Endocrine System
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Endocrine System






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Endocrine System Endocrine System Presentation Transcript

  • The Endocrine System: Did you know…
    • adrenal glands produce the greatest number of hormones
    • smallest endocrine gland = parathyroid
    • largest pure endocrine gland = thyroid
    • endocrine gland proportionately largest at birth = thymus
  • What are hormones?
    • Hormon = “to excite”
      • “ troph ” = to nourish, grow, change
    • Chemical messengers
    • Target most cells in the body
      • Note: endocrine system is not continuous
    • Endocrine glands produce
      • Vs. exocrine glands
      • Parenchyma (function) vs. stroma (form)
  • What do they do?
    • Alter activity (metabolism) of target cell
    • Alter PM permeability or voltage
    • Stimulates production of proteins/enzymes
    • Activates/deactivates enzymes
    • Stimulates mitosis
    • Induces secretory activity
  • How does the endocrine sys. compare to the nervous sys.?
    • Slow messages
    • Prolonged, continued response
    • Via blood
    • Can continue to adapt/respond to conditions for day or even weeks
    • Often general, widespread effects on many organs
  • What are the types of hormones?
    • Eicosanoids (paracrines)
    • Monoamines
    • Steroids
    • Peptides
  • What are the types of hormones?
    • Eicosanoids (paracrines)
      • More localized, lipids
      • Not true hormones
      • Leukotrines (inflammation)
      • Prostaglandins
        • Inc. bp, dec. uterine contractions, enhance clotting, etc.
  • What are the types of hormones?
    • Biogenic amines
      • AKA monoamines
      • From tyrosine (except melatonin from tryptophan)
      • Includes some neurotransmitters
        • NE, epinephrine, dopamine (catecholamines)
          • NE from SNS, E from adrenal medulla
      • Also thyroid hormones (TH)
  • What are the types of hormones?
    • Steroids
      • From cholesterol: lipid sol.
      • Sex steroids
      • Corticosteroids (cortisol, aldosterone, etc.)
    • Passes through PM
      • travel to cell via transport protein
        • proteins extend half-life
      • Bind to DNA receptor in nucleus
        • Activates transcription
        • 3 binding sites on DNA receptor molecule
          • Hormone
          • Chromatin acceptor site
          • DNA activation site
      • lipid-soluble hormone animation
  • What are the types of hormones?
    • Peptides
      • 3 to 200 aa’s
        • ADH, oxytocin
      • All releasing/inhibiting from hypothalamus
        • Most from anterior pituitary
      • Bind to PM receptor
        • Can’t pass through PM
        • Act through secondary messengers
      • peptide hormone activity
  • How do secondary messengers work again?
    • cAMP
      • Hormone binds to G protein
      • Activates adenylate cyclase
        • causes cAMP production
      • cAMP activates/deactivates kinases
    • By contrast: T3, T4 (direct cell entry, no secondary messenger)
      • binds to:
        • mitochondria
          • Stimulates oxidative metabolism
        • Ribosomes
          • Stimulates translation
        • Nucleus
          • Stimulates transcription
      • Na+-K+ pump controlled this way
  • What are the mechanisms of hormonal action?
    • Only cells w/ appropriate receptors respond to hormone
      • These are target cells
      • Receptors on PM, nucleus, mitochondria, other organelles
  • What are the mechanisms of hormonal action?
    • Receptors
      • Specificity
      • Saturation
      • Amplification
      • Up-regulation
        • More receptors
        • Greater sensitivity
        • Oxytocin receptors in late pregnancy
      • Down-regulation
        • Fewer receptors
        • Response to high concentrations
        • Adipocytes & insulin
  • How do hormones interact with each other?
    • Synergistic effects
      • Greater than sum
      • FSH + testosterone = adequate sperm production
    • Permissive effects
      • Hormone enhances target’s response to second hormone
        • Estrogen stimulates up regulation of progesterone receptors
    • Antagonistic effects
      • Opposing actions
      • Insulin vs. glucagon
      • Estrogen vs. prolactin
  • What is the pituitary gland?
    • Hypothalamus secretes: releasing/inhibiting hormones
    • Hypophysis = _______________
    • No nerve connection to adenohypophysis (anterior __________)
      • Releasing and inhibiting hormones sent via blood
        • hypothalamo-hypophyseal portal system
  • What is the hypothalamus-hypophysis axis?
    • Better question:
    • What IS an axis?
    • Let’s look at the portal system…
  • What is the hypothalamus-hypophysis axis?
  • What is the hypothalamus-hypophysis axis?
