Calcium Channel blockers in the cardiovascular system Flashcards
What are voltage-gated calcium channels responsible for in cellular signalling?
Voltage-gated calcium channels manage the electrical signaling of cells by allowing the selective diffusion of calcium ions in response to changes in the cellular membrane potential. They are activated by membrane depolarization, allowing the entry of calcium into the cells down its concentration gradient.
What is the role of L-type calcium channels in the cardiovascular system?
L-type calcium channels, which are long-lasting, play a key role in excitation-contraction coupling in vascular smooth muscle and ventricular myocytes. They are present in cardiac conduction tissues such as the Sino-atrial node and the atrioventricular node, impacting heart rhythm and contraction.
How do calcium channel blockers affect cardiac electrophysiology?
Calcium channel blockers, especially those that are more cardiac-selective, decrease the phase 0 up-slope in the action potential, which prolongs the overall cardiac cycle and slows down the heart rate.
What are the two main classes of calcium channel blockers, and how do they differ?
The two main classes of calcium channel blockers are:
Dihydropyridines (e.g., amlodipine): These are highly selective for vascular smooth muscle and are used for conditions like hypertension.
Non-dihydropyridines (e.g., verapamil and diltiazem): These are less selective than dihydropyridines and can have both vascular and cardiac effects, such as slowing heart rate.
What is the first-line treatment for hypertension and angina, and when might additional treatments be required?
For both hypertension and angina, amlodipine (a calcium channel blocker) is often used as a first-line treatment. However, calcium channel blockers alone may not be sufficient and may require additional treatments, such as ACE inhibitors or beta blockers.
What condition does calcium channel blockers treat in vascular spasms, and what are the symptoms of this condition?
Calcium channel blockers are used to treat vascular spasms such as Raynaud’s syndrome. Symptoms of this condition include constriction of the digital arteries, turning fingers white initially (due to lack of blood), then blue (due to lack of oxygenated blood), and red when blood flow is restored. The affected areas also experience pain and pins and needles.
How do calcium channel blockers help in the treatment of arrhythmias?
Calcium channel blockers, particularly non-dihydropyridine types (cardioselective), help treat arrhythmias by decreasing calcium influx at the sinoatrial and atrioventricular nodes. This slows the conduction and reduces the heart rate.
What is the mechanism of action of calcium channel blockers?
Calcium channel blockers target L-type calcium channels, which control the entry of calcium ions into cells. By blocking these channels, the drugs reduce calcium ion entry, lowering intracellular calcium levels. This leads to less contraction of vascular smooth muscle and a prolonged cardiac cycle in cardiomyocytes.
What effect do calcium channel blockers have on vascular smooth muscle?
Calcium channel blockers reduce the entry of calcium ions into vascular smooth muscle cells, leading to less muscle contraction. This can result in reduced arterial resistance, which helps to lower blood pressure.
In which types of cells are L-type calcium channels found, and what is their role?
L-type calcium channels are found in vascular smooth muscle and ventricular myocytes. They play a critical role in excitation-contraction coupling, helping regulate the contraction of these muscles by allowing calcium ions to enter the cells.
How do calcium channel blockers affect the sinoatrial and atrioventricular nodes?
Calcium channel blockers, particularly non-dihydropyridines, decrease the calcium influx at the sinoatrial (SA) node and the atrioventricular (AV) node, which slows down the electrical conduction and reduces heart rate.
What is the primary action of dihydropyridine calcium channel blockers like amlodipine?
Dihydropyridine calcium channel blockers like amlodipine are primarily used to reduce vascular smooth muscle contraction, thereby reducing arterial resistance and lowering blood pressure, making them effective for treating hypertension.
Why might calcium channel blockers be combined with other drugs in treating hypertension or angina?
Calcium channel blockers may not be sufficient alone for treating hypertension or angina, so they are often combined with ACE inhibitors, angiotensin receptor blockers, or beta blockers to improve treatment efficacy.
How does the action of calcium channel blockers help with conditions like angina and vascular spasms?
Calcium channel blockers reduce heart muscle’s metabolic requirements and can improve blood supply to the heart, helping to reduce chest pain in angina. For vascular spasms, they act as vasodilators, helping to relax constricted blood vessels and improve blood flow.
What is the clinical significance of the selective effects of non-dihydropyridine calcium channel blockers?
Non-dihydropyridine calcium channel blockers (like verapamil and diltiazem) are cardioselective, meaning they specifically affect the heart by slowing conduction in the sinoatrial and atrioventricular nodes. This makes them effective for treating arrhythmias and controlling heart rate.
What are the common clinical uses of calcium channel blockers?
Calcium channel blockers are commonly used to treat:
Hypertension
Angina
Vascular spasm (e.g., Raynaud’s syndrome)
Arrhythmias (especially fast heart rates)
What is the effect of blocking L-type calcium channels on vascular smooth muscle?
Blocking L-type calcium channels reduces the entry of calcium ions into vascular smooth muscle, which causes vasodilation (relaxation of the blood vessels) and leads to a reduction in vascular resistance, helping to lower blood pressure.
