Unit 8
Human Biology
Chapter 8.7
EndocrinologyClass 12 Biology – Endocrinology Notes PDF
On mobile, swipe inside the PDF to read all pages and pinch to zoom.
Introduction
Hormones coordinate growth, metabolism, stress responses, reproduction, water balance and many other long-term physiological processes.
1. General Features of Hormones
- Produced in very small quantities.
- Released by endocrine cells or glands.
- Transported to target tissues through blood or other body fluids.
- Act only on cells containing appropriate receptors.
- Often regulated by feedback mechanisms.
Fig. 1 – Endocrine Signalling
2. Major Endocrine Glands
Fig. 2 – Major Endocrine Glands in Human Body
3. Pituitary Gland
The pituitary lies below the hypothalamus and is often described as a major endocrine control gland because several of its hormones regulate other endocrine organs.
| Hormone / Group | Main Role |
|---|---|
| Growth hormone | Promotes growth and influences metabolism. |
| TSH | Stimulates thyroid gland. |
| ACTH | Stimulates adrenal cortex. |
| FSH and LH | Regulate reproductive organs and gamete-related functions. |
| Prolactin | Supports milk production. |
| ADH / oxytocin release | Posterior pituitary releases hypothalamic hormones involved in water balance and reproductive functions. |
4. Thyroid and Parathyroid Glands
Thyroid
Thyroid hormones influence metabolic rate, growth and development. Calcitonin contributes to calcium regulation.
Parathyroids
Parathyroid hormone helps regulate calcium and phosphate balance, generally acting to increase blood calcium when required.
Fig. 3 – Thyroid and Parathyroid
5. Endocrine Pancreas
Islets of Langerhans in the pancreas secrete hormones important in blood-glucose regulation.
Insulin
Lowers elevated blood glucose by promoting glucose uptake and storage in responsive tissues.
Glucagon
Raises blood glucose by promoting release of stored fuels, especially through liver metabolism.
Fig. 4 – Insulin and Glucagon Feedback
6. Adrenal Glands
Each adrenal gland has an outer cortex and inner medulla. The cortex secretes steroid hormones involved in metabolism, salt balance and stress responses; the medulla releases catecholamines such as adrenaline during acute stress.
7. Gonadal Hormones
Testes
Produce androgens such as testosterone, supporting male reproductive development and function.
Ovaries
Produce estrogens and progesterone, important in female reproductive development, menstrual-cycle regulation and pregnancy-related functions.
8. Hormonal Feedback Control
Fig. 5 – Hypothalamus-Pituitary-Target Gland Feedback
9. Quick Revision & Exam Points
- Define hormone and endocrine gland.
- Draw major endocrine glands in the human body.
- Write functions of important pituitary hormones.
- Explain the functions of thyroid and parathyroid hormones.
- How do insulin and glucagon regulate blood glucose?
- Write functions of adrenal hormones.
- State the major gonadal hormones.
- Explain negative feedback in endocrine control.
- Hormones act through specific receptors.
- Pituitary regulates several endocrine glands.
- Thyroid hormones affect metabolism.
- Parathyroid hormone regulates calcium.
- Insulin lowers high blood glucose.
- Glucagon raises low blood glucose.
- Adrenal medulla supports acute stress response.
- Negative feedback stabilizes hormone levels.
Source handling: The original handwritten PDF remains embedded above. The typed section follows the verified Nepal eNotes chapter scope and is designed as a searchable, mobile-friendly study companion. Where Google Drive does not expose the handwritten page text, the typed section is not presented as a word-for-word transcription.
Discussion
Share a helpful question, idea, or explanation with other students.