Resting Potentials

Question 1

What is flux

Answer 1

The rate of transfer of molecules, known as the number of molecules that cross a unit area per unit of time

Question 2

What are the units or flux

Answer 2

molecules m-2s-1

Question 3

Give some features of ion

Answer 3

They are charged molecules where opposite charges attract and like charges repel

Question 4

What is the significance of voltage to excitable cells

Answer 4

unit = volts

Generated by ions to produce a charge gradient

Question 5

What is the significance of current to excitable cells

Answer 5

unit = amps

Movement of ions due to a potential difference

Question 6

What is the significance of resistance to excitable cells

Answer 6

unit = ohms

Barrier that prevents the movement of ions

Question 7

How is membrane potential measured

Answer 7

place a reference electrode outside the cell (0V) and another inside the cell to measure the difference

Question 8

How does membrane potential differ between cells

Answer 8

It doesn’t

Question 9

What is the purpose of ion channels

Answer 9

Allows hydrophobic membranes to selectively allow ions through by changing permeability

Question 10

What affects the opening and closing of the ion channels

Answer 10

Trans-membrane voltage, activating ligands, mechanical forces

Question 11

Define equilibrium potential

Answer 11

The potential at which electrochemical equilibrium has been reached, preventing diffusion of the ion down its concentration gradient

Question 12

What is the Nernst equation used for

Answer 12

Calculating equilibrium potential

Question 13

What are the average quantities of sodium and potassium extra/intracellularly

Answer 13

sodium 150/10

potassium 5/150

Question 14

What is the Goldman Hodgkin Katz equation used for

Answer 14

Describes resting membrane potential, taking into account potassium, sodium and chloride concentrations.

Question 15

What is graded potential

Answer 15

Changes in membrane potential in response to stimulation

Question 16

What differentiates graded potentials from action potentials

Answer 16

AP = all or nothing, same potential each time
GP = potential changes

Question 17

Where do graded potentials occur

Answer 17

Synapses (convergence) or sensory/touch receptors

Question 18

How may graded potentials occur

Answer 18

stimulus cna induce a small depolarisation and hyper polarisation
A weak stimulus can induce a small depolarisation and a strong stimulus a large one
Depolarisation may dwindle as it moves down the cells

Question 19

Define depolarising

Answer 19

from -70mV to -mV

Question 20

Define overshoot

Answer 20

from 0 to more +ve

Question 21

Define repolarising

Answer 21

from +ve to more -ve

Question 22

Define hyperpolarising

Answer 22

from -70mV to more-ve