Lecture 17 (4/7)

Question 1

Dorsal Column Medial Lemniscal System

Answer 1

The most direct and specialized ascending systems

Carries information of conscious proprioception (limb awareness in space), fine, discriminative touch, and pressure. (Ex. a horse sitting on you)

Ascends ipsilaterally

Question 2

Dorsal Column Medial Lemniscal System (Location)

Answer 2

Located in the medulla

Has 2 Fasciculi
Gracilis
Cuneatus

Question 3

Fasiculi Gracilis

Answer 3

Lies medially

Carries sensory info from the waist down

Question 4

Fasciuli Cuneatus

Answer 4

Lies laterally

Carries sensory info from the waist up to the back of the neck

Question 5

Dorsal Column Medial Lemniscal System (Pathway - First Order Neurons)

Answer 5

Sensory info carried from the receptors -> dorsal root ganglia -> dorsal horn -> ascend ipsilaterally to the medulla where they synapse with the nucleus gracilis and nucleus cuneatus

Question 6

Dorsal Column Medial Lemniscal System (Pathway - Second Order Neurons)

Answer 6

Second order neurons take over from the nucleus gracillis and nucleus cuneatus

Question 7

Dorsal Column Medial Lemniscal System (Pathway - Second Order Neurons)

Answer 7

The axons of the second order neurons are called internal arcuate fibers, which decussate and ascend contra laterally to form the medial lemniscus.

Question 8

Internal Arcuate Fibers

Answer 8

Second order neurons

Decussate and ascend contra laterally and form the medial lemniscus

They carry the info into the thalamus where they synapse on the third order neurons, specifically the ventral posterior lateral nucleus

Question 9

Medial Lemniscus

Answer 9

Formed by the Internal Arcuate Fibers

Question 10

Dorsal Column Medial Lemniscal System (Pathway - Third Order Neurons)

Answer 10

Third order neurons ascend through the internal capsule and corona radiate and finally into the post central gyrus/somatosensory cortex

Question 11

Dorsal Column Medial Lemniscal System

Answer 11

When neurons enter the dorsal root, they divide into groups, neurons with long axons and neurons with short axons

Those with short axons stop in the dorsal horn and engage in the control of reflexes.