Pathways

Question 1

What are the major descending tracts?

Answer 1

1. Lateral Corticospinal tract

2. Ventral Corticospinal tract

Question 2

What are the major ascending tracts?

Answer 2

1. Dorsal Columns
2. Lateral Spinothalamic tract
3. Ventral spinothalamic tract

Question 3

What does the lateral corticospinal tract innervate?

Answer 3

-motor info to the Limb muscles

Question 4

Where does the cell bodies in the lateral and ventral corticospinal tract?

Answer 4

Pre-central gyrus (primary motor cortex)

Question 5

How does the axons travel in the lateral and ventral corticospinal tract?

Answer 5

The axons (1st order/Upper motor neurone) descend via the internal capsule, NOT the thalamus

Question 6

What happens at the medulla in the corticospinal tract?

Answer 6

At the medulla 75-90% of the fibres decussate – these are the fibres that will form the lateral CS tract and innervate the limbs

Question 7

What does the ventral corticospinal tract do?

Answer 7

Innervare axial (NOT desiccate)

Question 8

What is the corticobulbar tract?

Answer 8

• Connects the motor cortex to the medullar pyramids
• Leaves the internal capsule and enters the pons
• Terminate directly on alpha motor neurones or interneurones innervating alpha motorneurons in the brainstem. These control somatic motor activity in the head e.g. muscles that control mastication, expression and eye movement

Question 9

What does vestibulospinal tract?

Answer 9

provides info about head movement

Question 10

What is the tectospinal tract?

Answer 10

orientation of head and neck

Question 11

What is the reticulospinal tract?

Answer 11

breathing control and emotional motor function

Question 12

Rubrospinal tract?

Answer 12

innervates lower motor neurones of upper limb

Question 13

What does the dorsal column pathway do?

Answer 13

Mechanical
Fine discriminative touch
Pressure
Vibration
Proprioception

Question 14

What does the spinothalamic pathway do?

Answer 14

Mechanical, chemical & thermal
Crude touch
Pain
Temperature

Question 15

What happens when fibres enter the dorsal horn?

Answer 15

enter the ascending dorsal column pathways

Question 16

How do the lower limb and lower trunk axons travel?

Answer 16

Lower limb & lower trunk axons (T6 and below) travel ipsilaterally via the medially placed gracile fasciculus (part of dorsal column)

Question 17

How do the upper limb and upper trunk axons travel?

Answer 17

Upper limb & upper trunk axons (T5 and above) travel ipsilaterally via the laterally placed cuneate fasciculus (part of dorsal column)

Question 18

Where is the the first synapse of the gracile tract?

Answer 18

gracile nucleus

Question 19

What is the first synapse of the cuneate tract?

Answer 19

Cuneate nucleus

Question 20

Where do second order axons decssate? (dorsal)

Answer 20

• in the caudal medulla to make the contralateral medial meniscus tract
• Synapse in thalamus

Question 21

Where do 3rd order neurones from the thalamus project to?

Answer 21

• the somatosensory cortex
• Size of somatotopic areas is proportional to density of sensory receptors in that body region (somatosensory homunculus)

Question 22

Where does pain and temperature sensations ascend?

Answer 22

within the lateral spinothalamic tract

Question 23

Where does crude touch ascend?

Answer 23

within the anterior spinothalamic tract

Question 24

Where do primary afferent axons terminate?

Answer 24

upon entering the spinal cord

Question 25

Where do second order neurones decussate in the spinothalamic pathway?

Answer 25

immediately in the spinal cord and form the spinothalamic tract

Question 26

Where do second order neurones terminate?

Answer 26

Thalamus

Question 27

Where do the 3rd order neurones from thalamus project to?

Answer 27

Somatosensory cortex