sci_bio
Hormones
Chapter summary, hard words and model exam answers for ICSE Class 10 Hindi.
Free online summary and notes (ICSE Class 10 Hindi). Read it here, no PDF download needed.
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Biology · CBSE 10 · ICSE 10 · GCSE (AQA, Edexcel, OCR)
Summary
Endocrine glands are ductless, so they release hormones straight into the blood. A hormone reaches the whole body but only acts on its target organ - the cells with the right receptor.
It raises heart rate, widens the airways, releases glucose from the liver and sends blood to the muscles. The effect is fast but lasts only minutes.
At puberty the pituitary releases FSH and LH, making the testes produce testosterone and the ovaries produce oestrogen. These cause the secondary sexual characteristics.
Nerve impulses are electrical and act in milliseconds on one spot. Hormones travel in blood, take seconds to minutes, but reach many organs and last longer.
Hard words & meanings
| hormone | a chemical messenger made by an endocrine gland and carried in the blood to a target organ |
| endocrine gland | a ductless gland that secretes hormones directly into the bloodstream |
| target organ | an organ whose cells have the receptor for a hormone, so they respond to it |
| adrenaline | hormone from the adrenal glands that prepares the body for fight or flight |
| testosterone | the main male sex hormone, made by the testes |
| oestrogen | a female sex hormone from the ovaries that thickens the uterus lining and triggers the LH surge |
| progesterone | hormone from the corpus luteum that maintains the thickened uterus lining |
| ovulation | the release of a mature egg from the ovary, caused by the LH surge around day 14 |
Model exam answers, grammar & audio
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