Page 3 - LN-CH-22

Pancreas - acts as both endocrine and exocrine gland. Endocrine pancreas consists of
"Islets of Langerhans" which contain a-cells and b cells. The a-cells secrete hormone glucagon

and b-cells secrete insulin. Both hormones are involved in maintenance of blood sugar levels.

• Glucagon is a peptide hormone that stimulates glycogenolysis resulting in increased
blood sugar (hyperglycemia).

• Insulin is a peptide hormone that play major role in regulation of glucose
homeostasis. It triggers rapid movement of glucose from blood to hepatocytes and

adipocytes resulting in decreased blood glucose levels (hypoglycemia).

Testis - perform dual functions as a primary sex organ as well as endocrine glands. Leydig

cells or interstitial cells produce androgen mainly testosterone wh.ich regulate maturation of
primary sex organs and spermatogenesis.

Ovary- produce two groups of steroid hormones called estrogen and progesterone.

Estrogen is synthesized and secreted by growing ovarian follicles. After ovulation, ruptured

ovum called corpus luteum, secretes progesterone. Estrogen produces wide range actions like
growth of female secondary sex organs, development of growing ovarian follicles, and

regulation of female sexual behaviour.

Progesterone regulates pregnancy.

Hormones of Heart, Kidney and Gastrointestinal Tract

• Atrial wall of heart secretes peptide hormone called atrial natriuretic factor (ANF)
which decreases blood pressure.

• The juxtaglomerular cells of kidney produce erythropoietin hormone which stimulate

erythropoiesis.
• Gastro-intestinal tract secrete four major peptide hormones:

1. Gastrin stimulates the secretion of hydrochloric acid and pepsinogen.

2. Secretin acts on the exocrine pancreas and stimulates secretion of water and
bicarbonate ions.

3. Cholecystokinin (CCK) stimulates the secretion of pancreatic enzymes and bile juice
4.Gastric inhibitory peptide (GIP) inhibits gastric secretion and motility.

Mechanism of Hormone Action