Explain the following :
(1) Insulin lowers the blood sugar level.
(2) Adrenal medulla and the sympathetic nervous system function as a closely integrated system.
(3) Pituitary gland regulates the reproductive system.
(4) Feed back system controls the blood level of many hormones.
Hormone released when blood glucose level falls : Glucagon hormone is released when blood glucose level falls. It converts glycogen into glucose in liver. The glucose is released into blood and raises blood glucose level.
Hormone released when blood glucose level elevated : Insulin is the hormone released when blood glucose level is elevated. It converts glucose into glycogen in liver and thus reduces level of glucose in the blood.