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| Chapter 19: Chemical Coordination and Integration — Introduction to Endocrine Glands and Hormones for Class 11 Biology NEET Preparation |
Chapter 19: Chemical Coordination and Integration
Easy NEET Biology Notes (Line-by-Line Explanation)
Introduction
Original Idea:
The nervous system provides rapid coordination among organs.
Easy Explanation:
- Our body organs must work together properly.
- The nervous system controls body activities quickly using nerve impulses.
- Example:
- Touching a hot object → hand withdraws immediately.
Original Idea:
Neural coordination is fast but short-lived.
Easy Explanation:
- Nervous signals act very fast.
- But their effect lasts for a short time only.
- Example:
- Muscle contraction after a nerve impulse stops quickly.
Original Idea:
Nerve fibres do not innervate all cells.
Easy Explanation:
- Nerves cannot reach every cell of the body directly.
- Some body functions need continuous regulation.
Original Idea:
A special kind of coordination is needed.
Easy Explanation:
- Therefore, the body also uses chemical coordination.
- This coordination is slower but long-lasting.
Original Idea:
This function is carried out by hormones.
Easy Explanation:
- Chemical coordination is controlled by hormones.
- Hormones are chemical messengers.
Original Idea:
Neural and endocrine systems work together.
Easy Explanation:
- Nervous system + endocrine system together maintain body balance.
- They regulate:
- Growth
- Metabolism
- Reproduction
- Water balance
- Stress response
19.1 Endocrine Glands and Hormones
Endocrine Glands
Original Idea:
Endocrine glands lack ducts.
Easy Explanation:
- Endocrine glands are called ductless glands.
- They do not have tubes (ducts) to carry secretions.
Original Idea:
Their secretions are called hormones.
Easy Explanation:
- Endocrine glands release chemicals called hormones directly into blood.
Definition of Hormone
Classical Definition
Original Idea:
Hormones are chemicals produced by endocrine glands and transported by blood to target organs.
Easy Explanation:
- Hormones are made in endocrine glands.
- Blood carries them to specific organs called target organs.
- Example:
- Insulin acts on liver and muscles.
Modern Definition of Hormones
Original Idea:
Hormones are non-nutrient chemicals acting as intercellular messengers.
Easy Explanation:
- Hormones are:
- Not food substances
- Chemical messengers
- Carry signals from one cell to another
Original Idea:
Produced in trace amounts.
Easy Explanation:
- Very tiny amounts of hormones are enough to produce major effects.
- Even microgram quantities can regulate body functions.
Additional Information
Original Idea:
The new definition includes many molecules.
Easy Explanation:
- Scientists now include many signaling chemicals under hormones.
- Some organs other than endocrine glands also produce hormones.
Original Idea:
Invertebrates possess simple endocrine systems.
Easy Explanation:
- Animals without backbone (invertebrates) have simple hormone systems.
- Vertebrates (including humans) have highly developed endocrine systems.
Important NEET Points
Key Features of Hormones
| Feature | Description |
|---|---|
| Nature | Non-nutrient chemicals |
| Quantity | Produced in trace amounts |
| Transport | Through blood |
| Action | On target cells/organs |
| Function | Chemical coordination |
Difference Between Nervous and Endocrine System
| Nervous System | Endocrine System |
|---|---|
| Fast action | Slow action |
| Short duration | Long duration |
| Uses nerve impulses | Uses hormones |
| Point-to-point action | Widespread action |
Important Terms
Hormone
Chemical messenger produced in small quantity.
Endocrine Gland
Ductless gland releasing hormones into blood.
Target Organ
Organ affected by a hormone.
Chemical Coordination
Regulation of body activities using hormones.
NEET NCERT Highlight Line
⭐ “Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts.”
This line is extremely important for NEET direct questions.
Quick Revision
- Endocrine glands = ductless glands
- Hormones travel through blood
- Hormones act as chemical messengers
- Produced in very small amounts
- Nervous system → fast and short-lived
- Endocrine system → slow and long-lasting
Memory Trick
“ENDO”
- E → Enter blood directly
- N → Non-nutrient chemicals
- D → Ductless glands
- O → Organ coordination
NEET-Level MCQs
Q1. Endocrine glands are called ductless glands because:
A. They lack hormones
B. They lack blood supply
C. They lack ducts
D. They lack target organs
✅ Answer: C
Q2. Hormones are:
A. Nutrient chemicals
B. Intercellular messengers
C. Digestive enzymes
D. Antibodies
✅ Answer: B
Q3. Hormones are produced in:
A. Large amounts
B. Moderate amounts
C. Trace amounts
D. No fixed amount
✅ Answer: C
Q4. Neural coordination is:
A. Slow and long-lasting
B. Fast and short-lived
C. Slow and permanent
D. Fast and permanent
✅ Answer: B
PYQ-Type Question
Assertion:
Hormones act as chemical messengers.
