The Endocrine System
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The Endocrine System






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The Endocrine System The Endocrine System Presentation Transcript

  • The Endocrine System Chp. 6
    • Primary endocrine organs: main function is to secrete hormone(s)
    • Secondary endocrine organs: secrete hormones as a secondary function
  • Primary endocrine organs
    • Hypothalamus and pituitary gland secrete hormones and regulate other endocrine organs. They are the main regulatory organs of the endocrine system.
  • Hypothalamus
    • Located below the thalamus and above the pituitary gland (=epiphysis)
    • Regulates the pituitary gland secretions through two different mechanisms
  • Hypothalamus - neurohypophysis
    • 1- Neurons, receiving information from receptors, fire APs which travel down to the post pituitary gland and stimulate the release of stored neurohormones – Oxytocin (OT) and anti-diuretic hormone (ADH)
  • Hormones of the posterior pituitary - not enough: diabetes insipidus - too much: ↑ BP? - promote H2O reabsorption - DCT in kidney tubules ADH (vasopressin) Reflex (osmoreceptor) -- --
    • labor and delivery
    • - milk-let down
    - Uterus (smooth muscle) - breast tubules (smooth muscles) Oxytocin Reflex Pathology Action Target organ Hormone Regulation
  • Hypothalamus – adenohypophysis
    • 2- Upon stimulation, secretory cells located in the hypothalamus secrete “releasing” hormones which travel down a capillary bed toward the anterior pituitary gland (adenopituitary). Each type of releasing hormones will stimulate the secretion and release of a pituitary hormone.
    • Hormones which control the secretion of other hormones are tropic hormones (found in hypothalamus and pituitary gland
  • Hormones of the hypothalamus and anterior pituitary gland Figure 6.5
  • Figure 6.8 Anterior pituitary - infertility Stimulate gonadal gland secretion and gamete formation Stimulate gamete maturation Gonadotropin - Follicle stimulating hormone (FSH) - Luteinizing hormone (LH) GnRH - not enough: Addison's disease - too much: Cushing syndrome - stimulates secretion of adrenal cortex Adrenal cortex (3 layers) Adrenocorticotropic hormone (ACTH) CRH - not enough: hypothyroidism (cretinism in children) - too much: hyperthyroidism - promote thyroid gland secretion (T3 and T4) Thyroid gland Thyroid stimulating hormone (TSH) TRH -- - milk secretion Breast secretory cells Prolactin (PL) PRH - PIH - not enough: children  pituitary dwarfism too much: gigantism (children) – acromegaly (adult) Stimulate cell growth and cell division Many cells (bones..) Growth hormone (GH) GHRH and GHIH Pathology Action Target organ Hormone Regulation
  • Same Individual with Acromegaly (evolution over 20 years) Figure 23-17
  • Mechanism of control Figure 6.6
  • The thyroid gland - Chp 21 p 623-625
    • Located in the neck, just below the larynx
    • Secrete 2 types of hormone:
    • - thyroid hormones  stimulate cell metabolism, triiodothyronine (T3) and thyroxine (T4) – iodine is needed to synthesize these hormones
    • - calcitonin  decrease blood calcium
    Figure 6.8a
  • Thyroid hormones
    • T3 and T4 secreted by the follicular cells
    • Stored as colloid
    • Parafollicular cells (C cells) secrete calcitonin (Chp 19)
  • Thyroid Hormones T3 and T4
    • Target organs: all cells
    • Role: Increase cell metabolism, oxygen consumption
    • Permissive role for some other hormones (growth hormone)
  • Thyroid hormone regulation Figure 6.7
  • Goiter
    • Both hypo and hyperthyroidism can have goiter as a symptom
    • Goiter is a swelling of the neck due to hypertrophy of the thyroid gland
    • How can one explain that?
  • Goiter in hypothyroidism
    • Most often due to a lack of dietary iodine
    • The thyroid hormone is unable to synthesize a functional thyroid hormone (T3 and T4)
    • The person express symptoms of hypothyroidism
    • The nonfunctional T3/T4 cannot promote a negative feedback on TRH and TSH
    •  the hypotalamus and pituitary gland increase their secretions  the thyroid gland is stimulated to secrete more T3 and T4 …
    • In children, the lack of functional T3/T4 result in cretinism, a form a mental retardation
  • Goiter in hyperthyroidism
    • The cells secreting TRH or TSH on the hypothalamus and pituitary gland (respectively) have become abnormal and no longer are sensitive to the negative feedback  they continue to secrete TRH or TSH  continuous stimulation of the thyroid gland with excess thyroid hormones being formed
    •  symptoms of hyperthyroidism
  • Parathyroid glands
    • Four nodules located in the back of the thyroid gland
    • Secreted parathyroid hormone or parathormone or PTH
    • Action of PTH opposes action of calcitonin
    • Both hormones play a role in calcium metabolism
  • Roles of calcium
    • Most calcium ions are stored in the bones
    • Calcium is an important cofactor for enzymatic activity, plays a role in blood coagulation and action potentials.
    • Calcitonin and PTH participate in calcium regulation
    • Vitamin D helps PTH activity
  • Calcium regulation:
    • Calcitonin promotes blood calcium decrease, by:
    • 1. calcium deposition on bone
    • 2. calcium dumping by the kidney
    • PTH promotes blood calcium increase by:
    • 1. bone resorption
    • 2. calcium reabsorption by kidney
    • 3. increase calcium absorption by intestine
  • Calcium Metabolism: Figure 23-20: Calcium balance in the body
  • Figure 19.20
  • The adrenal glands
    • Two endocrine glands:
    • 1- Adrenal medulla: an extension of the sympathetic ANS  cell secrete epinephrine
    • 2- Adrenal cortex: 3 layers with 3 different hormones
  • Figure 6.12b
  • Figure 21.15
  • Adrenal gland hormones Infertility - Sex organ maintenance - Gamete development Sexual organs Estrogen Testosterone GnRH  GN Excess hormone: Cushing syndrome Mobilize fuels – stress adaptation Many cells Glucocorticoid = cortisone CRH  ACTH Not enough" Addison disease - promote sodium reabsorption DCT from renal tubule - Mineralocorticoid = aldosterone Adrenal cortex Blood Pressure Stress Fight/flight ANS target organs Epinephrine Adrenal medulla Reflex Pathology Action Target organs Hormones Glands Regulation
  • The pancreas
    • Located in the left upper abdominal cavity
    • Exocrine and endocrine glands
    • The endocrine function is due to the cells of the islets of the Langerhans
    • -- α cells  glucagon
    • -- β  insulin
    • -- δ  somatostatin
  • Glucose regulation
    • Glucose level controlled by insulin and glucagon
    • Insulin promotes a decrease in blood glucose
    • Glucagon promotes an increase in blood glucose
  • Glucose regulation
  • Fate of glucose Figure 3.21
  • Diabetes mellitus
    • Type I: autoimmune disease  beta cells of the islets of Langerhans are destroyed by antibodies
    • Type II: The cells become insulin-resistant  glucose does not enter the cells as readily
  • Diabetic foot