What are the effects of epinephrine in emergencies?

Epinephrine, also known as adrenaline, plays a crucial role in emergency situations, particularly in cases of severe allergic reactions (anaphylaxis) and cardiac arrest. The correct response highlights two primary effects: the dilation of airways and the constriction of blood vessels.

When epinephrine is administered, it binds to adrenergic receptors in the respiratory system, leading to bronchodilation, which opens up the airways. This is essential for patients experiencing difficulty breathing due to allergic reactions or asthma attacks, as it facilitates improved airflow and oxygen supply to the lungs.

Additionally, epinephrine causes vasoconstriction, which narrows the blood vessels. This effect increases blood pressure, crucial for maintaining blood flow to vital organs during anaphylaxis or shock. The overall response helps counteract the severe drop in blood pressure that can accompany an allergic reaction.

In contrast, the other choices do not accurately reflect the physiological effects of epinephrine. While increasing heart rate is part of its overall response, the combination of dilating airways and constricting blood vessels directly addresses the critical needs in emergency situations, making it a key reason why option B is the correct answer.