Hormones and Homeostasis

Homeostasis  Maintaining a stable internal environment despite unstable external conditions  Examples of systems with homeostasis  Blood pH  Maintained around 7.4  Uses buffers  Carbon dioxide concentration  Uses chemoreceptors in the walls of certain blood vessels  Blood glucose level  Body temperature  Water balance

Endocrine System  Consists of endocrine glands that produce hormones  Hormones are put into the blood stream  Only cells with special receptors will accept the hormones  Called target cells  Helps maintain homeostasis

Important Hormones  Thyroxin  Produced by the thyroid gland  Regulates metabolism in the cell  Regulates body temperature  Leptin  Produced by adipose tissue  Increased fat increases leptin secretion  Should decrease appetitie  Some people are leptin desensitized  Melatonin  Produced by the pineal gland  Regulates sleep cycles  Melatonin pills can be used to help induce sleep in children and when jet lagged from travel

Negative Feedback Loop  Control of a process by the result or effect of the process  Requires  Sensors to measure the current situation  A center in the brain that knows the optimum value of the situation  A way of bringing the situation to the optimum value  When this occurs the center turns off the mechanism used to bring it to optimum  Action changes things so that action is no longer needed

Negative Feedback Loop

Blood glucose regulation  Done with hormones located in the islets of langerhans (in the pancreas)  Contain chemoreceptors which are sensitive to the levels of glucose in the blood  Levels rise after a meal  Levels drop after exercise  If blood levels are too low  The alpha cells will release glucagon  Protein hormone that travels to all parts of the body but with the liver being the target  Liver cells respond by converting glycogen into glucose  Will also convert amino acids to glucose  If blood levels are too high  Beta cells will release insulin  Protein hormone released into the blood  Makes muscle cells absorb glucose  Makes liver cells turn glucose into glycogen  In fat tissues glucose is turned into fat

Diabetes  A metabolic disorder where the person does not produce enough insulin or the body does not properly react to insulin  Type I  No insulin or an insufficient level is produced by the beta cells  Caused by the bodies producing antibodies to the insulin or the beta cells  Treatment  Injection of insulin  Pancreas transplant  Type II  Insufficient levels produced or cells of the body become less sensitive to it  Unknown causes but might be  Obesity  Increase in age  Family history  Treatment  Reduced carbohydrate intake  Increased physical activity  Weight loss  medication Bozeman