What is the source of tobacco.

Explanation

**Step-by-Step Solution:**

1. **Understanding Tobacco**: Tobacco is a plant that has been used by humans for over 400 years. It is primarily known for its use in various forms such as smoking, chewing, or as snuff.

2. **Chemical Composition**: Tobacco contains a variety of chemical substances, with nicotine being one of the most notable. Nicotine is classified as an alkaloid, which is a type of naturally occurring organic compound that has significant pharmacological effects.

3. **Effects of Nicotine**: Nicotine stimulates the adrenal glands, which are endocrine glands responsible for producing hormones. The stimulation leads to the release of adrenaline and noradrenaline, hormones that are often referred to as emergency hormones due to their role in the body's fight-or-flight response.

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