Class 11 Biology Endocrine System Notes for NEET & CBSE

 

Endocrine System Summary Notes (NEET Biology – Easy Line by Line Explanation) 

- Dr.Sanjaykumar pawar

1. Hormones and Their Functions

• Hormones are special chemical messengers produced by endocrine glands.
• They help in:
  • Coordination of body activities
  • Regulation of body functions
  • Integration between organs
• Hormones control:
  • Metabolism
  • Growth
  • Development
  • Reproduction
  • Homeostasis

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2. Endocrine System Organs

The human endocrine system includes:

1. Hypothalamus
2. Pituitary gland
3. Pineal gland
4. Thyroid gland
5. Adrenal gland
6. Pancreas
7. Parathyroid gland
8. Thymus
9. Gonads:
   • Testis (male)
   • Ovary (female)

Other organs also producing hormones:

• Gastrointestinal tract
• Kidney
• Heart

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3. Pituitary Gland (Master Gland)

Divisions of Pituitary

The pituitary gland has 3 parts:

(i) Pars distalis (Anterior pituitary)

• Produces 6 trophic hormones.
• Trophic hormones regulate other endocrine glands.

(ii) Pars intermedia

• Secretes only one hormone:
  • MSH (Melanocyte Stimulating Hormone)

(iii) Pars nervosa (Posterior pituitary / Neurohypophysis)

• Secretes:
  • Oxytocin
  • Vasopressin (ADH)

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Functions of Pituitary Hormones

Pituitary hormones regulate:

• Growth of body tissues
• Development of organs
• Activities of endocrine glands

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4. Pineal Gland

Hormone Secreted

• Melatonin

Functions

Melatonin regulates:

• 24-hour biological clock (circadian rhythm)
• Sleep-wake cycle
• Body temperature rhythm

Important Term

Circadian Rhythm

• Daily biological rhythm occurring in about 24 hours.

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5. Thyroid Gland

Main Hormones

• Thyroxine (T4)
• Triiodothyronine (T3)

Functions

These hormones regulate:

• Basal metabolic rate (BMR)
• Growth and development
• Maturation of CNS
• Metabolism of:
  • Carbohydrates
  • Proteins
  • Fats
• Menstrual cycle
• Erythropoiesis (RBC formation)

---

Thyrocalcitonin (Calcitonin)

• Secreted by thyroid gland.
• Decreases blood calcium level.

Function

• Helps maintain calcium balance.

---

6. Parathyroid Glands

Hormone

• Parathyroid Hormone (PTH)

Functions

PTH:

• Increases blood calcium level
• Maintains calcium homeostasis

Important Point

• Calcitonin ↓ blood Ca²⁺
• PTH ↑ blood Ca²⁺

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7. Thymus Gland

Hormone

• Thymosins

Functions

Thymosins help in:

• Differentiation of T-lymphocytes
• Cell-mediated immunity

Additional Role

• Increase antibody production
• Supports humoral immunity

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8. Adrenal Gland

Structure

Adrenal gland has:

1. Adrenal medulla (inner part)
2. Adrenal cortex (outer part)

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9. Adrenal Medulla

Hormones

• Epinephrine (Adrenaline)
• Norepinephrine (Noradrenaline)

Functions

These are emergency hormones ("Fight or Flight Hormones").

They increase:

• Alertness
• Pupil dilation
• Sweating
• Heartbeat
• Strength of heart contraction
• Respiration rate
• Glycogenolysis
• Lipolysis
• Proteolysis

---

10. Adrenal Cortex

Hormones

1. Glucocorticoids
2. Mineralocorticoids

---

Glucocorticoids Functions

They stimulate:

• Gluconeogenesis
• Lipolysis
• Proteolysis
• Erythropoiesis

They also:

• Increase blood pressure
• Support cardiovascular system
• Increase GFR (glomerular filtration rate)
• Suppress immune response
• Reduce inflammation

Example

• Cortisol

---

Mineralocorticoids Functions

They regulate:

• Water balance
• Electrolyte balance

Example

• Aldosterone

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11. Endocrine Pancreas

Hormones

1. Glucagon
2. Insulin

---

Glucagon Functions

Glucagon increases blood glucose by:

• Glycogenolysis
• Gluconeogenesis

Result

• Hyperglycemia

---

Insulin Functions

Insulin:

• Increases glucose uptake by cells
• Promotes glycogenesis

Result

• Hypoglycemia

---

Diabetes Mellitus

Occurs due to:

• Insulin deficiency OR
• Insulin resistance

Symptoms

• High blood sugar
• Excess urination
• Excess thirst

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12. Testis

Hormones

• Androgens (mainly Testosterone)

Functions

Androgens help in:

• Development of male reproductive organs
• Secondary sexual characters
• Spermatogenesis
• Male sexual behavior
• Anabolic activities
• Erythropoiesis

