Final answer:
Nicotine primarily affects the reward pathways in the brain by increasing dopamine levels and interacting with acetylcholine receptors. It is highly addictive and also impacts the autonomic nervous system, with notable cardiovascular effects such as increased blood pressure.
Step-by-step explanation:
Nicotine affects brain pathways by interacting with acetylcholine receptors, which are part of the cholinergic system, and by increasing dopamine levels in the brain. Dopamine is a neurotransmitter that plays a key role in the reward and pleasure centers of the brain. When nicotine binds to nicotinic acetylcholine receptors, it increases the firing rate of neurons that release dopamine, hence enhancing the rewarding effects of nicotine. This mechanism contributes to nicotine's highly addictive nature.
Beyond its effects on dopamine release, nicotine also stimulates both the sympathetic and parasympathetic fibers of the autonomic nervous system. Notably, its cardiovascular effects can lead to an increase in blood pressure and potential arrhythmia due to its action on the heart. Nicotine's wide-ranging impact on the autonomic system is one of the reasons for its potential to contribute to cardiovascular disease.