2
Question Question 2
Thyroxine and insulin
| Sl. No. | Thyroxine | Insulin |
|---|---|---|
| 1. | It is secreted by thyroid gland. | It is secreted by islet of Langerhans. |
| 2. | It regulates the rate of cellular metabolism and body temperature. | It regulates the amount of of glucose in the blood and conversion of glucose into glycogen. |
| 3. | Irregular secretion leads to hyperthyroidism or hypothyroidism. | Irregular secretion leads to diabetes. |
BRIGHT TUTORIALS
BRIGHT TUTORIALS
ICSE Class VIII | Academic Year 2026-2027
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Biology | Chapter 7: Endocrine SystemWeb Content
Endocrine System – Interactive Study Guide
Quick Overview
The endocrine system consists of ductless glands that secrete hormones into the blood. Hormones are chemical messengers that regulate growth, metabolism, reproduction, and response to stress.
Endocrine vs Exocrine at a Glance
| Feature | Endocrine | Exocrine |
|---|---|---|
| Ducts | Ductless | Have ducts |
| Secretion | Hormones (into blood) | Enzymes, sweat (through ducts) |
| Examples | Pituitary, thyroid, adrenal | Salivary, sweat, liver |
Master Table: Glands, Hormones, Functions
| Gland | Hormone | Function | Disorder |
|---|---|---|---|
| Pituitary | GH | Growth | Dwarfism / Gigantism |
| Thyroid | Thyroxine | Metabolism (needs iodine) | Goitre / Cretinism |
| Parathyroid | Parathormone | Calcium regulation | Tetany |
| Adrenal | Adrenaline | Fight-or-flight | Addison's disease |
| Pancreas | Insulin / Glucagon | Blood sugar regulation | Diabetes mellitus |
| Testes | Testosterone | Male characters | — |
| Ovaries | Oestrogen | Female characters | — |
Feedback Mechanism
How It Works
High hormone level → Gland reduces production. Low hormone level → Gland increases production.
Example: High blood sugar → Insulin released → Sugar absorbed by cells → Sugar drops → Insulin production stops.
Self-Test Questions
Test Yourself
- Why is the pituitary gland called the master gland?
- What is goitre? How can it be prevented?
- Differentiate between insulin and glucagon.
- What happens during a fight-or-flight response?
- Explain the feedback mechanism with the example of blood sugar.