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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 theislets of Langerhans
Pancreas
• More than 2000 tiny islets, each containing thousands of cells, are scattered throughout the pancreas.
http://www.leedsth.nhs.uk/sites/diabetes/teenage/IsletsofLangerhans.php
Pancreas
• The islets contain beta and alpha cells that are responsible for the production of two hormones: – insulin – Glucagon
http://pathology2.jhu.edu/pancreas/anatphys/pancpart.htm
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.
http://www.biology.arizona.edu/biochemistry/problem_sets/carbomet/05t.html
Adrenal Glands
• The adrenal glands are located above each kidney.
• Each adrenal gland is made up of two glands encased in one shell.
http://genericlook.com/anatomy/Adrenal-Gland/
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
http://iahealth.net/adrenal-gland/
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.