The endocrine glands also help in control and coordination. The endocrine
glands produce chemical substances which help to control and coordinate
various activities in the body.
The endocrine glands in our body are :- pineal, hypothalamus, pituitary,
thyroid, parathyroid, thymus, adrenal, pancreas, testes and ovary.
Examples of coordination by endocrine glands :-
i) When we are frightened or angry, the adrenal glands produce more adrenalin hormone which is sent through the blood to the heart, rib muscles and diaphragm. This increases breathing rate to supply more oxygen to the muscles to prepare the body to either run away or fight with the enemy.
ii) Iodine is needed by the thyroid gland to produce the hormone thyroxin. Thyroxin controls the metabolism of carbohydrates, fats and proteins and helps in proper growth. If the diet is deficient in iodine it causes goitre.
iii) The pituitary gland produce growth hormones. Deficiency of this hormone in childhood causes dwarfism. Excess of this hormone causes tall growth.
iv) The pancreas produces the hormone insulin which controls the blood sugar level. Increase in blood sugar level causes diabetes. A diabetic patient has to take insulin injections to control his blood sugar level.
v) The testes in males produces the hormone testosterone which controls the production of sperms and changes during puberty.
Nerve cell (Neuron) :-
Neuron is the structural and functional unit of the nervous system. It has a cell body called cyton containing a nucleus and cytoplasm. It has several branched structures called dendrites. It has a long nerve fibre called axon which is covered by a protective covering called Myelin sheath. The junction between two neurons is called synapse.
Messages pass through the nerve cell in the form of chemical and electrical signals called nerve impulse. The dendrites receive the information and starts a chemical reaction which produce electrical impulse which passes through the axon.