Activation of which adrenergic receptor subtype on cardiac muscle cells leads to an increase in heart rate and contractility?

✓ Correct Answer: Option B

Beta-1 adrenergic receptors are predominantly found in the heart. Their activation by norepinephrine or epinephrine increases heart rate (chronotropy), contractility (inotropy), and conduction velocity (dromotropy), mediating the sympathetic 'fight or flight' response.