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13. Ovary

Hormones

1. Estrogen
2. Progesterone

---

Estrogen Functions

• Growth of female reproductive organs
• Development of female secondary sexual characters

---

Progesterone Functions

• Maintains pregnancy
• Mammary gland development
• Lactation support

---

14. Heart as Endocrine Organ

Hormone

• Atrial Natriuretic Factor (ANF)

Function

• Decreases blood pressure

---

15. Kidney as Endocrine Organ

Hormone

• Erythropoietin (EPO)

Function

• Stimulates RBC production

---

16. Gastrointestinal Tract Hormones

Hormones

• Gastrin
• Secretin
• Cholecystokinin (CCK)
• Gastric Inhibitory Peptide (GIP)

Functions

These hormones:

• Regulate digestive juices
• Help in digestion

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NEET Quick Revision Points

Gland	Hormone	Main Function
Pineal	Melatonin	Sleep cycle
Thyroid	T3/T4	Metabolism
Thyroid	Calcitonin	↓ Blood Ca²⁺
Parathyroid	PTH	↑ Blood Ca²⁺
Thymus	Thymosin	T-cell maturation
Adrenal Medulla	Adrenaline	Fight or flight
Pancreas	Insulin	↓ Blood glucose
Pancreas	Glucagon	↑ Blood glucose
Testis	Testosterone	Male characters
Ovary	Estrogen	Female characters
Ovary	Progesterone	Pregnancy maintenance
Heart	ANF	↓ Blood pressure
Kidney	EPO	RBC formation

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Important NEET Keywords

• Homeostasis
• Circadian rhythm
• Glycogenolysis
• Gluconeogenesis
• Lipolysis
• Hyperglycemia
• Hypoglycemia
• Erythropoiesis
• Cell-mediated immunity
• Humoral immunity 

ENDOCRINE SYSTEM

│

├── Hormones

│   ├── Chemical messengers

│   ├── Coordination & regulation

│   ├── Control metabolism

│   ├── Growth & development

│   └── Maintain homeostasis

│

├── Endocrine Glands

│   │

│   ├── Hypothalamus

│   │

│   ├── Pituitary Gland (Master Gland)

│   │   ├── Pars Distalis

│   │   │   └── 6 trophic hormones

│   │   ├── Pars Intermedia

│   │   │   └── MSH

│   │   └── Pars Nervosa (Neurohypophysis)

│   │       ├── Oxytocin

│   │       └── ADH / Vasopressin

│   │

│   ├── Pineal Gland

│   │   ├── Melatonin

│   │   └── Circadian rhythm

│   │       ├── Sleep cycle

│   │       └── Body temperature rhythm

│   │

│   ├── Thyroid Gland

│   │   ├── T3 (Triiodothyronine)

│   │   ├── T4 (Thyroxine)

│   │   │   ├── Metabolism

│   │   │   ├── Growth

│   │   │   ├── CNS maturation

│   │   │   ├── Protein metabolism

│   │   │   ├── Fat metabolism

│   │   │   └── Carbohydrate metabolism

│   │   └── Calcitonin

│   │       └── Decreases blood Ca²⁺

│   │

│   ├── Parathyroid Gland

│   │   └── PTH

│   │       ├── Increases blood Ca²⁺

│   │       └── Calcium homeostasis

│   │

│   ├── Thymus

│   │   └── Thymosins

│   │       ├── T-lymphocyte differentiation

│   │       ├── Cell-mediated immunity

│   │       └── Humoral immunity

│   │

│   ├── Adrenal Gland

│   │   │

│   │   ├── Adrenal Medulla

│   │   │   ├── Epinephrine

│   │   │   ├── Norepinephrine

│   │   │   └── Fight or Flight Response

│   │   │       ├── Increased heartbeat

│   │   │       ├── Sweating

│   │   │       ├── Alertness

│   │   │       ├── Respiration rate

│   │   │       ├── Glycogenolysis

│   │   │       ├── Lipolysis

│   │   │       └── Proteolysis

│   │   │

│   │   └── Adrenal Cortex

│   │       ├── Glucocorticoids

│   │       │   ├── Gluconeogenesis

│   │       │   ├── Lipolysis

│   │       │   ├── Proteolysis

│   │       │   ├── Anti-inflammatory action

│   │       │   └── Suppress immunity

│   │       └── Mineralocorticoids

│   │           ├── Water balance

│   │           └── Electrolyte balance

│   │

│   ├── Pancreas

│   │   ├── Glucagon

│   │   │   ├── Glycogenolysis

│   │   │   ├── Gluconeogenesis

│   │   │   └── Hyperglycemia

│   │   └── Insulin

│   │       ├── Glucose uptake

│   │       ├── Glycogenesis

│   │       └── Hypoglycemia

│   │

│   ├── Gonads

│   │   │

│   │   ├── Testis

│   │   │   └── Androgens (Testosterone)

