3.6: Action Potentials Flashcards
How is an action potential difference from a graded potential
An action potential is propagated through the entire membrane, and is non-decremental. Travels long distances and cannot sum , all or nothing response
What is absolute refractory period, when does it occur, and how
This is the time at which another action potential can absolutely not occur. Happens during phase 1 and two of an action potential up to just before the hyper polarization. Happens because sodium channels are in open and closed states but have open activation gates. 
What is a relative refractory period, when does it occur, and how
Occurs during phase 3 of an action potential when hyper polarization has occurred and is climbing back towards resting potential. Another action potential may take place but it’s less likely and requires a stronger stimulus. Occurs because sodium activation gates close and inactivation gate open – capable of opening and can respond to depolarization. Potassium gates are slowly closing
If of sufficient magnitude, graded potentials can trigger an action potential before they die out, bringing about depolarization of adjacent portions of membrane where action potential take place. Threshold potential much must be reached, what is this and what does it result in
Threshold potential is between -50 and -55 mV, and once reached explosive depolarization takes place (+30 mV). Membrane then re-polarizes and often experiences after hyper polarization( -80 mV) before resting potential is restored
How long does the process of an action potential take
In a nerve cell action potential is 1 ms, but last longer in muscle cells depending on what type of muscle it is
What are overshoot and spike in regards to actually potential
Overshoot is from 0 to +30 mV during depolarization, and the action potential can be referred to as the spike
What kind of gates does a sodium channel have
Activation gate which guards the channel by opening and closing like a hinge door, and an inactivation gate which is a ball and chain-like sequence of amino acids, the gate is open when the ball is dangling on the chain and close when the ball binds to its receptor at the channel opening, blocking the opening. Both must be open for passage
What’s three possible confirmations does the sodium channel have
Closed but capable of opening – activation gate is closed, inactivation gate is open
Open or activated – both gates are open
Closed and not capable of opening – activation gate is open and inactivation gate is closed
What dictates which conformation the sodium gates are in
The membrane potential, which is why they’re called voltage gated channels
How do potassium channels differ from sodium channels
Potassium channels have the same three confirmations as sodium channels, but have four individual subunits whose shape are changed by the electrical field changes, no activation and an activation gates
