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A Handbook of Biology

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Endocrine system includes endocrine (ductless) glands and their

secretions (hormones).

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Hormones are non-nutrient chemicals that act as intercellular

messengers and are produced in trace amounts.

(NEET 2013)

They include:

Hypothalamus

Pituitary

Pineal

Thyroid

Parathyroid

Thymus

Adrenals

Pancreas

(Islets of Langerhans)

Gonads (Testis & Ovary)

1. HÝPØTHÅLÅMÜS

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Neurosecretory cells (nuclei) of hypothalamus secrete the following

types of hormones :

01

Releasing hormones: Stimulate secretion of pituitary

hormones E.g. Gonadotropin Releasing hormone

(GnRH) stimulates release of gonadotrophins from

pituitary.

02

Inhibiting hormones: Inhibit secretion of pituitary

hormones E.g. Somatostatin inhibits release of

growth hormone from pituitary.

03

Oxytocin & vasopressin: These are transported

axonally and stored in pituitary. (See pituitary

gland).