Action potentials again

Question 1

Do glia engage in information processing?

How many cells in the brain are glial?

Answer 1

yes

3 (to 10) x as many glial cells as neurons

Question 2

What inhibits chemicals from passing through the BBB?

Answer 2

tight junctions

Chemicals pass through astrocytes instead

Question 3

Which glial cells can modulate excitability by changing driving force?

Answer 3

Astrocytes - change ionic environment inside cell

Question 4

What is the danger of bacterial infection in the brain compared to the rest of the body?

Answer 4

Microglia can’t have the same massive immune response the rest of the body can, so brain infections are more dangerous

Question 5

How do microglia move?

Answer 5

Move around in packs

Follow concentration gradient released by injured cell in cytoplasm

Question 6

How do glial cells modulate information processing?

Answer 6

Store neurotransmitters
Have receptors for transmitters
Control ion concentrations

Question 7

How do glial cells communicate with each other?

Answer 7

Use ATP

Question 8

What modulates the birth of new axons and the growth of those axons?

Answer 8

Glial cells (mostly astrocytes)

Question 9

What does Vm stand for?

Answer 9

Membrane potential (Ionic charge inside membrane compared to outside)

Question 10

What cell types receive sensory input in the skin, which gets turned into action potentials?

Answer 10

Pacinian corpuscles

Question 11

What do pacinian corpuscles look like?

Answer 11

Kinda like an onion with dendrite wound inside it. ‘onion layers’ rub against each other, causing ion channels to open

Glial cells are the ‘onion layers’.

Question 12

What do you know you’re talking about when you see ‘receptor potential’?

Answer 12

A specific class of neurons that receive information from the outside environment (e.g. pacinian corpuscles, rods/cones…)

Question 13

What is a distal axon?

Answer 13

Projects towards the periphery

Question 14

What is a proximal axon?

Answer 14

Projects towards CNS

Question 15

What happens at the initial segment of a pacinian corpuscle?

Answer 15

Voltage gated channels begin to allow Na+ in to cause action potentials

Question 16

What basic ion - K+, Na+, Ca2+, etc - has the most driving force?

Answer 16

Na+. Most bang for your buck; opening sodium channels changes the charge most

Question 17

What is a dermatome?

Answer 17

Skin slice. Region of the body innervated by sensory neurons from a single section of the spinal cord

Question 18

What are the nerves of the spine called? (top to bottom)

What are the segmental slices of skin in each segment (e.g. the skin of c2) called?

Answer 18

Cervical (c1…c8) > thoracic (T1..T12) > lumbar (L1..L5) > sacral (S1…S5)

Dermatomes

Question 19

What part of the spinal cord contains cell bodies of neurons?

Answer 19

The horns (ventral / dorsal)

White matter contains axons

Question 20

What in the spinal cord did surgeons think was a good idea to cut to prevent intractable pain in the 1950s?

Answer 20

rhizome; it was a bad idea

Question 21

What equation is used to calculate Vm?

Answer 21

(Sum of voltage in) - (Sum of voltage out)

Question 22

What equation is used to calculate Vm?

Answer 22

(Sum of voltage in) - (Sum of voltage out)

Question 23

What causes Na+/K+ pumps to increase or decrease activity?

Answer 23

Neural activity. How quickly the pump is working depends on the rate of activity of its neuron.

Question 24

What is the point of a leak channel?

Answer 24

Keep the membrane stable - otherwise it might randomly have action potentials

Question 25

What would happen if you cut a specific nerve?

Answer 25

Whatever dermatome the nerve innervates wouldn’t work

Question 26

What is a dermatome?

Answer 26

The whole area of the skin which is innervated by a spinal cord region

Question 27

What channels are open in at-rest neurons?

Answer 27

Leak channels. All leak channels are K+

K+ channels. Not all K+ channels are leak

Question 28

Where in the neuron are EPSPs and IPSPs summating?

Answer 28

initial segment

Question 29

Where would you see chemically-gated Na+ channels?

Answer 29

e.g. in the spine. Open from neurotransmitters

Question 30

What ionic species causes IPSPs?

Answer 30

Cl- in… chemically gated if in e.g. spinal cord

Could also be K+ out