Multiple choice

The heart rate is increased by

  1. an increase in the activity of the sympathetic nerves that supply the heart

  2. a decrease in the activity of the parasympathetic system

  3. an increase in the level of adrenalin in the circulation

  4. all of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Heart rate increases through multiple mechanisms: increased sympathetic nervous activity (A), decreased parasympathetic activity (B), and elevated circulating adrenaline (C). Since all three mechanisms increase heart rate, option D is correct.

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