Caffeine is a mind-altering drug, possibly the most popular drug there is, as we

Question

Caffeine is a mind-altering drug, possibly the most popular drug there is, as well as one of the most ancient. It occurs naturally in more than sixty plants that have been cultivated by humans since the beginning of recorded history. Whether they get their caffeine in coffee, tea, cocoa, headache remedies, energy drinks, or soft drinks, nearly everyone ingests at least some caffeine daily. Caffeine acts in a variety of ways in the body. One important effect of caffeine is to inhibit _______ enzymes that normally break down a substance called cyclic adenosine monophosphate (cAMP), cAMP is product in a cell's cytoplasm when certain hormones or neurotransmitters bind to their ligand-gated receptors on the cell membrane. Thus, if we think of the hormone or neurotransmitter as the "first messenger" in a signaling pathway, cAMP is the second messenger (1ike the second runner in a relay race). The second messenger takes the signal to its final destination by having an effect on the cell's function (e.g., by opening a type of ion channel). When epinephrine or norepinephrine binds to the beta-adrenergic receptors on heart cells, cAMP is produced in these cells and leads to the effects on heart rate and force of contraction. These effects are normally stopped by the breakdown of the cAMP. In the presence of caffeine, the breakdown of cAMP is ___. What do you predict will happen to heart rate and contractility with the addition of caffeine?

Explanation / Answer

Inhibition of breakdown of cAMP by caffeine is done by blocking the action of phosphodiesterase (PDE).

Thus in the presence of caffeine the breakdown of cAMP is inhibited. High levels of Caffeine will lead to increased levels of cAMP leading to high blood level of epinephrine which leads to:

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