What happens during the undershoot phase of an action potential?
The voltage-gated potassium channels stay open a little longer than needed to bring the membrane back to its resting potential. This results in a phenomenon called “undershoot,” in which the membrane potential briefly dips lower (more negative) than its resting potential.
What is the undershoot phase?
Afterhyperpolarization, or AHP, is the hyperpolarizing phase of a neuron’s action potential where the cell’s membrane potential falls below the normal resting potential. This is also commonly referred to as an action potential’s undershoot phase.
What happens in the depolarizing phase of an action potential?
The threshold potential opens voltage-gated sodium channels and causes a large influx of sodium ions. This phase is called the depolarization. During depolarization, the inside of the cell becomes more and more electropositive, until the potential gets closer the electrochemical equilibrium for sodium of +61 mV.
Which of the following occurs during the repolarization phase of the action potential?
c. An increase in the electrochemical gradient would increase K+ leak so cells would be more negative (more depolarized). Which of the following events begins with opening of potassium gates and the rushing out of K+? Na+ channels open during which of the following events?
Why does the Afterhyperpolarization not coincide with the peak K+ conductance during the action potential?
In addition to voltage-dependent changes in Na+ permeability, there are voltage-dependent changes in K+ permeability. These changes can be measured with the voltage-clamp technique as well. The figure shown to above indicates the changes in K+ conductance as well as the Na+ conductance. There are two important points.
Why does the undershoot occur?
As a result, potassium continues to flow out of the cell even after the membrane has fully repolarized. Thus the membrane potential dips below the normal resting membrane potential of the cell for a brief moment; this dip of hyperpolarization is known as the undershoot.
What are the phases of action potential?
The action potential can be divided into five phases: the resting potential, threshold, the rising phase, the falling phase, and the recovery phase. We begin with the resting potential, which is the membrane potential of a neuron at rest.
Which of the following drug prolongs the repolarization phase of the action potential?
Ivabradine is considered to act specifically on the sinoatrial node by inhibiting the If current (the funny current) to slow automaticity. However, in vitro studies show that ivabradine prolongs phase 3 repolarization in ventricular tissue.
Why does undershoot occur in action potential?
Undershoot: The open potassium channels add to the normal resting membrane permeability to potassium, and drives the membrane potential close to the equilibrium potential for potassium, thus hyperpolarizing the membrane. This means that more depolarizing current is necessary to initiate another action potential.
During what phase of the action potential does the neuron undershoot its resting membrane potential?
The rising phase is a rapid depolarization followed by the overshoot, when the membrane potential becomes positive. The falling phase is a rapid repolarization followed by the undershoot, when the membrane potential hyperpolarizes past rest. Finally, the membrane potential will return to the resting membrane potential.
