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Endocrine System

Endocrine System. Endocrine System. Primary function: produce ____________ Works together with __________ system to maintain ____________ Hormones act on specific target cells to produce specific effects No _________. Endocrine System vs. Nervous System.

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Endocrine System

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  1. Endocrine System

  2. Endocrine System • Primary function: produce ____________ • Works together with __________ system to maintain ____________ • Hormones act on specific target cells to produce specific effects • No _________

  3. Endocrine System vs. Nervous System Characteristic Endocrine System Nervous System General Function Maintain homeostasis Maintain homeostasis Reaction to stimuli slow rapid Duration of effect long short Target tissue entire body muscles and glands Chemical messenger hormone neurotransmitter Messenger producing cell endocrine gland neurons Distance to target cells long (via bloodstream) short (across synaptic space)

  4. Exocrine/Endocrine Glands GlandExocrineEndocrine Pancreas digestive enzymes insulin, glucagon Ovary egg estrogen, progesterone Testes sperm testosterone Kidney urine erythropoietin

  5. Hormones • Chemical messengers produced by endocrine glands • Secreted into interstitial fluid and absorbed into blood vessels • Contact all cells in body • Produce effects only on cells containing specific receptors • __________ cell • ‘Lock and key’arrangement causes a change in activity of target cell • Growth hormone—all cells • Prolactin—mammary tissue

  6. Control of Hormone Secretion ___________ feedback systems (like a thermostat) • If hormone level is low: • Appropriate endocrine gland is stimulated to produce more hormone • Once adequate hormone concentration is attained in the bloodstream: • Stimulation of endocrine gland is reduced and production of the hormone is stopped/reduced

  7. Control of Hormone Secretion • Direct stimulation from the nervous system • Secretion of some hormones is stimulated by ________________ nerve impulses when an animal feels threatened. • “Fight or flight" response

  8. Hypothalamus • Part of _____________ section of brain • Controls activities of pituitary gland • Portal system of blood vessels links hypothalamus with anterior portion of pituitary gland • Modified neurons in hypothalamus secrete releasing and inhibiting hormones into portal blood vessels • Specific for a particular anterior pituitary hormone

  9. GHRH, GHIH (Don’t memorize) Thyrotropin releasing hormone (TRH) Gonadaotropin releasing hormone (GnRH) PRH, PIH Corticotropin releasing hormone (CRH) Hypophyseal Portal System Growth hormone Thyroid stim hormone (TSH) Follicle stim hormone (FSH) Luteinizing hormone (LH) Prolactin Posterior pituitary Oxytocin Antidiuretic hormone (ADH) Adrenocorticotropic hormone (ACTH) Melanocyte stim hormone (MSH)

  10. Hypothalamus Modified neurons in hypothalamus also secrete antidiuretic hormone (ADH) and oxytocin Transported to posterior pituitary (along neurons) for storage Released into the bloodstream by nerve impulses from hypothalamus

  11. Pituitary Gland (Hypophysis) Rostral • Two separate glands with different structures, functions, and embryological origins • Anterior pituitary - _______hypophysis; rostral portion • Stimulated by hypothalamus (portal system) and direct (neg) feedback from target tissues to produce hormones • Posterior pituitary - _______hypophysis; caudal portion • Stores and releases hormones produced in hypothalamus (oxytocin, ADH) Caudal

  12. Growth Hormone (GH) • a.k.a. somatotropin and somatotropic hormone • Promotes body growth in young animals • Helps regulate metabolism of proteins, carbohydrates, and lipids in all body cells • The effect of GH on protein metabolism is to encourage anabolism (synthesis of proteins by body cells) • The effects of GH on carb and lipid metabolism are linked. • While lipids are broken down via catabolism for energy production, the use of carbs (especially glucose) as energy sources is discouraged. • Less glucose is removed from the blood and hyperglycemia occurs (hyperglycemic effect). • Important for the body to maintain a balance between GH and insulin to control blood glucose levels.

  13. Prolactin 1. Baby sucks/stimulates 2. ↓PIH, ↑PRH 3-4. Stimulates milk glands • Helps trigger and maintain __________ in females • Secretion of milk by mammary glands • Prolactin production continues as long as ________ are stimulated by nursing or milking • When prolactin stimulation stops: • Milk production stops • Mammary gland shrinks to original/nonlactating size

  14. Thyroid-Stimulating Hormone (TSH) • a.k.a. Thyrotropin/Thyrotropic Hormone • Stimulates growth/development of thyroid gland and causes thyroid to produce its hormones. • Secretion regulated by: • Feedback (neg) from thyroid gland hormone • Thyroid hormone levels too low- TSH production increases • Thyroid hormone levels too high- TSH production diminishes

  15. Adrenocorticotropic Hormone (ACTH) • Stimulates growth/development of adrenal cortex and the release of some of its hormones • Regulated by: • Release of CRF from hypothalamus to anterior pituitary through portal system • Negative feedback from adrenal hormones and administered cortisones • During sudden stress, ACTH can quickly be released after the hypothalamus is stimulated to send out ACTH- releasing factor (CRF/CRH) to the anterior pituitary via the portal system

  16. Follicle-Stimulating Hormone (FSH) Males- stimulates __________________ in the testes Females—stimulates growth/development of ovarian follicles – where oogenesis occurs Also stimulates the cells lining the follicles to produce/secrete ____________ Used to superovulate

  17. Luteinizing Hormone (LH) • Completes follicle development in ovary • Increasing amounts of estrogens feedback to the anterior pituitary and cause reduced production of FSH and increased production of LH • LH levels reach a peak when follicle is fully mature • Usually causes _______________

  18. Luteinizing Hormone (LH) • After ovulation, LH stimulates cells in empty follicle to multiply and develop into ________ __________(CL) • CL produces progesterone necessary for maintenance of ______________ • In males, LH stimulates interstitial cells to produce _______________

  19. Melanocyte-Stimulating Hormone (MSH) • Controls color changes in pigment cells (melanocytes) of reptiles, fish, and amphibians • Administration of artificially large amounts of MSH to higher mammals can cause darkening of skin from melanocyte stimulation (↑ melanin) • Effect at normal levels in mammals unknown

  20. Posterior Pituitary Posterior pituitary Oxytocin ADH • ________(does NOT produce) two hormones produced in hypothalamus • ______________ _________(ADH) and _______________ • Transported from hypothalmus to post pituitary along axons and stored in nerve endings • Periodically released into bloodstream in response to nerve impulses from hypothalamus

  21. Antidiuretic Hormone (ADH) • Helps prevent diuresis • Receptors in hypothalamus detect changes in osmotic pressure (concentration) of blood (due to dehydration - hemoconcentration) • Generates nerve impulses from hypothalamus- causes release of ADH • ADH causes kidneys to reabsorb more water from urine and return it to bloodstream • Urine then more concentrated • ADH deficiency causes Diabetes ____________ (PU/PD occurs)

  22. Oxytocin • Effects on uterus: • Causes ____________ of myometrium at breeding and at parturition • Induces uterine contractions that aid transport of spermatozoa to oviducts • Stimulates uterine contractions that aid in delivery of fetus and placenta • Effect on active mammary glands: • Stimulation of teat/nipple by nursing or milking causes oxytocin release into bloodstream • Causes contraction of musclelikemyoepithelial cells around mammary gland alveoli and small ducts • Forces milk into lower parts of gland, making it accessible for nursing/milking (______ __________)

  23. Oxytocin- positivefeedback

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