6 Membrane Potential and Action Potential Flashcards Preview

Physiology Test 1 > 6 Membrane Potential and Action Potential > Flashcards

Flashcards in 6 Membrane Potential and Action Potential Deck (28):
1

Ohm's Law

V = IR
electrical potential = volts*resistance

2

information is conveyed down axons by electrical signals called _____

action potentials

3

RMP of a cell

-65 to -75 mV

4

RMP def

electrical potential difference across the nerve membrane

5

true or false: maintenance of the RMP requires expenditure of metabolic energy?

true

6

hyperpolarized

membrane potential becomes more negative (increases)

7

depolarized

membrane potential becomes less negative

8

the only ions that can pass through the plasma membrane are

K+ ions

9

equilibrium potential for K+

aka Ek
the electrical potential at which there is no longer any net movement of K+ down its concentration gradient

10

Ek =

-90mV

11

ENa =

+60mV

12

ECl =

-70mV

13

if you increase the extracellular concentration of K+, the membrane potential becomes _______

depolarized (less negative)

((prolonged depolarization is lethal! - it make excitable tissues inexcitable))

14

if you increase the intracellular concentration of K+, the membrane potential becomes ______

hyperpolarized (more negative)

15

threshold

critical value of the membrane potential or the level of depolarization at which an impulse is initiated

16

"all or none"

a stimulus will trigger a complete action potential or none at all
a larger stimulus does not increase the size of the AP

17

upstroke

rapid depolarization (reduction) in membrane potential from resting values toward zero

18

overshoot

reversal of the membrane potential during the peak of the action potential

19

depolarization

reduction of membrane potential from resting value towards zero

20

repolarization

return of the action potential towards resting potential

21

hyperpolarization

increase in membrane potential from resting potential
the membrane overshoots and goes extra negative during this period, then levels off back at its normal negative level

22

absolute refractory period

time following an action potential during which a stimulus cannot elicit a second action potential - Na channels cannot open

23

relative refractory period

time during which only an extra strong stimulus can trigger an AP - some Na channels restored to primed state

24

explain how APs are conducted down unmyelinated axons

Na+ ions that produce the AP upstroke diffuse down the axon, depolarizing adjacent membranes - this opens voltage gated Na+ channels and starts the process at adjacent neurons

25

explain how APs are conducted down myelinated axons

APs spread by "saltatory conduction" jumping from one node of Ranvier to the next; local current spreads along the axon and depolarizes the membrane of the next node

*voltage gated sodium channels are restricted to the membrane at the nodes of Ranvier

26

Na+/K+ ATPase

pumps 3 Na+ out
pumps 2 K+ in
net loss of one positive charge from the intracellular space

27

unmyelinated fiber speed

Velocity is proportional to the square root of the axon diameter
invertebrates
pain signals in vertebrates

28

myelinated fibers

insulation causes velocity of signal to be approx. linearly related to axon diameter