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Homeostasis – Endocrine System

Homeostasis – Endocrine System. Chapter 8. The Endocrine System – 8.1. Hormones  chemical regulators produced by cells in one part of the body that affect cells in another part of the body. Endocrine hormones  produced in glands and secreted directly into blood .

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Homeostasis – Endocrine System

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  1. Homeostasis – Endocrine System Chapter 8

  2. The Endocrine System – 8.1 • Hormones chemical regulators produced by cells in one part of the body that affect cells in another part of the body. • Endocrine hormones  produced in glands and secreted directly into blood. • The adrenal gland, on top of the kidneys secretes the hormone adrenaline • Exocrine glands  secrete substances through ducts onto the body surface or into cavity. • Mucous & sweat

  3. The Endocrine System – 8.1 • Hormone Classification • Nontarget hormones – affect many tissues throughout the body • Growth hormone • long bone growth • Increases calcium retention, and strengthens and increases the mineralization of bone • Increases muscle mass • Increases protein synthesis • Stimulates the growth of all internal organs excluding the brain • Reduces liver uptake of glucose • Stimulates the immune system • Target hormones – affect specific cells or tissues in the body • Gastrin stimulates cells of the stomach to produce digestive enzymes.

  4. The Endocrine System • Chemical Messengers – how we know what we know? • 1889  von Mering and Minkowski with dog pancreases • If removed  slim and tired, ants • If present  normal, no ants • Pancreas controlled blood sugar • Radioactive tracers • Where hormones go and how they are broken down.

  5. The Endocrine System • Hormones do not affect all cells • Two types of hormones • Steroid Hormone made from cholesterol, include sex hormones, rings of CHO • Blood  ECF  Joins with receptor molecule in cytoplasm  complex enters nucleus  Joins chromatin which activates gene to start making a specific protein

  6. The Endocrine System • Protein Hormone made of chains of AA, include insulin and growth hormone • Blood  ECF  Joins to receptor site on outside of cell  Activates adenylyl cyclase  This enzyme converts ATP to cAMP  cAMP acts as a messenger activating enzymes in the cytoplasm.

  7. The Pituitary Gland • Gland at base of brain that, with hypothalamus, functions as a control centre coordinating the endocrine and nervous system. • Produces and stores hormones which are regulated by the hypothalamus • Posterior and Anterior lobes • Posterior  stores and releases hormones (ADH, oxytocin) • Anterior  produces its own hormones (GH, prolactin)

  8. Hormones & Blood Sugar - 8.2 • Pancreas contains two types of cells • Digestive enzyme producing cells • Hormone producing cells – islets of Langerhans: • produce insulin (beta)  released when blood sugar goes up and causes appropriate cells to become permeable to glucose. • produce glucagons (alpha)  released when blood sugar goes down and promotes the conversion of glycogen to glucose

  9. Diabetes  Insufficient production or use of insulin • After a meal you would experience hyperglycemia • Kidneys  high concentration of glucose in nephron pulls water out of the body • Three types • Type 1 (juvenile-onset)  early degeneration of beta cells, inject insulin to live, 10% of diabetics • Type 2 (adult-onset)  decrease in insulin production or efficiency, treated with sulfoamides which stimulate beta cells, 90% • Type 3 (gestational)  occurs in 2-4% of pregnancies, temporary yet increases risk • Banting and Best – isolated hormone (insulin) • Islet Cell Transplants

  10. Adrenal Glands • Made up of two glands • Adrenal Medulla – controlled by the nervous system, epinephrine and norepinephrine are produced (fight or flight response) • Increase blood sugar, heart rate • Adrenal Cortex – controlled by hormones • Glucocorticoids – associated with blood glucose levels and assist in dealing with stress (cortisol) • Mineralcorticoids – associated with regulation of salt-water balance, aldosterone increases sodium retention and therein water reabsorption.