│   │   │       ├── Male reproductive organs

│   │   │       ├── Secondary sexual characters

│   │   │       ├── Spermatogenesis

│   │   │       ├── Male sexual behaviour

│   │   │       └── Anabolic effects

│   │   │

│   │   └── Ovary

│   │       ├── Estrogen

│   │       │   ├── Female reproductive organs

│   │       │   └── Secondary sexual characters

│   │       └── Progesterone

│   │           ├── Pregnancy maintenance

│   │           ├── Mammary gland development

│   │           └── Lactation

│   │

│   ├── Heart

│   │   └── Atrial Natriuretic Factor (ANF)

│   │       └── Decreases blood pressure

│   │

│   ├── Kidney

│   │   └── Erythropoietin (EPO)

│   │       └── RBC production

│   │

│   └── Gastrointestinal Tract

│       ├── Gastrin

│       ├── Secretin

│       ├── Cholecystokinin (CCK)

│       ├── Gastric Inhibitory Peptide (GIP)

│       └── Digestion regulation

│

└── Disorders

    └── Diabetes Mellitus

        ├── Insulin deficiency

        ├── Insulin resistance

        └── High blood glucose 

Human Endocrine System Diagram showing major glands and hormones for Class 11 Biology and NEET preparation.

CBSE Class 11 Biology – Endocrine System Question Bank

Chapter: Chemical Coordination and Integration

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1. MCQs (Multiple Choice Questions)

1. Which gland is called the “Master Gland”?

A. Thyroid
B. Adrenal
C. Pituitary
D. Pineal

✅ Answer: C. Pituitary

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2. Melatonin is secreted by:

A. Thyroid
B. Pineal gland
C. Pituitary gland
D. Thymus

✅ Answer: B. Pineal gland

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3. Which hormone decreases blood calcium level?

A. PTH
B. Insulin
C. Calcitonin
D. Cortisol

✅ Answer: C. Calcitonin

---

4. Fight or flight hormone is:

A. Insulin
B. Adrenaline
C. Thyroxine
D. Estrogen

✅ Answer: B. Adrenaline

---

5. Insulin deficiency causes:

A. Hypoglycemia
B. Diabetes mellitus
C. Gigantism
D. Goitre

✅ Answer: B. Diabetes mellitus

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6. Hormone responsible for calcium homeostasis:

A. Thyroxine
B. PTH
C. Melatonin
D. Testosterone

✅ Answer: B. PTH

---

7. Which gland secretes thymosin?

A. Thymus
B. Thyroid
C. Pancreas
D. Pineal

✅ Answer: A. Thymus

---

8. Which hormone increases blood glucose level?

A. Insulin
B. Glucagon
C. Oxytocin
D. ADH

✅ Answer: B. Glucagon

---

9. Oxytocin is released from:

A. Thyroid
B. Pars distalis
C. Pars nervosa
D. Adrenal cortex

✅ Answer: C. Pars nervosa

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10. Erythropoietin is secreted by:

A. Heart
B. Kidney
C. Liver
D. Pancreas

✅ Answer: B. Kidney

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2. Very Short Answer Questions (1 Mark)

Q1. What are hormones?

✅ Hormones are chemical messengers secreted by endocrine glands.

---

Q2. Name the hormone regulating circadian rhythm.

✅ Melatonin

---

Q3. Which gland secretes insulin?

✅ Pancreas

---

Q4. Name the hormone responsible for milk ejection.

✅ Oxytocin

---

Q5. What is hyperglycemia?

✅ Increase in blood glucose level.

---

Q6. Name the hormone secreted by heart.

✅ Atrial Natriuretic Factor (ANF)

---

Q7. Which hormone stimulates RBC formation?

✅ Erythropoietin

---

Q8. Name the male sex hormone.

✅ Testosterone

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3. Short Answer Questions (2–3 Marks)

Q1. Differentiate between endocrine and exocrine glands.

Endocrine Glands	Exocrine Glands
Ductless glands	Have ducts
Release hormones into blood	Release secretions through ducts
Example: Thyroid	Example: Salivary gland

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Q2. Write functions of insulin.

✅ Functions:

1. Increases glucose uptake by cells
2. Promotes glycogenesis
3. Decreases blood sugar level

---

Q3. Write functions of adrenaline.

✅ Functions:

• Increases heartbeat
• Increases alertness
• Dilates pupils
• Increases respiration rate
• Prepares body for emergencies

---

Q4. What are glucocorticoids?

✅ Glucocorticoids are hormones secreted by adrenal cortex that regulate metabolism and suppress inflammation.

Example: Cortisol

---

Q5. State functions of thymosin.

