Sympathetic activation produces positive chronotropy. What does this mean for heart rate?

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Multiple Choice

Sympathetic activation produces positive chronotropy. What does this mean for heart rate?

Explanation:
Positive chronotropy means the heart rate increases. When the sympathetic system is activated, norepinephrine stimulates beta-1 receptors in the sinoatrial (SA) node, boosting the automaticity of pacemaker cells. This speeds up the rate of spontaneous depolarization (a steeper phase 4), so the SA node fires more often and the heart beats faster. This concept is about rate; separate terms describe how hard the heart contracts (inotropy) or how quickly impulses pass through the conduction pathways (dromotropy). Parasympathetic activity, by contrast, slows the rate (negative chronotropy).

Positive chronotropy means the heart rate increases. When the sympathetic system is activated, norepinephrine stimulates beta-1 receptors in the sinoatrial (SA) node, boosting the automaticity of pacemaker cells. This speeds up the rate of spontaneous depolarization (a steeper phase 4), so the SA node fires more often and the heart beats faster. This concept is about rate; separate terms describe how hard the heart contracts (inotropy) or how quickly impulses pass through the conduction pathways (dromotropy). Parasympathetic activity, by contrast, slows the rate (negative chronotropy).

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