Figure 19.7 • Schematic representation of an ion channel existing in an equilibrium of resting (R), open (0), and inactivated (I) states.

and diltiazem do not bind to a channel in the resting state, only after the channel has been opened. They are ionized, water-soluble Ca2+-entry blockers that reach their binding sites by the hydrophilic pathway when the channel is open. Verapamil and diltiazem are use dependent (i.e., their Ca2+-blocking activity is a function of the frequency of contractions). An increase in contraction frequency causes a reduction, rather than an augmentation, of contractions. Nifedipine is a neutral molecule at physiological pH and can cause interference with the Ca2+ in the open or closed state. In the closed state, nifedipine can traverse the phospholipid bilayer to reach its binding site because of its lipid solubility.

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Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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