Excitable Membranes

Question 1

Cells that can initiate an action potential

Answer 1

neurons
muscle
endocrine
eggs

Question 2

action potential

Answer 2

rapid sequence of changes in the voltage across an excitable cell membrane

Question 3

stages of an action potential

Answer 3

resting stage
depolarization
repolarization
hyperpolarization

Question 4

Resting membrane potential

Answer 4

-70 mV
more K+ and organic anions inside the cell
more Na+ and Cl- outside the cell

Question 5

diffusion potentials

Answer 5

internal membrane potential is negative when potassium ions diffuse and positive when sodium ions diffuse

Question 6

sodium-potassium pump

Answer 6

uses ATP
transports 3 Na+ out and 2 K+ in
negatively charges inside of cell membrane

Question 7

cell type RMP sensitivities

Answer 7

erythrocyte (-8 to -12)
hair (cochlea) (-15 to -40)
neurons (-60 to -70)
cardiac muscle (-80 to -90)

Question 8

depolarization

Answer 8

neuron receives a stimulus
Na+ rushes in
outside cell = negative
inside cell = positive
action potential occurs when TMP reached

Question 9

all-or-none principle

Answer 9

threshold must be met to produce an action potential and once met, action potential will occur

Question 10

repolarization

Answer 10

membrane is re-polarized
K rushes out
outside cell = positive
inside cell = negative

Question 11

hyperpolarization

Answer 11

efflux of K+ overshoots the RMP causing the membrane potential to briefly become more negative that the resting state

Question 12

refractory period

Answer 12

absolute: time during which membrane potential is over the threshold and cannot be stimulated
relative: time during which membrane potential is under the threshold and could be stimulated with a big enough stimulus

Question 13

plateau

Answer 13

prolonged period of depolarization
occurs after initial rapid depolarization but before repolarization

Question 14

rhythmical discharges of excitable tissues

Answer 14

rhythmical beat of the heart
rhythmical peristalsis
rhythmical control of breathing

Question 15

leak channels

Answer 15

ungated channels that allow a net movement of Na+ into the cell and K+ out of the cell

Question 16

equilibrium potential

Answer 16

the membrane potential at which the electrochemical and concentration gradients become equal in magnitude but opposite in direction and no net movement of ions occurs

Question 17

voltage gated Ca++ channel

Answer 17

calcium ions flow into the cell when it depolarizes

Question 18

tetany

Answer 18

caused by increased permeability of sodium channels when there is a calcium deficit

Question 19

Nernst Potential

Answer 19

the theoretical membrane potential at which the net flow of a specific ion across the cell membrane becomes zero
*the potential inside the membrane

Question 20

saltatory conduction

Answer 20

the process by which nerve impulses propagate along myelinated axons in a rapid and energy-efficient manner
-node to node conduction

Question 21

spatial summation

Answer 21

Excitatory potentials from MANY neurons trigger TP
*think of a classroom of little kids poking you

Question 22

temporal summation

Answer 22

Many excitatory potentials from ONE neuron trigger TP
*think of a little kid poking you repeatedly

Question 23

membrane stabilizers

Answer 23

decrease excitability
*ex. local anesthetics

Question 24

local anesthetics

Answer 24

-bind to and inhibit voltage-gated sodium channels
-prevent influx of sodium ions and depolarization
-prevent generation of action potential