  11. Hormones & Metabolism - 8.3 • Thyroid Gland • Thyroxine (T4) and triiodothyronine (T3) regulate body metabolism and the growth and differentiation of tissues. • T4 • Regulates metabolic rates • Sugars get oxidized faster by people with a “faster” rate of metabolism

  12. Thyroid Gland • Control of the hormones is accomplished by negative feedback • Metabolic rate decreases  hypothalamus gets signal  thyroid releasing hormone (TRH) is released  pituitary gland releases thyroid stimulating hormone (TSH)  blood transports TSH to thyroid and thyroxine is released  blood sugar goes up due to thyroxine stimulating increased sugar utilization. • The process gets shut off when thyroxine levels get high as it inhibits the release of TRH

  13. Parathyroid Gland • Responds to immediate surroundings to help maintain homeostasis…a little different then other endocrine glands which are regulated by hormones. • Low Ca2+ levels in blood cause parathyroid hormone (PTH) to be released which corrects that issue (absorb more from intestines and kidneys and break down bones)

  14. Anterior Pituitary Gland • Produces growth hormone (somatotropin) • Increases growth of bones and cartilage, if growth plates have fused, other bones will respond  acromegaly • Increases muscle cell size and connective tissue by promoting protein synthesis and inhibiting protein breakdown. • Relationship between aging and GH. • As you get older production of growth hormone decreases. Growth hormone is responsible for stimulating ribosomes to follow genetic information for protein synthesis. • Cellular repair and protein replacement is compromised…protein is often replaced by fat as we age.

  15. Stress – 8.4 • Connection between long-term stress from a noxious stimulus. • A general adaptation syndrome results from exposure to prolonged stress • Stress Hormones  (p.388, table 1). • More energy required so hormones make more glucose available in blood • Increase in blood pressure and an elevated metabolic rate • Problems with Long-Term Stress (p.389, table 2) • Steroids – what do you think? • p. 391, table 3

  16. Reproductive Hormones – 8.5 • Male Reproductive System • Sex hormones – androsterone & testosterone produced in the interstitial cells (between seminiferous cells) of the testes. • Androsterone (ADT) is a steroid hormone with weak androgenic activity. It is made in the liver from the metabolism of testosterone • Testosterone stimulates spermatogenesis (spermatogonia divide and mature); influences development of male secondary characteristics at puberty • Hypothalamus and pituitary gland control the production of sperm and male sex hormones

  17. Male Reproductive System • Negative feedback ensures adequate numbers of sperm cells and testosterone are maintained. • Pituitary produces and stores gonadotropic hormones which regulate functions of testes: • Follicle stimulating (FSH)  promotes production of sperm cells • Luteinizing (LH)  promotes production of testosterone • Gonadotropin-releasing (GnRH)  hypothalamus secretes GnRH to the pituitary to release FSH and LH • Once high levels of testosterone are detected by the hypothalamus, negative feedback is activated in that GnRH stops being released.

  18. Female Reproductive System • Oogenesis & Ovulation • Ovaries contain fibrous connective tissue and small groups of cells called follicles • Follicles are made up of two types of cells • Primary oocyte - contain 46 chromosomes, undergoes meiosis, ovum • Granulosa cell – nutrient production for oocyte • 400 000 total follicles in each ovary  approximately 400 will mature in a woman’s life • birth defects and older follicles?

  19. Menstrual Cycle • Flow phase – shedding of endometrium (5 days) • Follicular phase – development of follicles within ovary, estrogen secreted (day 6-13) • Ovulatory phase – egg bursts from ovary, estrogen and progesterone released (endometrium development). Progesterone inhibits further ovulation and prevents contractions (day 14). • Luteal phase – preparation of uterus for fertilized egg. No fertilization means estrogen and progesterone decrease  weak contractions which cause endometrium to pull away from uterus.

  20. Hormonal Control of the Female Reproductive System • Hypothalamus-pituitary complex regulates estrogen and progesterone via gonadotropins • FSH and LH • GnRH signals puberty and allows release of FSH and LH • Negative feedback  as estrogen levels increase the pituitary gland picks this up and turns off FSH • Positive feedback  as estrogen levels increase the pituitary gland picks this up and releases more LH

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