Spinal tracts

Question 1

what is the VPMn

Answer 1

ventral posterior medial nucleus
- in thalamus
- carries somatosensory info from the head, face, and neck

Question 2

what is the VPLn

Answer 2

ventral posterior lateral nucleus
- in the thalamus
- carries somatosensory info from everything below the neck

Question 3

what is the DCML

Answer 3

dorsal column medial lemniscus tract
- pathway from periphery through the dorsal column of the spine to the medial lemniscus to S1
- carries cutaneous info

Question 4

where do the dorsal and anterior spinocerebellar pathways travel

Answer 4

lower limbs to the cerebellum

Question 5

what is the dorsal spinocerebellar pathway

Answer 5

• somatosensory info from GTO and muscle spindle axons enters the dorsal horn of the spinal cord
• travels up the ipsilateral side of the dorsal horn
• synapses at clarkes nucleus
• travels up DSCT until it reaches junction of medulla and pons
• info enters cerebellum via inferior cerebellar peduncle
• some info decussates and continues to the contralateral S1 via the thalamus through DCML
  no decussation in main pathway

Question 6

where are the decussation points in the dorsal spinocerebellar pathway

Answer 6

there are none
- info from right side of body enters right cerebellum

Question 7

where are the synapse(s) in the dorsal spinocerebellar pathway

Answer 7

clarkes nucleus

Question 8

how many orders of neurons are there in the dorsal spinocerebellar pathway and where do they travel

Answer 8

1st order
- from info to clarkes nucleus
2nd order
- from clarkes nuclues to the cerebellum

Question 9

what is clarkes nucleus

Answer 9

major spinal relay centre
- composed of neurons in the dorsal horn of the spinal cord
- only interacts with the dorsal spinocerebellar pathway

Question 10

what is the anterior spinocerebellar pathway

Answer 10

• somatosensory info from GTOs enters the dorsal horn of the spinal cord
• decussates into spinal cerebellar tract (same info in DSCT)
• travels up ASCT until juntion of medulla and pons
• decussates at the caudal medulla
• enters cerebellum vai superior cerebellar peduncle

Question 11

where are the decussation points in the anterior spinocerebellar pathway

Answer 11

1. at the level of the spine where info enters
2. caudal medulla

• info from right side of body enters the right side cerebellum (double cross)

Question 12

where are the synapse(s) in the anterior spinocerebellar pathway

Answer 12

1st synapse = at the level of entry into the spine
2nd synapse = cerebellum

Question 13

how many orders of neurons are there in the anterior spinocerebellar pathway and where do they travel

Answer 13

1st order
- from info to the entry into the dorsal horn
2nd order
- from level of entry into the spine to the cerebellum

Question 14

what is the reason for the double cross in the anterior spinocerebellar pathway

Answer 14

help survive certain spinal cord injuries
another afferent copy of the same info is travelling on the other side of the spine

Question 15

what are the equivalent pathways for the upper limbs compared to the ASCT and DSCT

Answer 15

ASCT (lower limbs) = rostral spinocerebellar tract (upper limbs)
DSCT (lower limbs) = cuneocerebellar tract (upper limbs)

Question 16

where does info go after being processsed by the cerebellum

Answer 16

contralateral sensory and motor areas via the thalamus

Question 17

why are DSCT and ASCT important

Answer 17

important for unconsicous proprioception
- increased force to counteract a force
- motor commands are generated without “permission” from M1 and then we feel it afer

Question 18

explain the pathway of DCML

Answer 18

• sensory neurons travel to the dorsal horn
• info travels up the dorsal columns in the gracile or cuneate fascicle
• decussates in the medulla
• info travels up medial lemniscus through brainstem to the thalamus
• synapses at the thalamus onto internal capsule
• info travels in internal capsule from the thalamus to S1

Question 19

where are the decussation points in DCML

Answer 19

only at the caudal medulla
- info innervates contralateral side of brain

Question 20

where are the synapse(s) in DCML

Answer 20

1. caudal medulla (decussation pt)
2. thalamus
3. S1 - to integrate with more neurons

Question 21

how many orders of neurons are involved in DCML and where do they travel

Answer 21

1st order
- info from sensroy to teh medulla (through spinal cord)
2nd order
- info from medulla to thalamus
3rd order
- info from thalamus to S1 (through internal capsule)

Question 22

is there a difference in the info carried by DSCT and ASCT

Answer 22

no - copies of the same info, just travel on different sides of the spine

Question 23

where are the VPMn and VPLn located

Answer 23

thalamus

Question 24

what is the somatotropic organisation of the dorsal column of the spinal cord

Answer 24

organised by bodoy part
- distal body parts = medial
- proximal body parts = lateral

Question 25

which spinal tract(s) are used in the descending pathway from S1

Answer 25

ventral/anterior corticospinal tract (10%)
lateral corticospinal tract (90%)

Question 26

what info does the lateral CST carry

Answer 26

all periphery (not trunk and core)

Question 27

what info does the ventral CST carry

Answer 27

trunk and core (innervates bilaterally)

Question 28

what percent of CST neurons come from S1

Answer 28

~30%

Question 29

what side of the body is affected by damage to descending neuron ABOVE the pyramidal decussation

Answer 29

contralateral side of the body

Question 30

what side of the body is affected by damage to descending neuron BELOW the pyramidal decussation

Answer 30

ipsilateral side

Question 31

what are the pyramids

Answer 31

protuberance of descending neurosn arising from different areas of cerebral cortex
- lateral CST decussation point

Question 32

what type of info is carried in the DCML

Answer 32

proprioceptive info