Module B-02

Question 1

Current flows passively in direction denoted by _________ in electrical field

Answer 1

movement of cations

Question 2

cations move towards _______

Answer 2

cathode (negative terminal) by electrodiffusion

Question 3

Anions move towards _______

Answer 3

anode (positive terminal)

Question 4

What causes the resting membrane potential in cells?

Answer 4

the charge storing ability or capacitance of membranes

Question 5

electric potentials vary based on _______

Answer 5

permeability of membranes to particular ions

Question 6

Mean resting membrane potential of neurons

Answer 6

-65mV and -40mV

Question 7

What channels are open at rest

Answer 7

• Potassium
• Chlorine
• few Sodium channels ( more in Photoreceptors)

Question 8

Define membrane potential (Vm)

Answer 8

electrical potential of the interior of the cell relative to the exterior

Question 9

net loss of positive charge by Na-K ATPase is offset by

Answer 9

passive leak channels

Question 10

___ moles of influx of sodium ions can lead to depolarization of 100mV

Answer 10

10^-12 moles

Question 11

Hyperkalemia - high extracellular K+ causes_______

Answer 11

depolarization

Question 12

how are solutes and water transported across membrance

Answer 12

simple diffusion

active and passive transport

Question 13

describe ion channels

Answer 13

• members of superfamily of membrane proteins
• has subunits surround a central aqueous pore
• ion selective filter
• non gated channels are leak channels

Question 14

ionic movement through channels is influenced by

Answer 14

electric and ion concentration gradients

Question 15

Transport of molecule in the same direction

Answer 15

Symport

Question 16

Transport of molecule in the opposite direction

Answer 16

Antiport

Question 17

Open probability

Answer 17

Proportion of time an ion channel remains in the open state

Question 18

Open probability of voltage gated ion channels is dependant on __________

Answer 18

membrane potential

Question 19

Open probability of Transmitter gated ion channels is dependant on __________

Answer 19

Transmitter concentration

Question 20

Flow of charged ions is called__________ and its units are in _________

Answer 20

Conductance; Siemens (S)

Question 21

Ohm’s law

Answer 21

V=IR

Question 22

conductance formula

Answer 22

g=I/V

Question 23

total membrane conductance formula for an ion (x)

Answer 23

gx= (Nx) (yx)
Nx- number of ion channels for x
yx- single channel conductance

Question 24

two types of gates in voltage gated ion channel

Answer 24

1) Activation gate

2) Inactivation gate

Question 25

Nernst equation

Answer 25

E = (61.5 / z) log { [X]o / [X]i } mV

Question 26

Equation for electrochemical gradient for an ion

Answer 26

Electrochemical Gradient for ion X = (Vm - Ex ) mV

Question 27

Equation for total ionic current

Answer 27

Im = INa + IK + ICl. (Ca is negligible)

Question 28

At rest Im=

Answer 28

0

Question 29

Eg of channelopathy that is due autoimmune attack

Answer 29

Myasthenia Gravis

Question 30

damage due to cellular swelling

Answer 30

cytotoxic edema

Question 31

how does cytotoxic edema arise in ischemia?

Answer 31

failure of Na-K pumps due to lack of ATP causes accumulation of NaCl inside the cell which drives water in and the cell swells

Question 32

What are 2 effects of Ischemic Cerebral edema

Answer 32

• Cytotoxic edema

- Secondary Vasogenic edema (damaged blood vessels allow leakage of blood)