Week 2 Flashcards
Electrical charge that runs down the axon from the axon hillock to the terminal buttons. It is a brief electrical signal that provides the basis for conduction of information along an axon
Action Potential
Transmission of signal is dependent on the movement of ___
Ions (Charged Particles)
What are Ions?
Charged Particles
Ions are ______ distributed between the inside and outside of the cell
unequally
Ions enter and leave the cell through
Ion Channels
When all voltage-gated Na+ channels and most K+ channels are closed, and the Sodium-Potassium Pump moves 2 K+ into cell and 3 Na+ out of the cell to maintain an electrical gradient, this is known as
Resting Potential
The Sodium-Potassium pump (Ion Channel) is an example of a
protein
complex
When at rest, the neuron membrane maintains an _____ ______
Electrical gradient (because of the difference of charges from Ions on either side)
What is the approximate voltage of resting potential
-70 (mV)
When at resting potential, the membrane is labelled as
Polarized
The neuron membrane controls or is less open to certain chemicals moving freely across, this is known as
Selective Permeability
- What protein complex repeatedly pumps out 3 NA+ Ions, and brings in 2 NA+
- Why does it do this
Sodium Potassium Pump
To maintain the -70 mv resting potential (electrical gradient / polarization), as if it didn’t the neuron would depolarize.
difference in electrical charge between the inside and outside of the cell
electrical gradient
the difference in distribution of ions
across the membrane
concentration gradient
how is the electrical gradient voltage measured
voltmeter
When Some Na+ channels open allowing Na+ ions to enter cell, and the charge across the membrane lessens, this is known as
Depolarization
What is needed for all Na+ channels to suddenly open
threshold of excitation from a stimulus
- When do Na+ Channels start to close and K+ leaves the cell
- When Na+ channels close while K+ channels open, and K+ leaves cell. This is known as
- Peak Action Potential
- Repolarization, all the way until Hyperpolarization (once lots of k+ fully leave cell)
a stimulus needs to change the approximate voltage / electrical gradient to approx ____ to activate action potential
-55 (mV)
What is the approximate voltage / electrical gradient at PEAK action potential
+ 30- 40 (mV) (slides says 40)
2 Principles for Conduction of Action Potential
- All or None Law: Once an action potential is triggered in an axon, even by the minimum stimulus, neurons will fire always with the maximum response, even if intensity of stimulus increases or endures.
- Rate Law: the more intense a stimulus is, the FASTER the neuron will fire, but to the same level response as in All or none law.
What direction down the neuron does the action potential travel
Cell Body –> Axon – > Axon Terminal (depolarization moves in this order, while behind is repolarized, and ahead is still resting)
What is the approximate voltage / electrical gradient at Hyperpolarization
slightly higher than -70, up to 75 (mV)
Insulating layer that allows electrical impulses to transmit quickly and efficiently along nerve cells
Myelin Sheath
