Ch 5 Membrane Potential and Action Potential

Question 1

after-hyperpolarization

Answer 1

membrane potential following an action potential.

Question 2

Which ions are actively concentrated within and which extruded to generate membrane potential?

Answer 2

K+: in. Na+, Cl-, and Ca2+: out

Question 3

reversal potential

Answer 3

the membrane potential at which the net current flips

Question 4

membrane potential

Answer 4

difference in electrical potential between the interior and exterior of cells

Question 5

grand mal/tonic-clonic seizure

Answer 5

large numbers of neurons on the cerebral cortex dump K+

Question 6

Na+ -K+ pump

Answer 6

moves Na+ out of the cell while moving -K+ in through hydrolysis

Question 7

equilibrium potential

Answer 7

K+ ions flowing out due to concentration gradient is offset by K+ ions entering due to negative potential inside the cell

Question 8

How many Na to K are transferred in the pump?

Answer 8

3 Na for 2 K

Question 9

Na+ Ca2+ exchanger

Answer 9

keeps Ca low inside the cell by exchanging 1 for 1

Question 10

3 properties that influence passive charge response

Answer 10

membrane resistance, axial resistance, membrane capacitance

Question 11

capacitance

Answer 11

the ability to store electrical charge

Question 12

axial resistance

Answer 12

resistance in the movement of axial current due to properties of organelles and cytoplasm

Question 13

length constant

Answer 13

the point at which membrane potential drops to 37%

Question 14

TTX

Answer 14

Tetradotoxin, poison found in the pufferfish that blocks voltage dependent Na+ currents

Question 15

differences in Na and K action potentials

Answer 15

K+ current activates slowly. Na+ activates and deactivates rapidly.

Question 16

mutagenesis

Answer 16

genetic material is changed in a stable manner

Question 17

Graded Potential, 3 things…

Answer 17

1) Depolarization or hyperpolarization
2) Travel short distances
3) Lose strength as travel through cell

Question 18

Action potential, 3 things…

Answer 18

1) Large uniform depolarizations
2) Travel rapidly without losing strength
3) Travel long distances

Question 19

Where do graded potentials begin?

Answer 19

Dendrites or cell body at point of ion entry

Question 20

In a graded potential what determines amplitude size. hyperpolarization?

Answer 20

More Na+ channels open, higher amplitude. K+ open, hyperpolarization.

Question 21

Trigger Zone

Answer 21

Where the action potential occurs, where there are a lot of sodium channels.

Question 22

Where are the trigger zones?

Answer 22

MOTOR neurons: axon hillock. SENSORY neurons, the 1st unmyelinated area (first node of ranvier).

Question 23

What do axon potentials result from?

Answer 23

Changes in membrane permeability to Na+ and K+

Question 24

3 phases of an action potential

Answer 24

1. rising (Na+ open) 2. falling (K+ channels open) 3. hyperpolarization (due to excess K+)

Question 25

Na channel gates, resting vs. depolarized

Answer 25

Resting: Activation gate closed/inactivation gate open.
Depolarized: opens activation gate and opens channel

Question 26

Which ions are usually high inside and low outside?

Answer 26

Potassium and Phosphates

Question 27

Which ions are usually low inside and high outside?

Answer 27

Sodium and Chloride

Question 28

Which 3 ions generally determine membrane potential?

Answer 28

Na+, K+, Cl-