    • Neurohypophysis—not a true gland (posterior _________)
      • Mass of axons from hypothalamus
        • Hypothalamo-hypophyseal tract
        • Hormones stored in neurohypophysis
          • Oxytocin
          • ADH
        • Nerve signal stimulates release
  • Anterior pituitary hormones Reg. Stress response Stim. Ad. cortex to secrete glucocorticoids (glucose, fat and protein metabolism) Adrenal cortex Pancreas (insulin release) Adrenocorticotropic hormone (ACTH) Stim. thyroid growth and hormone secretion (metabolism) Thyroid gland Thyroid-stimulating hormone (TSH) Stim. Egg release & corpus luteum to release progesterone Stim. Interstitial testicular cells to release testosterone Ovaries, testes (a gonadotropin) Peak at mid-menstrual cycle Luteinizing hormone (LH) Stim egg dev. Stim. Sperm prod. Ovaries, testes (A gonadotropin) Follicle-stimulating hormone (FSH) Action Target cell(s) Hormone
  • Anterior pituitary hormones Stim. Hyperplasia (growth by mitosis) and hypertrophy (growth by increase in cell size) of tissues Increases fatty acid metabolism, decreases muscle uptake of glucose Liver: stim. Somatomedins production (insulin-like growth factors, IGF); this stim. fat, cartilage, bone, tissue Bone growth at epiphyseal plates Many Esp. liver Secreted mainly at night Growth Hormone (GH) or Somatotropin Stim. milk synthesis after birth Sensitizes testes to testosterone (permissive) Mammary glands Testes Prolactin (PRL) Action Target cell(s) Hormone
  • What does the posterior pituitary secrete?
    • ADH --antidiuretic hormone
      • AKA vasopressin
        • Causes vasoconstriction at very high levels
      • Inc. water retention (lower urine vol.)
      • Prevent dehydration
    • Oxytocin
      • Stims uterine contractions
      • Stims milk secretion after birth
    • Nerve system stimulation controls both
      • Nursing stimulus
      • Osmoreceptors in blood vessels detect inc. osmolarity and stim. ADH
      • Stretching of baroreceptors inhibits ADH
  • How do negative feedback loops control secretion?
    • Products from target organs often inhibit further secretion of hormone
    • Example:
      • Dehydration lowers blood volume and pressure
      • Osmoreceptors detect
      • Stimulates hypothalamus to secrete ADH via posterior pituitary
      • Blood volume/pressure increases
      • Osmoreceptors detect
      • Inhibit further ADH release
    • Another example: thyroid hormone (see p. 645 (new) (646, old) if you’re interested)
  • What are some pituitary disorders?
    • In juveniles
      • Hyposecretion (hypopituitarism)
        • Pituitary dwarfism
      • Hypersecretion: gigantism
    • In adults
      • Hypersecretion: acromegaly
    • Posterior lobe hyposecretion: diabetes insipidus (which is: ___________)
      • WHY?
  • What is the pineal gland?
    • Roof of third ventricle
    • Produces serotonin
      • Converted to melatonin
      • Possible sexual maturation control
        • Prevent early maturation?
  • What is the thymus?
    • Location: mediastinum
    • Involution after puberty (shrinks like pineal)
    • Secretes thymopoietin
      • Regulates development of T-lymphocytes
  • What is the thyroid?
    • Largest endocrine gland
      • Wraps around trachea
    • Contains
      • Sacs: thyroid follicles
        • Lined with follicular cells which secrete T 3 and T 4
        • Increases BMR, HR and heart contraction
      • C cells
        • Produce calcitonin
          • Stores calcium by stimulating osteoblasts, inhibiting osteoclasts
        • Antagonistic to parathyroid hormone (PTH)
    • Regulation via the hypothalamo-hypophyseal-thyroid axis
  • What are some thyroid diseases?
    • Hyposecretion
      • Congenital hypothyroidism
        • facial thickening, low body temp, lethargy, brain damage
      • Adults: myxedema
        • Low BMR, sluggish, sleepy, weight gain, cold, tissue swelling
    From: http://www.type2hypothyroidism.com/Type1VsType2.html
  • What is goiter?
    • Another thyroid disorder; two types
    • Endemic goiter: dietary deficiency of iodine
      • No TH produced so pituitary receives no neg. feedback and more more TSH produced
      • Results in hypertrophy
    • Toxic goiter (Grave’s disease)
      • Autoimmune disease
      • Abnormal antibodies mimic TSH, raising TH levels
        • Called thyroid-stimulating immunoglobin
      • Causes high BMR & HR, sleeplessness, weight loss, exophthalmos
    From: http://www.medstudents.com.br/image/endoc/imgend1.htm
  • What are the parathyroids?
