1. A heart attack occurs when there is a blockage in the coronary arteries that
ID: 211759 • Letter: 1
Question
1. A heart attack occurs when there is a blockage in the coronary arteries that bring blood to the muscle cells in the heart. If the blockage is bad enough, the heart muscle cells will begin to die of hypoxia (lack of oxygen). Paramedics will often administer nitroglycerin to patients who appear to be suffering from a heart attack. In addition, patients who have previously suffered a heart attack often carry nitroglycerin pills they can take if they feel the signs of another heart attack. Based on what you now know, explain why the nitroglycerin pills would be used when a heart attack is suspected.
a. An erection also relies on nitric oxide (NO). Sexual stimulation of the male organ causes a local release of NO which dilates the blood vessels in the corpus cavernosum tissues of the male organ allowing an erection to occur. The common erectile dysfunction drug, Viagra, works by inhibiting the enzyme phosphodiesterase type 5 (PDE5). Look up this enzyme and explain how this drug works to overcome erectile dysfunction.
Explanation / Answer
1. When coronary artery gets blocked sufficient blood does not get supplied to the heart muscle cells and in turn they suffer condition called hypoxia (low oxygen due to lack of blood supply) which leads to necrotic death of cells. To overcome blockage of artery, a common medication is to dilate the vessel wall. Nitric oxide is the signalling molecule involved in dilating the vessel wall by acting on smooth muscle cells. Nitroglycerin is an organic precursor of nitric oxide which which when supplied artificially vessel walls get dilated and recovered from blockage.
a. Viagra (Sildenafil) inhibits the enzyme phosphodiesterase. As explained earlier, nitric oxide (NO) acts as an signaling molecule. Initially, NO synthesized by endothelial cells acts in paracrine mode and binds to the NO receptor (Guanylyl cyclase) on smooth muscle cells. Binding of NO on receptor causes synthesis of cGMP (cyclic guanine monophosphate) which in turn activates PKG (phosphokinase-G). PKG mediates the relaxation of smooth muscle cell and hence vasodilation.
Phosphodiesterase present in smooth muscle cell converts cGMP into GMP and hence shuts down the signalling cascade. Viagra blocks the activity of phosphodiesterase and hence continuously activates the vasodilation process mediated by NO.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.