Chapter 11 The Endocrine System

Endocrine vs. Exocrine Exocrine – have ducts (tubes) Endocrine - ductless Secreted directly into body fluids Regulated by NS and ES Target cells Steroid hormones – link to cell, bind to nucleus, activate genes to make specific proteins

Responding to hormones Lock and key system –hormone fits receptor on “target” cell target cell non- target cells secreting cell can’t read signal

Prostaglandins Made from organs Act locally Potent Produced just before released Produce diverse and opposite effects

Control of Hormonal Secretions Negative feedback Hypothalamus  pituitary  other endocrine glands NS  glands directly Changes in internal environment  glands Example: pancreas

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

Glands

Pituitary – base of brain, anterior and posterior lobes, **master gland Growth Hormone (GH) – stimulates size and division increases Pituitary dwarfism and giantism Prolactin (PRL) – stimulates and sustains milk production Effect in males not understood TSH – controls thyroid secretions FSH – follicle-stimulating hormone

Thyroid – in neck Thyroxine – regulates metabolism of carbohydrates, proteins, and lipids Requires iodine to make Hyper and hypo Calcitonin – regulates blood calcium and phosphate As calcium goes up, calcitonin increases This triggers osteoblasts and kidneys.

Goiter Why we use iodized salt

Thyroid Gland (thyroxin) Hypo Secretion (too little) –Low metabolic rate –Person is tired and often over weight Hyper Secretion (too much) –High metabolic rate –Person is “Hyper” and often thin

Parathyroids – in thyroid Parathyroid hormone (PTH) – increases calcium in blood Triggers osteoclasts and kidneys Hyper – bones soften and easily fracture, kidney stones Hypo – tetanic contractions

Pancreas – inferior to stomach Exocrine and endocrine Islets of Langerhans Alpha cells – glucagon – increases blood sugar – how? Beta cells – insulin – decreases blood sugar – how? SkR4http:// SkR4

liver pancreas liver Regulation of Blood Sugar blood sugar level (90mg/100ml) insulin body cells take up sugar from blood liver stores sugar reduces appetite glucagon pancreas liver releases sugar triggers hunger high low Feedback Endocrine System Control Diabetes: insulin deficiency- results in an elevated blood sugar level (glucose)

Diabetes Mellitus Type I – insulin-dependent (IDDM) Immune system destroys beta cells Usually before age 20 Type II – non-insulin-dependent (NODDM) Beta cells function, but body cells lose sensitivity to insulin Usually after age 40

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