Resting and Action Potentials

Question 1

What is a membrane potential

Answer 1

Membrane potential is the potential difference between the inside and outside of a cell
It is measured in millivolts 1mv = 0.001V or 1x10-3V

Question 2

What are channels

Answer 2

Electrochemical gradient, fast
Eg Na, k, p2x

Question 3

What are carriers and exchangers

Answer 3

Concentration gradient
Eg GLUT 1-4

Question 4

What is primary active transport

Answer 4

Uses ATP as energy source
Eg na/k atpase

Question 5

What is secondary active transport

Answer 5

Uses ionic gradient as energy source
Eg Na/ca exchanger

Question 6

What is the resting amplitude in mV of neurones

Answer 6

-65

Question 7

What is the resting amplitude in mV of cardiac muscle

Answer 7

-85

Question 8

What is the resting amplitude in mV skeletal muscle

Answer 8

-90

Question 9

What is Depolarisation

Answer 9

A decrease in the size of the membrane potential from its normal value cell interior becomes less negative eg change from -70 mV to -50 mV

Question 10

What is hyperpolarisation

Answer 10

An increase in the size of membrane potential from its normal value. Cell interior becomes more negative
Eg. A change from -70 to -90

Question 11

What are the 2 things to consider for setting up a membrane

Answer 11

1)Diffusion moving from and area of high to low concentration
2)ions in solution are charged and exert electrostatic forces on each other even across a membrane

Question 12

Setting up a resting potential

Answer 12

Membrane is more permeable to k+ then other ions at rest which creates a chemical diffusion gradient
Electrochemical gradient for k+ in other direction because inside cell is more negative which creates equal opposite there will be no net movement of k+ but will be negative membrane potential
Potential at which chemical and electrical gradient for k+ are equal but opposite is termed the k+ equilibrium
Resting potential membrane arises because membrane is more permeable tonk+ then its other ions

Question 13

Changing membrane ion permeability

Answer 13

increasing membrane permeability to a particular ion moves the membrane potentiL towards equilibrium potential for that ion
Membrane potential arise as a result of selective e ionic permeability
Ion flow down to electrochemical gradient which is the difference between the membrane potential and reversal potential of ion channel

Question 14

Where to synaptic connections occur

Answer 14

Nerve cell- nerve cell
Nerve cell- muscle cell
Nerve cell - gland cell
Sensory cell - nerve cell

Question 15

What is synaptic transmission

Answer 15

Chemical transmitter released from presynaptic cell binds to receptors on postsynaptic membrane

Question 16

Excitatory synapses

Answer 16

Excitatory transmitters open ligand-gated channels that cause membrane depolarisation
Can be permeable to na+ ca2+ or sometime cations in general
Resulting change in membrane potential is called editors synaptic potential
Excitatoty transmitters include acetylcholine and glutamate

Question 17

Inhibitory synapses

Answer 17

Inhibitory transmitters open ligand-gated channels that cause hyper polarisation
Can be permeable to K+ or CL-
Resulting change in membrane potential called inhibitory post-synaptic potential
Inhibitory transmitters include glycine and gaba

Question 18

What are 2 other factors that influence membrane potential

Answer 18

1) changes in ion concentration
2) electrogenic pumps

Question 19

Properties of action potentials

Answer 19

Change in voltage across membrane
Depends on ionic gradients and relative permeability of the membrane
Only occurs if threshold level is reached
All or nothing
Propagated without loss of amplitude

Question 20

What do you need to generate an action potential

Answer 20

1) method of depolarising the membrane potential rapidly
2) a way of depolarising the membrane potential
3) the ability to generate another action potential soon after
4) mechanism where action potential can travel along cd,k from one end to the other without loss of amplitude
5) events need to occur with minimal energy expenditure

Question 21

What is ARP

Answer 21

Absolute action potential
Nearly all na+ inactivated state

Question 22

What is RRP

Answer 22

Relative refractory period na+ channels recovering from inactivation excitability returns towards normal as number of na + channels inactivated decrease and voltage gated k+ channels close