Monday, January 18, 2010

Know the mechanisms of hormonal control (positive and negative feedback, antagonistic hormones).?

I really don't understand it, it's not Homework btwKnow the mechanisms of hormonal control (positive and negative feedback, antagonistic hormones).?
Hormones are chemicals that run throughout the body and lead other organs to produce reactions. Positive and negative feedback has to do with feedback inhibition mechanisms, where the presence of the product of the reaction directly affects later reactions of the same type by affecting the hormone that started it all.





In a negative inhibition case, the body either produces hormones to counter reactions that are going on or it stops producing the hormones that are causing the reactions. Most feedback inhibition instances in the body are negative. See ';trp operon'; for an example of a gene feedback inhibition.





In a positive feedback case, the body produces a hormone which leads to a reaction. The product of the reaction causes more hormone production, which causes increased product, which causes increased hormone, etc. Obviously, positive feedback cases never spontaneously stop, so they are only used when the cells are not permanently part of the organism. The best example is in plant hormone ethylene and ripening fruit. Ethylene makes fruit begin to ripen. The presence of ripened tissue increases the amount of ethylene, which increases the ripening and so on until the fruit is so ripe, it falls off the plant. Another example is oxytocin and the formation of endometrial wall in the uterus.





Antagonistic hormones are pairs of hormones that produce opposite results at different times, depending on what your body needs. A good example is blood sugar level. When sugar conent is high in the blood, your pancreas produces insulin, a hormone, to cause cells to take up the sugar and therefore blood sugar levels drop (until you eat more sugar). (Lack of insulin means cells cannot take up the sugar which leads to diabetes.) If there is not enough sugar in your blood, your pancreas produces glucagon, a different hormone that causes your organs to release stored sugar in order to increase the blood sugar level. Therefore: insulin= decrease in sugar level; glucagon= increase in sugar level: antagonistic hormones.

No comments:

Post a Comment