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The Endocrine System


The Endocrine System Part 3: Integration & Control – PowerPoint PPT presentation

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Title: The Endocrine System

The Endocrine System
  • Part 3 Integration Control

The Endocrine System
  • Endocrinology The study of the endocrine system.
  • Endocrine System Communicates with helps
    control body systems via hormones.
  • Communication is slower than in the nervous
    system has longer-lasting effects.
  • Hormones Chemicals secreted directly into the
    bloodstream to affect target cells or organs.

  • Exocrine Glands Secrete hormones into ducts,
    which then drain the hormones into another
  • E.g., salivary and sweat glands.

  • Endocrine Glands Secrete the hormones directly
    into the bloodstream. Typically rely on
  • Negative Feedback Systems Releases hormones to
    counteract the effects of other hormones with the
    goal of maintaining homeostasis.

  • Three Chemical Classes of Hormones
  • Steroid Hormones
  • Amines
  • Peptide (Protein) Hormones
  • Local Hormones
  • Eicosanoids

  • Steroid Hormones
  • Lipid-soluble
  • Hydrophobic (NOT water-soluble)
  • Must bind to transport proteins to effect target
  • Examples
  • Aldosterone
  • Estrogen
  • Calcitriol
  • Testosterone

  • Amines aka Biogenic Amines
  • Require tyrosine (an amino acid) for synthesis.
  • Hydrophilic (water-soluble)
  • Examples
  • Epinephrine
  • Dopamine
  • Thyroid hormones

  • Peptide Hormones aka Protein Hormones
  • Amino acid polymers
  • Hydrophilic (water-soluble)
  • Examples
  • Oxytocin
  • ADH
  • hGH

  • Eicosanoids aka Local Hormones
  • Considered paracrine secretions
  • Have very brief effect on many cells f the body.
  • Eicosanoids Include
  • Prostoglandins Secreted by organs to serve
    various functions.
  • Leukotrienes Control allergic inflammatory
  • Examples
  • Prostadcyclin Inhibits blood clotting
  • Thromboxanes Override the effects of
    prostacyclin when injured.

Hormone Effects
  • Hormone Receptors Protein or glycoprotein
    molecules on target cells.
  • Site of binding for hydrophobic hormones on the
    cell nucleus.
  • Binding allows alterations in the gene expression
    of the cell, which triggers the receptor cells
  • Second-Messenger Systems System for hormone
    binding for hydrophilic hormones.
  • Causes the activation of enzyme molecules to
    catalyze the desired reaction.

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Hormone Effects
  • Up-Regulation Hormones increase the number of
    receptors therefore sensitivity.
  • Down-Regulation Hormones decrease the number of
    receptors therefore sensitivity.
  • Synergistic Effects Hormones work together to
    produce a combined greater effect.
  • Permissive Effects One hormone enhances the
    target cells response to another hormone.
  • Antagonistic Effects Hormones oppose each
    others effects.

Feedback Systems
  • Negative Feedback Mechanisms Maintains the body
    condition in question within a small normal
    range of its set point.
  • MOST hormones work using negative feedback!
  • Examples
  • Blood sugar range (80-120mg/ml)
  • Body Temperature (36.5-38C)
  • Blood pH
  • Your thermostat!

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Endocrine Glands Hypothalamus
  • Hypothalamus Controls primary functions,
    including water balance, sleep sex drive,
    acts as a main controller for the ANS.
  • Produces 9 Major hormones
  • 7 control the Pituitary gland
  • Oxytocin (OT) Stored in Posterior Pituitary
  • Antidiuretic Hormone (ADH) Stored in Posterior
    Pituitary Gland.
  • Infundibulum Stalk that connects the
    hypothalamus pituitary glands.
  • Sella Turcica Bony saddle-shaped structure on
    the superior surface of the sphenoid.

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Endocrine Glands Pituitary
  • Pituitary Gland aka Hypophysis The master
    gland of the endocrine system, controlled by the
    hypothalamus. Two parts
  • Anterior Pituitary Gland aka Adenohypophysis
  • Posterior Pituitary Gland aka Neurohypophysis

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Endocrine Glands Pituitary
  • Anterior Pituitary Gland
  • Made up of..
  • Anterior Lobe
  • Pars Tuberalis
  • Hypothalamo-Hypophyseal Portal System Allows
    blood to flow from capillaries in the
    hypothalamus into the portal veins of the
    anterior pituitary.
  • Transports the inhibitory releasing hormones
    from the hypothalamus to control the APG.

