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THE ENDOCRINE SYSTEM

THE ENDOCRINE SYSTEM. Like the Nervous System, the Endocrine System work through a group of chemical messengers. The endocrine messengers are called hormones.

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THE ENDOCRINE SYSTEM

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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

  2. FUNCTIONS OF THE ENDOCRINE SYSTEM The Endocrine System helps to control and integrate: 1- Reproduction 6- Energy balance 2- Growth 7- Cellular metabolism 3- Development 4- Defense against stress 5- Water, electrolyte and nutrient balance The Endocrine system helps to maintain homeostasis by coordinating and regulating the activities of cells, tissues, organs, and systems throughout the body

  3. o 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 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.

  4. o o Temperature: - 20 C Temperature: + 50 C Homeostatic Control Mechanisms maintain the temperature of the bodies near to 37 C, and both men are in good health o

  5. F E E D B A C K S Y S T E M S 1- Negative feedback mechanisms: Causes the variable to change in a direction opposite to that of the initial change. or 2- Positive feedback mechanisms: Causes the variable to accelerate the change in the same direction that the initial disturbance. or

  6. Parathyroid hormone is released by parathyroid gland Stimulates the osteoclasts to resorb bone, releasing calcium to 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 1- ENDOCRINE SYSTEM IN NEGATIVE FEEDBACK MECHANISMS First Hormonal Mechanism [Calcium] in blood Second Hormonal Mechanism [Calcium] in blood

  7. Example: Neural electrical impulses HYPOTALAMUS CONTROL CENTER SENSOR EFFECTOR PITUITARY GLAND 2- ENDOCRINE SYSTEM IN POSITIVE FEEDBACK MECHANISMS Positive feedback mechanisms are used to amplify or perpetuate events. They are referred as “cascades”. OXYTOXIN DELIVERY! Uterine contractions

  8. Control of Hormone Secretion Most of hormone secretions are controlled by the Hypothalamus and the Pituitary gland Hypothalamus Pituitary gland

  9. Corpus callosum Septum pellucidum Pineal gland Pituitary gland Hypothalamus Intermediate mass Fornix Thalamus Epi- thalamus Anterior commissure Optic chiasm Mamillary body

  10. Three mechanisms of Hypothalamic Control over Endocrine Function

  11. Posterior lobe Anterior lobe TSH, FSH, LH, ACTH, GH, PRL, MSH Oxytoxin and Antidiuretic Hormone (ADH)

  12. melanocyte stimulating hormone

  13. Hormones produced by the Anterior Lobe or Adenohypophysis (1) 2 1 5

  14. Hormones produced by the Anterior Lobe or Adenohypophysis (2) 4 Gonadotropins 3 3 6 melanocyte stimulating hormone

  15. Hormones produced by the Hypothalamus and released by the posterior pituitary

  16. 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

  17. Hormonal Control of Water Retention in the Body

  18. Neural electrical impulses HYPOTALAMUS CONTROL CENTER SENSOR OXYTOXIN EFFECTOR DELIVERY! Uterine contractions PITUITARY GLAND

  19. The Thyroid Gland Isthmus Right lobe Left lobe

  20. Calcitonin T4 or Thyroxine T3 or Triiodothyronine

  21. Thyroid Hormones 1- T4 or thyroxine Follicular hormones (they are produced by the follicular cells) 2- T3 or triioodothyronine 1- T4 or thyroxine 2- T3 or triiodothyronine 3- Calcitonin 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

  22. Calcitonin hormone is released by thyroid gland Inhibits osteoclasts to resorb bone, and encourages calcium salt deposit in bone matrix [Calcium] in blood 3- Calcitonin It is released in response to high levels of calcium in the blood [Calcium] in blood

  23. Thyroid gland, posterior view Parathyroid glands Parathyroid glands The Parathyroid Glands

  24. 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 The Parathyroid Hormone It increases calcium blood levels by targeting bone and kidneys 1- In bones [Calcium] in blood 2- In kidneys - It increases calcium reabsortion - It increases formation and secretion of calcitriol

  25. Adrenal or Suprarenal Glands

  26. Medulla (It is considered part of Sympathetic Autonomic nervous System) Catecholamines (Epinephrine and Norepinephrine) Sex hormones ( androgens) Glucocorticoids (Cortisol, Cortisone and Corticosterone) Mineralocorticoids (Aldosterone)

  27. -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 Hormones of the Adrenal Glands 1- Mineralocorticoides (Aldosterone) Aldosterone secretion is regulated by the renin-angiotencin mechanism 2- Glucocorticoids (Corticosterone and Cortisol)

  28. -They are masculinizing hormones. - In females they stimulate sexual drive. After menopause they are converted to estrogens. -Cardiac activity -Blood pressure They increase: -Glycogen breakdown -Blood glucose levels -Triglyceride breakdown 3- Gonadocorticoids or Sex Hormones(Androgens) 4- Catecholamines (Epinephrine and Norepinephrine)

  29. Three mechanisms of Hypothalamic Control over Endocrine Function

  30. The Pancreas

  31. Endocrine pancreas Exocrine pancreas Islets of Langerhans Pancreatic acini They secrete large quantities of an alkaline, enzyme rich fluid 1- Beta cells: Insulin 2- Alpha cells: Glucagon 3- Delta cells: Somatostatin 4- F cells: Pancreatic polypeptide

  32. -It stimulates the liver to produce glucose -It stimulates to breakdown glycogen Glucose in blood Pancreas Glucagon Liver Glycogen (Alpha cells) Glucose 1- Glucagon (Released by alpha cells)

  33. - High blood glucose - Parasympathetic stimulation - High level of some aminoacids Pancreas (Beta cells) 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 2- Insulin (Released by beta cells)

  34. Spermatogonia Primary spermatocyte Seminiferous tube Secondary spermatocyte Spermatids Sperm (immature) Sustentacular or Sertoli cells: Produce Inhibin Interstitial or Leydig cells: Produce androgens (testosterone) The Gonads

  35. The Development of the Egg Secondary follicles Tertiary follicles Corpus luteum : Progesterone Primary oocytes Primary follicles Follicles: Estrogens and Inhibin

  36. Pineal gland 1- Inhibiting reproductive functions 2- Protecting against damage for free radicals 3- Setting circadian rhythms The Pineal Gland Melatonin:

  37. 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

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