Continuing with our telephone analogy for brain communication, the body uses both land-based telephones (nerves from the brain to all organs of the body) as well as mobile telephony. The mobile telephones are represented by the hormonal system. We saw that chemical messengers from the sympathetic nerve endings direct the organs to respond to stressful events. If the same chemicals are released into the blood and affect events far and wide, they are called hormones. The hormones are transported in the common medium (blood) just like the mobile telephone messages travel through the air.<\/p>\n
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There are a number of glands in the body that secrete hormones. Extending our analogy further, it is clear that the message will be understood only by the telephone system for which it is intended. In our daily usage, there are multiple mobile phone companies and each requires a special card that must be put in our phone before we can make and receive calls. Similarly, there are multiple hormones but the organs respond to the hormones for which they have the correct ‘phone-card’\u2014receptor (to give it the correct scientific name).<\/p>\n
Most hormones circulate in the blood and essentially come into contact with all the cells. Only those cells with the receptors for that hormone will react to the hormonal message. These cells, not surprisingly are called target cells for the hormone. Hormone receptors are found either exposed on the surface of the cell or within the cell, depending on the type of hormone.<\/p>\n
In very basic terms, the binding of a hormone to a receptor triggers a cascade of reactions within the cell that affects its function. So, what is the purpose of introducing all this information on hormone receptors and target cells? It will help us to understand one of the key control mechanisms as well as the cause of diseases which will be discussed in the following chapters.<\/p>\n
The receptor mechanism allows the body to control the effects of certain hormones. Metaphorically, say, the cells take a dislike to some hormone like insulin because it keeps pestering them all the time. They decide they have had enough bossing from insulin and they simply reduce the number of receptors for insulin.<\/p>\n
Neat trick; the cell is no longer as sensitive to the hormone signals as it was before. To give the correct scientific jargon\u2014the cell has downgraded the receptor for that particular hormone. Good for the cell, not so good for the rest of the body. This is pretty much what happens in the case of people who get Type-II diabetes. Just as the cells downgrade the receptors, the sympathetic system downgrades the receptors for particular hormones when it wishes to minimize the hormonal effects.<\/p>\n
Depending on the binding, there are two important terms for the molecules that perform the actual binding\u2014<\/p>\n
\u2022 Agonists3 are molecules that bind to the receptor and induce all the post-receptor events that lead to the desired biological effect. Natural hormones are themselves agonists.<\/p>\n
\u2022 Antagonists are molecules that bind to the receptor and block binding of the agonist, but fail to trigger intracellular signalling events.<\/p>\n
Antagonists are like bureaucrats\u2014they do not perform useful work themselves, but block the activities of those that do have the capacity to contribute! Hormone antagonists are widely used as drugs for obvious reasons. Suppose, some hormone is being produced like crazy in the body\u2014all the ‘With my tongue firmly in cheek, I suggest that this is an impressive term to use in casual party chatter! Conveys the impression that you are well versed.<\/p>\n
Better yet, try to use this term as part of some new management jargon. Come up with a slogan like\u2014the manager is an agonist! Be an agonist! Let your subordinates scramble to decipher your new directive.fancy control systems seem to have failed. The simple solution is to have a chemical that will act as an antagonist. And hey presto! The effects of the hormone are dramatically reduced! This is like talking on the phone to somebody else all the time so that other phone calls cannot come through. No wonder the hormone cannot get through to the cell as it finds the receiver busy. It does not matter how much hormone is present\u2014the listener has not heard the message.<\/p>\n","protected":false},"excerpt":{"rendered":"