Action Potential Flashcards
Exam 1
What do we use to measure Action Potential?
Microelectrode inside the axon
Graded potentials
SHORT distances; does not reach threshold
Action potentials
LONG distances; reach the threshold
Depolarization
Membrane potential becomes more (+); Away from RMP
Repolarization
Membrane potential becomes more (-); Towards RMP
Hyperpolarization
Membrane potential becomes even more (-) than normal resting potential because
What causes action potentials? (2)
- Incoming signals from another neuron
- Sensory signals from environment
What is the value of threshold?
-55mV
What is the value of RMP?
-70mV
What is the value of peak AP?
+30mv
What is happening during resting state of AP?
All gated Na+ and K+ channels are closed; only leak channels are open
Voltage-Gated channels
Open at a certain voltage specific to the subtype
What maintains RMP? (2)
The Na+/K+ ATPase pump and leak channels
What is happening at threshold of AP?
The membrane has been depolarized by 15-20mV; Na+ permeability increases
For an axon to fire, _________________________
depolarization must reach threshold
If a depolarization event does not produce an AP, it produces a
graded potential
Conformational change
Membrane repels positive amino acids in the NA+ Voltage channels
Voltage sensor
Part of the channel that is sensitive to membrane voltage changes
What is happening at the depolarization phase of AP?
At threshold, all Na+ channels open; voltage reaches +30 mV; SIGNAL IS PROPOGATED
Why does the peak value top off at +30mV?
- Kinetics (timing) of the VG Na+ channels
- At +30mv, VG K+ channels open
How do the Na+ channels temporarily close?
The ball and chain that plugs the Na+ pore
Does K+ flow in or out of the membrane?
Out
What happens at the repolarization phase of AP?
VG K+ channels open up; positive K leaves the cell, making it more negative; Internal negativity is restored
What happens during hyperpolarization in AP
K+ keeps leaving because of a slow gate, so the cell becomes extra negative
What is the refractory period?
The period during/right after AP that the neuron cannot fire again
Are there more VG channels or leak channels in the membrane?
Voltage-gated channels
During the refractory period, the Na+ channels are ____________ and the K+ channels are _________
Closed; open
Repolarization restores ________ conditions
electrical
Na+/K+ pumps restore _____________ conditions
Ionic
What are the four principles of action potential?
All-or-none principle, refractory period, forward propagation, and rate code