Class 11 Biology Chapter 19 Chemical Coordination and Integration – Revision Notes

Chemical Coordination and Integration explains how glands such as the pituitary, thyroid, and adrenal regulate the body through peptide and steroid hormones, with negative feedback keeping hormone levels in check.

Last Updated: September 23, 2026

Major Glands

• Pituitary (master gland), Thyroid (thyroxine, metabolic rate), Parathyroid (Ca²⁺), Adrenal (cortisol/adrenaline), Pancreas (insulin/glucagon), Gonads.

Hormone Action

• Peptide hormones: surface receptors, second messengers.
• Steroid hormones: lipophilic, intracellular/nuclear receptors, direct gene expression.

Regulation

• Negative feedback maintains hormone homeostasis (e.g. thyroxine → suppresses TSH).

Disorders

• Diabetes mellitus, goitre (iodine deficiency), dwarfism/gigantism (GH imbalance).

One-Line Summary

The endocrine system uses hormones secreted by glands like the pituitary, thyroid, adrenal, and pancreas to regulate body functions through peptide (surface-receptor) or steroid (gene-regulating) mechanisms, maintained by negative feedback.

Frequently Asked Questions

What is the difference between the nervous system and the endocrine system in coordinating body functions?
The nervous system coordinates functions through fast electrical nerve impulses acting for a short duration, while the endocrine system coordinates functions through slower-acting chemical messengers called hormones, carried by the blood with often longer-lasting effects.

What is a hormone, and how does it act on a specific target organ?
A hormone is a chemical messenger secreted directly into the bloodstream by an endocrine gland, and it acts specifically on target cells that carry matching receptor molecules capable of recognising and binding to that hormone.

Written by Satish

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