Tuesday, August 11, 2020

Chemical Coordination and Integration - Notes | Class 11 | Part 5: Mechanism of Hormone Action

22. CHEMICAL CO-ORDINATION AND INTEGRATION

MECHANISM OF HORMONE ACTION

Hormones produce their effects by binding to the specific proteins (hormone receptors) located in target tissues.

A hormone binds to its specific receptor to form hormone-receptor complex. It leads to biochemical changes in target tissue and thereby regulates metabolism and physiological functions.

Hormone receptors are 2 types:

1. 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+). It in turn regulates cellular metabolism and causes physiological effects.

2. 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. 
  • Cumulative biochemical actions result in physiological and developmental effects.
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