Caffeine lowers the heart rate by increasing rates of depolarization at the SA node True False
Caffeine lowers the heart rate by increasing rates of depolarization at the SA node
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Nicotine raises the heart rate because it stimulates the activity of the sympathetic neurons in medulla oblongata
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The Frank-Starling Law of the Heart states that the force of heart contraction is directly proportional to the initial length of the muscle fiber, within optimal limits of length
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If the sarcomeres stretched beyond the optimal length, the force of contraction would go down, but that can potentially happen only during open heart surgery when the heart is not constrained by the pericardium, lungs, ribs and diaphragm.
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It is the Na+ channel-driven spontaneous depolarization that is affected by sympathetic and parasympathetic inputs to speed up or slow down the firing rate of the SA node and other conductive cells.
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