    • PTH: stim’s osteoclasts, inhibits osteoblasts
      • Calcium released
    • Hypoparathyroidism
      • If parathyroid removed:
        • Decreased calcium levels
        • tetany and death without HRT
    • Hyperparathyroidism:
      • Bone softening, fragility, deformity
      • Renal calculi formation
  • What are the adrenal glands?
    • Adrenal medulla
      • Sympathetic neurons innervate
      • Secrete catecholamines
    • Adrenal cortex
      • Makes more than 25 corticoids (AKA corticosteroids)
      • Small amounts of sex steroids ( androgen/estrogen)
        • Including DHEA (an androgen) which is converted to testosterone
  • What are the adrenal glands?
      • Mineralcorticoids
        • Mostly aldosterone (retain Na + , secrete K + )
      • Glucocorticoids
        • Secreted in response to ACTH
        • Cortisol (hydrocortisone) is most important
          • Stimulate gluconeogenesis (fat and protein catabolism)
          • Also glycolysis
          • Stress response
          • Suppresses immune system
  • What are some adrenal disorders?
    • Regulated by hypothalamo-hypophyseal-adrenocortico axis
    • Cushing syndrome
      • Via adrenal tumor or ACTH excess
        • Hyperglycemia, hypertension, muscular weakness, edema, “moon face”, “buffalo hump”
  • What are some adrenal disorders?
    • Addison disease
      • Hyposecretion of glucocorticoids and mineralcorticoids
        • Hypoglycemia, Na/K imbalance, loss of stress resistance, hypotension,
        • Via excess ACTH secretion (b/c no neg. feedback)
        • Bronzing b.c ACTH stimulates melanin production
        • Fatal if not treated with corticoids
    From: http://www.historyplace.com/specials/portraits/presidents/
  • What does the pancreas secrete?
    • Mostly exocrine digestive tissue
    • Some endocrine tissue in pancreatic islets
      • Islets of Langerhans
  • What does the pancreas secrete?
    • These secrete:
      • Insulin via beta cells
        • A peptide hormone
        • Stimulates glycogenesis and inhibits glycogenolysis and gluconeogenesis
        • Recruits glucose transporter proteins (GLUTs)
      • Glucagon via alpha cells
        • Stimulates gylcogenolysis (glycogen hydrolysis)
      • Somatostatin (GHIH) via delta cells
        • Paracrine secretion
        • Modulates beta and alpha cell secretions
  • What are some pancreatic disorders?
    • Hyperinsulinism
      • Sometimes pancreatic tumor causes
      • Sometimes accidental over-injection
      • Causes hypoglycemia, weakness, hunger,
        • Hypoglycemia stimulates E, glucagon, GH secretion
          • Anxiety, hi HR, sweating
          • Insulin shock—brain deprived of glucose
            • Disorientation, convulsions, unconsciousness
  • What are some pancreatic disorders?
    • Diabetes mellitus (DM)
      • Diabetes = “to syphon or run through
        • Mellitus = “sweet”; insipidus = “tasteless”
      • Hyposecretion or inaction of insulin
      • Three signs:
        • Polyuria (excessive urine output)
        • Polydipsia (intense thirst)
        • Polyphagia (intense hunger)
      • Tests reveal hyperglycemia, glycosuria, ketonuria
    From: http://www.bbc.co.uk/health/conditions/urinarytract2.shtml
  • What types of DM can patients have?
    • Type I—insulin-dependent (IDDM)
      • 10% of cases
      • Autoimmune destruction of beta cells
      • AKA juvenile diabetes (age 12)
    • Type II—non-insulin dependent (NIDDM)
      • Insulin resistance
        • Adipocytes secrete resistin?
        • Shortage of insulin receptors?
        • Heredity, age, obesity
        • AKA adult onset (age 40)
  • What do the gonads secrete?
    • Exocrine products: egg and sperm
    • Endocrine products: gonadal hormones
    • We’ll cover this more at the end of the semester
  • What is stress and how do we adapt to it?
    • Any stimulus that upset homeostasis
      • Body copes via stress response (AKA general adaptation syndrome, GAS)
    • Alarm reaction
      • NE from sympathetic, E from adrenals = Fight or flight
  • What is stress and how do we adapt to it?
    • Stage of resistance
      • If stress continues, glycogen reserves drop
      • Cortisol dominates to provide fuels for metabolism
        • Long-term cortisol exposure suppresses immune system
    • Stage of exhaustion
      • Fat reserves exhausted, rely on protein
        • Body wasting and weakening
      • Rapid decline and death: heart/kidney failure, infection