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…