Hormones that Affect Blood Sugar Insulin, glucagon, epinephrine, norepinephrine and cortisol

Pancreatic enzymes The pancreas contains two types of cells: – one type produces digestive enzymes – the other type produces hormones The hormone-producing cells are located in structures called the islets of Langerhans

Pancreas More than 2000 tiny islets, each containing thousands of cells, are scattered throughout the pancreas.

Pancreas The islets contain beta and alpha cells that are responsible for the production of two hormones: – insulin – Glucagon

Effect of Insulin Insulin is produced in the beta cells of the islets of Langerhans and is released when blood sugar levels increase.

Effect of Insulin Insulin causes cells of the muscles, the liver, and other organs to become permeable to the glucose The glucose leaves the blood and enters the cells

Effect of Insulin In the liver, the glucose is converted into glycogen, the primary storage form for glucose. Insulin enables the blood sugar level to return to normal and to maintain homeostasis

Glucagon Glucagon is produced by the alpha cells of the islets of Langerhans, Glucagon is released when blood sugar levels are low, such as after periods of fasting.

Glucagon Glucagon promotes the conversion of glycogen to glucose, which is released into the blood. As glycogen is converted to glucose in the liver, the blood sugar level returns to normal.

Adrenal Glands The adrenal glands are located above each kidney. Each adrenal gland is made up of two glands encased in one shell.

Adrenal Glands The inner gland, the adrenal medulla, is surrounded by an outer casing, called the adrenal cortex. The adrenal medulla is regulated by the nervous system The adrenal cortex is regulated by hormones

Adrenal medulla The adrenal medulla produces two hormones: – epinephrine (also known as adrenaline) – norepinephrine (noradrenaline) The nervous system and the adrenal medulla are linked by the fact that both produce epinephrine.

Reaction to Stress The hormone-producing cells within the adrenal medulla are stimulated by sympathetic nerves in times of stress. Epinephrine and norepinephrine are released from the adrenal medulla into the blood.

Effects of Epinephrine and Norepinephrine Blood sugar level rise Glycogen is converted into glucose The increased blood sugar level ensures that a greater energy reserve will be available for the tissues of the body.

Effects of Epinephrine and Norepinephrine Epinephrine and norepinephrine cause an increase in: – heart rate increase – breathing rate – cell metabolism

Effects of Epinephrine and Norepinephrine Blood vessels dilate, allowing more oxygen and nutrients to reach the tissues. The iris of the eye dilates, allowing more light to reach the retina

The Adrenal Cortex The Adrenal cortex produces three different types of hormones: – the glucocorticoids – the mineralocorticoids – small amounts of sex hormones

Glucocorticoids The glucocorticoids are associated with blood glucose levels. Cortisol increases the level of amino acids in the blood in an attempt to help the body recover from stress. The amino acids are converted into glucose by the liver, thereby raising the level of blood sugar. Any of the amino acids not converted into glucose are available for protein synthesis. The proteins can be used to repair damaged cells.

Effects of Cortisol Fats in adipose tissue are broken down into fatty acids. A second source of energy is provided, helping conserve glucose in times of fasting. Under the influence of cortisol, blood glucose uptake is inhibited in many tissues, especially in the muscles

Long-term stress responses The brain identifies stressful situations. The hypothalamus sends a releasing hormone to the anterior lobe of the pituitary The pituitary secretes corticotropin, also called adrenocorticotropic hormone (ACTH). The blood carries the ACTH to the target cells in the adrenal cortex.

Long-term stress response The cells of the adrenal cortex secrete mineralocorticoids and glucocorticoids which are carried to target cells in the liver and muscles. As cortisol levels rise, cells within the hypothalamus and pituitary decrease the production of regulatory hormones, and, eventually, the levels of cortisol begin to fall. This process is called a long-term stress response.

Short-term stress response The brain identifies stressful situation The hypothalamus sends a nerve signal to the adrenal medula The adrenal medulla secretes epinephrine and norepinephrine.

Mineralocorticoids Aldosterone is a mineralocorticoids prdoced by the adrenal cortex Secretion of aldosterone increases sodium retention and water reabsorption by the kidneys, thereby helping to maintain body fluid levels.

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