THE CELL
CELL COMMUNICATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Cardiac cells have more receptors for epinephrine than do intestinal cells
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Epinephrine circulates to the heart first and thus is in higher concentration around cardiac cells
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The two types of muscle cells have different signal transduction pathways for epinephrine and thus have different cellular responses
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Cardiac muscle is stronger than intestinal muscle and thus has a stronger response to epinephrine
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Detailed explanation-1: -protein phosphatase-enzyme that transfers a phosphate group from ATP to a protein, causing a shape change that usually activates that protein. When epinephrine binds to cardiac (heart) muscle cells, it speeds their contraction. When it binds to muscle cells of the small intestine, it inhibits their contraction.
Detailed explanation-2: -Epinephrine potentiates muscle twitches via the second messenger, cAMP, secondary to hormone binding to membrane-bound beta-receptors. Cyclic AMP then acts to increase carbohydrate metabolism, alter sodium/potassium exchange, phosphorylate myosin isozymes, and/or alter intracellular calcium exchange.
Detailed explanation-3: -Systole occurs when the heart contracts to pump blood out, and diastole occurs when the heart relaxes after contraction. The SA node generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood. So, the correct answer is ‘Systole’.
Detailed explanation-4: -Cardiac muscle contraction occurs via the sliding filament model of contraction, much like skeletal muscle. Once calcium is bound to troponin-C and the conformational change of tropomyosin has occurred, myosin heads can bind to actin.