CBSE Class 11 Biology – Chemical Coordination and Integration | NCERT Study Module & Revision Notes

Course & Examination Details

• Course: CBSE Class 11 Biology
• Prescribed By: Central Board of Secondary Education
• Based On: NCERT
• Unit: Unit V – Human Physiology
• Chapter: Chapter 22 – Chemical Coordination and Integration
• Chapter Importance: A core chapter of Human Physiology explaining hormonal regulation, endocrine glands, and disorders frequently asked in CBSE examinations

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Chemical Coordination and Integration Class 11 Biology – NCERT Study Module & Revision Notes

CBSE Board Examination Relevance

This chapter is regularly assessed through:

• Definitions and examples of hormones
• Structure and functions of endocrine glands
• Feedback mechanisms
• Hormonal disorders
• Differences between neural and chemical coordination

It is also highly important for NEET foundation level, as hormonal regulation is a recurring concept.

Introduction: Chemical Coordination and Integration

Coordination in living organisms is achieved by two major systems:

1. Nervous system – fast, short-lived responses
2. Endocrine system – slow, long-lasting responses

Chemical coordination involves hormones, which are chemical messengers secreted by endocrine glands directly into the bloodstream. These hormones regulate growth, development, metabolism, reproduction, and homeostasis.

1. Endocrine System

The endocrine system is a collection of ductless glands that secrete hormones directly into blood.

1.1 Characteristics of Endocrine Glands

• Ductless glands
• Secrete hormones in small quantities
• Hormones act on specific target organs
• Effects are usually slow but long-lasting
• Regulated by feedback mechanisms

1.2 Differences Between Endocrine and Exocrine Glands

2. Hormones

Hormones are non-nutrient chemical messengers that regulate physiological processes.

2.1 Properties of Hormones

• Secreted in minute quantities
• Highly specific in action
• Regulate metabolism, growth, and reproduction
• Can be peptides, steroids, or amines

2.2 Classification of Hormones

(A) Based on Chemical Nature

1. Peptide hormones – Insulin, Growth hormone
2. Steroid hormones – Testosterone, Estrogen
3. Amino acid derivatives – Adrenaline, Thyroxine

(B) Based on Solubility

• Water-soluble hormones – Peptide hormones
• Lipid-soluble hormones – Steroid hormones

2.3 Mechanism of Hormone Action

Water-Soluble Hormones

• Cannot cross cell membrane
• Bind to membrane receptors
• Act via second messengers (e.g., cAMP)

Lipid-Soluble Hormones

• Cross cell membrane
• Bind to intracellular receptors
• Directly influence gene expression

3. Hypothalamus

Hypothalamus links the nervous system and endocrine system.

3.1 Hormones of Hypothalamus

• Releasing hormones (RH)
• Inhibiting hormones (IH)

These regulate secretion of pituitary hormones.

4. Pituitary Gland (Master Gland)

Pituitary gland controls the activity of other endocrine glands.

4.1 Location and Structure

• Located at base of brain
• Connected to hypothalamus by infundibulum
• Divided into:
  • Anterior pituitary (Adenohypophysis)
  • Posterior pituitary (Neurohypophysis)

4.2 Hormones of Anterior Pituitary

Growth Hormone (GH)

• Stimulates growth of bones and muscles
• Deficiency → Dwarfism
• Excess → Gigantism / Acromegaly

Thyroid Stimulating Hormone (TSH)

• Stimulates thyroid gland

Adrenocorticotropic Hormone (ACTH)

• Stimulates adrenal cortex

Follicle Stimulating Hormone (FSH)

• Regulates gametogenesis

Luteinizing Hormone (LH)

• Triggers ovulation and testosterone secretion

Prolactin (PRL)

• Stimulates milk production

4.3 Hormones of Posterior Pituitary

Oxytocin

• Causes uterine contraction
• Milk ejection

Vasopressin (ADH)

• Regulates water balance
• Deficiency → Diabetes insipidus

5. Pineal Gland

5.1 Hormone: Melatonin

• Regulates circadian rhythm
• Controls sleep–wake cycle
• Influences puberty timing

6. Thyroid Gland

6.1 Hormones of Thyroid

• Thyroxine (T₄)
• Triiodothyronine (T₃)

6.2 Functions of Thyroid Hormones

• Regulate basal metabolic rate
• Influence growth and development
• Essential for normal nervous system development

6.3 Role of Iodine

• Iodine is essential for synthesis of thyroid hormones
• Deficiency leads to goitre

7. Parathyroid Glands

7.1 Hormone: Parathyroid Hormone (PTH)

• Regulates calcium and phosphate balance
• Increases blood calcium level

7.2 Disorders

• Hyposecretion → Tetany
• Hypersecretion → Bone demineralization

8. Adrenal Glands

Each adrenal gland has:

• Adrenal cortex
• Adrenal medulla

8.1 Hormones of Adrenal Medulla

Adrenaline & Noradrenaline

• “Emergency hormones”
• Increase heart rate, blood pressure
• Prepare body for stress

8.2 Hormones of Adrenal Cortex

Glucocorticoids (Cortisol)

• Regulate metabolism
• Anti-inflammatory

Mineralocorticoids (Aldosterone)

• Regulate sodium and potassium balance

Sex Corticoids

• Minor role in sexual development

9. Pancreas (Islets of Langerhans)

Pancreas is a heterocrine gland.

9.1 Hormones of Pancreas

Insulin

• Lowers blood glucose level
• Deficiency → Diabetes mellitus

Glucagon

• Increases blood glucose level

9.2 Regulation of Blood Glucose

• Insulin and glucagon act antagonistically
• Maintains glucose homeostasis

10. Gonads

10.1 Testes

Hormones

• Testosterone

Functions

• Development of male secondary sexual characters
• Spermatogenesis

10.2 Ovaries

Hormones

• Estrogen
• Progesterone

Functions

• Development of female secondary sexual characters
• Regulation of menstrual cycle

11. Hormonal Disorders

11.1 Diabetes Mellitus

• Due to insulin deficiency
• High blood glucose level
• Excess glucose excreted in urine

11.2 Goitre

• Enlargement of thyroid gland
• Caused by iodine deficiency

11.3 Cushing’s Syndrome

• Excess cortisol
• Obesity, muscle weakness

11.4 Addison’s Disease

• Deficiency of adrenal hormones
• Fatigue, weight loss

11.5 Dwarfism and Gigantism

• Caused by GH imbalance

12. Feedback Mechanism

Feedback mechanism regulates hormone secretion.

12.1 Negative Feedback

• Increased hormone level inhibits further secretion
• Maintains hormonal balance

Example: Thyroxine inhibiting TSH secretion

Quick Revision Notes (CBSE Exam Focus)

• Hormones are chemical messengers
• Endocrine glands are ductless
• Pituitary is master gland
• Thyroid regulates metabolism
• Insulin lowers blood glucose
• Adrenaline is emergency hormone
• Feedback mechanism maintains balance
• Hormonal disorders are frequently asked

NCERT & CBSE Compliance Confirmation

✔ Strictly based on NCERT Class 11 Biology
✔ Terminology and concepts as per CBSE guidelines
✔ No out-of-syllabus content
✔ Ideal for CBSE Class 11 board examinations

Conclusion

The chapter Chemical Coordination and Integration explains how hormones regulate and integrate body functions. Understanding endocrine glands, hormone actions, and disorders is essential for mastering Human Physiology and scoring well in CBSE Class 11 Biology examinations.