Introduction
Hormones are chemical messengers produced by special glands in the body called endocrine glands. These hormones travel through the bloodstream and control different body activities such as:
- Growth and development
- Metabolism (energy production and use)
- Reproduction
- Mood and emotions
- Water balance
- Blood sugar regulation
- Response to stress
Hormones work slowly compared to nerve impulses but their effects usually last longer.
Definition of Hormones
Hormones are chemical substances secreted by endocrine glands directly into the blood to regulate and coordinate body functions.
Key Features of Hormones
| Feature | Description |
|---|---|
| Nature | Chemical messenger |
| Produced by | Endocrine glands |
| Transport | Through blood |
| Target | Specific organs/cells |
| Function | Regulation and coordination |
| Effect | Usually slower but long-lasting |
What Is the Endocrine System?
The endocrine system is a collection of glands that release hormones directly into the bloodstream.
Characteristics of Endocrine Glands
- Ductless glands
- Produce hormones
- Hormones enter blood directly
- Control body coordination and regulation
Major Endocrine Glands and Their Hormones
| Gland | Hormone | Main Function |
|---|---|---|
| Pituitary gland | Growth Hormone (GH) | Controls body growth |
| Thyroid gland | Thyroxine | Controls metabolism |
| Pancreas | Insulin | Controls blood sugar |
| Adrenal gland | Adrenaline | Stress response |
| Testes | Testosterone | Male characteristics |
| Ovaries | Estrogen, Progesterone | Female characteristics |
1. Pituitary Gland – Master Gland
The pituitary gland controls many other endocrine glands.
Hormones Produced
- Growth Hormone (GH)
- Thyroid Stimulating Hormone (TSH)
- Reproductive hormones
Functions
- Body growth
- Development
- Control of other glands
2. Thyroid Gland
Located in the neck.
Hormone
Thyroxine
Functions
- Regulates metabolism
- Supports growth
- Helps maintain body energy
Important Note
Iodine is necessary for thyroxine production.
3. Pancreas
Acts as both:
- Endocrine gland
- Digestive gland
Hormone
Insulin
Function
- Maintains blood glucose level
4. Adrenal Glands
Located above kidneys.
Hormone
Adrenaline
Functions
- Increases heartbeat
- Prepares body during emergency
- Called fight or flight hormone
Effects:
- Faster breathing
- Increased blood circulation
- More energy release
5. Reproductive Glands
In Males – Testes
Hormone:
- Testosterone
Functions:
- Development of male characteristics
- Supports reproduction
In Females – Ovaries
Hormones:
- Estrogen
- Progesterone
Functions:
- Development of female characteristics
- Control reproductive cycle
How Do Hormones Work?
Step-by-Step Process
- Endocrine gland produces hormone
- Hormone enters bloodstream
- Blood carries hormone to target organ
- Target organ responds
Example:
- Pancreas releases insulin
- Insulin reaches cells
- Blood sugar decreases
Hormones vs Nervous System
| Basis | Hormones | Nervous System |
|---|---|---|
| Signal Type | Chemical | Electrical |
| Speed | Slow | Fast |
| Duration | Long-lasting | Short |
| Transport | Blood | Nerves |
Importance of Hormones
Hormones help in:
- Growth and body development
- Maintaining internal balance
- Reproduction
- Energy regulation
- Stress management
- Emotional response
Hormonal Disorders (Basic NCERT Understanding)
| Hormone | Disorder |
|---|---|
| Insulin | Diabetes |
| Growth Hormone | Dwarfism / Gigantism |
| Thyroxine | Goitre |
Interesting Facts About Hormones
- The pituitary gland is called the master gland.
- Hormones act only on target cells.
- Some hormones work within seconds.
- Tiny amounts of hormones can create major body changes.
Quick Revision
- Hormones = Chemical messengers
- Produced by endocrine glands
- Travel through blood
- Control body functions
- Examples: Insulin, Thyroxine, Adrenaline
Practice Questions with Answers
1. What are hormones?
Hormones are chemical messengers secreted by endocrine glands into blood.
2. Why are hormones important?
They regulate growth, metabolism, reproduction, and body balance.
3. Which gland is called the master gland?
Pituitary gland.
4. Which hormone controls blood sugar?
Insulin.
5. Which gland produces adrenaline?
Adrenal gland.
Fill in the Blanks
- Hormones are ______ messengers.
Answer: chemical - Hormones travel through ______.
Answer: blood - Thyroid gland produces ______.
Answer: thyroxine - Insulin is produced by ______.
Answer: pancreas - The pituitary gland is called the ______ gland.
Answer: master
10 MCQs with Answers
1. Hormones are:
A. Nutrients
B. Chemical messengers
C. Vitamins
D. Enzymes
Answer: B
2. Hormones travel through:
A. Air
B. Blood
C. Bones
D. Skin
Answer: B
3. Which gland controls growth?
A. Pancreas
B. Pituitary
C. Thyroid
D. Kidney
Answer: B
4. Thyroxine is produced by:
A. Thyroid
B. Liver
C. Skin
D. Heart
Answer: A
5. Insulin controls:
A. Temperature
B. Blood sugar
C. Hearing
D. Vision
Answer: B
6. Adrenaline is known as:
A. Sleep hormone
B. Emergency hormone
C. Digestive hormone
D. Growth hormone
Answer: B
7. Endocrine glands are:
A. Duct glands
B. Ductless glands
C. Bone glands
D. Muscle glands
Answer: B
8. Testosterone is produced by:
A. Ovaries
B. Testes
C. Pancreas
D. Thyroid
Answer: B
9. Hormones help in:
A. Growth
B. Reproduction
C. Metabolism
D. All of these
Answer: D
10. Which system controls hormones?
A. Digestive system
B. Endocrine system
C. Respiratory system
D. Excretory system
Answer: B
