3.5 Flashcards
what is resting potential?
when no impulse is travelling along an axon
what is resting potential measure as?
-70mV
describe resting potentials value
1- the sodium potassium pump. there is active transport of 2K+ into the axon and 3Na+ out of the cell
2- gated ion channels are open for K+ to move out of the axon
3- gated ion channels are closed for Na+ to move into axon
4- there are large negative ions inside the axon that cant leave
why is resting potential a negative value?
there are more + ions outside the axon compared to the inside
what is the membrane described as being at resting potential?
polarised
what is action potential?
when an impulse is travelling along an axon
what is action potential measured as?
+40mV
describe action potential
1- a stimulus produces a voltage opening the gated ion channels for Na+ so the membrane becomes permeable to Na+
2- Na+ move in by facilitated diffusion which depolarises the axon
3- Na+ diffuse within the axon to the next node of ranvier (local circuit)
4- the presence of Na+ stimulates the opening of the gated channels
what does the impulse do?
jump from node to node
what is the impulse jumping called?
saltatory conduction
how does myelination speed up conduction?
myelin is an electrical insulator so ions can move in/out at nodes
how does a stimulus result in active potential?
meeting the threshold potential
why is active potential referred to as all or nothing?
the impulse either reaches the threshold or it doesnt
what happens when theres a stronger stimulus?
the frequency of action potential increases
what factors affect speed of conduction and how?
1- myelination
2- temperature (increase in temp = increase in rate. ions have more kinetic energy so theres a faster rate of diffusion. but too high temp = proteins denature)
3- axon diameter (increase in diameter = increase in rate. lower resistance within axon to movement of ions. increase in SA so more ion channels)