Endocrine Glands Pituitary
  • Anterior Pituitary Hormones 7 Major Hormones
  • Gonadotrophs Hormones that target sex hormones.
  • Follicle-Stimulating Hormone (FSH) Stimulates
    follicle egg development in females sperm
    production in males, stimulates estrogen
  • Luteinizing Hormone (LH) Stimulates ovulation in
    females testosterone secretion in males.

Endocrine Glands Pituitary
  • Trophic Hormone Gonadotrophin
  • Thyrotrophs Stimulates the seceretion of thyroid
  • Thyroid-Stimulating Hormone (TSH) aka
  • Somatotrophs Stimulates Human Growth Hormone
    (HGH) for body growth development metabolism
  • HGH also controls Insulinlike Growth Factors,
    important in regulating hypoglycemic
    hyperglycemic reactions.

Endocrine Glands Pituitary
  • Lactotrophs Trigger mammary glands to produce
    milk via prolactin (PRL).
  • Can indirectly stimulate testosterone secretion
    in males.
  • Corticotrophs Hormones that stimulate the
    adrenal cortex to secrete glucocorticoids.
  • Adrenocorticotropic Hormone (HCTH) aka
    Corticotropin Stimulates adrenal cortex.
  • Melanocyte-Stimulating Hormone (MSH) Can darken
    skin when levels are too high.

Endocrine Glands Pituitary
  • Posterior Pituitary Gland Doesnt synthesize
    hormones, but stores hypothalamus-produced
  • Oxytocin (OT) Important in enabling
    positive-feedback mechanism of labor in the
    ejection of milk from mammary glands.
  • Antidiuretic Hormone (ADH) Decreases the
    production of urine from the kidneys to prevent
  • Increases blood volume U pressure due to water
    retention in kidneys, sweat glands, blood

Endocrine Glands Pineal
  • Pineal Gland Mass of neural and secretory
    (pinealocytes) cells siitting on the roof of the
    brains 3rd ventricle.
  • Melatonin Only hormone produced acts as an
    antioxidant, regulates internal biological clock,
    circadian rhythms.
  • Production is INCREASED in darkness and DECREASED
    in bright light.
  • Seasonal Affective Disorder (SAD) Depression
    triggered by overproduction of melatonin during
    the winters lack of natural light.

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Endocrine Glands Thyroid
  • Thyroid Glands Largest most vascular endocrine
    gland inferior to larynx with lobes on either
    side of the trachea.
  • Thyroid Follicles Sacs that make up the majority
    of the thyroid gland and store the hormones
  • 3 Specialized Thyroid Hormones
  • Triiodothyronine
  • Thyroxine
  • Calcitonin

Endocrine Glands Thyroid
  • 3 Specialized Thyroid Hormones
  • Triiodothyronine aka T3 Increases Basal
    Metabolic Rate (BMR) to increase the rate of
    oxygen consumption increases ATP production,
    accelerates growth, stimulates protein
  • Contains 3 iodine atoms produced by follicles
    diffused into blood stream.
  • Released during cold, pregnancy, low metabolic
    rates, or low thyroid hormone levels.
  • Release is regulated by the hypothalamus.

Endocrine Glands Thyroid
  • 3 Specialized Thyroid Hormones
  • Thyroxine aka Tetraiodothyronine aka T4 Produces
    the same basic effects as T3, but is less potent
    released in much larger quantities.
  • Contains 4 iodine atoms produced by the
    follicles diffuses into the bloodstream.
  • Target cells may concert T3 to T4
  • Calcitonin Lowers the level of calcium in the
    blood by inhibiting osteoclasts.
  • Produced by the parafollicular cells in between
    the follicles of the thyroid triggered by high
    Ca2 levels in the bloodstream.

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Thyroid Disorders
  • Hypothyroidism Lowered production of thyroid
    hormones. Can be passed down by the mother and
    result in stunted growth, low body temperature,
    and possible mental retardation.
  • Myxedema Low metabolism, increased weight gain,
    high blood pressure due to low levels of
    thyroid hormones.

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Thyroid Disorders
  • Goiter Pathological enlargement of the thyroid
    gland, typically caused by iodine deficiency.
  • Graves Disease An autoimmune disease where
    antibodies cause the thyroid to grow abnormally.
  • Can lead to lead to elevated heart rates and
  • Triggered by a goiter becoming toxic.

