Resting and Action Potentials Flashcards
What is a membrane potential
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
What are channels
Electrochemical gradient, fast
Eg Na, k, p2x
What are carriers and exchangers
Concentration gradient
Eg GLUT 1-4
What is primary active transport
Uses ATP as energy source
Eg na/k atpase
What is secondary active transport
Uses ionic gradient as energy source
Eg Na/ca exchanger
What is the resting amplitude in mV of neurones
-65
What is the resting amplitude in mV of cardiac muscle
-85
What is the resting amplitude in mV skeletal muscle
-90
What is Depolarisation
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
What is hyperpolarisation
An increase in the size of membrane potential from its normal value. Cell interior becomes more negative
Eg. A change from -70 to -90
What are the 2 things to consider for setting up a membrane
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
Setting up a resting potential
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
Changing membrane ion permeability
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
Where to synaptic connections occur
Nerve cell- nerve cell
Nerve cell- muscle cell
Nerve cell - gland cell
Sensory cell - nerve cell
What is synaptic transmission
Chemical transmitter released from presynaptic cell binds to receptors on postsynaptic membrane
Excitatory synapses
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
Inhibitory synapses
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
What are 2 other factors that influence membrane potential
1) changes in ion concentration
2) electrogenic pumps
Properties of action potentials
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
What do you need to generate an action potential
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
What is ARP
Absolute action potential
Nearly all na+ inactivated state
What is RRP
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
