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  • 1. THE ENDOCRINE SYSTEM Like the Nervous System, the Endocrine System work through a group of chemical messengers. The endocrine messengers are called hormones. Hormones : Substances secreted by one group of cells that travel through the blood stream and regulate the metabolic functions of other cells. Hormones can affect only cells that have receptors that can bind the hormone Target cells : Those cell types that can be affected by a given hormone
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  • 3. FUNCTIONS OF THE ENDOCRINE SYSTEM The Endocrine system helps to maintain homeostasis by coordinating and regulating the activities of cells, tissues, organs, and systems throughout the body The Endocrine System helps to control and integrate: 1- Reproduction 2- Growth 3- Development 4- Defense against stress 5- Water, electrolyte and nutrient balance 6- Energy balance 7- Cellular metabolism
  • 4. Homeostasis It is the ability of the human body to maintain relatively stable internal conditions (temperature, PH, etc) even though the outside world changes continuously. A good homeostasis is indispensable to maintain the organism in good health. Most diseases can be regarded as a result of disturbance of homeostasis. Example: The body temperature must be near to 37 C (98.6 F). When temperature increases only three degrees (to 40 C), the organism is in danger. o o o
  • 5. Temperature: - 20 C Temperature: + 50 C o o Homeostatic Control Mechanisms maintain the temperature of the bodies near to 37 C, and both men are in good health o
  • 6. F E E D B A C K S Y S T E M S Causes the variable to change in a direction opposite to that of the initial change. Causes the variable to accelerate the change in the same direction that the initial disturbance. 1- Negative feedback mechanisms : 2- Positive feedback mechanisms : or or
  • 7. [Calcium] in blood First Hormonal Mechanism Second Hormonal Mechanism [Calcium] in blood 1- ENDOCRINE SYSTEM IN NEGATIVE FEEDBACK MECHANISMS Parathyroid hormone is released by parathyroid gland Stimulates the osteoclasts to resorb bone, releasing calcium to the blood Calcitonin hormone is released by thyroid gland Inhibits osteoclasts to resorb bone, and encourages calcium salt deposit in bone matrix [Calcium] in blood [Calcium] in blood
  • 8. Positive feedback mechanisms are used to amplify or perpetuate events. They are referred as “ cascades ”. 2- ENDOCRINE SYSTEM IN POSITIVE FEEDBACK MECHANISMS Uterine contractions OXYTOXIN DELIVERY! SENSOR EFFECTOR HYPOTALAMUS CONTROL CENTER Example: PITUITARY GLAND Neural electrical impulses
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  • 10. Hypothalamus Control of Hormone Secretion Most of hormone secretions are controlled by the Hypothalamus and the Pituitary gland Pituitary gland
  • 11. Fornix Anterior commissure Thalamus Intermediate mass Mamillary body Optic chiasm Epi- thalamus Corpus callosum Septum pellucidum Pineal gland Hypothalamus Pituitary gland
  • 12. Three mechanisms of Hypothalamic Control over Endocrine Function
  • 13. TSH, FSH, LH, ACTH, GH, PRL, MSH Oxytoxin and Antidiuretic Hormone (ADH) Posterior lobe Anterior lobe
  • 14. melanocyte stimulating hormone
  • 15. Hormones produced by the Anterior Lobe or Adenohypophysis (1) 2 1 5
  • 16. Hormones produced by the Anterior Lobe or Adenohypophysis (2) melanocyte stimulating hormone 4 3 3 6 GONADOTROPINS
  • 17. Hormones produced by the Hypothalamus and released by the posterior pituitary
  • 18. Hormonal Control of Water Retention in the Body The body controls how much water is either sent to the bladder (in urine) or retained in circulation through a hormone called “antidiuretic hormone” (ADH) When the body needs water, receptors in the hypothalamus sense the increase of solute concentration in the blood, and the hypothalamus orders the release of ADH from the pituitary gland . ADH works on the distal nephron tubule and the collecting duct increasing their permeability to water. Consequently, more water moves out of the nephron tubule and collecting duct and thus back into circulation
  • 19. Hormonal Control of Water Retention in the Body
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  • 22. The Thyroid Gland Right lobe Left lobe Isthmus
  • 23. T4 or Thyroxine T3 or Triiodothyronine Calcitonin
