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Flashcards in Motor Systems Deck (55)
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1

Which type of musculature is regulated by the LCST?

Proximal (arms, hands, legs)

2

Which type of musculature is regulated by the ACST?

Distal (trunk)

3

Which two descending tracts are highly localized in the internal capsule?

Corticospinal and corticobulbar tracts

4

What descending tract takes up the most space in the IC?

Corticopontine

5

Where does the corticobulbar tract originate?

Cortical areas related to head and face

6

Where does corticobulbar tract terminate

Brainstem nuclei (bilateral)

7

What is the VL thalamus involved in?

Motor integration (involved in feedback loops via pons, cerebellum, dentate gyrus, and red nucleus)

8

What are the two divisions of the corticospinal tract?

1) Lateral CST; 2)Anterior CST

9

What is the target function of efferents originating in the ACST?

Postural adjustment

10

What is the target function of efferents originating in the LCST?

Skilled movement of extremities

11

Which somatotopic portion of the LCST is supplied most by the POSTERIOR spinal arteries?

the Cervical (most medial) > thoracic > lumbar > sacral; all are supplied by both the posterior and anterior spinal arteries

12

Describe the somatotopic preservation of motor fibres travelling through the posterior IC

(Arms most rostral, legs most caudal)

13

What proportion of the crus cerebri (anterior midbrain) is devoted to descending motor fibres?

The middle 3/5ths

14

In what portion of the brainstem does the corticospinal tract travel as pyramids?

Rostral/anterior medulla

15

What proportion of the the corticospinal tract fibres remain uncrossed at the level of the caudal medulla?

10-15% -- form ACST

16

Where do fibres in the ACST cross the midline?

SC at the level where they terminate on their LMNs

17

Descending UMNs form the __ before converging in the posterior limb of the IC

Corona radiata

18

Where are the UMNs for the corticobulbar tract?

Head and face regions of the primary motor cortex (precentral gyrus)

19

Which cranial nerve motor nuclei do fibres from the cortical bulbar tract terminate on bilaterally

1) Nucleus ambiguus; 2) Hypoglossal nucleus; 3) facial motor nucleus ROSTRAL region (upper facial muscles)

20

Which 2 cranial nerve motor nuclei do fibres from the cortical bulbar tract terminate on NOT bilaterally (exceptions to bilateral innervation)

1) Spinal accessory nucleus (ipsi projections for sternomastoid, contralateral for trapezius); 2) Facial motor nucleus (contralateral innervation to caudal part of nucleus (lower facial muscles)

21

Where does the corticobulbar tract descend in the IC?

At the genu

22

Where do fibres of the corticopontine tract originate?

Frontal, parietal, and temporal lobes

23

Which limbs of the IC does the corticopontine tract descend in?

Anterior AND posterior limbs

24

Which proportion of the crus cerebri is devoted to the corticopontine tract?

Lateral and medial 1/5

25

Where does corticopontine tract terminate?

Pontine nuclei

26

Where do the post-synpatic neurons of the corticopontine tract cross the midline?

In basal pons as TRANSVERSE PONTINE NUCLEI in the pontocerebellar tract

27

Where does the pontocerebellar tract terminate?

Contralateral cerebellar hemispheres

28

Which cerebellar peduncle is associated with the pontocerebellar tract?

Middle CP

29

Where do fibres of the dentarubrothalamic tract originate?

Dentate nucleus of cerebellum

30

Where do efferent fibres of the dentarubrothalamic tract exit the cerebellum?

Superior cerebellar peduncle