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Endocrine System

Endocrine System . Role of the Endocrine System Hormones: Types Transport of Hormones Interaction of Hormones with Target Cells Effects of Hormones on Target Control Mechanisms of Endocrine Glands Endocrine Organs Pituitary (Anterior and Posterior) Thyroid Parathyroids

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Endocrine System

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  1. Endocrine System • Role of the Endocrine System • Hormones: Types • Transport of Hormones • Interaction of Hormones with Target Cells • Effects of Hormones on Target • Control Mechanisms of Endocrine Glands • Endocrine Organs • Pituitary (Anterior and Posterior) • Thyroid • Parathyroids • Adrenals (Cortex, Medulla) • Pancreas • Gonads • Ovaries • Testes

  2. The Endocrine System • A more broad-based and long-lasting communication system than the nervous system • Uses chemical messages (hormones) that are released into the blood • Hormones control several major processes • Reproduction • Growth and development • Mobilization of body defenses • Maintenance of much of homeostasis • Regulation of metabolism

  3. Types of Hormones • Protein-based hormones • Steroid hormones • Prostaglandins and catecholamines Insulin Growth hormone

  4. Hormones as Chemical Messengers Endocrine gland (source) Target organs or glands Hormones move through the bloodstream to target organs

  5. Hormone Interaction with Target Cells • Hormones bind to receptors sticking out from the plasma membrane of target cells or within target cells growth factor insulin epinephrine Hormones Receptors Examples of receptors found in the plasma membrane of cells

  6. Effects Caused by Hormones • Changes in electrical state of the cell, stimulating change • Causes enzymes to be made, changing metabolic abilities of target cell • Turn on or off enzymes that alter metabolism inside cell • Stimulate cell division and multiplication • Turn on certain genes

  7. Control Mechanisms of Endocrine Glands Hormonal: Chemical stimulus (i.e. endocrine glands are activated by other hormones) Humoral/Blood-Based: Changing blood levels of certain ions stimulate hormone release Neural: Nerve impulses stimulate hormone release; most are under control of the sympathetic nervous system

  8. Location of Major Endrocrine Organs Figure 9.3

  9. Pituitary Gland Flip and enlarge Nervous system that hormones can drip down on blood portal system glandular tissue nervous tissue

  10. Hormones of the Anterior Pituitary • Six anterior pituitary hormones • Two affect non-endocrine targets • Four stimulate other endocrine glands (tropic hormones) • Characteristics of all anterior pituitary hormones • They are proteins (or peptides) • They act through second-messenger systems • They are regulated by hormonal stimuli, mostly negative feedback

  11. Hormones of the Anterior Pituitary Causes aldosterone, glucocorticoid, or androgen release Increases bone and skeletal mass Causes milk secretion in breasts Stimulates thyroid hormone secretion Causes follicle and sperm maturation, ovulation and testosterone production

  12. Hormones of the Posterior Pituitary Stimulates uterine muscle contraction in labor and intercourse; causes milk ejection Inhibits diuresis (urine production) and increases blood pressure

  13. Thyroid Gland Consists of two lobes and a connecting isthmus Thyroid hormone Controls rate of cellular respiration. All body cells are targets. Calcitonin Decreases blood calcium levels by causing bone calcium deposition. Made by parafollicular cells. Figure 9.6

  14. Thyroid Hormone • Lack of Dietary Iodine: Goiter • Hyposecretion of thyroxine ( hypothyroidism in adults) • Hyperthyroidism (Grave's disease)

  15. Calcitonin (Calcium deposition) • Decreases blood calcium levels by causing its deposition on bone • Antagonistic to parathyroid hormone • Produced by C (parafollicular) cells Figure 9.9

  16. Parathyroid Glands (Calcium removal) Found on posterior surface of thyroid • Parathyroid hormone • Stimulates osteoclasts to remove calcium from bone • Stimulates the kidneys and intestine to absorb more calcium • Raises calcium levels in the blood

  17. Adrenal Glands • Two parts that act as if separate glands • Cortex – outer glandular region in three layers • Medulla – inner neural tissue region • Sits on top of the kidneys Ad-renal both mean “upon or Epi-nephros next to the kidney” &

  18. Adrenal Hormones and Their Locations • Adrenal Cortex • Outer portion produces mineralocorticoids like aldosterone • Middle layer produces glucocorticoids like cortisone and cortisol • Innermost layer produces androgens like estrogens and testosterone • Medulla produces catecholoamines like epinephrine and norepineprhine

  19. Adrenal Cortex (Outer Portion) Aldosterone release causes salt and water retention, increasing blood pressure

  20. Hormones of the Innermost Cortex Layer • Sex hormones (steroids) • Produced in the inner layer of the adrenal cortex • Androgens (male) and some estrogen (female) -- both produced regardless of gender • Hypersecretion causes masculinization (regardless of gender) - most obvious effects in females • Hyposecretion causes Addison's disease

  21. Hormones of the Adrenal Medulla • Produces two similar hormones (catecholamines) • Epinephrine • Norepinephrine • These hormones prepare the body to deal with short-term stress • Sympathetic system stimulates catecholamine release in fight or flight: increased heart rate, blood pressure, blood gluocose, respiratory rate

  22. Pancreatic Islets • The pancreas is a mixed gland • The islets of the pancreas produce hormones • These hormones are antagonists that maintain blood sugar homeostasis

  23. Pancreatic Islets • Insulin • Allows glucose to cross plasma membranes into cells from beta cells (hypoglycemic hormone) • Glucagon • Allows glucose to enter the blood from alpha cells (hyperglycemic hormone) Figure 9.13

  24. Pancreatic Hormones and Blood Sugar Figure 9.14

  25. Pineal Gland • Found on the third ventricle of the brain • Secretes melatonin • Helps establish the body’s wake and sleep cycles • May have other as-yet-unsubstantiated functions

  26. Hormones of the Ovaries • Estrogens • Produced by Graafian follicles or the placenta • Stimulates the development of secondary female characteristics • Matures female reproductive organs • Helps prepare the uterus to receive a fertilized egg • Helps maintain pregnancy • Prepares the breasts to produce milk

  27. Hormones of the Ovaries • Progesterone • Produced by the corpus luteum • Acts with estrogen to bring about the menstrual cycle • Helps in the implantation of an embryo in the uterus

  28. Hormones of the Testes • Interstitial cells of testes are hormone-producing • Produce several androgens • Testosterone is the most important androgen • Responsible for adult male secondary sex characteristics • Promotes growth and maturation of male reproductive system • Required for sperm cell production

  29. Other Hormone-Producing Tissues and Organs • Parts of the small intestine • Parts of the stomach • Thymus • Kidneys • Heart • Many other areas have scattered endocrine cells

  30. Developmental Aspects of the Endocrine System • Most endocrine organs operate smoothly until old age • Menopause is brought about by lack of efficiency of the ovaries • Problems associated with reduced estrogen are common • Growth hormone production declines with age • Many endocrine glands decrease output with age

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