Final answer:
Smoking increases the risk of heart disease due to limited parasympathetic regulation of blood pressure and conflicting signals that affect the heart rhythm.
Step-by-step explanation:
Smoking increases the risk of heart disease due to two reasons related to autonomic function. Firstly, smoking has limited parasympathetic regulation of blood pressure, so nicotine, which is present in cigarettes, causes the vascular tone to become more sympathetic, leading to increased blood pressure. Secondly, the autonomic control of the heart is unique, as cardiac muscle is intrinsically active and generates its own action potentials. The autonomic system does not cause the heart to beat, but it can speed it up (sympathetic) or slow it down (parasympathetic), leading to conflicting signals that can affect the heart rhythm.