Unit 5: Notes 2 Flashcards
what speeds up an action potential
Myelin and diameter
what is the condition of a nerve cell at resting potential (charge, location of different ions)?
-70, inside K+, outside Na+.
which Japanese delicacy is risky? and why?
The puffer fish. It contains tetrodotoxin, A substance that makes them and foul tasting and often lethal to fish
to humans, TTX is deadly, up to 200 times more poisonous than cyanide
what is an action potential
-how neurons communicate
-nerve impulse
-self propagating (following rules of dominoes)
-A large change in the membrane potential (difference in electrical charge)
> from - to +, back to -
> result from movement of Na+ and K+ through membrane channels
what are the types of channels in the axon?
leakage channels and gated channels
what are leakage channels
they allow small steady streams of ions to leak across the membrane
what are gated channels
Open and close on command
> voltage gated channels open in response to a change in membrane potential
resting neuron
resting neurons have a charge of -70 mV compared to outside
> A positive charge on the outside, negative charge on the inside
what is happening inside the neuron at rest
higher concentration of K+, so it leaks out fast
what is happening outside of the neuron at rest
higher concentration of Na+, so it leaks in slowly
what is the sodium potassium pump
- The small Na+ inward leak and larger K+ outward leak is offset by the Na+/K+ pump
- maintains resting membrane potential
name the steps of an action potential
depolarization, peak, repolarization, hyperpolarization
depolarization
- stimulus causes voltage gated Na+ channels to open and Na+ rushes into the cell
- cell becomes more positive
- threshold = minimum level of stimulus (-55)
Peak
- K+ channels begin to open and K+ begins to leave cell
- Na+ channels begin to close
Repolarization
- K+ voltage gates fully open, K+ leaving cell
- all Na+ Gates are closed
- cells becoming more negative