Reason:
Hormones are transported through blood to target organs.
✅ Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion.
CHEMICAL COORDINATION AND INTEGRATION
│
├── BODY COORDINATION SYSTEMS
│ │
│ ├── Nervous System
│ │ ├── Fast action
│ │ ├── Short-lived effect
│ │ ├── Uses nerve impulses
│ │ └── Point-to-point coordination
│ │
│ └── Endocrine System
│ ├── Slow action
│ ├── Long-lasting effect
│ ├── Uses hormones
│ └── Chemical coordination
│
├── ENDOCRINE GLANDS
│ │
│ ├── Ductless glands
│ ├── Release hormones directly into blood
│ ├── Rich blood supply
│ └── Maintain body regulation
│
├── HORMONES
│ │
│ ├── Non-nutrient chemicals
│ ├── Intercellular messengers
│ ├── Produced in trace amounts
│ ├── Transported through blood
│ └── Act on target organs
│
├── FUNCTIONS OF HORMONES
│ │
│ ├── Growth regulation
│ ├── Metabolism control
│ ├── Reproduction
│ ├── Water balance
│ ├── Stress response
│ └── Homeostasis maintenance
│
├── TARGET ORGAN
│ │
│ ├── Specific organ/tissue
│ ├── Contains hormone receptors
│ └── Responds to hormone action
│
├── IMPORTANT FEATURES
│ │
│ ├── Effective in very small quantity
│ ├── Specific action
│ ├── Chemical messenger role
│ └── Coordination between organs
│
├── NERVOUS vs ENDOCRINE SYSTEM
│ │
│ ├── Nervous → Fast, short duration
│ ├── Endocrine → Slow, long duration
│ ├── Nervous → Electrical impulses
│ └── Endocrine → Hormonal signals
│
└── NEET IMPORTANT LINE
│
└── “Hormones are non-nutrient chemicals
acting as intercellular messengers
and produced in trace amounts.”
 |
| Human endocrine system showing major endocrine glands and hormonal coordination in the body. |
Class 11 Biology
Chapter: Chemical Coordination and Integration
CBSE + NEET Exam Practice Questions with Answers
1. MCQs (Multiple Choice Questions)
Q1. Endocrine glands are called ductless glands because they:
A. Lack blood supply
B. Lack hormones
C. Lack ducts
D. Lack enzymes
✅ Answer: C. Lack ducts
Q2. Hormones are:
A. Nutrient chemicals
B. Digestive juices
C. Intercellular messengers
D. Antibodies
✅ Answer: C. Intercellular messengers
Q3. Hormones are produced in:
A. Large amounts
B. Moderate amounts
C. Trace amounts
D. Unlimited amounts
✅ Answer: C. Trace amounts
Q4. Neural coordination is:
A. Slow and long-lasting
B. Fast and short-lived
C. Permanent
D. Hormonal
✅ Answer: B. Fast and short-lived
Q5. Which system mainly controls chemical coordination?
A. Respiratory system
B. Digestive system
C. Endocrine system
D. Skeletal system
✅ Answer: C. Endocrine system
Q6. Hormones travel through:
A. Nerves
B. Muscles
C. Blood
D. Bones
✅ Answer: C. Blood
Q7. The target organ contains:
A. Hormones
B. Receptors
C. Enzymes
D. Pigments
✅ Answer: B. Receptors
Q8. Which one is NOT a feature of hormones?
A. Non-nutrient chemical
B. Produced in trace amount
C. Stored in bones
D. Chemical messenger
✅ Answer: C. Stored in bones
2. Very Short Answer Questions (1 Mark)
Q1. What are hormones?
✅ Hormones are non-nutrient chemical messengers produced in trace amounts.
Q2. Why are endocrine glands called ductless glands?
✅ Because they do not possess ducts.
Q3. Name the medium through which hormones are transported.
✅ Blood.
Q4. What is a target organ?
✅ An organ on which a hormone acts is called a target organ.
Q5. Define chemical coordination.
✅ Regulation of body functions through hormones is called chemical coordination.
3. Short Answer Questions (2–3 Marks)
Q1. Differentiate between nervous and endocrine system.
| Nervous System | Endocrine System |
|---|---|
| Fast action | Slow action |
| Short duration | Long duration |
| Uses nerve impulses | Uses hormones |
Q2. Write any three characteristics of hormones.
