Week 1: Somatosensory Pathways

Question 1

Other names for tract

Answer 1

• Column
• Lemniscus
• Fascicle

Question 2

Naming convention for somatosensory pathways

Answer 2

• They are named for the origin and termination of the second neuron in the tract
• EX: spinothalamic tract- second neuron originates in the spinal cord and ends in thalamus

Question 3

Parts of a 3-neuron pathway

Answer 3

• First-order neuron
• Second-order neuron
• Third order neuron

Question 4

First-order neuron

Answer 4

• Receptor to spinal cord

- 2-axon neuron

Question 5

2-axon neuron

Answer 5

Has a distal and proximal portion, with the cell body in between

Question 6

Distal axon

Answer 6

Conducts info from the receptor to the cell body

Question 7

Proximal axon

Answer 7

Conducts info from the cell body to the spinal cord/brainstem

Question 8

Second-order neuron

Answer 8

• Spinal cord or brainstem to the thalamus

- Decussation occurs here

Question 9

Third order neuron

Answer 9

Thalamus to cerebral cortex

Question 10

What is high vs low fidelity?

Answer 10

• Degree of exactness

- Nerves provide accurate details about the stimulus (i.e. touch, stretch, etc)

Question 11

Somatotopic organization

Answer 11

• Nerves are organized in a manner that reflects the anatomy of where the signal originates
• Info about the thumb goes to a place close to where info about the index finger goes

Question 12

Where does somatosensory information go?

Answer 12

Primary somatosensory cortex (postcentral gyrus)

Question 13

Describe the somatotopic organization of the primary somatosensory cortex

Answer 13

• Medial: foot, lower limb
• Superomedial: upper limb, hand
• Lateral: face and throat