospinal tract
- Medial: Vestibulospinal and reticulospinal tracts
what would damage to paravermal region look like?
- deficits in distal limb musculature, lack of rate/range/force of distal limb mm.
what would damage to vermis look like?
- defitis in axial limb mm, huge deficit in coordination, balance and postural mm. widebased stance
know spinocerebellar tract, influencing axial/proximal limb mm.
- 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.
know spinocerebellar tracts for distal limb mm.
- 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.
where will cerebellar lesions present?
ipsilateral defecits in unilateral lesion. coordination will be ipsilateral to the lesion - see motor ataxia ipsilateral to lesion - dysrythmia dysmetria - intention tremor - dysdiadochokinsia
where will cerebellar lesions present?
ipsilateral defecits in unilateral lesion. coordination will be ipsilateral to the lesion - see motor ataxia ipsilateral to lesion - dysrythmia dysmetria - intention tremor - dysdiadochokinsia
intention tremor
- 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
intention tremor
- 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
motor ataxia
- uncoordinated movements ipsilaterally to the lesion.
motor ataxia
- uncoordinated movements ipsilaterally to the lesion.
Dysrythmia
abnormal timing, seen ipsilateral to cerebellar lesion
Dysrythmia
abnormal timing, seen ipsilateral to cerebellar lesion
dysmetria
abnormal trajectory, (i.e. past pointing) - seen ipsilateral to cerebellar lesion
dysmetria
abnormal trajectory, (i.e. past pointing) - seen ipsilateral to cerebellar lesion
dysdiadochokinesia
inability to rapidly alter movement - seen ipsilateral to cerebellar lesion.
dysdiadochokinesia
inability to rapidly alter movement - seen ipsilateral to cerebellar lesion.
Midline lesion effects?
“Vermal Lesion” - results in unsteady gait and truncal sway
- wide based stance
- uncoordinated eye movments
Lateral lesion effects?
“Paravermal lesion”
- results in ataxia of limbs (appendicular ataxia)
- past pointing
- dysdiadochokinsia
sensory ataxia?
- 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
Romberg’s Sign
- 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.
