Lecture 2

Question 1

Ionic Channels

Answer 1

specific to ionic size and charge

Question 2

Size Exclusion

Answer 2

sodium channel can exclude calcium/ potassium ions due to diff molecule size

Question 3

Charge Exclusion

Answer 3

Interior of channel will be lined with charged amino acids, will prevent ions from crossing

Question 4

Leak Channels

Answer 4

always open

some K+ and Cl- channels

Question 5

Gated Channels

Answer 5

closed until stimulus opens

Question 6

Ligand Gated Channels

Answer 6

Remain closed until proper ligand binds, and stays open until its removed
Nicotinic receptors in skeletal m

Question 7

2nd Messenger Gated Channels

Answer 7

open when 2nd messenger is around, closes when removed

Ca2+ channels in smooth m

Question 8

Voltage Gated Channels

Answer 8

closed until membrane potential hits certain value
stays open while in certain range
Na+ channels in mm

Question 9

Ionic Movement

Equilibrium Potential

Answer 9

ions move down gradient until certain charge is met that stops the movement
move in response to conc and charge

Question 10

Nerst Equation

Answer 10

calculate equilibrium potential

Question 11

Resting Membrane Potential

Answer 11

charge difference across cell membrane due to conc gradients of permeant ions

Question 12

Resting Membrane Potential ranges and averages

Answer 12

• 20 to -100 mV

- 70 in neurons, -90 in skeletal and cardiac mm

Question 13

Action Potentials

Answer 13

rapid changes in membrane potentials

Question 14

Stages of Action Potential

Answer 14

RMP
Depolarization
Overshoot
Repolarization
Hyperpolarization
RMP

Question 15

Na K ATPase

Answer 15

necessary for RMP
3 Na+ out, 2 K+ in
makes cell more negative

Question 16

Threshold

Answer 16

-60 mV
if reached, action potential must occur
voltage gated Na channels open- causes depolarization

Question 17

Overshoot

Answer 17

due to rapid influx of Na+
+35 mV
inactivation gates close, no Na+ movement
K+ channels open

Question 18

Repolarization

Answer 18

Na slows, K rises

positive charges leave cell

Question 19

Hyperpolarization

Answer 19

membrane becomes more negative than RMP

Question 20

Hyperkalemia

Answer 20

too much K

less of a gradient, more positive RMP

Question 21

Hypokalemia

Answer 21

not enough K

higher gradient, more negative RMP

Question 22

Refractory Periods

Answer 22

from cell’s inability to depolarize- channels dont reset

Question 23

Absolute RP

Answer 23

No AP

activation gate of Na not closed

Question 24

Relative RP

Answer 24

need greater than normal stimulus

K flux hyperpolarizes cell, harder to get to threshhold