Biology 30 Rock the Diploma Unit notes & Problems

1. Biology 30Rock the DiplomaUnit notes & Problems Unit A – Endocrine system

2. Function of the endocrine System • whereas the nervous system makes short-term changes to restore homeostasis, the endocrine system works more slowly and tends to make more long-term changes • hypothalamus can be considered part of both the nervous and endocrine systems • hypothalamus regulates the pituitary gland, the master gland, through nerve stimulation • pituitary gland stimulates other endocrine glands secrete chemicals that affect the nerve activity of the hypothalamus

3. Hormones • chemical regulators, from the Greek word hormonwhich means “to set into motion” • hormones act to speed up or slow down body processes • produced in one part of the body, but affect another part • hormones do not affect all cells, only those with the correct receptor for that particular hormone • classified according to where they work (activation site) • most hormones target a specific target tissue • e.g. parathyroid hormone (regulates calcium levels) • e.g. gastrin (stimulates stomach cells to produce digestive enzymes) • non-target hormones affect cells throughout the body • e.g. human growth hormone (cause long bones to grow) • e.g. insulin (produced by the islets of Langerhans in the pancreas, secreted when blood sugar levels are high & regulates blood sugar) • e.g. epinephrine (adrenaline) (produced in times of stress)

4. Negative feedback control • negative feedback control system • prevents chemical imbalances in the body • when a hormone causes a body response, it triggers receptors and the response is inhibited, restoring homeostasis • e.g. pituitary gland produces male LH (luteinizing hormone)  activates testosterone production in the testes  testosterone levels increase  high levels of testosterone inhibits the release of male LH • when negative feedback systems fail, medical disorders can result • e.g. gigantism results from a failure to turn off the production of growth hormone

5. stimulus • high blood glucose Negative Feedback loops • responding gland • pancreas • Islet βcells • hormone produced • insulin • target • fat cells • liver cells • other cells • result • blood glucose falls • negative feedback • pancreas β cells no longer getting high blood glucose message • stop producing insulin • effects • conversion of glucose into glycogen • glucose uptake

6. Endocrine Glands Numbered: • Thyroid • Adrenal Cortex • Adrenal Medulla • Pancreas • Ovaries • Testes Not numbered: • hypothalamus • pituitary • parathyroid

7. Pituitary gland (Master gland) • pituitary gland • controls all other endocrine glands • connected to the hypothalamus in the brain • composed of two lobes • posterior lobe (towards the back) • receives hormones produced by the hypothalamus via special nerve cells • stores and releases hormones into the blood when necessary • antidiuretic hormone (ADH) • acts on the kidneys to increase water reabsorption by the kidney • oxytocin • acts on the uterus to initiate strong contractions during labour • acts on the mammary glands to trigger milk production

8. Pituitary gland(master gland) • anterior lobe (towards the front) • produces its own hormones • release of pituitary hormones regulated by the hypothalamus via other hormones • thyroid-stimulating hormone (TSH)  protein hormone • stimulates thyroid gland to release thyroxine, which stimulates cell metabolism • corticotrophin adrenal steroid (ACTH)  steroid hormone • stimulates adrenal cortex to release hormones involved in stress • growth hormone (GH) a.k.a. somatotropin protein hormone • targets most cells but effects are most pronounced in bones and cartilage, promotes growth • disorders related to GH • dwarfism – underproduction of GH • gigantism – overproduction of GH • acromegaly – continued growth of jaw, forehead, fingers and toes into adulthood • production inhibited when hypothalamus releases somatostatin

9. Pituitary gland(master gland) • follicle-stimulating hormone (FSH) • in ovaries, stimulates follicle development • in testes, promotes the development of sperm cells • luteinizing hormone (LH) • in ovaries, stimulates ovulation • in testes, stimulates the production of testosterone • prolactin (PRL) • targets mammary glands and stimulates and maintains milk production • production inhibited when hypothalamus releases dopamine

10. thyroid gland • located at the base of the neck in front of the windpipe • produce hormones involved in regulating metabolism and tissue growth and differentiation • thyroxine • promotes the oxidation of sugars and other nutrients • 50% released as heat • 50% converted to ATP • control of thyroxine • receptors in hypothalamus are informed of low metabolic rate  thyroid-releasing factor (TRF) stimulates pituitary to release TSH  carried by blood to thyroid gland  thyroid releases thyroxine stimulates cells to use more sugar • high levels of thyroxine inhibits TRF from hypothalamus

11. Thyroid Gland • thyroid disorders • goiter • caused by low levels of iodine, a main component of thyroxine • thyroxine no longer completes negative feedback loop • TRF keeps being produced, so thyroid keeps being stimulated, causing it to enlarge • why table salt contains iodine (iodized salt) • hyperthyroidism • people with high thyroid activity are typically • thin • warm, • overactive • excess glucose is converted to heat and ATP • hypothyroidism • people with low thyroid activity are typically • less thin • intolerant of the cold • tend to have dry skin • because excess glucose is converted to fat once glycogen stores are full

12. parathyroid gland • The parathyroid glands are small glands in the neck that produce parathyroid hormone. • Humans have four parathyroid glands, which are usually located behind the thyroid gland • control the amount of calcium in the blood and within the bones

13. Adrenal glands • located above each kidney • each gland is composed of two smaller glands • adrenal medulla • inner gland, • stimulated by sympathetic nerves in times of stress • produces hormones that initiate fight-or-flight response • epinephrine • norepinephrine

14. Adrenal glands • adrenal cortex • outer gland, surrounds adrenal medulla • produces two main types of hormones • glucocorticoids – e.g. cortisol • affect blood glucose levels • mineralocorticoids – e.g. aldosterone • help maintain body fluid levels • cortisol • help body recover from stress, increases amino acid levels in blood • converted into glucose by liver, or used in protein synthesis to repair damaged cells • as cortisol levels rise, cells within the hypothalamus and pituitary gland decrease the production of regulatory hormones and cortisol levels drop • aldosterone • increase sodium retention and water reabsorption by the kidney

15. Pancreas • contains two types of cells • digestive enzyme producing cells • hormone producing cells • located in Islets of Langerhans • produce two hormones • insulin • produced in the beta cells • released when blood sugar level is high • makes liver and muscle cells permeable to glucose • in the liver, excess glucose is stored as glycogen, which helps return blood glucose levels to normal • glucagon • produced in the alpha cells • causes an increase in blood sugar levels after a period of fasting causes blood glucose to drop • promotes the conversion of glycogen back to glucose

16. Regulating blood glucose

17. Diabetes • Several different types of diabetes exist, and there is often confusion on the part of the public about which type is which. • Unless “diabetes insipidus” is specified, it is assumed the type of diabetes being discussed is diabetes mellitus. • Type I and Type II diabetes are both subtypes of diabetes mellitus.

18. Diabetes