MECHANISM Of ACTION OF HORMONES

suspect the presence of a hormone in 1890, aithough Sir "Ernie" (Starting) for the first time in 1905 actually established the presence öf seaetin. sir Edward was a pioneer plnysologist, histochemist and histologist, he autored some classic practical text books on histology and expenmental physiology and was thus a pioneer man in this line of authorship The term hormone (from GK "hermin" ) means, l rouse or l excite (However. we know now that some hormones cause innibiDnn) B .Allosteric regulalors and allostenc proteins mean, 'hormones' and 'receptors' rgspectively CLASSIFICATION Based on their Chemical structures. the hormones have been dassifrfied äs follows MECHANISM Of ACTION OF HORMONES General mechanism of action has already been desribed To epeat, a honnone (or any chemical Signal) reacches the target cells (= the cells which contain specific receptors for the hormone non target cells may be bathed by the hormone and yet there will be no effect becäuse theyhave no recepor Recall, the hormone is traversing all parts of the body, via blood, so that most organs come in contacl with tne hormone) at target cells the hormone molecule binds (combines) with its specific receptors after such binding, post receptor events develop with in the cell the final effect (s) develops we are therefore. to know (i) something gbout the recetpors äs weil äs aboutl (ii) the post receptor binding events RECEPTORS Chemical Signals like hormone molecules reach the tar-get cells where they become bound by receptors Receptors äre proten macromolecules At least, vast majority of cells of our body (if not all cells of out body) have receptors There are many types of receptors, each ceil posseses several types of receptors Most (but not all)drugs aiso act via receptors that is. the drug moiecule is bound by the specific receptor and subsequently the drug produces its effectsit may sound surpnsing becouse