Friday, 6 December 2013

ICSE Biology Quick Revision Material

                                                  Endocrine Glands
1.      Glands are of two types- Exocrine glands and Endocrine glands.
.Exocrine glands are duct (having tube) glands- secrete enzymes.
.Endocrine glands are ductless (tube lacking) glands secrete enzymes.
2.      Hormones are chemical messengers which are produced at one part of our body and have influence at some other parts (target organs) of our body.
Characteristics of hormones:
1.      Hormones are always poured or secreted into blood by endocrine glands.
2.      Hormones always act away from the source of their secretion.
3.      Hormones are produced in  trace quantity but they have wide influence  all over our body.
4.      Same hormone produced in different species will have the same influence.
5.      Hormones cannot be stored in our body but  will be excreted after their action.
6.      Hormones regulate physiological process by chemical means.
7.      Chemically hormones are peptides (insulin), amine (adrenaline), steroids (testosterone).
8.      Secretion of a hormone less (hypo/under secretion) or more (hyper/over secretion) leads to some defects in the body.
1.     THYROID GLAND:   
Location: A butterfly shaped gland present below larynx and above trachea. The two wings of thyroid gland are connected by a bridge like region called isthmus.
Hormones secreted: Thyroxine and Calcitonin
Principal activities of Thyroxine hormone:-
1.      Regulate basal metabolism ( Cellular oxidation resulting in heat production).
2.      It influences general growth of the body, ossification of bones, mental development and body heat content.
Hypo secretion or under secretion (Hypothyroidism) of this hormone leads to three defects.
a.      Simple Goiter: Thyroid gland present below the neck region become swollen.
Symptom: Abnormal swelling of thyroid gland present below the neck region.

Reason: Lack of iodine in diet. Iodine helps in the synthesis of thyroxine hormone by thyroid gland.
People live in hilly plains most commonly suffer from this defect due to iodine gets leached away from the sloppy soils. Hence the food produced from these crops lack iodine mineral.
b.      Cretinism: It is a defect caused in child or at infancy.
Symptoms: Dwarfism, Mental retardation.
c.       Myxoedema:  disease caused in old people. Person become sluggish. Swelling can be Iseen in face and hands.
Over secretion /Hyper secretion (Hyperthyroidism) leads to Exophthalmic Goiter.
Symptoms: 1. Eyes protrude out.
2.     Metabolic and heart beat rate increases.
3.     Shortness of breath
4.     Goiter in the neck.
This gland acts as both exocrine and endocrine gland. Pancreas is present below the stomach region. Pancreas as an exocrine gland it secret enzymes and as an endocrine gland secrete hormones. Patches of endocrine cells present in pancreas together known as Islets of Langerhans.  
a.      Beta cells of Islets of Langerhans secret Insulin.
Principal activities of Insulin hormone:
1.      Insulin promotes proper utilization of glucose by our body cells.
2.      Insulin converts excess glucose present in blood to glycogen and store it in liver.
b.      Alpha cells of  Islets of Langerhans secret Glucagon.  
Glucagon converts glycogen present in liver to glucose and put into blood circulation.
c.       Delta cells of Islets of Langerhans secrete Somatostatin. This hormone control secretions of both insulin and glucagon hormones.