Compare and contrast the neuronal action potential vs cardiac action potential. Focus in the steps of the both action potentials and identify the difference.
What is the significance and involvement of Calcium ions in the cardiac action potentials? Why are Calcium ions not necessary in the neuronal action potentials, but essential in the myocardial AP?
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Introduction:
Action potentials are vital for the proper functioning of excitable cells such as neurons and cardiac muscle cells. Neuronal action potentials and cardiac action potentials share some similarities but also exhibit significant differences. In this section, we will compare and contrast the steps of neuronal and cardiac action potentials and examine the role of calcium ions in the cardiac action potential.
1. Compare and contrast the neuronal action potential vs cardiac action potential. Focus in the steps of the both action potentials and identify the difference.
Both neuronal action potentials and cardiac action potentials are initiated by depolarization, where a rapid change in membrane potential occurs. However, the steps of the two action potentials differ significantly. Neuronal action potentials consist of four phases: the resting phase, depolarization phase, repolarization phase, and the hyperpolarization phase. In contrast, the cardiac action potential consists of five phases: the resting phase, the rapid depolarization phase, the plateau phase, the repolarization phase, and the resting state.
The major difference between neuronal and cardiac action potentials lies in the repolarization phase. In neurons, repolarization is rapid and occurs through potassium efflux, leading to the restoration of the resting potential. In contrast, the repolarization phase in the cardiac action potential is slow and is caused by the opening of voltage-gated potassium channels and the closing of voltage-gated calcium channels.
2. What is the significance and involvement of Calcium ions in the cardiac action potentials? Why are Calcium ions not necessary in the neuronal action potentials, but essential in the myocardial AP?
Calcium ions play a crucial role in the cardiac action potential. During the plateau phase, calcium ions enter the cytosol of the cardiac myocyte from the extracellular space via voltage-gated calcium channels. This leads to muscle contraction, which is the underlying event that drives the pumping action of the heart.
In contrast, calcium ions are not necessary in the neuronal action potential as they do not contribute to the generation of action potentials in neurons. Neuronal action potentials are generated primarily by the movement of sodium ions into the cell and by the movement of potassium ions out of the cell.
Overall, the role of calcium ions in the cardiac action potential is vital to the contractility and pumping function of the heart. In contrast, neuronal action potentials do not rely on calcium ions for their generation, but rather on sodium and potassium ions.
