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Flashcards in Unit 5: Notes 2 Deck (18)
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1

what speeds up an action potential

Myelin and diameter

2

what is the condition of a nerve cell at resting potential (charge, location of different ions)?

-70, inside K+, outside Na+.

3

which Japanese delicacy is risky? and why?

The puffer fish. It contains tetrodotoxin, A substance that makes them and foul tasting and often lethal to fish

to humans, TTX is deadly, up to 200 times more poisonous than cyanide

4

what is an action potential

-how neurons communicate
-nerve impulse
-self propagating (following rules of dominoes)
-A large change in the membrane potential (difference in electrical charge)
> from - to +, back to -
> result from movement of Na+ and K+ through membrane channels

5

what are the types of channels in the axon?

leakage channels and gated channels

6

what are leakage channels

they allow small steady streams of ions to leak across the membrane

7

what are gated channels

Open and close on command
> voltage gated channels open in response to a change in membrane potential

8

resting neuron

resting neurons have a charge of -70 mV compared to outside
> A positive charge on the outside, negative charge on the inside

9

what is happening inside the neuron at rest

higher concentration of K+, so it leaks out fast

10

what is happening outside of the neuron at rest

higher concentration of Na+, so it leaks in slowly

11

what is the sodium potassium pump

-The small Na+ inward leak and larger K+ outward leak is offset by the Na+/K+ pump
-maintains resting membrane potential

12

name the steps of an action potential

depolarization, peak, repolarization, hyperpolarization

13

depolarization

-stimulus causes voltage gated Na+ channels to open and Na+ rushes into the cell
- cell becomes more positive
-threshold = minimum level of stimulus (-55)

14

Peak

-K+ channels begin to open and K+ begins to leave cell
-Na+ channels begin to close

15

Repolarization

-K+ voltage gates fully open, K+ leaving cell
-all Na+ Gates are closed
-cells becoming more negative

16

Hyperpolarization

-K+ Gates slowly close so cell becomes more negative than the resting value (-70)
- leaking restores -70

17

absolutely refractory period

Second action potential absolutely cannot occur

18

relative refractory period

Second action potential difficult but not impossible