2 - Ascending & Descending Pathways

Question 1

how many neurones do ascending pathways have?

Answer 1

3
* primary - same side as sensatin
* secondary - decussates
* tertiary - within the brain

Question 2

what 3 ascending tracts are responsible for conscious sensation/

Answer 2

spinothalamic
spinal reticular
dorsal column

Question 3

what is the role of the spinothalamic tract?

Answer 3

anterior - crude touch and pressure
lateral - pain and temperature sensation

Question 4

describe the route of each neuron in the spinothalamic tract:

Answer 4

first order - peripheral receptors to dorsal horn
secondary - decussates to other side of spinal cord and travels to thalamus
thrid order - thalamus to somatosensory cortex through internal capsule

Question 5

what is the role of the spinalreticular tract?

Answer 5

automatic response to pain

Question 6

what is the role of the dorsal column pathway?

Answer 6

fien tough, two touch discrimination, vibration, proprioception

Question 7

where does the spinothalamic tract decussate?

Answer 7

spinal cord

Question 8

where does the dorsal column pathway synsapse?

Answer 8

medulla

Question 9

describe the routes of the neurones in the dorsal column:

Answer 9

• first order - travel through fasciculus cuneatus or fasciculus gracilis
• second order - synapses in medulla and travels to thalamus via medial lemniscus
• third order - to somatosensory cortex

Question 10

what is the role of the fasciculus cuneatus?

Answer 10

carries upper limb info (T6 and above)

Question 11

what is the role of the fasciculus gracilis?

Answer 11

carries infor from the lower limb (below T6)

Question 12

what ascending pathways are responsible for unconscious perception?

Answer 12

dorsal spinocerebellar
anterior spinocerebellar
cuneocerebellar

Question 13

what is the role of the dorsal spinocerebellar tract?

Answer 13

transmits proprioceptive info from lower limbs to cerebellum

Question 14

what is the role of the ventral spinocerebellar tract?

Answer 14

transmits proprioceptive info from lower limbs to cerebellum

Question 15

what is the role of the cuneocerebellar tract?

Answer 15

transmits proprioceptive info from upper limb and neck

Question 16

describe the route of the neurones in the dorsal spinocerebellar tract

Answer 16

• 1st synapses onto second in dorsal horn
• second travels to cerebellum
• completely ipsilateral

Question 17

describe the route of the neurones in the ventral spinocerebellar tract

Answer 17

• ipsilateral but decussates twice
• decussates on entry to spinal cord and in white matter of cerebellum

Question 18

lesions in the spinothalmic tract result in what?

Answer 18

loss of contralateral:
* crude touch
* pressure
* pain
* temp

Question 19

lesions in the dorsal column pathway result in what?

Answer 19

loss of ipsilateral:
* proprioception
* vibration
* fine touch

Question 20

spinocerebellar lesions lead to what?

Answer 20

loss of ipsilateral coordination

Question 21

what are the two pyramidal descending pathways?

Answer 21

• corticospinal tract
• corticobulbar tract

Question 22

what is the corticospinal tract responsible for?

Answer 22

muscle control of the body

Question 23

describe the route of neurones in the corticospinal tract:

Answer 23

1. cell bodies in cerebral cortex
2. pass through internal capsule
3. pass through crus cerebri
4. pass through pons
5. at pyramids of medulla 75% fibres decussate (lateral) and synapse with LMN in ventral horn
6. 25% do not decussate (anterior) - later decussate at cervical and thoracic levels

Question 24

where does the corticospinal tract decussate?

Answer 24

75% - pyramids of medulla
25% - cervical and thoracic levels

Question 25

what is the role of teh corticobulbar tract?

Answer 25

voluntary control of face, head and neck

Question 26

what is the route of the neurones in the corticobulbar tract?

Answer 26

* originate in cerebral cortex * pass through intenral capsule * do not descend into spinal cord but synapse onto cranial nerve nuclei

Question 27

the neurones of the corticobulbar tract innervate how?

Answer 27

bilaterally * provide motor sensation to both sides of face

Question 28

what are the 4 extrapyrimidal descending tracts?

Answer 28

1. rubrospinal tract 2. reticulospinal tract 3. vestibulospinal tract 4. tectospinal tract

Question 29

what is the role of the rubrospinal tract?

Answer 29

motor control

Question 30

where does the rubrospinal tract originate?

Answer 30

red nucleus

Question 31

what is the role of the reticulospinal tract?

Answer 31

* medial - facilitates contraction and increases tone * lateral - inhibits contraction

Question 32

where does the reticulospinal tract originate?

Answer 32

medial - pons lateral - medulla

Question 33

where does the vestibulospinal tract originate?

Answer 33

vstibular nuclei

Question 34

what is the role of the vestibulospinal tract?

Answer 34

balance and posture

Question 35

where does the tectospinal tract originate?

Answer 35

superior colliculus

Question 36

what is the role of the tectospinal tract?

Answer 36

head and eye coordination

Question 37

what are signs of extrapyrimidal tract injuries?

Answer 37

* parkinsonisms * chorea * athetosis * dystonia

Question 38

how many cranial nerve nuclei are motor?

Answer 38

10

Question 39

how many cranial nerve nuclei are sensory?

Answer 39

8

Question 40

Label the cranial nerve nuclei

Answer 40