The Endocrine System

1. The Endocrine System

2. What is the Endocrine System • Group of ductless glands that secrete substances (hormones) directly into the bloodstream • Do not secrete into an organ but directly into the bloodstream • These hormones have a direct effect on a target organ/tissue

3. Hormones • chemical substances produced & secreted by the endocrine glands • Purpose • Stimulate exocrine glands • Stimulate other endocrine glands • Regulate growth & development • Regulate metabolism • Maintain fluid & electrolyte balance • pH of body fluids • Control reproduction processes

4. How do they work? • Negative Feedback – acts on a stimuli & then feedback to the gland; gland then decreases the secretion • Releasing hormones – tell other glands to secrete hormones • Antagonistic – effect blood chemistry

5. Different glands • Pituitary • Thymus • Thyroid • Parathyroid • Pancreas • Adrenals • Ovaries • Testes

6. Pituitary • “Master Gland” • Works closely with the hypothalamus • Hangs from the hypothalamus & enclosed in the sphenoid bone • Has an anterior & posterior secreting area

7. Anterior Posterior • Growth Hormone (GH) • Thyroid stimulating hormones (TSH) • Adrenocorticotropic hormone (ACTH) • Prolactin • Follicle-stimulating hormone (FSH) • Luteinizing hormone • Antidiuretic hormone (ADH) • oxytocin

8. Antidiuretic Hormone (ADH) • Increases the reabsorption of H20 from the kidneys • This decreases the amount of urine produced • Decreases sweating • Increases blood volume; Increases BP • Hypothalamus “monitors” the saltiness of the blood • Hypothalamus tells the pituitary to release ADH • Alcohol inhibits the secretion of ADH

9. Oxytocin • Stimulates the uterus to contract • Releases milk • Dilation of the cervix triggers the pituitary to secrete • Positive feedback; delivery of baby & placenta will decrease the release • Placenta secretes large amounts of oxytocin (Trigger labor?) • “let down” effect from nipples • ADH & oxytocin promote mother-baby bonding

10. Growth Hormone (GH) • Also known as somatotropin • Increases amino acids into cells • Increases protein synthesis • Increases mitosis in cells • Bones • muscles • As adults, replaces tissue that has aged • Growth Hormone Releasing Hormone (GHRH) is produced by the hypothalamus when hypoglycemia & exercise to INCREASE blood amino acids

11. Thyroid Stimulating Hormone (TSH) • Acts on the thyroid • Causes the thyroid to produce T3 & T4 • Hypothalamus tells the pituitary to produce

12. Adrenocorticotropic (ACTH) • Acts on the adrenal glands • Causes the release of cortisol & other adrenal hormones • Activates in stressful state • Injury • Exercise • Disease • Hypoglycemia (hunger)

13. Prolactin • Produced for lactation • Maintains milk production in women • Prolactin releasing hormone (PRH) & Prolactin inhibiting hormone (PIH) from hypothalamus

14. Follicle Stimulating Hormone (FSH) • Development (maturity) of ova (eggs) every 28 days • Stimulates the ovaries to secrete estrogen • Initiates sperm production in testes • Gonadotropin-releasing hormone (GnRH) by hypothalumus • Inhibin – by the ovaries or testes to decrease secretion of GnRH

15. Luteinizing Hormone • Gonadotropic hormone • Women – responsible for ovulation • Follicle (ovum) develops into a corpus luteum (secretes progesterone) • Men – causes the cells in the testes to secrete testosterone

16. Thyroid Gland • Located front of the trachea • Divided into Left Lobe; Right Lobe; & Isthmus(Middle) • Produce T3 & T4 • Needs iodine for hormones (T3 – 3 molecules of iodine) (T4 – 4 molecules of iodine) • Calcitonin

17. T3 & T4 • Regulate energy production • Protein synthesis • Increases cellular respiration • Increases energy & heat production • Increases protein synthesis • Needed for normal mental development & physical growth • Maturation of sex organs • Controls day-to-day metabolic rate • Can live without but needed for optimal physical & mental ability & growth