Lecture 3- Sensory System

Question 1

Both touch+pressure and pain+temp enter the dorsal root and go where?

Answer 1

Touch+pressure goes in and splits up, going to the white matter of the dorsal columns( gracile Fasciculus-lower limb and cuneate Fasciculus-upper limbs), and also into the gray matter. Somatotopic representation.

Pain+temp goes into the dorsal most gray matter and then travels along the VENTRAL WHITE COMMISSURE to the spinothalamic tract.

Question 2

Reflex arc

Answer 2

Can occur where message goes straight to the lower motor Neuron to innervate a muscle fibre.

Question 3

Name the pathway of discriminative sensation

Answer 3

Dorsal column-medial lemniscal system

Question 4

Name the pathway of non-discriminative sensation

Answer 4

Lateral Spinothalamic tract

Question 5

From skin to brain give discriminative pathway

Answer 5

1. Sensory nerve stimulated and enters spinal cord via dorsal root. 2. 1st order fibre enters dorsal column
2. Travels up dorsal fasciculus/funiculus
3. Reaches cuneate/gracile Nuclei where Decussation occurs via the internal Arcuate fibres
4. 2nd order fibres travel up medial lemniscus
5. Reaches Ventral posterior nucleus of Thalamus
6. 3rd order neuron travels via internal capsule to primary sensory cortex

Question 6

From skin to brain describe non-discriminative pathway

Answer 6

1. Sensory nerve stimulated and impulse enters spinal cord via dorsal root.
2. Decussation at spinal level via ANTERIOR WHITE COMMISSURE
3. 2nd order fiver travels up lateral Spinothalamic tract
4. Joins medial lemniscus
5. Enter ventral posterior nucleus of thalamus
6. 3rd order neuron travels up internal capsule and onto the primary sensory cortex.

Question 7

Leison at the brain/brainstem level?

Answer 7

Associative sensory loss

Both are opposite to side of damage

Question 8

Leison at the spinal cord level

Answer 8

Dissociative sensory loss
(Touch and pressure is the same side.
Pain and temp is opposite)

Question 9

Compare and contrast
(Discriminative vs non) 
1.myelination
2.conduction speed
3. Function
4.1st neurone terminates?
5. Decussation position?

Answer 9

1. Yes, No
2. 50 m/s, 1m/s
3. Touch pressure, pain temp
4. Cuneate/gracile nucleus, dorsal part of spinal cord (anterior white commissure)
5. Internal Arcuate fibres, within spinal cord (white commissure)