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Endocrine Glands Parathyroid
  • Parathyroid Glands Regulates calcium, magnesium,
    phosphate ion levels in the blood via
    parathyroid hormone (PTH).
  • Found behind the thyroid, attached to the
  • PTH Calcitonin work together to regulate
    homeostasis of calcium in the bloodstream.
  • Stimulates Calcitriol to aid in calcium
    absorption from food.

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Parathyroid Disorders
  • Hyperparathyroidism Too much parathyroid hormone
    is produced, causing elevated levels of calcium
    in the bloodstream.
  • Leads to softening of the bones a risk for
    kidney stone formation.
  • Hypoparathyroidism Too little parathyroid
    hormone is produced, causing the spontaneous
    creation of action potentials.
  • Leads to muscle twitches, spasms, tetany.

Endocrine Glands Thymus
  • Thymus Gland Assists the immune system.
  • Produces hormones responsible for developing
    regulating T-cells crucial to the autoimmune
  • Thymosin
  • Thymic Humoral Factor (THF)
  • Thymic Factor (TF)
  • Thymopoietin

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Endocrine Glands Adrenals
  • Adrenal Glands Located on top of the kidneys.
  • Adrenal Cortex Outer layer
  • Zona Glomerulosa Secrete mineralcorticoids to
    maintain homeostasis.
  • The enzyme renin to stimulate aldosterone
    (regulates sodium potassium levels controls
    blood pressure by increasing blood volume.)
  • Zona Fasciculata Secretes glucorticoids to
    increase energy supplies, regulate metabolism,
    break down protein tryglycerides, help resist
  • Cortisol (90 of glucorticosteroid activity) is
    released in response to stress. Release
    controlled by the hypothalamus increases
    metabolism, lowers inglammation, depresses immune

Endocrine Glands Adrenals
  • Zona Reticularis Responsible for the synthesis
    secretion of androgens (masculinizing hormones).
  • Dehydroepiandrosterone (DHEA) is important for
    female sex drive can be converted to estrogen.
  • Adrenal Medulla Inner Layer composed of
    autonomic nervous system ganglia.
  • Chromaffin cells Ganglia that release stress
    hormones instead of neurochemicals that increase
    heart rate, blood pressure, blood flow, oxygen
    intake, glucose production.
  • Epinephrine aka Adrenaline
  • Norepinephrine aka Noradrenaline

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The Pancreas
  • Pancreas Functions as both an endocrine
    exocrine gland.
  • Pancreatic Islets aka Islets of Langerhans
    Function as endocrine glands series of 4
    different cells.
  • Alpha Cells (A Cells) Secrete glucagon to raise
    the blood sugar level by triggering
    glycoeogenesis in the liver.
  • Beta Cells (B Cells) Secrete insulin to lower
    the blood sugar level by increasing the synthesis
    of glycogen, protein, fat.

The Pancreas
  • Delta Cells (D Cells) Secrete somatostatin to
    inhibit growth hormone regulate the secretion
    of insulun glucagon.
  • F Cells Secrete Pancreatic Polypeptide to
    inhibit somatostatin secretion the secretion of
    enzymes from the gallbladder pancreas.

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  • Gonads The ovaries (females) and testes (males).
  • Ovaries Produces estrogen, progesterone,
    inhibin, relaxin.
  • Mammary gland production, the menstrual cycle,
    and pregnancy are maintained by progesterone,
    estrogen, FSH, LH.
  • Inhibin inhibits the secretion of FSH.
  • Relaxin is important for delivery.
  • Testes Produce testosterone, which regulates the
    production of sperm helps develop masculine
    features (facial hair, deep voice, etc.)

Other Hormones
  • Atrial Natriuretic Factor (ANF) Produced by the
    heart when blood pressure is too high, causing
    the kidneys to increase urine output lower the
    blood pressure.
  • Calcitriol Produced by the kidneys and used to
    regulate calcium levels and works with FPO to
    stimulate red blood cell production.
  • Humon Chorionic Gonadotropin (HCG) Produced by
    the placenta to support pregnancy.
  • Stomach small intestine secrete hormones that
    help regulate digestion.

General Adaptation Syndrome
  • General Adaptation Syndrome The three stages the
    body goes through in fight or flight mode or
    during times of stress.
  • Alarm (Fight or Flight) Reaction Norepinephrine
    and epinephrine are released to arouse the body.
  • Blood glucose, aldosterone, and angiotension
    levels increase.
  • Resistance Reaction If stress continues,
    cortisol is increased to break down fats
    proteins to glucose for instant energy.
  • Exhaustion If the stress still continues,
    cortisol levels become too high and cause
    headache, ulcers, immune compromise.

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