Endocrine System

The endocrine system is made up of glands that release hormones directly into the bloodstream (no ducts). The major endocrine glands you’re usually expected to know are:

  • Hypothalamus – links the nervous system to the endocrine system

  • Pituitary gland – often called the “master gland”

  • Pineal gland

  • Thyroid gland

  • Parathyroid glands

  • Adrenal glands

  • Pancreas

  • Ovaries (females) / Testes (males)

Each gland releases specific hormones that target certain organs or tissues.

What purpose the endocrine system serves

The endocrine system’s main job is to regulate and coordinate body functions using hormones. It works more slowly than the nervous system, but its effects last much longer.

It helps control things like:

  • Growth and development

  • Metabolism (how your body uses energy)

  • Blood sugar levels

  • Stress responses

  • Mood and emotions

  • Puberty and reproduction

  • Sleep–wake cycles

  • Homeostasis (keeping internal conditions stable)

Basically, if something in your body needs long-term regulation, hormones are usually involved.

Key details to know (the “exam-friendly” stuff)

1. Hormones

  • Hormones are chemical messengers

  • They travel through the bloodstream

  • Only target cells with the correct receptors respond to a hormone

2. Pituitary gland (the “master gland”)

  • Controls other endocrine glands

  • Releases hormones that affect growth, reproduction, and water balance

  • Controlled by the hypothalamus

3. Thyroid gland

  • Produces hormones that control metabolic rate

  • Affects energy levels, body temperature, and growth

4. Pancreas (endocrine role)

  • Regulates blood glucose levels

  • Releases:

    • Insulin → lowers blood sugar

    • Glucagon → raises blood sugar

5. Adrenal glands

  • Produce adrenaline and cortisol

  • Involved in the stress response (“fight or flight”)

6. Feedback mechanisms

  • Hormone levels are controlled by negative feedback

  • If there’s too much of a hormone, production is reduced

  • If there’s too little, production increases
    This keeps the body in balance.

Endocrine vs nervous system (quick comparison)

  • Endocrine: slow, long-lasting, hormones, bloodstream

  • Nervous: fast, short-lived, electrical signals, nerves