resting membrane potential

Question 1

what ions are involved for bioelectricity?

Answer 1

K+, Na+, Cl-, Ca2+

Question 2

what ions have higher/lower concentration inside/outside the cell?

Answer 2

K+ and organic anions are present in higher concentration inside the cell.
Na+ and Cl- are present in higher concentration outside the cell.

Question 3

resting membrane potential: define

Answer 3

the steady potential difference across the cell membrane of an unstimulated cell.
(under resting conditions, cells have a potential difference across their plasma membranes. the ICF is negatively charged, while the ECF is positively charged.

Question 4

electrical potentials are generated across cell membranes because:

Answer 4

1. there are differences in the concentrations of ions across cell membranes.
2. membranes are selectively permeable to some of these ions.

Question 5

resting membrane potential (RMP) results from the combined effects of:

Answer 5

1. the diffusion of ions down their gradients through plasma membrane, provided there are channels available.
2. selective permeability of the membrane, allowing some ions to pass more readily than others.
3. the electrical attraction between cations and anions, and the repulsion between like charges.

Question 6

what are some types of channels that enable diffusion?

Answer 6

mechanically gated, voltage-gated, ligand-gated, leaky channels

Question 7

mechanically gated channels

Answer 7

channel is physically opened in response to mechanical change in surrounding tissue, like pressure, touch and temperature.

Question 8

voltage gated channels

Answer 8

opens when the transmembrane voltage changes. contribute to action potential

Question 9

ligand gated channels

Answer 9

opens when a ligand binds to the extracellular region of the channel

Question 10

leaky channel

Answer 10

has an intrinsic rate of switching between open and closed states. very important for resting membrane potential.

Question 11

what are channels and why are they needed?

Answer 11

channels are proteins in the membrane. the ions cannot pass directly through the hydrophobic lipid region of the membrane, because they are charged. the channel proteins provide a hydrophilic tunnel across the membranes.

Question 12

how is resting membrane potential determined?

Answer 12

it is a weighted mean of the equilibrium potentials of the different permeant ions.

Question 13

equilibrium potential: define

Answer 13

the voltage difference across a membrane that produces a flux of a given ion species that is equal but opposite to the flux due to the concentration gradient of the same ion.

Question 14

what is the equation used to calculate the membrane potential with multiple ions?

Answer 14

the GHK equation

Question 15

movement of chloride and RMP

Answer 15

Cl- does not influence RMP, instead membrane potential passively influences Cl- distribution. when membrane potential changes, Cl- moves into/out of the cell.

Question 16

excitable cell: define

Answer 16

a cell that is able to be electrically excited, resulting in the generation of action potential.

Question 17

how is a neuron resting membrane potential produced?

Answer 17

see notion notes: Class notes A/resting, graded and action potential

Question 18

is the cell membrane more permeable to K+ or Na+?

Answer 18

K+. there are considerably more K+ leaky channels than Na+ leaky channels.

Question 19

ion channels are selective.
For example, a small channel lined with negatively charged groups will be selective for _____ and exclude ____ and _________. Conversely, a small channel lined with positively charged groups will be selective for ______ and exclude _____ and ____________.

Answer 19

small cations; anions; large solutes;

small anions; cations; large solutes.

Question 20

what does the conductance of a channel depend on?

Answer 20

the probability that the channel is open. The higher the probability that a channel is open, the higher the conductance, or permeability.

Question 21

how to calculate the equilibrium potential at a given concentration difference of a permeable ion across a cell membrane?

Answer 21

using the Nernst equation.

Question 22

what is the resting membrane potential of a cell?

Answer 22

-70mV.

Question 23

what is the K+ equilibrium potential?

Answer 23

-85mV

Question 24

what is the Na+ equilibrium potential?

Answer 24

+65mV

Question 25

what is the effect of a concentration gradient?

Answer 25

Substances tend to diffuse down a concentration gradient provided there are channels of transport/communication available

Question 26

how many times more concentrated is ICF K+ than Na+?

Answer 26

40

Question 27

how many times more concentrated is ECF Na+ than K=?

Answer 27

12

Question 28

how many times more permeable is the cell membrane to potassium than to sodium?

Answer 28

25-30 times more.

Question 29

is the 3Na/2K/ATPase pump passive or active?

Answer 29

the pump is a mode of active transport. it uses ATP.

Question 30

what is the principal ECF anion, and how is it transported?

Answer 30

Cl- is the principal ECF anion.

it is highly permeant and passively diffuses across the cell membrane.

Question 31

what is the equilibrium potential of Cl-?

Answer 31

-70mV.

Question 32

what does the Na/K pump do?

Answer 32

it pumps 3 Na+ out of the cell, and 2 K+ into the cell.