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The Endocrine System

The Endocrine System. Chemical Control. The Endocrine System. The endocrine system has similar functions to the nervous system Controls and integrates functions in the body Growth of body and reproductive organs Mobilization of defences to stress Balance of chemicals in blood

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The Endocrine System

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  1. The Endocrine System Chemical Control

  2. The Endocrine System • The endocrine system has similar functions to the nervous system • Controls and integrates functions in the body • Growth of body and reproductive organs • Mobilization of defences to stress • Balance of chemicals in blood • control of O2 use by cells

  3. Hormones • The endocrine system uses chemical messengers to “communicate” with targets • A hormone is a specific messenger molecule synthesized and secreted by a group of specialized cells called an endocrine gland. • endocrine glands are ductless, their secretions (hormones) are released directly into the bloodstream and travel to target organs. • Note that this is in contrast to digestive glands (exocrine), which have ducts for releasing the digestive enzymes. Endocrine/Parathyroid hormone animation MHHE

  4. Hormones and Receptors • Each hormone’s shape is specific and can be recognized by only specific binding sites on target cells called hormone receptors.

  5. Hormones • There are two general groups of hormones. They are classified by chemical structure, not function • Steroid hormones • Peptide hormones (protein related)

  6. Steroid Hormones • steroid hormones • Lipid molecules made from cholesterol • Not water soluble • Male and Female sex hormones • testosterone, estrogen, progesterone • Cortisol • Enables stress recovery

  7. Peptide Hormones • peptide hormones • Chains of amino acids • Water soluble • most numerous/diverse group of hormones. • Insulin, glucagon, growth hormone

  8. Hormones and Receptors • The regulation of hormones depends on negative feedback loops to maintain balance and homeostasis

  9. Endocrine Glands • Hypothalamus and pituitary gland • The pituitary gland is called the “master gland” as many of the hormones released by the pituitary control the other endocrine glands of the body • the pituitary is under the control of the hypothalamus which uses both neural and hormonal communication

  10. Hypothalamus and pituitary

  11. Hypothalamus and pituitary • Neural control by hypothalamus • Neurons from the hypothalamus run axons down into the posterior lobe of the pituitary gland • ADH and oxytocin are secreted from axon terminals which then move into capillaries for circulation

  12. Hypothalamus & post. pit.

  13. Posterior Pituitary Hormones • ADH • Promotes water reabsorption from collecting duct of nephrons in the kidneys • Oxytocin • Promotes uterine contraction (+ feedback) • Promotes lactation (breast milk production) • Causes smooth muscle contraction in male and female reprod. organs

  14. Hypothalamus & anterior pit. • Hormonal control by hypothalamus • Neurons in hypothalamus secrete releasing hormones (releasing factors) into capillaries in the hypothalamus which travel to the anterior pituitary

  15. Hypothalamus & anterior pit.

  16. Anterior Pituitary Gland • Hormones released from the anterior pituitary include: • Thyroid stimulating hormone (TSH) • Corticotropin adrenal steroid (ACTH) • Somatotropin or Growth Hormone (STH) or (GH) • Follicle stimulating Hormone (FSH) • Luteinizing Hormone (LH) • Prolactin (PRL) Two animations Life Wire Endocrine/TSH animation MHHE

  17. Feedback Control

  18. Other Endocrine Glands

  19. Thyroid Gland • Thyroid hormones regulate metabolism, therefore body temperature and weight

  20. Thyroid Gland • The thyroid hormones contain iodine which is needed to manufacture the thyroid’s hormones. • If a person lacks iodine in their diet, the thyroid cannot make the hormones, causing a hormonedeficiency • In response to the body’s feedback loops calling for more thyroid hormones, the thyroid gland enlarges to attempt to compensate (goiter)

  21. Thyroid Gland • Thyroid Hormores (TH) • Thyroxin Hormone • Regulates metabolic rate • Increase thyroxine = increase metabolism • Slower metabolism • Slower use of glucose = gylcogen storage and any excess stored as fat

  22. Parathyroid Glands • Located on the posterior surface of the thyroid gland

  23. Parathyroid Glands • Secrete parathyroid hormone (PTH) which raises blood Ca2+ • Blood Ca2+ increased by • Being released from bone • Increase reabsorption from distal tubule of kidney • Activation of vitamin D (stimulates uptake of Ca2+ from intestine) • Ca2+ regulation animation

  24. The Adrenal Glands • Located above each kidney, the adrenal glands have two main divisions • Adrenal Medulla • Adrenal Cortex

  25. Adrenal Medulla • The adrenal medulla is involved in responses to stressful stimuli • Regulated by sympathetic neural pathways • During stress, epinephrine and norepinephrine are released into the blood which promotes increases in: • blood glucose levels • HR, BP, & vasodilation, • pupil dilation • metabolism

  26. Adrenal Cortex • Produces steroid hormones that help the body cope with stress • Regulated by hormones from the ant. pituitary • Make sure that brain gets glucose • Forces other cells to use fat and amino acid metabolism for energy • Three types of hormones • Glucocorticoids • Mineralocorticoids • Sex hormones

  27. Adrenal Cortex Hormones • Glucocorticoids • Cortisol • Increases amino acid levels in the blood so that they can be • converted to glucose in the liver • used to repair damaged cells • Excess amounts have an antiinflammatory action • Controlled by adrenocorticotropin hormone (ACTH) • Trace the hormonal control pathway

  28. Adrenal Cortex Hormones • Mineralocorticoids • Aldosterone • Helps maintain body’s water balance • Secreted when blood pressure/volume drop below normal • Increases Na+/water reabsorption in kidneys • Controlled by ACTH

  29. Adrenal Cortex Hormones • Sex Hormones from Adrenal Cortex • Dehydroepiandrosterone (DHEA) • Stimulates sex drive • induces labor • We’ll talk about this when you’re older!

  30. Pancreas • Produces 2 hormones responsible for maintaining constant blood glucose levels • Insulin • Glucagon

  31. Insulin • Produced by beta cells in the islets of Langerhans • Released into circulatory system when glucose levels are higher than normal • where is blood glucose level “sensed”? • binds with receptors on cell membranes to open glucose channels • Liver cells take in glucose and store excess as glycogen • Note: know Diabetes Mellitus inside and out

  32. Insulin

  33. Glucagon • Produced by alpha cells in islets of Langerhans • Glucagon is released when blood sugar levels are low • Promotes release of glucose from glycogen stores in liver

  34. Honorable Mentions • Pineal Glands • Melatonin secreted when dark • Promotes sleep • Prostaglandins • Have affect on localized cell area • Aid in response to stress • Ovary and Testis will be covered in next section

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