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Endocrine System

Endocrine System. Chapter 39. Group of cells or organ that releases (secretes) a substance that will be used somewhere else in body Exocrine glands – release secretions via ducts (ex: sweat glands) Endocrine glands – release secretions directly into bloodstream. Gland. Made of glands

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Endocrine System

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  1. Endocrine System Chapter 39

  2. Group of cells or organ that releases (secretes) a substance that will be used somewhere else in body Exocrine glands – release secretions via ducts (ex: sweat glands) Endocrine glands – release secretions directly into bloodstream Gland

  3. Made of glands Communication system Endocrine glands produce hormones Hormones are distributed to body cells Endocrine System

  4. Hormones • Chemicals that act on target cells & tissues • Travel through bloodstream to target cells & attach to target cells • Produce a response on those target cells • Target cells – have receptors (locations for hormone to bind) for a hormone

  5. Endocrine System Glands • Hypothalamus • Pituitary gland • Thyroid • Parathyroids • Adrenal glands • Pineal body • Thymus • Pancreas • Reproductive glands (incl. ovaries & testes)

  6. Specialized cells located in lower central part of brain Influenced by levels of hormones in blood & by sensory information coming from CNS Hypothalamus

  7. Main link between endocrine & nervous systems Controls the pituitary gland (has nerve cells that release chemicals that regulate pituitary gland) Hypothalamus

  8. Located at base of the brain beneath the hypothalamus Makes/secretes hormones that control body functions & several other endocrine glands (most important part of the endocrine system) Pituitary Gland

  9. Hypothalamus provides sensory information from CNS to pituitary. Pituitary production & release of hormones acts in response to factors such as emotions, environmental changes. Pituitary & Hypothalamus

  10. Pituitary & Hypothalamus

  11. Pituitary Gland – Hormones Secreted • ADH (antidiuretic hormone) • Oxytocin • FSH (follicle-stimulating hormone) • LH (luteinizing hormone) • TSH (thyroid-stimulating hormone) • ACTH (adreno-corticotropic hormone) • GH (growth hormone) • Prolactin • MSH (melanin-stimulating hormone)

  12. Located at base of neck & wraps around trachea Regulates body’s metabolism(breaking down, putting together materials such as food) Thyroid

  13. Thyroid - Hormones • Thyroxine – affects metabolic rates of all body cells - increased levels of thyroxine = increased rate of cellular respiration (more energy released by cells) • Calcitonin – decreases level of calcium in blood

  14. 4 glands on back surface of thyroid Work with thyroid to maintain homeostasis in amount of calcium in blood PTH (parathyroid hormone) increases reabsorption of Ca in kidneys & uptake in digestive system Parathyroid Glands

  15. Adrenal Glands • 2 glands; 1 on top of each kidney • Help body respond to stress • 2 parts: adrenal cortex & adrenal medulla

  16. Adrenal Glands - Hormones • Corticosteroids - about 24 different hormones produced by adrenal cortex • Aldosterone – regulates reabsorption of Na+ & excretion of K+ by kidneys • Cortisol – regulates metabolism of carbs, fats, proteins • Epinephrine • Norepinephrine

  17. Adrenal Glands – “Fight or Flight” • Result of adrenal medulla responding to stress stimulus • Nerve impulses from sympathetic nervous system stimulate adrenal medulla • Release of epinephrine & norepinephrine • General increase in body activity prepares body for intense physical activity

  18. Pineal Gland • Located deep within brain • Involved in biological rhythms such as sleep • Secretes melatonin

  19. Thymus • In top portion of chest • Stimulates production of cells involved in immune system

  20. Also part of digestive system As endocrine gland, regulates amount of glucose in blood. Certain cells in it release hormones Islet of Langerhans- cells that release insulin & glucagon Pancreas

  21. Pancreas – Insulin & Glucagon • Insulin – causes cells in liver to take sugar (glucose) from blood & store it • Glucagon – stimulates cells in liver to release glucose

  22. Pancreas – Insulin & Glucagon • Diabetes mellitus – disease caused when pancreas does not produce enough insulin • What happens if the pancreas does not produce enough insulin? • Diabetes type 1- pancreas does not secrete insulin • Diabetes type 2- typically produce low to normal amount of insulin but cells do not respond to it

  23. Reproductive Glands (Gonads) • Produce gametes • Secrete sex hormones • Females • ovaries (produce eggs) • Estrogen, progesterone • Males • testes (produce sperm) • testosterone

  24. Feedback Loops • How nervous system uses endocrine system to regulate body conditions • Feedback inhibition – an increase in a substance sends signal to inhibit (stop) process that produces that substance • Analogy- turning on heater causes it to heat room until the air in the room reaches set temperature…then that warmer air causes heater to shut off

  25. Feedback Mechanisms • Negative – high levels of substance (hormone) slow production of it • Positive – low levels of substance increase production of it

  26. Negative Feedback - Insulin

  27. Blood sugar rises after eating -pancreas secretes insulin -Glucose stored as glycogen in liver Decrease in blood sugar - glucagon secreted - liver breaks down glycogen glucose released Regulation of Blood Glucose

  28. Hypothalamus senses low level of thyroxine in blood & sends signal (thyroid-releasing hormone) to pituitary gland Pituitary releases TSH Thyroid secretes thyroxine Hypothalamus releases less TSH as thyroxine level rises, less thyroxine produced Cycle continues Feedback Mechanism:Hypothalamus, Pituitary, Thyroid

  29. Leptin – hormone that helps regulate body weight, metabolism; produced by fat cells Decrease in body fat reserves = less leptin Less leptin in blood stimulates appetite center of brain Increase in leptin inhibits (prevents) hunger (negative feedback) Feedback Loops - Leptin

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