deck 1

Question 1

where does the 1st order sensory enter the spinal cord?

Answer 1

dorsal horn at the dorsal root entry zone (DREZ)

Question 2

Where does touch and conscious proprioception primary axons collect at?

Answer 2

as the dorsal column

Collateral branches are involved in intra- and intersegmenal reflexes

Question 3

Where does Aalpha and Abeta fibers enter?

Answer 3

medially near the dorsal column

more myelin ids more darker

Question 4

What does the lower limb axons below T6 form?

Answer 4

gracile fasciculus

Question 5

What does the upper limb axons above T6 form?

Answer 5

collect to form the cuneate fasciculus

Question 6

How are dorsal column somatopy fibers added?

Answer 6

fibers are added from medial to lateral

This avoids having upper fibers pass through the tract to take up position

Question 7

Where does each dorsal fascilucus ends/

Answer 7

caudal medulla at a corresponding nucleus

1st order axons of the fascicles synapse on 2nd order neurons in the nuclei

Question 8

Where does does 2nd order neurons decussate?

Answer 8

as internal arcuate fibers

Question 9

Where does the gracile fibers decussate?

Answer 9

cross to a ventral position

Question 10

Where does cuneate fibers decussate?

Answer 10

cross to a dorsal position

Question 11

What does the internal arcuate fibers organize as?

Answer 11

the vertical rectangular medial lemniscus Vertical medial lemniscus passes inferior olivary nuc. to upper medulla

Question 12

how does the medial lemniscus shift?

Answer 12

At the medullopontine junction, medial lemniscus begins to shift
Ventral part (foot) swings laterally (slips on inferior (oily) olivary nucleus)
By mid-pons, medial lemniscus is horizontal

Question 13

How does the medial lemniscus shift through pons and midbrain?

Answer 13

Through pons and midbrain, the lateral end continues to swing upward
Midbrain somatotopy has the little headless half-man upside down

Question 14

Where does 2nd order neurons of the ML synapse on 3rd order neurons?

Answer 14

2nd order neurons of the ML synapse on 3rd order neurons of the ventral posterolateral thalamus (VPL)

Question 15

Where does the 3rd order neurons of the VPL enter where?

Answer 15

enter posterior limb of internal capsule (PLIC)

These thalamocortical fibers ascend in PLIC and corona radiata to terminate in appropriate parts of the sensory homunculus of the postcentral gyrus

Question 16

How are the somatotopy for DC-ML pathway arrange?

Answer 16

leg posterior, arm anterior

Question 17

what does lesions of the ML, VPL thalamus and PLIC and medial and upper lateral post central gyrus (above the internal arcuate fibers)

Answer 17

produce contralateral loss of descriminative touch and conscious proprioception from the limbs and trunk

Question 18

What does lesions of the dorsal column or gracile and cuneate nuclei produce (below the internal arcuate fibers)

Answer 18

produce ipsilateral loss of descriminative touch and conscious proprioception from the limbs and trunk

Question 19

How is Loss of lower limb conscious proprioception can be tested?

Answer 19

Romberg test

Question 20

Where does MS attack usually happens at?

Answer 20

The dorsal column is a common locus of attack for multiple sclerosis, a demyelinating disease.

Question 21

Where does unconscious proprioception originate for lower limb?

Answer 21

2nd order tracts originate in the dorsal horn (2 proprioceptor-mechanoceptor combinations for each of 2 limbs)
from LOWER limb: dorsal (posterior) & ventral (anterior) spinocerebellar tracts – DSCT (PSCT) & VSCT (ASCT)

Cerebellum receives all (and only ) signals originating on ipsilateral side

Question 22

Where does unconscious proprioception originate for upper limb?

Answer 22

2nd order tracts originate in the dorsal horn (2 proprioceptor-mechanoceptor combinations for each of 2 limbs)
from UPPER limb: cuneo- & rostral spinocerebellar tracts - CCT & RSCT

Cerebellum receives all (and only ) signals originating on ipsilateral side

Question 23

Where does the Cuneocerebellar and dorsal spinocerebellar tracts switch over at?

Answer 23

T6

Question 24

Where does Ventral spinocerebellar and rostral spinocerebellar tracts switch?

Answer 24

C8

Question 25

Where does he dorsal/ventral/Rostral and Cuneo CT originates?

Answer 25

Dorsal SCT originates in dorsal nucleus (of Clark)
Ventral SCT originates from spinal border cells (mostly lamina VII)
Cuneo CT originates in accessory cuneate nucleus of caudal medulla
Rostral SCT originates in lamina VII