Ascending and Descending pathways.

Question 1

Name this tract and state if it’s ascending or descending.

Pathway[5 marks].

Answer 1

Spinothalamic Pathway.

• Ascending pathway.
• Transmits pain

First order–>2nd –>3rd.

Nociceptors–>decussation before travelling upwards–>Reticular formation–>Ventropostolateral nucleus(thalamus)–> Somatosensory cortex.

Question 2

Name this tract, ascending or descending?

Pathway?

Steps involved in 1st, 2nd and 3rd order neurons?

Answer 2

Dorso medial lemniscus pathway,

• Ascending pathway.
  
  • Function: proprioception and fine touch.

Pathway:

1st order neurons:

• Stimulus to Fasciculus cuneatus( upper limb/lateral part of dorsal column), >T6
• Stimulus to Fasciculus gracilis(lower limb/ medial part of dorsal column).

2nd order: decussate(medulla), travel up medial lemniscus.–> thalamus

3rd order:

• thalamus–> ipsilateral primary sensory cortex.

Question 3

Name this tract and state if it is a descending or ascending tract.

Pathway?divisions?

1st, 2nd and 3rd order neuronal pathway.

The difference in function between the 2 divisions?

Where does Decussation occur?

Answer 3

Pyramidal Tract.

Descending pathway: Corticospinal + Corticobulbar tract.

Corticospinal tract:

• Motor/premotor and Supplementary area–> internal capsule—>Crus cerebri—>Tract divides:

Lateral:

• Terminates at Ventral horn of all segments( muscles of the body).

Anterior:

• Remains ipsilateral: terminate at the ventral horn on cervical and upper thoracic.
  
  • movement of trunk and proximal musculature.

Decussation occurs at the pyramids.