Endocrine System Hormones Homeostasis Regents Biology Homeostasis u

Endocrine System Hormones & Homeostasis Regents Biology

Homeostasis u maintaining internal balance in the body organism must keep internal conditions stable even if environment changes also called “dynamic equilibrium” u example: body temperature humans: w too cold = shiver w too warm = sweat Regents Biology lizard: w too cold = bask in sun w too warm = hide in shade

Regulation How we maintain homeostasis u nervous system u nerve signals control body functions endocrine system hormones chemical signals control body functions Regents Biology

Nervous System Control Feedback Controlling Body Temperature nerve signals brain sweat high body temperature low brain constricts surface shiver blood vessels Regents Biology nerve signals dilates surface blood vessels

Hormones Why are hormones needed? chemical messages from one body part to cells in other parts of body u communication needed to coordinate whole body u maintaining homeostasis u Regents Biology growth hormones

Endocrine System Endocrine system releases hormones u glands which secrete (release) chemical signals into blood Regents Biology chemicals cause changes in other parts of body w growth hormones w sex hormones w response hormones w metabolism hormones w and more….

Responding to hormones Lock and key system u hormone fits receptor on “target” cell target cell secreting cell Regents Biology can’t read signal nontarget cells can’t read signal

Glands Pineal u Pituitary u insulin, glucagon Ovary u adrenaline Pancreas u thyroxine Adrenal u many hormones: master gland Thyroid u melatonin estrogen Testes u testosterone Regents Biology

Feedback Maintaining homeostasis hormone 1 lowers body condition gland high specific body condition low raises body condition Regents Biology gland hormone 2

Negative Feedback Response to changed body condition u if body is high or low from normal level u signal tells body to make changes that will bring body back to normal level once body is back to normal level, signal is turned off gland hormone 1 lowers body condition high Regents Biology specific body condition

Endocrine System Control Regulation of Blood Sugar Feedback insulin liver stores sugar body cells take up sugar from blood pancreas high liver blood sugar level (90 mg/100 ml) low triggers hunger Regents Biology liver releases sugar liver pancreas glucagon reduces appetite