Physiology In the presence of a drug that blocks all effects of norepinephrine and epinephrine on the heart, the autonomic nervous system can: A Raise the heart rate above its intrinsic rate B Lower the heart rate below its intrinsic rate C Raise and lower the heart rate above and below its intrinsic rate D Neither raise nor lower the heart rate from its intrinsic rate 💡 Explanation In the presence of a drug that blocks all effects of norepinephrine and epinephrine on the heart, the autonomic nervous system can: ✓ Correct Answer: B. Lower the heart rate below its intrinsic rate