Final answer:
Blocking β-adrenergic receptor sites reduces heart rate, blood pressure, and cardiac output, which aids in treating cardiovascular diseases such as hypertension and prevents further heart complications.
Step-by-step explanation:
Blocking β-adrenergic receptor sites leads to a decrease in heart rate, blood pressure, and the force of heart contractions by preventing adrenaline (epinephrine and norepinephrine) from binding to these receptors. This action dilates blood vessels and reduces cardiac output, which is particularly useful in treating conditions such as high blood pressure (hypertension), congestive heart failure, and can prevent future heart attacks. Common medications in this class include metoprolol, which specifically blocks the β1-receptors, and propranolol, which non-specifically blocks β-receptors. These β-blockers are essential in managing cardiovascular diseases, and their use should be balanced to avoid side effects such as bradycardia or heart stoppage.