Hormones and regulation

Hormones: molecules released by endocrine glands directly into blood. Act as messengers on specific target cells

An endocrine gland is a gland that secretes hormones directly into the blood. Do not have ducts.

An exocrine gland is a gland that secretes molecules into a duct that carries molecules.

The first messenger is the hormone that transmits a signal around the body e.g adrenaline. Binds to receptor which activates second messenger.

The second messenger e.g cAMP transmits a signal inside the cell.

Functions of adrenal gland:

• Adrenal medulla - manufactures and releases adrenaline which prepares body for activity and includes the following effects:
  • relax smooth muscle in bronchioles
  • increase stroke volume of the heart
  • increase heart rate
  • cause vasoconstriction to raise blood pressure
  • stimulate conversion of glycogen to glucose
  • dilate pupils
  • increase action of gut
  • cause body hair to erect
• Adrenal cortex - uses cholesterol to produce certain steroid hormones that can:
  • control concentrations of Na and K in blood
  • control metabolism of carbohydrates and proteins in liver

Regulation of blood glucose

• The pancreas is both an exocrine and endocrine organ:
  • exocrine = secretion of enzymes through the pancreatic duct
  • endocrine = secretion of hormones from islets of langerhans
• Islets of langerhans consist of alpha and beta cells:
  • alpha cells secrete glucagon - causes blood sugar levels to rise
  • beta cells secrete insulin - causes blood…