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The flow of calcium into the cell is an important component of the upstroke phase of action potentials in

a. Cardiac ventricular muscle
b. Intestinal smooth muscle
c. Skeletal muscle fibers
d. Nerve cell bodies
e. Presynaptic nerve terminals

1 Answer

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Final answer:

The upstroke phase of action potentials in cardiac ventricular muscle cells involves calcium ions entering through voltage-gated calcium channels, causing a sustained plateau in the action potential and allowing a longer contraction period.

Step-by-step explanation:

The flow of calcium into the cell is a key component of the upstroke phase of action potentials in different types of muscle and nerve cells. Specifically, for cardiac ventricular muscle, the influx of calcium ions (Ca2+) through voltage-gated calcium channels in the sarcolemma during action potential is crucial.

This Ca2+ entry causes a sustained depolarization plateau, elongating the action potential, and allows for a longer contraction relative to skeletal muscle action potentials. This is distinct from skeletal muscle, where the majority of Ca2+ comes from the sarcoplasmic reticulum (SR), and contraction is generally triggered more rapidly without the plateau phase.

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