2.3 -- Action Potential Flashcards
What are the three states of voltage-gated Na+ channels in order and when does it happen?
Closed channel, open channel, and inactivation channel back to closed
Closed to open at -55 mV
Open to inactivation at +30 mV
Inactivation to closed after ~ 2 ms
Does sodium rush into or out of the cell?
Sodium rushes into the cell
What is the threshold of voltage-gated sodium channels?
-55 mV
What states are the activation gate open and what states are the inactivation gate open?
Activation Gate Open: Open and inactivation
Inactivation Gate Open: Closed and open
Local anaethestics like lidocaine, novocaine, and xylocaine block the channel so no what is sent in, stopping action potential? This would also have no “pain” signal reaching the brain
Na+ in
When do voltage-gated K+ channels open? What does this cause?
+30 mV, causing repolarization
What are large, rapid reversal of membrane potential in a region of the cell that allows electrical impulse to be carried over long distances?
Action potentials
What are refractory periods?
Periods when the membrane can’t respond or is less sensitive to depolarizing stimuli
What is the absolute refractory period? What state are the Na+ channels in?
No action potential capability, where the Na+ channels are inactivated
What is the relative refractory period? What state are the Na+ channels and K+ channels in?
Hyperpolarization phase, where it takes more to stimulate an action potential. Na+ channels are in the closed state and K+ channels are still open
What is a physiological consequence of the refractory period?
One way movement of electrical signal
Each action potential remains a separate, what event?
All-or-none event
The action potential at one location serves as the what stimulus for the next region of the axon?
Depolarizing stimulus
When can a new stimulus cause another action potential in that area?
After the absolute refractory period is over
Does the size of the stimulus affect the size of the action potential?
No
While the size of the stimulus won’t affect the duration of the action potential, more stimulus at the cell body can make action potentials do what?
Occur more frequently
Myelin improved the insulation, improving what?
Speed
Salatory conduction is when action potentials do what from node to node?
“Leap”
What forms myelin sheaths in the CNS?
Oligodendrocytes
What forms myelin sheaths in the PNS?
Schwann cells
Action potential conduction speed is increased by what and increased what of the neuron?
Myelination and increased diameter of the neuron