✅ Functions:

• Helps maturation of T-lymphocytes
• Supports immunity
• Increases antibody production

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4. Long Answer Questions (5 Marks)

Q1. Explain structure and functions of adrenal gland.

Structure

Adrenal gland has:

1. Adrenal medulla
2. Adrenal cortex

---

Adrenal Medulla

Secretes:

• Adrenaline
• Noradrenaline

Functions

• Fight or flight response
• Increases heartbeat
• Increases blood glucose
• Increases alertness

---

Adrenal Cortex

Secretes:

1. Glucocorticoids
2. Mineralocorticoids

Functions

• Regulate metabolism
• Maintain electrolyte balance
• Control inflammation
• Regulate blood pressure

---

Q2. Explain functions of thyroid hormones.

✅ Thyroid hormones:

• Regulate BMR
• Help growth and development
• Control metabolism of carbohydrates, fats and proteins
• Help CNS maturation
• Support erythropoiesis

Calcitonin decreases blood calcium level.

---

5. Assertion and Reason Questions

Q1.

Assertion (A): Insulin decreases blood glucose level.
Reason (R): Insulin promotes glucose uptake by cells.

A. Both A and R are true and R is correct explanation
B. Both A and R are true but R is not correct explanation
C. A is true but R is false
D. A is false but R is true

✅ Answer: A

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Q2.

Assertion (A): PTH decreases blood calcium level.
Reason (R): PTH regulates calcium homeostasis.

✅ Answer: D
(A is false but R is true)

---

Q3.

Assertion (A): Adrenaline is called emergency hormone.
Reason (R): It prepares body for stress conditions.

✅ Answer: A

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6. Fill in the Blanks

1. Hormones are secreted by ________ glands.
   ✅ endocrine

2. ________ hormone regulates sleep cycle.
   ✅ Melatonin

3. Insulin is secreted by ________.
   ✅ Pancreas

4. PTH increases ________ calcium level.
   ✅ blood

5. Adrenaline is secreted by adrenal ________.
   ✅ medulla

6. Diabetes mellitus occurs due to deficiency of ________.
   ✅ insulin

7. Thymosin helps maturation of ________ cells.
   ✅ T-lymphocyte

8. ANF decreases ________ pressure.
   ✅ blood

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7. Match the Columns

Column A	Column B
1. Pineal gland	a. Insulin
2. Pancreas	b. Melatonin
3. Kidney	c. Erythropoietin
4. Thymus	d. Thymosin

✅ Answers: 1 → b
2 → a
3 → c
4 → d

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8. Statement-Based Questions

Q1. Read the statements carefully:

1. Calcitonin increases blood calcium level.
2. PTH regulates calcium homeostasis.
3. Melatonin regulates sleep cycle.
4. Insulin increases blood sugar level.

Choose the correct statements.

A. 1 and 2
B. 2 and 3
C. 1 and 4
D. 3 and 4

✅ Answer: B

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Q2.

1. Adrenaline is secreted by adrenal medulla.
2. Cortisol is a mineralocorticoid.
3. Aldosterone regulates electrolyte balance.

Choose correct option:

A. 1 only
B. 1 and 3 only
C. 2 and 3 only
D. All are correct

✅ Answer: B

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9. Case Study Questions

Case Study 1

A student feels increased heartbeat, sweating and rapid breathing before an examination.

Questions

1. Which gland is activated?

✅ Adrenal gland

2. Name the hormone secreted.

✅ Adrenaline

3. Which part secretes this hormone?

✅ Adrenal medulla

4. What is this response called?

✅ Fight or flight response

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Case Study 2

A person has high blood sugar level due to improper insulin action.

Questions

1. Which disease is this?

✅ Diabetes mellitus

2. Which gland is affected?

✅ Pancreas

3. Which hormone regulates blood glucose?

✅ Insulin

4. Name another pancreatic hormone.

✅ Glucagon

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10. Important CBSE Board Questions

1. Why is pituitary gland called master gland?

✅ Because it controls activities of many endocrine glands.

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2. Differentiate between insulin and glucagon.

Insulin	Glucagon
Decreases blood sugar	Increases blood sugar
Causes glycogenesis	Causes glycogenolysis
Causes hypoglycemia	Causes hyperglycemia

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3. Explain fight or flight response.

✅ It is an emergency response caused by adrenaline during stress, fear or danger that prepares body for action.

---

11. HOTS Questions

Q1. Why are endocrine glands called ductless glands?

✅ Because they release hormones directly into blood without ducts.

---

Q2. Why does removal of thymus reduce immunity?

✅ Because thymus produces thymosin which helps maturation of T-lymphocytes needed for immunity.

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12. Diagram-Based Question

Q. Draw labelled diagram of:

1. Pituitary gland
2. Adrenal gland
3. Thyroid gland

✅ Practice diagrams with labels for board exams.

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