W2 L2 (Action potential) Flashcards
Action potential
Short-term change and rapid change in Vm due to coordinated action of certain voltage-gated channels
What 2 things do actions potentials do?
- Code info 2. Trigger other neurons, muscles or glands
What happens during an action potential?
The inside and outside of the cell reverse in polarity ie. the inside becomes positive and outside negative.
How are action potentials like binary code or a light switch?
Action potentials are either on or off there is no in-between or graded response. For example, like in binary, they are a 0 or a 1.
Threshold
The strength of stimulus required for an action potential to be initiated.
What does a stronger stimulus entail with regards to action potentials?
It means that there will be more action potentials, not bigger ones (b/c it is not a graded response).
What is the duration of a neuron and heart action potential respectively?
Neuron: 1-5ms Heart: 300-400ms
What threshold must be reached for an action potential?
There is really a range depending on the cell between -20mV and -60mV. For this class assume the threshold to be -55mV.
What does it mean that action potentials travel in a non-decremental fashion?
It means that their intensity is constant and doesn’t diminish over their very short life.
Explain why the portion of the membrane that creates graded potentials doesn’t experience action potentials?
Typically, the portion of the excitable membrane where graded potentials are produced in response to a triggering event does not undergo action potentials. Instead, the graded potential, by electrical or chemical means, brings about depolarization of adjacent portions of the membrane where action potentials can take place.
Threshold potential
The critical potential that must be reached before an action potential is initiated in an excitable cell
AP diagram
What are transmembrane voltage sensors and what do they do?
They are positively charged amino acids meaning the sensor moves to open the gate of a channel when the inside is positive
Explain the steps of an action potential
- Resting State -The membrane is in a resting state (-60mV) with both channels activation gates closed. The inside is negative and the outside is positive.
- Activation/Triggering event - Depolarization proceeds slowly until an explosive depolarization (-55mV) happens.
- Depolarization (-55mV to approx 30mV) - Na+ enters the cell down its concentration and electrical gradient causing the Vm to go towards Vk.
- Repolarization (30mV to less than -60mV) -
Overshoot also give an example during an action potential
When a signal exceeds its steady-state value, for ex. when the action potential causes the Vm to go to +30mV instead of just 0mV.
What is another name for an action potential?
Spike