6.6 – Hormones, homeostasis and reproduction

Homeostasis Keeping the body within certain physiological limits pH, CO2 and glucose concentrations of blood, water balance, and body temperature Much energy in your body is used to maintain homeostasis Negative feedback mechanisms – work like a thermostat a. If certain limit is reached, triggers a response to bring body back within normal range Nervous and endocrine systems work together to maintain a. Autonomic nervous system triggers glands to release hormones which travel through blood to target cells

Hormones and their functions A. Thyroxin – amino acid and iodine 1. Thyroid – butterfly shaped gland in neck 2. 2 forms – T3 and T4 (# of iodines) 3. Target cells – most all in body 4. Transcription regulator (stimulates) 5. Increases metabolism in cell -> requires more energy -> requires more O2 6. Also helps regulate body temp (increased activity increases temp)

Leptin Produced by adipose tissue More fat -> more leptin produced Target cells = hypothalamus Function is to decrease appetite (since there is enough supply in reserves) Obesity – desensitized to leptin, tend to have higher levels, but does not suppress appetite

Melatonin Produced by pineal gland in brain Regulates circadian rhythms Produced mostly at night Production disrupted by exposure to light at irregular times

III. Diabetes A. Insulin – produced by beta cells in pancreas – decreases blood sugar 1. Opens protein channels on cell membranes so that glucose goes into the cell (and out of the blood) 2. Stimulates hepatocytes (liver cells) to convert glucose to glycogen B. Glucagon produced by alpha cells in pancreas – increases blood sugar 1. Stimulates liver to break down glycogen into glucose

Hyperglycemia (high blood sugar) Type I – beta cells don’t produce enough insulin, a. Genetic, auto-immune, unknown b. Controlled with insulin injections Type II – body cell receptors don’t respond to insulin (insulin-resistance) a. Genetic, over-consumption of sugar, obesity b. Treated with diet and various medications

Effects 1. Blindness 2. Kidney failure 3. Nerve damage 4. High risk of cardiovascular disease 5. Poor wound healing