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The Endocrine System

The Endocrine System. Nervous vs. Endocrine. Intro to Endocrine System Animation. Both systems oversee cell-to-cell communication using chemical signals Chemical signals both bind to receptor molecules Receptors are VERY specific to only respond to certain signals. Exocrine vs Endocrine.

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The Endocrine System

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  1. The Endocrine System

  2. Nervous vs. Endocrine Intro to Endocrine System Animation • Both systems oversee cell-to-cell communication using chemical signals • Chemical signals both bind to receptor molecules • Receptors are VERY specific to only respond to certain signals

  3. Exocrine vs Endocrine Classified by location of secretion Exocrine: Through tube or duct to a surface (outside) Ex: skin, lining of digestive tract Endocrine: Secrete into internal environment Help regulate metabolic processes How? Controlling rate of chemical rxns, aiding in transport of substances , regulating H2O and electrolytes Ex: Thymus, hypothalamus, pineal, adrenal

  4. Endocrine Glands Can be cell, tissue, or organ (gland) Secrete hormones Hormones are chemical messengers Diffuse from interstitial fluid into the blood stream, eventually acting on a target cell Target cell Receives the message Receptor for hormone Hormone creates a response in target cell Tropic hormones Hormone whose target cell is another endocrine gland

  5. Other Chemical Messengers “Local Hormones” Never reach bloodstream 2 types: Paracrine - affect neighboring cells Autocrine - affect only cell secreting them Prostaglandins Lipids messenger usually affecting organ secreted into Ex: inducing childbirth, treat glaucoma, treat erectile dysfunction

  6. Types of Hormones Two types: 1) Cholesterol Derivatives Ex: Steroids (estrogen, testosterone, aldosterone, cortisol) 2) Amino Acid Derivatives Ex: Amines (norepinephrine, epinephrine) Ex: Peptides (ADH, oxytocin) Ex: Proteins (Parathyroid hormones, growth hormones, prolactin) Ex: Glycoprotein (follicle-stimulating hormone, luteinizing hormone, thyroid-stimulating hormone)

  7. Hormone Action Steroid Hormone Characteristics: Must be carried by plasma proteins through blood Insoluble in water Made of rings of carbon and hydrogen atoms Action sequence of events for steroids: Diffuse into any cell Binds to receptor in cell , enters the cell Activates specific area of DNA Protein synthesis is end result Examples: Estrogen, testosterone, aldosterone, cortisol

  8. Hormone Action (cont) Nonsteriod hormone (amines, peptides, proteins) Characteristics: Activate proteins which alter cellular processes Ex: altering membrane permeabilities, activating enzymes, stimulating metabolic processes, release of other hormones Ex: growth hormone, epinephrine, oxytocin Sequence of events in nonsteroids: Hormone (primary messenger) binds to receptor on outside of cell Binding causes activity center inside cell to activate a messenger (sometimes cAMP) – called second messenger This messenger then causes change

  9. Hormonal Control Controlled by increasing or decreasing hormone secretion (VERY precise!) See Figure 11.5!!!!!!! Stimulation of hormone release: All use negative feedback mechanisms Hypothalamus and pituitary Nervous system Changing internal environment Inhibition of hormone release: Negative feedback loop

  10. Hypothalamus • Located deep inside the brain • Releasing and inhibiting hormone secretion to anterior pituitary • Direct innervations to posterior pituitary

  11. Pituitary Gland • Located deep within the brain • Divided into 2 sections: • Anterior Pituitary • glandular epithelium with many blood vessels • 2) Posterior Pituitary • nerve fibers and neuroglial cells

  12. Tropic Hormones of the Anterior Pituitary Thyroid-stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Gonadotropins: 2 types Follicle-stimulating hormone (FSH) Lutenizing hormone (LH)

  13. Thyroid-stimulating hormone (TSH) Stimulation: Thyrotropin-releasing hormone (TRH) from hypothalamus Inhibition: Circulating thyroid hormones decrease TSH and TRH secretion Target Cell: Thyroid gland/cells Action: Increase thyroid secretions

  14. Adrenocorticotropic hormone (ACTH) Stimulation: Corticotropin-releasing hormone (CRH) from hypothalamus Target Cell: Adrenal cortex Action: Increase adrenal cortex secretions

  15. Follicle-stimulating hormone (FSH) Stimulation: Gonadotropin-releasing hormone from hypothalamus Target Cell: Gonads (testes in males and ovaries in females) Action: Female- maturation of egg; secretion of estrogen Male- development of sperm

  16. Lutenizing hormone (LH) Also called Interstitial cell stimulating hormone (ICSH) Stimulation: Gonadotropin-releasing hormone from hypothalamus Target Cell: Gonads (testes in males and ovaries in females) Action: Female- release of mature egg from ovary (ovulation) Male- development of interstitial cell; secretion of male sex hormones

