Ontario Paramedic Practice Exam

What effect does adrenaline have on heart function?

1. It decreases heart rate

2. It leads to arrhythmias

3. It increases heart rate and contractility

4. It has no effect on heart function

The correct answer is: It increases heart rate and contractility

Adrenaline, also known as epinephrine, is a powerful hormone and neurotransmitter that significantly impacts heart function. When adrenaline is released, especially in response to stress or danger, it binds to adrenergic receptors in the heart. This interaction leads to an increase in heart rate, known as positive chronotropic effect, and an enhancement of the strength of heart contractions, referred to as positive inotropic effect. These effects are vital during situations requiring a rapid response, such as during a fight-or-flight response, where increased heart rate and contractility help improve blood flow to vital organs and muscles. This physiological response enables the body to react swiftly and effectively to stressors. While moderately increased heart rate and contractility are beneficial in acute situations, excessively high levels of adrenaline can potentially lead to arrhythmias; however, this is more a potential adverse effect when adrenaline levels are uncontrolled rather than a primary effect of its normal physiological action. Additionally, adrenaline is known to have a profound and stimulating effect on heart function, rather than decreasing it or having no effect at all.