Question

List the role or roles of DHPR (L-type calcium channels) in the contractile cardiac cells.

a) Prolong the action potential
b) Let calcium into the cytosol from the extracellular space
c) Let calcium into the cytosol from the sarcoplasmic reticulum
d) Terminate the action potential

Answer 1

The DHPR (L-type calcium channels) perform the roles of prolonging the action potential, allowing calcium into the cytosol from both the extracellular space and the sarcoplasmic reticulum.

Step-by-step explanation:

The L-type calcium channels, also known as DHPR, play multiple roles in contractile cardiac cells.

1. They prolong the action potential by contributing to the plateau phase and absolute refractory period, which allow the cardiac muscle to function properly.
2. They let calcium into the cytosol from the extracellular space, which is essential for the initiation of contraction in the sarcomeres of the muscle fibers.
3. They also let calcium into the cytosol from the sarcoplasmic reticulum, which further contributes to the availability of calcium for contraction.