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.
(1) Insulin is reponsible for lowering the blood sugar level by converting excess of glucose to gylcogen which is stored in muscles and liver.
(2) Adrenal medulla and the sympathetic nervous system are closely integrated systems as noradrenaline is secreted during danger when nerve impulse reaches adrenal medulla via the sympathetic nerves.
(3) Gonadotrophic hormone secreted by pituitary gland controls spermatogenesis in male and ovulation of mature follicles , growth and development of ovarian follicles and maintenance of corpur luteum in females.
(4) Hormones maintain homeostasis. Hormones produced in body are under the control of hormones secreted by pituitary gland and hormones of pituitary gland are further controlled by hormones of hypothalamus. All this control of hormones is done by feed back mechanism. For example, if thyroxin amount is more in blood then it stimulates hypothalamus to secrete less thyrotropin releasing hormones which decreases thyroxine secretion. On decrease in amount of thyroxine below normal, thyrotrophin releasing hormone accelerates the release of thyroxine secretion. This is feed back control.