Lecture 4 vocab Flashcards
What is the speed of thought classically measured by?
Reaction time
What speed range from 1 to 270 mph?
Speed of action potential propagation
What 3 factors does speed depend on?
Distance, Neuron characteristics, and complexity
What are action potentials?
It uses electricity to convey information very fact. relies on the electrical gradient across the cells membrane, is all or none, and may convey information over long distances
Is there a difference between speed or strength in action potentials?
No
When do the membrane potentials change?
When ions move in and out of the neurons
What defines the phases of the action potential?
K+ and Na+ ion movement
What are the stages of action potentials in a neuron?
resting state, depolarizing phase, rising/falling phase, and the refractory period
What happens in the resting state?
The leak channels are open(both Na&K but more K leak channels). resting membrane potential is maintained, the net negative charge inside cell is -65mV
What happens when neurons start to receive information?
Neurons sum up inputs at the axon hillock
What happens when EPSP(the depolarization unit) are inputted during the resting state?
it opens Na+ voltage channels and depolarize the membrane
What happens when the axon hillock depolarizes beyond threshold?
you get an action potential
What happens during an action potential?
Voltage gated sodium ion channels in the axon hillock open(allowing more sodium into the cell)
What happens in the depolarizing phase?
Leak channels open, membrane potential becomes more positive as Na+ enters the cell
At what mV does the action potential have to pass for it to occur?
At ~ -40/50mV many more Na+ channels open and an action potential is triggered
What are the two key players in an action potential?
Voltage-gated Na+ channels & voltage-gated K+ channels
What do Voltage-gated Na+ channels do
They cause large depolarization and it occurs in the rising phase
What do Voltage-gated K+ channels do
They cause repolarization and occur in the falling phase
When do Voltage-gated Na+ channels open?
They are closed at rest and open in response to depolarization past threshold, letting in Na+
What happens in the rising phase?
An action potential has been triggered and many Na+ channels open, Na+ channels then become inactive, contributing to undershoot K+ channels are triggered to open, but with a short delay, Membrane potential spikes toward maximum
What determines the amplitude of the rising phase?
The number of open channels
What happens in the falling phase?
Na+ channels are inactive, K+ channels open and K+ flows out of the cell membrane, Membrane potential decreases towards resting potential
What happens during the refractory period(undershoot)?
Na+ channels are inactive and then close, K+ channels remain open, Membrane potential is below resting potential and closer to EK
What are the two phases of the refractory period?
There is the absolute refractory phase(1st) and the relative refractory phase(2nd)
