6 Membrane Potential and Action Potential

Question 1

Ohm’s Law

Answer 1

V = IR

electrical potential = volts*resistance

Question 2

information is conveyed down axons by electrical signals called _____

Answer 2

action potentials

Question 3

RMP of a cell

Answer 3

-65 to -75 mV

Question 4

RMP def

Answer 4

electrical potential difference across the nerve membrane

Question 5

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

Answer 5

true

Question 6

hyperpolarized

Answer 6

membrane potential becomes more negative (increases)

Question 7

depolarized

Answer 7

membrane potential becomes less negative

Question 8

the only ions that can pass through the plasma membrane are

Answer 8

K+ ions

Question 9

equilibrium potential for K+

Answer 9

aka Ek

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

Question 10

Ek =

Answer 10

-90mV

Question 11

ENa =

Answer 11

+60mV

Question 12

ECl =

Answer 12

-70mV

Question 13

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

Answer 13

depolarized (less negative)

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

Question 14

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

Answer 14

hyperpolarized (more negative)

Question 15

threshold

Answer 15

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

Question 16

“all or none”

Answer 16

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

Question 17

upstroke

Answer 17

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

Question 18

overshoot

Answer 18

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

Question 19

depolarization

Answer 19

reduction of membrane potential from resting value towards zero

Question 20

repolarization

Answer 20

return of the action potential towards resting potential

Question 21

hyperpolarization

Answer 21

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

Question 22

absolute refractory period

Answer 22

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

Question 23

relative refractory period

Answer 23

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

Question 24

explain how APs are conducted down unmyelinated axons

Answer 24

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

Question 25

explain how APs are conducted down myelinated axons

Answer 25

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

Question 26

Na+/K+ ATPase

Answer 26

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

Question 27

unmyelinated fiber speed

Answer 27

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

Question 28

myelinated fibers

Answer 28

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