7. CONTROL AND COORDINATION
HORMONES
IN ANIMALS (ENDOCRINE SYSTEM)
Electrical impulses can instruct only few tissues to prepare for an activity. So, in animals, there is another way of control & coordination called Endocrine system.
It includes endocrine glands and their
secretions called hormones (chemical signals). They can reach all cells and provide wide-ranging changes. E.g.
Adrenal glands secretes adrenaline.
Adrenaline prepares body to cope with emergency
situations. E.g. E.g. a scary animal such as squirrels prepare to fight or
run away. It needs more energy.
Though fighting & running are
different, both have some common preparations.
Adrenaline is secreted into
blood and carried to different body parts. As a result, the following events
occur:
o Heart beats
faster to supply more oxygen to muscles.
o Blood to the
digestive system and skin is reduced by contracting muscles around small
arteries in these organs. This diverts the blood to skeletal muscles.
o Breathing rate
increases due to the contraction of diaphragm and rib muscles.
These responses prepare the
body to deal with the situation (fighting and running).
The timing and amount of
hormone released are regulated by feedback mechanisms. E.g. if the blood
sugar level increases, it is detected by cells of pancreas and
produce more insulin. As the blood sugar level falls, insulin secretion
is reduced.
SOME IMPORTANT
HORMONES AND THEIR FUNCTIONS
|
Endocrine Gland |
Hormone |
Functions & other info |
|
Hypothalamus |
Releasing hormones |
Stimulates pituitary gland to release hormones. E.g. growth hormone
releasing factor stimulates pituitary gland to release GH. |
|
Pituitary gland |
Growth
hormone (GH) |
Stimulates growth & development of the body. Dwarfism: Deficiency of GH in childhood. Gigantism: Overproduction of GH in childhood. |
|
Thyroid gland |
Thyroxine |
Regulates carbohydrate, protein & fat metabolism for
balanced growth. Iodine is essential for synthesis of thyroxin. Iodised
salts provide iodine. Deficiency of iodine causes goitre.
Swollen neck is the main symptom. |
|
Pancreas |
Insulin |
Regulates blood sugar level. Deficiency of insulin causes diabetes (sugar
level increases). Such patients are given insulin injections. |
|
Adrenal gland |
Adrenaline |
Prepares
body to cope with emergency situations. |
|
Testes (in male) |
Testosterone |
Changes during puberty. Development of male sex organs,
behaviour etc. |
|
Ovaries (in female) |
Oestrogen |
Changes during puberty. Development of female sex
organs, regulates menstrual cycle, etc. |
Select Your Next Topic 👇
👉 Part 1: Animals- Nervous System
👉 Part 2: Coordination in Plants
👉 Part 3: Hormones in Animals
