cerebellar prac

Question 1

1. Feedback mechanism:

Answer 1

In an ongoing movement, the cerebellum continuously receives copies of both motor commands and resultant sensory feedbacks.
- the cerebellum acts as a comparator and error detector, when it acts in such a feedback mechanism. In case, the cerebellum detects an error, it corrects the error to make the movement smooth and to maintain a coordinated movement

Question 2

CEREBLLUM SUMMARY

Answer 2

In summary, the cerebellum is a comparator, error detector (in ongoing movements), and is involved in the process of error correction (of ongoing movements) to establish coordinated movements. A brief functional description of the cerebellum is that it coordinates movements (controls the timing and strength of muscular contractions [= muscle tone] during movement).

Question 3

Feed forward mechanism

Answer 3

, the cerebellum does not have time to wait for a sensory feedback of a motor action to arrive;
The prediction of an outcome of a motor action
- IN feed forward mechanism, the cerebellum utilizes the experience you have gathered so far and predicts a positive outcome of your jump and feeds this information into all relevant motor pathways to achieve a predictable outcome.

Question 4

CEREBELLUM OTHER FUNCTIONS

Answer 4

is also involved in maintenance of equilibrium (balance) and body posture by influencing the extrapyramidal pathways (vestibulospinal and reticulospinal pathways

Question 5

CEREBLLAR SEGMENTS

Answer 5

♣ Superior cerebellar segment is supplied by one superior cerebellar artery
♣ Inferior cerebellar segment is supplied by two inferior cerebellar arteries

Question 6

Purkinje cell

Answer 6

contains one axon And massive amounts of branches of apical dendritic tree.

Question 7

The cerebellum has three functional loops that work independently (= are modular). Why are they independent?

Answer 7

CONSCIOUS AND NON-CONSCIOUS. EACH FORM A COMPONENT IN A CLOSED ANATOMICAL LOOP THAT SENDS AND RECEIVES PROJECTIONS FROM SPECIFIC AREA OF THE CNS

Question 8

The spinocerebellar pathways

Answer 8

carry sensory information upward to the brain. However, as these pathways connect to the cerebellum, the information that they convey is not consciously perceived.

Question 9

The posterior spinocerebellar pathway

Answer 9

originates from Clarke’s nucleus, a prominent nucleus that is a characteristic feature for the upper lumbar and thoracic spinal cord. The Clarke’s nucleus is referred to as Clarke’s column as it extends from the upper thoracic spinal cord to the upper lumbar spinal cord (T1-L2). The posterior spinocerebellar pathway transmits unconscious proprioceptive and cutaneous sensory information from the lower limbs and torso (e.g. from muscle spindles) to the cerebellum.

Question 10

the cuneocerebellar pathway

Answer 10

For the upper limbs, similar information is provided to the cerebellum via the cuneocerebellar pathway; the latter arises from the accessory cuneate nucleus in the medulla. Both projections are ipsilateral.

Question 11

anterior (ventral) and superior (rostral) spinocerebellar pathways

Answer 11

There is also an anterior (ventral) and superior (rostral) spinocerebellar pathways that originate from neurons in the ventral horns (motor neurones); they provide the cerebellum primarily with a copy (feedback) of the descending motor command that they extract from the spinal motor neurones. This copy is very important as this is the motor command that has converged from pyramidal tract, extrapyramidal tracts, and spinal interneurons into the spinal motor neurones and is the final copy that is dispatched into the periphery to the muscles.
Unlike posterior spinocerebellar pathway that stays ipsilateral when it courses towards the cerebellum,

Question 12

anterior spinocerebellar pathway

Answer 12

anterior spinocerebellar pathway crosses over to contralateral in the spinal cord. It, however, crosses back at the midbrain level (or within the cerebellum) to stay ipsilateral (“it undertakes double-crossing” to stay ipsilateral). The anterior spinocerebellar pathway enters the cerebellum via the superior cerebellar peduncle.

Question 13

superior spinocerebellar PATHWAY

Answer 13

A pathway homologue of the anterior spinocerebellar pathway for the upper limbs & shoulder is the so-called superior spinocerebellar pathway with which the anterior spinocerebellar pathway enters the cerebellum through the superior cerebellar peduncle.

Question 14

NOTE 1

Answer 14

• the dorsal column-lemniscal pathway conveys conscious proprioceptive signals to cerebrum, whereas posterior spinocerebellar & cuneocerebellar tracts convey unconscious proprioceptive signals to cerebellum.

Question 15

NOTE 2

Answer 15

It should be understood that the proprioceptive information conveyed to the cerebellum is similar to the proprioceptive information conveyed to the cerebrum via dorsal column-lemniscal pathway