Chapter 1 pt. 2

Question 1

Action Potentials (AP)… background

Answer 1

● Resting potential of neuron is -70mV (millivolts)

Question 2

Hyperpolarization

Answer 2

increase in the negative charge inside the neuron (more polarized)

Question 3

Depolarization

Answer 3

decrease in the negative charge inside the neuron (less polarized)

Question 4

During AP

Answer 4

rapid depolarization continues to around +40 mV then returns to resting
potential, very quick, millisecond process

Question 5

All-or-none Law

Answer 5

neurons either fire or they don’t, there is no variety in the
strength/intensity of the neuron firing
○ Like toilet flushing: pressing harder or lighter on the lever does not affect the
intensity of the toilet flushing, flushes the same way every time

Question 6

Refractory Period

Answer 6

the period of rest between AP where it cannot fire
○ Like toilet: there is a period where you cannot flush the toilet between flushes

Question 7

AP’s are

Answer 7

electrochemical processes

Question 8

Electrical gradient

Answer 8

keeps substances where they are, either the inside or outside
■ Positively charged ions on outside are attracted to the negatively charged
inside of the cell

Question 9

Concentration/chemical gradient

Answer 9

things more from greater concentrations to
less concentrations
■ More sodium concentration on outside of cell, wants to enter the cell
where there is less sodium

Question 10

Neurons are more negatively charged on the inside

Answer 10

relative to the outside, except
when firing!
○ Na+ (sodium) and CI- ( chlorine) on outside of cell
○ K+ (potassium) and negative charged proteins A- on inside
■ Pass through channels in the semi-permeable membrane

Question 11

1. With slight depolarization:

Answer 11

Na+ channels open slightly
a. Something is touching you, but it is not enough to fire AP

Question 12

2. If threshold is reached:

Answer 12

Na+ channels open wide and Na+ ions rush into cell
a. Sodium is very attracted to the inside of the cell due to the attraction from
electrical and concentration gradients

Question 13

3. K+ Channels:

Answer 13

begin to open as charge approaches peak

Question 14

4. At peak of AP:

Answer 14

as positively charged as the inside of the cell is going to get, very brief
a. Na+ channels closed, K+ channels open wide to let K+ flow out of the cell

Question 15

5. K+ channels begin to close

Answer 15

begins to close

Question 16

6. Hyperpolarized cell:

Answer 16

cell becomes hyperpolarized and overshoots resting potential
(briefly) and goes to -80mV instead of -70mV

Question 17

7. Sodium-Potassium Pump:

Answer 17

gets the cell ready to fire again
a. Puts K+ back into the cell, and Na+ out to get back to -70mV

Question 18

Most axons have myelin sheaths around them…

Answer 18

which blocks channels

Question 19

Nodes of Ranvier:

Answer 19

short, unmyelinated sections of axon, where AP occurs

Question 20

Saltatory conduction:

Answer 20

AP hops over the myelin to each node which is a fast,
efficient, and saves energy, AP refires at each Node of Ranvier

Question 21

● A-Alpha Nerve Fibers:

Answer 21

fastest, 250mph
○ Contributes to proprioception: knowing where you and your limbs are without
looking at them them

Question 22

● A-beta Nerve Fibers:

Answer 22

more common than A-alph
○ Carry info on touch

Question 23

● A-delta:

Answer 23

weakly myelinated, 50- 60mpg
○ Carry info on light pain and temperature

Question 24

● C-nerve fibers :

Answer 24

a small percentages of unmyelinated axons, go 1mph
○ Carry info on dull deep pain, temperature, and itch

Question 25

● Lidocaine/novocaine:

Answer 25

attach to sodium channels and blocks it so no AP can occur
○ Blocks all messages, not just pain messages
○ Acts in periphery only, not systemic

Question 26

● General anesthesia (ether and chloroform):

Answer 26

opens K+ gates in central nervous system
○ Neurons fire more slowly, slows AP’s, lose consciousness

Question 27

● Propofol:

Answer 27

: new general anesthetic
○ Na+ channel blocker in the central nervous system
○ Needs to be given in hospital