Hormone | Endocrinology | Types | Mechanism | Functions| Physiology| Biology|

        HormonesHORMONES

Keywords: Endocrine| Glands| Fate of hormones| Chemical nature| Steroids| Protein, and peptides| Amino acid derivatives| Eicosanoids| Gases| Receptors|

    Table of contents

1.	Introduction
2.	Fate of hormones
3.	Chemical nature of hormones Ø Steroids Ø Protein and  peptides Ø Amino acid derivatives Ø Eicosanoids Ø Gases
4.	Receptors
5.	Mechanism of action
6.	Neurohormones
7.	Inactivation of hormones

 In Greek, the word hormone means 'setting in motion. A hormone is any class of signaling molecules in multicellular organisms, transported by intricate biological processes to distant organs to control physiology and behavior.

Hormones are required to properly develop human beings and other animals, plants, and fungi.

A hormone is a signaling molecule that usually acts on a distant tissue.

In response to specific biochemical signals, endocrine glands secrete hormones by exocytosis. Other membrane transport methods secrete hormones directly into the bloodstream through fenestrated capillaries and are often subject to negative feedback regulation. For example, high blood sugar stimulates insulin secretion.

Paracrine hormones diffuse to the nearby target tissue. They are short-lived, so they cannot diffuse to a long distance.

                                                        Fate of hormones

After secretion

·    Water-soluble hormones are transported through the circulatory system.

·    Water-insoluble hormones are lipid-soluble. These hormones combine with carrier plasma glycoprotein, e.g., thyroxine-binding globulin, to form a 'ligand-protein complex' and are transported through the circulatory system.

·    Some lipid-soluble hormones circulate as prohormones that are activated in specific cells.

·    The peripheral tissue removes the hormones.

                                                         Chemical nature of hormones

Chemically hormones are:

·    Eicosanoids-e.g.prostglandin

·    Amino acid derivatives - e.g., adrenalin,

·    Protein and peptides- e.g., insulin

·    Steroids -e.g., Thyroxin, and

·    Gases - e.g., Nitrous oxide.

Hormones impart information between organs and tissues to regulate all physiological processes and behavior, e.g., digestion, sleep, metabolism, and respiration.

                                                        Mechanism of action

This description is an oversimplification of the hormonal signaling process.

The hormone activates a signal transduction pathway that typically activates gene transcription resulting in increased expression of target proteins.

However, hormones can also act in rapid, non-genomic pathways synergizing with genomic effects.

Water-soluble hormones cannot enter the cell, so they bind with receptors on the surface of target cells, which stimulates a cascade of secondary effects within the cytoplasm. This is 'signal transduction and causes the formation of a second messenger, 'cyclic AMP.'

 Lipid soluble hormones generally pass through target cells' plasma membrane and bind with cytoplasmic and nuclear receptors to act within their nuclei. These receptors are the 'nuclear receptors' family of ligand-activated 'transcription factors.

                                                        Receptors

Receptors on the plasma membrane are usually 'G protein-coupled receptor' class of seven 'alpha helix transmembrane protein.'

 Hormonal signaling involves the following steps

·    Synthesis of a particular hormone in a specific tissue.

·    Storage, secretion, and breakdown of the hormone.

·    Actively preparation of the body for a new phase of life such as puberty

·    Menopause and control of the reproductive cycle, and

·    Hunger craving.

Hormonal signals travel throughout the circulatory system, but neural signals travel only through the pre-existing tracks.

                                                        Neurohormones 

Neurohormones are produced by endocrine cells that receive input from neurons. The endocrine glands secrete both classic hormones and neurohormones. However, neurohormones are secreted as a result of a combination between endocrine reflexes and neural reflexes creating a neuroendocrine pathway. The endocrine pathways produce chemical signals in the form of hormones. The neuroendocrine pathways cause the electrical signal 'neurohormone.'

To know about differences between enzymes and hormones pl. read my blog

https://learn-and-fly.co.in/differences-between-hormones-and-enzymes.  

 

Hashtags: Endocrine# Glands# Fate # Chemical nature# Steroids# Protein and peptides# Amino acid derivatives# Eicosanoids# Gases# Receptors#

Internal link: https://blog.totalphysiology.com/2021/03/2021-google-ductless|glands-we-must-know.html

                https://blog.totalphysiology.com/2022/01/ endocrinology-adrenal gland- html.

                https://blog.totalphysiology.com/2022/01/ pituitary gland-secretion hormones-gland- html.

                https://blog.totalphysiology.com/2022/02/ thyroid hormones|endocrine gland- html.

https://learn-and-fly.co.in/differences-between-hormones-and-enzymes.  

 

External link: https://en.m.wikipedia.org>wiki