✅
- Non-nutrient chemicals
- Produced in trace amounts
- Act as intercellular messengers
Q3. Explain why hormones are effective even in small quantities.
✅ Hormones are highly active chemical messengers. Even tiny amounts can produce major physiological changes in target organs.
Q4. What are endocrine glands? Give one example.
✅ Endocrine glands are ductless glands that release hormones directly into blood.
Example: Pituitary gland.
4. Long Answer Questions (5 Marks)
Q1. Explain the importance of endocrine glands and hormones in the human body.
✅ Answer:
- Endocrine glands are ductless glands.
- They secrete hormones directly into blood.
- Hormones regulate body activities.
- They help in:
- Growth
- Metabolism
- Reproduction
- Water balance
- Stress management
- Hormones act on target organs containing receptors.
- The endocrine system works together with the nervous system to maintain coordination and homeostasis.
Q2. Describe the major differences between neural coordination and hormonal coordination.
| Neural Coordination | Hormonal Coordination |
|---|---|
| Controlled by nervous system | Controlled by endocrine system |
| Uses electrical impulses | Uses hormones |
| Fast response | Slow response |
| Short-lived effect | Long-lasting effect |
| Specific action | Widespread action |
5. Assertion and Reason Questions
Q1.
Assertion:
Hormones are called chemical messengers.
Reason:
They carry signals from one organ to another through blood.
✅ Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion.
Q2.
Assertion:
Endocrine glands are called ductless glands.
Reason:
Their secretions are released directly into blood.
✅ Answer: Both Assertion and Reason are true, and Reason correctly explains Assertion.
Q3.
Assertion:
Neural coordination is long-lasting.
Reason:
Nerve impulses act rapidly.
✅ Answer: Assertion is false but Reason is true.
6. Fill in the Blanks
-
Hormones are produced in ______ amounts.
✅ trace -
Endocrine glands are also called ______ glands.
✅ ductless -
Hormones travel through ______.
✅ blood -
Hormones act on specific ______ organs.
✅ target -
The nervous system provides ______ coordination.
✅ rapid
7. Match the Following
| Column A | Column B |
|---|---|
| 1. Hormones | a. Chemical messengers |
| 2. Endocrine glands | b. Ductless glands |
| 3. Blood | c. Transport medium |
| 4. Target organ | d. Site of hormone action |
✅ Answers:
1 → a
2 → b
3 → c
4 → d
8. Statement-Based Questions
Q1. Identify True or False:
-
Hormones are nutrient chemicals.
✅ False -
Endocrine glands possess ducts.
✅ False -
Hormones act as intercellular messengers.
✅ True -
Neural coordination is very slow.
✅ False -
Hormones are transported through blood.
✅ True
9. Case Study Questions
Case Study 1
Ravi touched a hot object and immediately removed his hand. Later, his heartbeat remained high for several minutes due to stress hormone release.
Questions:
Q1. Which system helped Ravi remove his hand quickly?
✅ Nervous system
Q2. Which system caused long-lasting effects on heartbeat?
✅ Endocrine system
Q3. Why is hormonal action long-lasting?
✅ Hormones remain in blood for a longer time and act slowly.
Q4. Name the chemical messengers involved in endocrine coordination.
✅ Hormones
Case Study 2
A doctor explained that hormones are released directly into blood and act on target organs even in very small amounts.
Questions:
Q1. Which glands release hormones?
✅ Endocrine glands
Q2. Why are these glands called ductless glands?
✅ Because they lack ducts.
Q3. What are target organs?
✅ Organs affected by hormones.
Q4. In what quantity are hormones produced?
✅ Trace amounts.
10. Important NCERT Line for Exams
⭐ “Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts.”
11. HOTS Questions
Q1. Why can hormones regulate distant organs whereas nerves cannot?
✅ Hormones travel through blood and can reach distant target organs, while nerves connect only specific body parts.
Q2. Why is endocrine coordination necessary even though the nervous system exists?
✅ Because nervous control is short-lived and nerves cannot reach all body cells. Hormones provide long-term regulation.
Internal Links
Neural Control and Coordination Notes
Human Physiology NEET Notes
Nervous System MCQs for NEET
Endocrine Glands Detailed Diagram
Homeostasis in Human Body
Class 11 Biology Chapter Wise Notes
NEET Biology Mock Tests
Cell Signalling and Hormonal Regulation
Synapse and Reflex Action Notes
Human Reproduction Notes
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