Sensory & Motor Pathways & MS

Question 1

What are receptor potentials? What do they generate?

Answer 1

Specialized endings enable mechanical stimulation to cause a receptor potential. If the receptor potential is sufficient depolarization to reach threshold, then APs are fired

Question 2

What are the 3 degrees of neurons in the touch pathway?

Answer 2

1*= periphery to medulla 
2* = medulla to thalamus (cross midline in medulla) 
3*= thalamus to SS cortex

Question 3

What are the 3 degrees of neurons in the proprioception pathway?

Answer 3

1*= periphery to medulla via dorsal horns
2*= medulla to thalamus (cross midline in medulla)
3*= thalamus to SS cortex

Question 4

What are the 3 degrees of neurons in the pain and temperature pathway?

Answer 4

1= periphery to spinal cord
2=spinal cord to thalamus (cross midline in spinal cord)
3*= thalamus to SS cortex

Question 5

What does damage to the thalamus in the somatosensory pathways cause?

Answer 5

Contralateral hemianesthesia

Question 6

What does a spinal cord hemisection in the somatosensory pathways cause?

Answer 6

Ipsilateral touch loss, contralateral pain loss

Question 7

What is commissural syndrome? Where does it occur?

Answer 7

Occurs where pain signals cross in Spinal cord, causes bilateral pain loss at level of lesion

Question 8

What happens in demyelinated axons?

Answer 8

When axons are demyelinated, the membrane is leaky so the current dissipated and there is not enough depolarization to reach threshold at the next patch of Na+ channels.
Axonal transport along microtubules is disrupted by Ca2+ and this can cause organelles to aggregate

Question 9

What is Multiple Sclerosis (MS)?

Answer 9

A chronic progressive neuroinflammatory disease that damages myelin and neurons in the brain & spinal cord

Question 10

What are the risk factors for MS?

Answer 10

Geography: prevalence increases in northern hemisphere
Genetic risk
Viral infection: EBV
Birth month: incidence increases when born in winter
Smoking

Question 11

What are the different T helper cells involved in MS disease progression? What do they do?

Answer 11

CD4+ : release pro-inflammatory cytokines that attract macrophages and microglial cells
CD8+ : kill oligodendrocytes

Question 12

What is the role of B cells in MS progression?

Answer 12

B cells are antibody producing cells of the immune system made in bone marrow

Question 13

What happens during remission of MS?

Answer 13

Remyelination attracts OPCs to the lesion that proliferate into oligodendrocytes that myelinate axons.

Question 14

What do Interferon-B-1a and Interferon-B-1b do?

Answer 14

Attenuated inflammation by shifting the balance of Th to Treg cells

Question 15

What are some experimental treatments for MS?

Answer 15

Cooling temperature, Increase Vitamin D, K+ channel blockers, Na+ channel blockers, Estrogen, Diet, Cannabis, stem cells

Question 16

Why would a K+ channel blocker be effective in MS?

Answer 16

K+ channels blocked broadens the action potential due to slower repolarization. This allows current to jump across a demyelinated segment

Question 17

Why would a Na+ channel blocker be effective in MS?

Answer 17

In MS after neurons are demyelinated, there are more sodium channels expressed and this can lead to persistent influx of Na+ ions, therefore the Na+/K+ atpase need to work harder to pump Na+ out. Na+ channel blockers help prevent Na+ influx in neurons