Chemical Coordination and Integration

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Several other non- endocrine tissues secrete hormones called growth

factors. These are essential for the normal growth of tissues and their

repairing or regeneration.

BÅSËD ØÑ THË ÇHËMÏÇÅL ÑÅTÜRË, HØRMØÑËS ÅRË ØF VÅRÏØÜS TÝPËS:

Peptide,

polypeptide, protein

hormones: E.g.

insulin, glucagon,

pituitary hormones,

hypothalamic

hormones etc.

Steroids:

E.g. cortisol,

testosterone,

estradiol &

progesterone.

Iodothyronines

(thyroid

hormones)

Amino-acid

derivatives:

E.g., Adrenaline,

nor-adrenaline

(NEET 2018)

MËÇHÅÑÏSM ØF HØRMØÑË ÅÇTÏØÑ

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Hormones produce their effects by binding to the specific proteins

(hormone receptors) located in target tissues.

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A hormone binds to its specific receptor to form hormone receptor

complex.

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It leads to biochemical changes in target tissue and thereby regulates

metabolism and physiological functions.

HØRMØÑË RËÇËPTØRS ÅRË ØF 2 TÝPËS

Membrane-bound receptors:

Some hormones (e. g. protein

hormone, FSH) interact with

membrane-bound receptors

(do not enter the target

cell). It generates second

messengers (e. g. cyclic AMP,

IP3, Ca²⁺) which in turn regulates

cellular metabolism and

causes physiological effects.

(AIPMT 2016)

Intracellular receptors (mostly

nuclear receptors): Some

hormones (e. g. steroid hormones,

iodothyronines) interact with

intracellular receptors. They

mostly regulate gene expression

or chromosome function by

the interaction of hormone-

receptor complex with the

genome. (NEET 2019) Cumulative

biochemical actions result in

physiological and developmental

effects.