How doe nicotine affect the brain?

Nicotine primarily affects the brain by "hijacking" its reward system. The core mechanism of its action is to quickly mimic key neurotransmitters and trigger a series of complex chain reactions. The following diagram clearly illustrates this process:

?? Special harm to the adolescent brain
The adolescent brain, which is in the developmental stage (typically up to around 25 years old), is particularly sensitive to nicotine. Exposure to nicotine can lead to:
Damage to the prefrontal cortex: Impacts the development of judgment, impulse control and decision-making abilities.
Long-term cognitive effects: May lead to persistent decline in attention, impairment of learning ability, and increase the risk of future addiction to other substances.
?? Key Points Summary
Fast Addiction: Nicotine establishes an addictive cycle extremely quickly through the dopamine mechanism.
Dual effects: It can temporarily boost mood and concentration, but it leads to long-term dependence.
Brain remodeling: Long-term use can alter the number and sensitivity of receptors, leading to increased tolerance and withdrawal pain.
Developmental risk: It has a definite negative impact on the development of a teenager's brain.
This is related to your previous inquiries: Considering your previous questions about e-cigarettes, hookahs, and detoxification, nicotine is the fundamental cause of addiction and withdrawal symptoms in these products (even if they do not contain tobacco, they may still contain nicotine). Those feelings of wanting to quickly eliminate nicotine or relieve throat discomfort are directly related to the effects of nicotine on the nervous and cardiovascular systems.