Somatosensory

Question 1

What three general sense types are part of the Dorsal Column-Medial Leminscus (DCML) pathway?

Answer 1

• Proprioception (muscle stretch, tension and joint position)
• Vibration
• Fine (discriminative) touch

Question 2

Thicker and more Myelination affect the speed of conduction how?

Answer 2

both make the conduction faster

Question 3

Rank, proprioceptors, pain, temperature and mechanorecptors from fastest conduction to slowest conduction

Answer 3

Proprioceptors (fastest) Mechanoreceptors from skin, pain/temperature(myelinated), Temperature/pain/itch (slowest, unmyelinated)

Question 4

Where are receptive fields the smallest and most dense? Largest and least dense?

Answer 4

Fingers, back

Question 5

The ________ branch is from the terminal to the cell body. Whereas the ________ branch is from the cell body to the CNS

Answer 5

Peripheral, central

Question 6

Trace the path of sensation from Dermatome to Post-central gyrus in the DCML

Answer 6

1-Dermatome sensation
2-1st order neuron (dorsal root ganglion)
3-2nd order neuron (gracile/cuneate nuclei in medulla)
4-3rd order neuron (Vental Posterolateral (VPL) nucleus in thalamus)
5-Post central gyrus (in respective region)

Question 7

The gracile tract (medial tract) contains axons from which half of the body?

Answer 7

Lower half

Question 8

The cuneate tract (lateral tract) contains axons from which half of the body?

Answer 8

upper half

Question 9

When does the decussation of the signal take place for the DCML?

Answer 9

2nd order neurons decussate in the internal arcuate and ascend in the medial leminscus (in the caudal medulla)

Question 10

What three general sensations make up the Anterior Lateral System (ALS)?

Answer 10

• Crude (non-discriminative) touch
• Temperature
• Pain

Question 11

What else is the anterolateral system associated with?

Answer 11

Emotion and driving behavioral motivation

Question 12

What is different about the terminal end of ALS neurons vs. DCML neurons?

Answer 12

ALS have free nerve endings

DCML have specialized terminals

Question 13

Which type of ALS nerve fiber is not myelinated?

Answer 13

C-fiber

*A-delta fibers are lightly myelinated

Question 14

Sharp pain (first pain) is transmitted by what?

Answer 14

A-delta-nociceptors

Question 15

Slower burning pain is transmitted by what?

Answer 15

C-nociceptors

Question 16

Where do first order neurons of the ALS synapse with 2nd order neurons?

Answer 16

In the dorsal horn of the spinal cord (ipsilateral)

*can travel up the spinal cord a little before synapsing

Question 17

What tract do the 1st order neurons of ALS travel up?

Answer 17

Tract of lissauer

Question 18

After synapsing with 1st order neurons, where do ALS 2nd order neurons decussate?

Answer 18

anterior white comissure. they then ascend in the anterolateral system

Question 19

Where does the 2nd order neuron synapse with the 3rd order neuron in the ALS?

Answer 19

Thalamus (VPL)