HORMONES: Biology Notes for RRB Exams – Railway ALP and Group D – General Science

HORMONES

·  Endocrine is a collection of gland which secrete certain chemical messages called hormones

·  Endocrine glands lack ducts and are also called as ductless glands

·  Different endocrine glands present in the human body are

Pituitary	Located in a bone cavity called sella tursica Secretes : Growth Hormone Prolactin TSH – Thyroid Stimulating Hormone
Pineal	Located on the dorsal side of the forebrain Secretes : Melatonin – Helps in maintaining the Sleep-Wake cycle , Body Temperature etc…
Adrenal	Located at the anterior part of each kidney Comprises of two tissues: Adrenal Medulla – secretes adrenaline and noradrenaline which are rapidly released in case of stress which are commonly called as Hormones of Fight, these hormones are also responsible for increase in concentration of glucose in Blood and Adrenal Cortex – secretes many hormones called Corticoids
Thyroid	Located on either side of Trachea Secretes : T4 – Throxine T3 – Triiodothyronine Iodine is essential for the synthesis of Hormone in Thyroid GlandDeficiency of Iodine causes Hypothyroidism and enlargement of gland known as GoiterThyroid hormone also assist in formation of Red Blood Cells, Metabolism, Water and Electrolyte Balance and calcium levels in Blood
Pancreas	Pancreas is a composite gland containing exocrine and endocrine system Contain Millions of Islets of Langerhans which contain a-cells – which secrete Glucagon and p-cells – which secrete Insulin
Parathyroid	Present on the Backside of the Thyroid Gland Secretes : Parathyroid Hormone (PTH) which increases the calcium levels in the blood
Thymus	Located behind the Lungs on the ventral side of oarta Secretes : Thymosins Plays a major role in the development of Immune System
Gonads	Consists of important parts TESTIS and OVARY

HORMONES

Hormones are classified into three types based on their structure

Steroids	These are lipids derived from Cholesterol. These are secreted by Gonads, Adrenal, Cortex and Placenta
Peptides	Majority of the hormones are peptides, they are characterized by short chain of amino acids and are secreted by Pituitary, Parathyroid, Heart, Stomach, Liver and Kidneys
Amines	These are derived from amino acid tyrosine and are secreted from Thyroid gland and adrenal medulla

·  Antagonism is the paired process of contraction and simultaneous expansion of various muscles in the body

·  Immunity is the body’s ability to repel foreign substances and cells

·  Cell Wall is absent in Animals

·  Cells in an animal burst when surrounded by Hypertonic medium

·  Cells in Plant doesn’t burst when surrounded by Hypertonic Medium due to the presence of Cell Wall

·  Lysosomes are also called the Suicidal Bags of a cell

·  Water constitutes the major component of the cell

·  The chemical process that occurs in a living organism to continue life is called Metabolism

·  Carbohydrates are the important biomolecules that are a major part of the living organisms. They are also called as the Hydrates of Carbon and are primarily produced by Plants