Exam 2: Control of motor function II

Question 1

General Functions of the cerebellum

Answer 1

• electrical excitation of the cerebellum does not cause any conscious sensation and rarely causes any motor movement.
• Removal of the cerebellum causes body movements to become highly abnormal.

Question 2

What are the two hemispheres of the cerebellum separated by? how is each hemisphere divided?

Answer 2

Separated by vermis, each is divided into an intermediate and lateral zone.

Question 3

How is the cerebellum divided into 3 lobes?

Answer 3

Anterior to posterior:
Anterior lobe,
Posterior Lobe,
Flocculonodular lobe:
-associated with vestibular system.

Question 4

What control functions are found in the vermis?

Answer 4

Muscle movements of the axial body, neck, shoulders, and hips.

Question 5

What is the intermediate zone of the cerebellum concerned with?

Answer 5

controlling muscle contractions in the distal portions of the upper and lower limbs, esp. hands, feet, fingers, and toes.

Question 6

What is the lateral zone associated with?

Answer 6

cerebral cortex with planning of sequential motor movements.

Question 7

Transversely arranged narrow gyri called folia are associated with?

Answer 7

The cortex of the the gray matter of cerebellum

Question 8

These fibers project in to the red nucleus and lesions in these nuclei lead to extremity ataxia:

Answer 8

Globose, Embolifom, Dentate Nuclei.

Question 9

What would a lesion in the fastigial nuclei lead to?

Answer 9

Trunk ataxia

Question 10

Fibers of this nuclei project to reticular formation and vestibular nuclei? What is it related to?

Answer 10

Fastigial nuclei. Related to postural activity and limb movements via reticulospinal and vestibulospinal tracts.

Question 11

What are the four parts of the intracerebellar nuclei?

Answer 11

Dentate, Emboliform, Globose, and Fastigial.

Question 12

What cells of the cerebellar cortex provide lateral inhibition on adjacent purkinje cells to prove damping?

Answer 12

Basket and Stellate Cells.

Question 13

Cells of the cerebellar cortex:

Granular Cells-

Answer 13

Axons from parallel fibers in cortex (+)

Question 14

Cells of the cerebellar cortex:

Golgi cells-

Answer 14

Project from parallel fibers to granular cell bodies (-)

Question 15

Cells of the cerebellar cortex:

Basket cells-

Answer 15

Project from parallel fibers to purkinje axon hillock (-)

Question 16

Cells of the cerebellar cortex:

Stellate Cells-

Answer 16

Project from parallel fibers to purkinje dendrites (-)

Question 17

Cells of the cerebellar cortex:

Purkinje Cells-

Answer 17

• Extensive dendritic branching.
• Receive input from parallel fibers (20K synapses between parallel fiber and one purkinje cell. )
• Project to intracerebellar nuclei (-)
• ONLY output from cortex**

Question 18

Functional unit of Cerebellar Cortex:

Answer 18

• 30M functional units in cerebellar cortex
• Each Function unit (F.U) is centered on a Purkinje cell and a corresponding deep nuclear cell.
• output from F.U. is from deep nuclear cell.
• Afferent inputs to the cerebellum are mainly from the climbing and mossy fibers.

Question 19

Where do all climbing fibers originate from?

Answer 19

the inferior olives.

Question 20

Mossy fibers enter cerebellum from a variety of sources, what do they do?

Answer 20

send excitatory collaterals to deep nuclear cells and then synapse in granular layer with thousands of granule cells.

Question 21

Where do granule cells send axons?

Answer 21

to outer cerebellar surface; axons branch in tow direction parallel to folia.

Question 22

Dendrites of purkinje fibers project to these

Answer 22

parallel fibers.

Question 23

Direct stimulation by _______ and _____ fibers excites deep nuclear cells. _______ cells signals inhibit deep nuclear cells.

Answer 23

Climbing and mossy. Purkinje.

Question 24

Basket cells and stellate cells also function as

Answer 24

inhibitory cells.

Question 25

Nervous system uses cerebellum to coordinate motor control functions at three levels

Answer 25

• vestibulocerebellum
• spinocerebellum
• cerebrocerebellum

Question 26

What does the Vestibulocerebellum consist of?

Answer 26

flocculondular lobes and vermis. Evolved about the same time as vestibular system

Question 27

Where does the vestibulocerebellum receive fibers from? Where does it send output primarily?