  • 24. Thyroid Hormones 1- They increase the rate of oxygen uptake and the basal metabolic rate 2- They enhance the effects of sympathetic stimulation (increasing heart rate, blood pressure, nervousness, and sweating) 3- They help to maintain body temperature 4- They help to regulate growth, development, and intracellular metabolism by increasing protein synthesis and lipid breakdown 5- They stimulate RBC formation, and speed up bone turnover 1- T4 or thyroxine 2- T3 or triiodothyronine 3- Calcitonin 1- T4 or thyroxine 2- T3 or triioodothyronine Follicular hormones (they are produced by the follicular cells)
  • 25. 3- Calcitonin It is released in response to high levels of calcium in the blood [Calcium] in blood Calcitonin hormone is released by thyroid gland Inhibits osteoclasts to resorb bone, and encourages calcium salt deposit in bone matrix [Calcium] in blood
  • 26. The Parathyroid Glands Thyroid gland, posterior view Parathyroid glands Parathyroid glands
  • 27. The Parathyroid Hormone It increases calcium blood levels by targeting bone and kidneys 2- In kidneys - It increases calcium reabsortion - It increases formation and secretion of calcitriol 1- In bones [Calcium] in blood Parathyroid hormone is released by parathyroid gland Stimulates the osteoclasts to resorb bone, releasing calcium to the blood [Calcium] in blood Increases absorption of calcium and phosphate from the intestines
  • 28. Adrenal or Suprarenal Glands
  • 29. Mineralocorticoids (Aldosterone) Glucocorticoids (Cortisol, Cortisone and Corticosterone) Sex hormones ( androgens) Medulla (It is considered part of Sympathetic Autonomic nervous System) Catecholamines (Epinephrine and Norepinephrine)
  • 30. Hormones of the Adrenal Glands 1- Mineralocorticoides (Aldosterone) Aldosterone secretion is regulated by the renin-angiotencin mechanism 2- Glucocorticoids (Corticosterone and Cortisol) -It increases sodium ion and water reabsortion in kidneys -It increases potassium secretion in kidneys Blood pressure or plasma solute concentration Renin-angiotencin mechanism Aldosterone secretion -They help the body to resist stressors -They depress the immune system and the inflammatory response
  • 31. 3- Gonadocorticoids or Sex Hormones (Androgens) 4- Catecholamines (Epinephrine and Norepinephrine) -They are masculinizing hormones. - In females they stimulate sexual drive. After menopause they are converted to estrogens. -Blood glucose levels They increase: -Cardiac activity -Blood pressure -Glycogen breakdown -Triglyceride breakdown
  • 32. Three mechanisms of Hypothalamic Control over Endocrine Function
  • 33. The Pancreas
  • 34. Pancreatic acini They secrete large quantities of an alkaline, enzyme rich fluid Islets of Langerhans 1- Beta cells: 2- Alpha cells: 3- Delta cells: 4- F cells : Insulin Glucagon Somatostatin Pancreatic polypeptide Endocrine pancreas Exocrine pancreas
  • 35. 1- Glucagon (Released by alpha cells) -It stimulates the liver to produce glucose -It stimulates to breakdown glycogen Glucose in blood Glucagon (Alpha cells) Pancreas Liver Glycogen Glucose
  • 36. 2- Insulin (Released by beta cells) - High blood glucose - Parasympathetic stimulation - High level of some aminoacids (Beta cells) Pancreas Insulin - It increases the rate of glucose uptake by cells - It increases cellular metabolism - It increases the storage of lipid and glycogen - Increases aminoacids absorption and protein synthesis
  • 37. The Gonads Seminiferous tube Primary spermatocyte Secondary spermatocyte Spermatids Sperm (immature) Spermatogonia Interstitial or Leydig cells : Produce androgens (testosterone) Sustentacular or Sertoli cells : Produce Inhibin
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  • 40. The Development of the Egg Primary oocytes Primary follicles Corpus luteum : Follicles : Estrogens and Inhibin Progesterone Secondary follicles Tertiary follicles
  • 41. The Pineal Gland Melatonin: Pineal gland 1- Inhibiting reproductive functions 2- Protecting against damage for free radicals 3- Setting circadian rhythms
  • 42. Hormones of the Kidneys 1- Calcitriol: It stimulates uptake of calcium and phosphate ions from the gut 2- Erythropoietin: It stimulates the production of red blood cells by red bone marrow 3- Renin: It converts angiotensinogen into angiotensin-I and starts the cascade of enzymatic changes known as the renin-angiotensin system Atrial Natriuretic Peptide (ANP) It is produced by the atrial cells of the heart It reduces the blood volume and blood pressure