Somatosensory Pathways Flashcards
What is polymodal C?
Nociceptor
- Thin and non-myelinated
- slower and signal burning pain
In the caudal medulla, describe the position of…
ALS
DCML
Caudal Medulla
- ALS = Contralateral
- DCML = Contralateral
Which system has extra branches (collateral branches) in the brainstem?
What do these fibers do?
The ALS system has extra branches in the brainstem. they activate regulatory centers in the brainstem and control autonomic responses
Where to 2nd order neurons synapse with 3rd order neurons in the ALS and DCML system?
Both ALS and DCML synapse in the Ventral posteriolateral nucleus of the Thalamus
How does the DCML 3rd order neuron ascend to its destination?
via the internal capsule. The ALS system also ascends via the internal capsule
What is the destination of both the ALS and DCML system?
Post Central Gyrus - primary somatosensory cortex
Difference of Gracile and Cuneate tracts?
Gracile tract - lower 1/2 f body below T6
Cuneate tract -upper 1/2 of body above T6
what is the tract of Lissauer?
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.
Where do the decussations take place in the ALS and DCML systems?
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
The neurons of the Anteriorlateral pathway ascend the spinal cord via the
anterolateral system
ALS 1st order neurons synapse in what part of the body?
Superficial layer of the dorsal horn of the spinal cord
The neurons of the DCML pathway ascend the spinal cord via the
gracile and cuneate tracts
Neurons from the ALS and DCML pathways ascend the brainstem via the
ALS pathways- Anteriolateral system
DCML - via medial lemniscus
What does the DCML pathway do?
Sensory pathway that senses vibration proprioception and fine touch
Where are free nerve ending located and what do they do?
Free nerve endings detect pain, temperature and itch
ALS system
what is a receptor field?
examples of areas?
area detected by 1 single receptor neuron
hand- small receptor fields
back - large receptor fields
Alpha delta neurons
thin neuron and thinly myelinated
-senses pain and temperature
-sharp pain signal - first pain
(polymodal-C is slower bc non myelinated)
What is Nocieception?
signals for tissue damage or the potential for tissue damage
Difference of ALS and DCML receptor neurons?
ALS neurons lack specialized terminals
What does ALS system do?
temperature, no discriminative touch, pain, itch, tickle, visceral sensations, hunger, thirst
- associated with emotion
- drives behavioral motivation
what makes a neuron faster?
more myelin and thicker axon
what happens to the medial lemniscus as you ascend the brainstem?
it gets flatter
difference of the pre-central gyrus and post-central gyrus
pre-central gyrus - motor cortex
post-central gyrus- somatosensory cortex
The DCML 1st synapse is where?
Dorsal Column Nucleus - in the caudal medulla