Answer 27

The vestibular system and oculomotor system (pontocerebellar fibers). Primary output is to the vestibular system.

Question 28

Loss of flocculonodular lobes leads to

Answer 28

extreme disturbance of equilibrium and postural movements.

Question 29

In the vestibulocerebellum system movements are often pendular and tend to overshoot. Why?

Answer 29

B/c of momentum. The damping system can stop movement precisely at intended point with appropriate learned subconscious signals from intact cerebellum.

Question 30

Changes that occur when cerebellum is removed:

Answer 30

• movements are slow to develop
• force developed is weak
• movements are slow to turn off.

Question 31

Spinocerebellum

Answer 31

consists mostly of vermis and intermediate zone.
-Receives info from motor cortex and red nucleus telling cerebellum intended sequential plan of movement for the next few fractions of a second.

-Feedback info from periphery telling cerebellum what actual movements results.

Question 32

The spinocerebellum compares two sources of information and sends corrections to:

Answer 32

• motor cortex via thalamus

- Magnocellular portions of red nucleus.

Question 33

Cerebrocerebellum:

Answer 33

• consists of lateral parts of hemispheres
• mostly associated with the premotor and the primary and association somatosenosry areas of teh cerebral cortex.
• Receives corticopontocerebellar projections.

Question 34

The cerebrocerebellum is involved in coordination of skilled movements and speech. What is meant by it’s “motor” imagery” ?

Answer 34

Plans as much as tenths of a second in advance of actual movements.

Question 35

Dysmetria

Answer 35

refers to a lack of coordination of movement typified by the undershoot or overshoot of intended position with the hand, arm, leg, or eye. It is a type of ataxia. It is sometimes described as an inability to judge distance or scale.

Question 36

Ataxia:

Answer 36

the loss of full control of bodily movements.

Question 37

past pointing:

Answer 37

means that in the absence of the cerebellum, a person ordinarily moves the hand or some other moving part of the body considerably beyond the point of intention. This results from the fact that normally the cerebellum initiates most of the motor signal that turns off a movement after it is begun; if the cerebellum is not available to do this, the movement ordinarily goes beyond the intended mark. Therefore, past pointing is actually a manifestation of dysmetria.

Question 38

Dysdiadochokinesia

Answer 38

is a feature of cerebellar ataxia and may be the result of lesions to either the cerebellar hemispheres or the frontal lobe (of the cerebrum), it can also be a combination of both.

Question 39

Dysarthria

Answer 39

difficult or unclear articulation of speech that is otherwise linguistically normal.

Question 40

Cerebellar nystagmus

Answer 40

Tremor of the Eyeballs

Question 41

hyptonia:

Answer 41

Decreased Tone of the Musculature

Question 42

Path of afferent corticopontocerebellar:

Answer 42

Motor and premotor cortices/Somatosensory cortex –> pontine nuclei –> lateral divisions of cerebellum

Question 43

Vestibulocerebellar afferent path

Answer 43

Terminates in flocculonodular lobes

Question 44

afferent path of reticulocerebellar

Answer 44

terminates primarily in vermis

Question 45

afferent path of spinocerebellar

Answer 45

dorsal and ventral.

transmits signals at 120 m/second

Question 46

All of the afferent tracts to the cerebellum for the __________ that terminate on the ________ cells in the Cerebellar cortex (+)

Answer 46

mossy fibers, granule

Question 47

What does the dorsal spinocerebellar apprise the cerebellum of momentary status of?

Answer 47

• muscles contractions
• degree of tension on the muscle spindles
• positions and rates of movement of parts of the body.
• forces acting on surfaces of the body.

Question 48

Dorsal spinocerebellar pathway

Answer 48

muscle fibers —> ipsilaterally in vermis and intermediate zones.

Question 49

This afferent tract to the cerebellum terminates both ipsilaterally and contralaterally?

Answer 49

Ventral spinocerebellar.

Question 50

What does the ventral spinocerebellar tell cerebellum?

Answer 50

• which motor signals have arrived at the anterior horns.

- this feedback= efference copy of the anterior horn motor drive.

Question 51

How is the ventral spinocerebellar excited?

Answer 51

Excited by:

• Coretex via corticospinal and rubrospinal tracts
• internal motor pattern generators within spinal cord.