Endocrine System Anatomy and Physiology Notes Ch. 13d Endocrine System Anatomy and Physiology

Adrenal Glands The adrenal glands sit on top of each kidney. There are 2 parts of the adrenal gland. The center is called the adrenal medulla and an outer part called the adrenal cortex.

The adrenal medulla is connected to the sympathetic division of the nervous system. The adrenal cortex makes up most of the adrenal gland.

Hormones of the Adrenal Medulla The adrenal medulla secretes 2 main hormones – epinephrine (or adrenalin) and norepinephrine (noradrenalin). The effects of these hormones are: increased heart rate, elevated blood pressure, increased breathing rate, and decreased digestive activity. This part of the adrenal gland is very important for our “fight or flight” response.

Hormones of the Adrenal Cortex The adrenal cortex produces more than 30 different steroids, including several hormones (corticosteroids). Some of these hormones are vital and a person cannot live without them. The most important adrenal cortex hormones are aldosterone, cortisol, and certain sex hormones.

Aldosterone This hormone helps regulate the concentration of mineral electrolytes like sodium and potassium ions. It causes the kidney to conserve sodium ions and get rid of potassium ions. This hormone responds to changes in blood pressure and sodium ion concentration. This hormone is also very important for maintaining blood pressure.

Cortisol Cortisol – affects glucose metabolism. It can also influence protein and fat metabolism. It inhibits the making of protein in certain tissues increasing the blood concentration of amino acids. It stimulates the liver to make glucose. It promotes the release of fatty acids from fat tissue so we don’t use all of our glucose up.

Sex Hormones The adrenal gland secrete male hormones but some of them are converted into female hormones by the skin, liver, and fat tissue. These hormones are important to early development of the reproductive organs.

Pancreas The pancreas has 2 functions – to secrete digestive juice through a duct and to release hormones into body fluids. The hormones secreted by the pancreas are alpha cells (secrete glucagon), beta cells (secrete insulin), and delta cells (secrete somatostatin).

Hormones of the Pancreatic Islets Glucagon – stimulates the liver to break down glycogen into glucose. It also turns fats into fatty acids and glycerol. This prevents hypoglycemia – blood glucose levels getting too low.

Insulin – stimulates the liver to form glycogen from glucose Insulin – stimulates the liver to form glycogen from glucose. It also helps move glucose through membranes of cells that have insulin receptors like fat tissue, liver, cardiac muscle, and skeletal muscle. Overall insulin decreases blood glucose levels and makes and stores fat.

Somatostatin – helps regulate glucose being made by inhibiting the secretion of glucagon and insulin.