A calcium channel blocker has been prescribed for a client with hypertension. The nurse explains that this drug affects the function of the L-type calcium channel by which action?
1. Enhancing the action potential along the cell membrane
2. Changing the shape of the L-type calcium channel
3. Blocking sympathetic input to the cell membrane
4. Competing for calcium receptors on the L-type calcium channel
Correct Answer: 2
Rationale 1: Opening of the calcium channel and entry of calcium into myocytes and vascular smooth muscle cells occur in response to the action potential, but calcium channel blockers do not exert their therapeutic effects by interfering with the action potential.
Rationale 2: By altering the shape of the calcium channel, calcium channel blockers prevent entry of calcium into cells.
Rationale 3: The L-type calcium channel opens in response to sympathetic stimulation, but calcium channel blockers do not inhibit this input.
Rationale 4: The role of the calcium channel is to control entry of calcium into cells. The calcium channel blockers prevent entry of calcium through the channel without competing for receptors with calcium ions.
Global Rationale: By altering the shape of the calcium channel, calcium channel blockers prevent entry of calcium into cells. Opening of the calcium channel and entry of calcium into myocytes and vascular smooth muscle cells occur in response to the action potential, but calcium channel blockers do not exert their therapeutic effects by interfering with the action potential. The L-type calcium channel opens in response to sympathetic stimulation, but calcium channel blockers do not inhibit this input. The role of the calcium channel is to control entry of calcium into cells. The calcium channel blockers prevent entry of calcium through the channel without competing for receptors with calcium ions.
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