The Endocrine System
What Is the Endocrine System?
The endocrine system is a communication system that uses hormones to control and coordinate body processes.
💡 Key Concept: Hormones are chemical messengers carried in the blood to target organs.
Hormones vs Nerves
Feature | Nervous System | Endocrine System |
Signal Type | Electrical impulses | Hormones (chemicals) |
Speed | Very fast | Slower |
Effect Duration | Short-term | Long-lasting |
Target | Specific muscles or glands | Many cells/organs |
Main Endocrine Glands & Their Functions
Gland | Hormone Produced | Function |
Pituitary gland | Multiple (e.g. FSH, LH, ADH) | “Master gland” – controls other glands and body growth. |
Thyroid | Thyroxine | Regulates metabolism, heart rate, and temperature. |
Pancreas | Insulin & Glucagon | Controls blood glucose levels. |
Adrenal glands | Adrenaline | Prepares body for ‘fight or flight’. |
Ovaries (females) | Oestrogen, Progesterone | Controls menstrual cycle and development of female secondary sex characteristics. |
Testes (males) | Testosterone | Controls sperm production and male characteristics. |
How Hormones Travel
- Hormones are released from a gland into the bloodstream.
- They travel in the blood to a target organ.
- The organ responds to the hormone signal (e.g. increases metabolism, stores glucose, starts puberty).
💡 Key Fact: Hormones can affect many organs, unlike nerves which are very specific.
Questions
- What is the endocrine system made of?
- How do hormones travel around the body?
- Name the gland that controls other glands.
- What hormone controls blood glucose levels?
- What does the adrenal gland release?
Summary
- The endocrine system controls body functions using hormones.
- Hormones are slower but longer-lasting than nerve impulses.
- Key glands include the pituitary, thyroid, pancreas, adrenal glands, ovaries and testes.
- Hormones affect growth, metabolism, glucose levels, reproduction, and response to danger.