  17. Other hormones of the Anterior Pituitary Growth Hormone (GH) Stimulation: GH-releasing hormone from hypothalamus Inhibition: GH release-inhibiting hormone Target Cell: Somatic cells (non-sex cells) Action: Enhances movement of amino acids across cell membrane; speeds up rate of carbohydrate utilization

  18. Other hormones of the Anterior Pituitary Prolactin (PRL) Stimulates breast development necessary for lactation Stimulates breast to secrete milk after birth

  19. Posterior Pituitary Antidiuretic hormone (ADH) Stimulation: Nerve Impulse from hypothalamus when osmoreceptors sense dehydration Target Cell: kidneys Action: Kidneys produce less urine to conserve water Oxytocin (OT) Stimulates contraction of the pregnant uterus Stimulates “let-down” of milk

  20. Thumbs Up, Thumbs Down TSH is released by thyroid gland DOWN! Most pituitary-released hormones are controlled/stimulated by hypothalamus UP! Prolactin stimulates gonad development DOWN! Oxytocin helps uterus to contract during labor UP! ADH prevents you from becoming dehydrated by preventing your kidneys from making urine UP!

  21. Thyroid Quick Review of Pituitary control • Location: attached to front of trachea • Contains follicles • Follicles have hollow center cavity filled with colloid

  22. Thyroid (cont) Follicular cells of thyroid secrete two hormones: 1) Thyroxine (tetraiodothyronine) - T4 2) Triiodothyronine - T3 (much more potent) Increases metabolism of carbohydrates, lipids, and proteins Extrafollicular cells of thyroid secrete calcitonin Lowers blood calcium level by inhibiting osteoclasts (bone cells) Makes kidney secrete more calcium in urine

  23. Parathyroid glands Located on the thyroid in four patches Highly dense, secretory cells Secrete Parathyroid hormone (PTH) Raises blood calcium levels Inhibits osteoblasts Stimulates osteoclasts Makes kidneys conserve calcium Increase absorption of calcium in intestine Opposite of calcitonin

  24. Adrenal glands Very closely related to kidneys Located/Sit on top of kidneys Consists of two parts: Adrenal cortex Adrenal medulla

  25. Adrenal Cortex Three layers: Outer, middle, and inner Closely packed masses of epithelial tissue Makes up bulk of adrenal glands Well-supplied with blood

  26. Outer Layer of Cortex Outer (glomerulosa) Mineralocorticoid (MC)- regulate mineral electrolytes Ex: Aldosterone hormone Stimulated by decrease in blood levels of sodium, increase in potassium in blood levels, or decrease in blood pressure Cause kidneys to retain sodium and secrete potassium into urine Indirectly, water is retained – IMPORTANT!

  27. Adrenal Cortex (cont) Middle (fasciculata) Glucocorticoids- affects glucose metabolism Ex: Cortisol or hydrocortisone hormones Increase gluconeogenisis (glucose synthesis) Inhibition of protein synthesis Promotion of fatty acid release from adipose tissue Produce state of stress

  28. Adrenal Cortex (cont) Inner (reticularis) Secretes sex hormones Produces androgen hormones Can be used to synthesize female sex hormones like estrogens

  29. Adrenal Medulla Irregularly shaped cells Well supplied with blood Composed of modified neurons Secrete epinephrine (adrenaline) and norepinephrine (noradrenaline) Important in “Fight or Flight” response Directly innervated by sympathetic nervous system

  30. Pancreas Structure and Location: Elongated, somewhat flattened Posterior to stomach Duct joins pancreas to intestine Dual function: 1) Exocrine gland: secretes digestive juices 2) Endocrine gland: releases hormones Contains groups of cells closely related to blood vessels Called islets

  31. Pancreatic Islets (Islets of Langerhans) Made of two types of secretory tissues/cells: Alpha cells Secrete hormone: glucagon Accelerates process of gylcogenolysis Beta cells Secrete hormone: Insulin Increases movement of glucose inside of cells for metabolism Stimulates liver to produce glycogen

  32. Exit Slip 1) T3 is released by what gland? 2) Which hormone (cortisol or T4) produces a state of stress? 3) The pancreas has a duct/tube which connects it directly to what digestive system organ? GRADING TIME!!!! 1) Thyroid 2) Cortisol 3) Intestines

  33. Thymus • Located in mediastinum cavity • Secretes hormones called thymosins • Important function in development of immune system

  34. Pineal gland Releases hormone melatonin Regulates body clock and sleep cycle

  35. Female Sex Glands Ovaries Ovarian follicles Corpus luteum We will discuss these (and their hormones) in the reproductive chapter!

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