Question

Explain chemical co-ordination in humans and give the names and functions of some hormones.

Answer 1

Chemical co-ordination in humans :

• In humans chemical co-ordination is brought about with the help of certain chemical substances called hormones. 
• Hormones are secreted by endocrine glands. These glands are also called ductless glands. 
• These glands do not have any arrangement of their own to either store or carry their secretions. So, the hormones are directly released into the blood circulation. 
• Though the endocrine glands are present at specific locations in our body, their secretions reach all parts of the body via the blood. 
• Endocrine glands along with the nervous systems are responsible for control and coordination in our body. These two systems help each other to control and integrate the various activities of the body.
• A marked difference between these two systems is that nerve impulses are fast but short-lived whereas the actions of hormones are very slow but long-lasting.
• It is very important that hormones are secreted only in the required quantity and there is a special mechanism which controls the quantity and timing of hormone secretion.
• For example, whenever there is an increase in blood glucose level, certain cells in the pancreas get stimulated and as a response, they release a greater quantity of insulin, thus bringing down the sugar level to normal.

Hormone	Function
(1) Growth hormone	Stimulates growth of bones.
(2) Luteinizing hormone	Controls menstrual cycle and ovulation.
(3) Thyroxine	Controls growth of body and metabolic activities.
(4) Insulin	Stimulates liver to convert excess blood glucose to glycogen.
(5) Testosterone	Stimulates growth of secondary sexual characters like beard, mustache, hoarse voice, etc. in men.