After injection of epinephrine from an EpiPen, which physiological response would you expect in a patient experiencing an allergic reaction?

• A. Constriction of the bronchioles and decreased heart rate
• B. Increased digestive activity and pupil constriction
• C. Dilation of the bronchioles and increased heart rate
• D. Decreased blood pressure and increased salivation

Answer: (C)

Verified step by step guidance

1. Understand the role of epinephrine: Epinephrine is a hormone and neurotransmitter that activates the sympathetic nervous system, also known as the 'fight or flight' response. It is commonly used in emergencies to counteract severe allergic reactions (anaphylaxis).
2. Analyze the physiological effects of epinephrine: Epinephrine binds to adrenergic receptors (alpha and beta receptors) in various tissues. Beta-2 adrenergic receptors in the lungs cause bronchodilation, which helps open airways. Beta-1 adrenergic receptors in the heart increase heart rate and contractility, improving blood circulation.
3. Eliminate incorrect options: Constriction of the bronchioles and decreased heart rate are opposite to the effects of epinephrine. Increased digestive activity and pupil constriction are associated with parasympathetic activation, not sympathetic activation. Decreased blood pressure and increased salivation are also inconsistent with epinephrine's effects.
4. Focus on the correct physiological response: Epinephrine causes dilation of the bronchioles (to improve breathing) and increased heart rate (to enhance blood flow), which are critical during an allergic reaction to counteract symptoms like airway constriction and low blood pressure.
5. Relate the response to the clinical use of an EpiPen: The EpiPen delivers epinephrine to rapidly reverse life-threatening symptoms of anaphylaxis, such as difficulty breathing and circulatory collapse, by promoting bronchodilation and increasing heart rate and blood pressure.