ascending tracts

Question 1

what is the function of the ascending tracts?

Answer 1

neural pathways

sensory info from peripheral nerves is transmitted to cerebral cortex

Question 2

functionally, what can the ascending tract be divided into?

Answer 2

into type of info they trasmit:
conscious
unconscious

Question 3

what are the conscious tracts comprised of?

Answer 3

• dorsal column-medial lemniscal pathway

- anterolateral system

Question 4

what are the unconscious tracts comprised of?

Answer 4

spinocerebellar tracts

Question 5

what modalities does the DCML carry?

Answer 5

sensory modalities of fine touch, vibration and proprioception

Question 6

where does the name, DCML come from?

Answer 6

• in spinal cord, info travels via dorsal columns

- in brainstem travels via medial lemniscus

Question 7

what are the first order neurones in the DCML?

Answer 7

2 different pathways which first order neurones take:

• signals from upper limb (T6 and above): travel in fasciculus cuneatus, synapse in nucleus cuneatus of medulla
• signals from lower limb (below T6): travel in fasciculus gracilis, synapse in nucleus gracilis of medulla

Question 8

describe the passage of the second order neurones

Answer 8

• begin in cuneate nucleus or gracilis
• deliver info to 3rd order neurones in thalamus
• within medulla, these fibres decussate
• travel in contralteral medial lemniscus to reach thalamus

Question 9

describe the passage of the third order neurones

Answer 9

• transmit sensory signals from thalamus to ipsilateral primary sensory cortex of brain
• ascend from ventral posterolateral nucleus of thalamus
• through internal capsule
• terminate at sensory cortex

Question 10

what 2 tracts is the anterolateral system made up of?

Answer 10

• anterior spinothalamic tract

- lateral spinothalamic tract

Question 11

what modalities does the anterior spinothalamic tract carry?

Answer 11

sensory

crude touch, pressure

Question 12

what modalities does the lateral spinothalamic tract carry?

Answer 12

sensory

pain and temp

Question 13

describe the first order neurones of anterolateral system

Answer 13

• arise from sensory receptors in periphery
• enter spinal cord
• ascend 1-2 vertebral levels and synpase at tip of dorsal horn (substantia gelatinosa)

Question 14

describe the passage of the second order neurones

Answer 14

• substantia gelatinosa to thalamus
• synpase w/ first order neurones
• fibres decussate within spinal cord
• then form 2 distinct tracts (anterior and lateral)

Question 15

describe the passage of the third order neurones

Answer 15

• thalamus to ipsilateral primary sensory cortex of brain
• ascend from ventral posterolateral nucleus of thalamus
• travel through internal capsule
• terminate at sensory cortex

Question 16

what is the function of the spinocerebellar tracts ?(unconscious)

Answer 16

help our brain co-ordinate and refine motor movements

transmit info from muscles to cerebellum

Question 17

within the spinocerebellar tract, what are the 4 individual pathways?

Answer 17

• posterior spinocerebellar tract
• cuneocerebellar tract
• anterior spinocerebellar tract
• rostral spinocerebellar tract

Question 18

what is the function of the posterior spinocerebellar tract?

Answer 18

carries proprioceptive info from lower limbs to ipsilateral cerebellum

Question 19

what is the function of the cuneocerebellar tract?

Answer 19

carriers proprioceptive infro from upper lumbs to ipsilateral cerebellum

Question 20

what is the function of the anterior spinocerebellar tract?

Answer 20

carries proprioceptive infro from lower limbs

fibres decussate twice so terminate in ipsilateral cerebellum

Question 21

what is the function of the rostral spinocerebellar tract?

Answer 21

carriers proprioceptive info from upper limbs to ipsilateral cerebellum

Question 22

what would happen if there was a lesion of the DCML pathway?

Answer 22

• loss of proprioception and fine touch
• but there is a small number of tactile fibres in anterolateral system so pt is still able to perform tasks in tactile info

Question 23

if the lesion occurs in the spinal cord, what side will the sensory loss be?

Answer 23

ipsilateral

Question 24

what would injury to the anterolateral system produce?

Answer 24

impairment of pain and temp sensation

Question 25

what side will the sensory loss be?

Answer 25

contralteral

spinothalamic tracts decussate within spinal cord

Question 26

what is Brown-Sequard syndrome?

Answer 26

• hemisection (one sided lesion) of spinal cord
• most often due to traumatic injury
• involved both anterolateral sytem and DCML pathway
• DCML - ipsilateral loss of touch, vibration, proprioception
• AL system - contralteral loss of pain and temp sensation

Question 27

what will lesions of the spinocerebellar tract present with?

Answer 27

ipsilateral loss of muscle co-ordination