Ascending spinal tracts - Dorsal columns

Question 1

Which two large fasciculi form the dorsal column?

Answer 1

fasciculus gracilis and fasciculus cuneatus

Question 2

What information does the dorsal column transmit?

Answer 2

Tract carries impulses concerned with proprioception (movement and joint position sense) and discriminative (fine) touch - information about the ipsilateral side of the body

Question 3

Where do the first order neurones carry the sensory information to in the dorsal columns?

Answer 3

medulla oblongata

Question 4

What are the two different pathways which first order neurons take in the dorsal columns?

Answer 4

1. Signals from the upper limb (T6 and above) - travel in the fasciculus cuneatus (lateral part of the dorsal column) and synapse in the nucleus cuneatus of the medulla oblongata
2. Signals from the lower limb (below T6) - travel in the fasciculus gracilis (medial part of the dorsal column) and synapse in the nucleus gracilis of the medulla oblongata

Question 5

What nucleus do signals from the lower limb synapse at in the medulla oblongata?

Answer 5

nucleus gracilis

Question 6

What nucleus do signals in the upper limb synapse at in the medulla oblongata?

Answer 6

nucleus cuneatus

Question 7

What is the role of the second order neurons in the dorsal columns?

Answer 7

The second order neurons begin in the cuneate nucleus or gracilis. These fibres receive the information from the preceding neurones and deliver it to the third order neurones in the thalamus

Question 8

Where do the fibres decussate in the dorsal column pathway?

Answer 8

Within the medulla oblongata - second order neurones cross to the other side and travel in the contralateral medial lemniscus to reach the thalamus

Question 9

Where does the medial lemniscus terminate?

Answer 9

In the ventral posterior (VP) nucleus of the thalamus

Question 10

Where do the third order neurones project to?

Answer 10

Ascend from the VP nucleus of the thalamus, travel through the internal capsule and project to the somatosensory cortex located in the postcentral gyrus of the parietal lobe

Question 11

Clinical link - In MS, specific damage to the fasciculus cuneatus of the cervical spinal cord can lead to what?

Answer 11

Loss of proprioception in the hands and fingers causing loss of dexterity and inability to identify the shape and nature of objects by touch along (astereognosis)