Neuro 3 Flashcards
(27 cards)
Does voltage travel actively or passively?
Passive
Which membranes have the ability to generate action potentials?
Excitable membranes
** the presence of Na channels make the membrane excitable
3 phases of action potential
Depolarization
Repolarization
After - hyper polarization
If a membrane potential is measured at the site of stimulus and again at the axon hillock, where will the membrane potential be greater?
At the site of the stimulus
Decays as it travels
An action potential will only be triggered if the membrane potential reaches which value
-50
How are action potentials different from graded potentials?
Action potentials have the same size and duration for any particular Neuron and are usually conducted the entire length of an axon without decaying
Do graded potentials depend on an all or nothing principle?
No. Only action potentials depend on that property
During the rapid depolarization of an Action potential the membrane potential is closer to ENa or EK?
Na will rush in causing the potential of the cell to be closer to ENa
Which potentials bring the membrane to threshold?
Graded
What does threshold trigger?
Rapid opening of Na channels
Slow closing of Na channels
Slow opening of K channels
Which 2 gates are associated with the sodium channel?
- Activation gate
2. Inactivation gate
3 main points about the Activation Gate
- Voltage dependent
- Opens at threshold and depolarization
- Positive feedback
3 important points on Inactivation Gate
- Voltage and time dependent
- Close during depolarization
- Open during depolarization
Define the all or nothing principle
Minimum depolarization necessary to induce the regenerative mechanism for the opening of the sodium channel
What is a refractory period
The period of time following an action potential
Marked by decreased excitability (some or all Na channels are inactivated)
What are the two types of refractory period
- Absolute - none of the Na channels are reconfigured
2. Relative - some Na channels are reconfigured
When and why does the absolute refractory period occur ?
When - soon after opening of the Na channels
Why - so that second AP cannot be generated
When and why does the relative refractory period occur?
When - last part of the Repolarization phase
Why - able to generate another AP (small one)
True/false
A stimulus a little stronger than normal is necessary to generate an action potential late in the refractory period
True
True/false
A stimulus a little stronger than normal is necessary to generate an action potential early in the refractory period
False
-much stronger than normal
Propagation of action potentials depend on the presence or absence of:
Myelin
What is the mechanism by which action potentials are prolog aged in unmyelinated axons
ELECTROTONIC conduction
How does an action potential travel down an unmyelinated axon
The region of depolarization continues to move down the axon. A refractory period then occurs behind the region of depolarization
The region of depolarization in an unmyelinated axon is more positive where
On the inside
