Somatosensory Pathways

Question 1

What is polymodal C?

Answer 1

Nociceptor

• Thin and non-myelinated
• slower and signal burning pain

Question 2

In the caudal medulla, describe the position of…
ALS
DCML

Answer 2

Caudal Medulla

• ALS = Contralateral
• DCML = Contralateral

Question 3

Which system has extra branches (collateral branches) in the brainstem?
What do these fibers do?

Answer 3

The ALS system has extra branches in the brainstem. they activate regulatory centers in the brainstem and control autonomic responses

Question 4

Where to 2nd order neurons synapse with 3rd order neurons in the ALS and DCML system?

Answer 4

Both ALS and DCML synapse in the Ventral posteriolateral nucleus of the Thalamus

Question 5

How does the DCML 3rd order neuron ascend to its destination?

Answer 5

via the internal capsule. The ALS system also ascends via the internal capsule

Question 6

What is the destination of both the ALS and DCML system?

Answer 6

Post Central Gyrus - primary somatosensory cortex

Question 7

Difference of Gracile and Cuneate tracts?

Answer 7

Gracile tract - lower 1/2 f body below T6

Cuneate tract -upper 1/2 of body above T6

Question 8

what is the tract of Lissauer?

Answer 8

1st order neurons can enter the dorsal root and then travel up through the tract of Lissauer the dorsal horn of 1 or 2 spinal cord levels above or below to synapse in the dorsal horn with a second order neuron of the ALS system.

Question 9

Where do the decussations take place in the ALS and DCML systems?

Answer 9

ALS - Decussates at ventral white commissure in the spinal cord (middle of butterfly) - then ascend via Anteriorlateral System

DCML - Decussates in the Medulla at the internal arcuate then ascends via medial lemniscus

Question 10

The neurons of the Anteriorlateral pathway ascend the spinal cord via the

Answer 10

anterolateral system

Question 11

ALS 1st order neurons synapse in what part of the body?

Answer 11

Superficial layer of the dorsal horn of the spinal cord

Question 12

The neurons of the DCML pathway ascend the spinal cord via the

Answer 12

gracile and cuneate tracts

Question 13

Neurons from the ALS and DCML pathways ascend the brainstem via the

Answer 13

ALS pathways- Anteriolateral system

DCML - via medial lemniscus

Question 14

What does the DCML pathway do?

Answer 14

Sensory pathway that senses vibration proprioception and fine touch

Question 15

Where are free nerve ending located and what do they do?

Answer 15

Free nerve endings detect pain, temperature and itch

ALS system

Question 16

what is a receptor field?

examples of areas?

Answer 16

area detected by 1 single receptor neuron
hand- small receptor fields
back - large receptor fields

Question 17

Alpha delta neurons

Answer 17

thin neuron and thinly myelinated
-senses pain and temperature
-sharp pain signal - first pain
(polymodal-C is slower bc non myelinated)

Question 18

What is Nocieception?

Answer 18

signals for tissue damage or the potential for tissue damage

Question 19

Difference of ALS and DCML receptor neurons?

Answer 19

ALS neurons lack specialized terminals

Question 20

What does ALS system do?

Answer 20

temperature, no discriminative touch, pain, itch, tickle, visceral sensations, hunger, thirst

• associated with emotion
• drives behavioral motivation

Question 21

what makes a neuron faster?

Answer 21

more myelin and thicker axon

Question 22

what happens to the medial lemniscus as you ascend the brainstem?

Answer 22

it gets flatter

Question 23

difference of the pre-central gyrus and post-central gyrus

Answer 23

pre-central gyrus - motor cortex

post-central gyrus- somatosensory cortex

Question 24

The DCML 1st synapse is where?

Answer 24

Dorsal Column Nucleus - in the caudal medulla