Final answer:
Smoking leads to increased sympathetic vascular tone and raised blood pressure, as well as potential arrhythmias due to conflicting autonomic signals to the heart, both of which are risk factors for heart disease.
Step-by-step explanation:
Why Smoking Increases the Risk of Heart Disease
Smoking increases the risk of heart disease for several reasons related to autonomic function. First, nicotine from cigarette smoke preferentially causes vascular tone to become more sympathetic, leading to an increase in blood pressure. This is because there is no significant parasympathetic regulation of blood pressure, and nicotine stimulates the sympathetic ganglia, which increases blood pressure. Second, nicotine affects the autonomic control of the heart. The heart generates its own action potentials and is intrinsically active. The autonomic system influences the heart rate by speeding it up (sympathetic) or slowing it down (parasympathetic). However, these mechanisms are not mutually exclusive and can send conflicting signals to the heart, potentially causing arrhythmias. Both high blood pressure and arrhythmias are major risk factors for heart disease.