The Endocrine System

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The Endocrine System

• Part 3 Integration Control

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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.

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Glands

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

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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.

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Hormones

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

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Hormones

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

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Hormones

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

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Hormones

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

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Hormones

• 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
  reactions.
• Examples
• Prostadcyclin Inhibits blood clotting
  vasoconstriction
• Thromboxanes Override the effects of
  prostacyclin when injured.

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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
  response.
• 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.

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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
  Gland.
• 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.

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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
  secretion.
• Luteinizing Hormone (LH) Stimulates ovulation in
  females testosterone secretion in males.

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Endocrine Glands Pituitary

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

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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.

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Endocrine Glands Pituitary

• Posterior Pituitary Gland Doesnt synthesize
  hormones, but stores hypothalamus-produced
  hormones.
• 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
  dehydration.
• Increases blood volume U pressure due to water
  retention in kidneys, sweat glands, blood
  vessels.

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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
  produced.
• 3 Specialized Thyroid Hormones
• Triiodothyronine
• Thyroxine
• Calcitonin

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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
  synthesis.
• 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.

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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
  metabolism.
• 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
  thyroid.
• 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.

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Endocrine Glands Thymus

• Thymus Gland Assists the immune system.
• Produces hormones responsible for developing
  regulating T-cells crucial to the autoimmune
  responses.
• 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
  stress.
• Cortisol (90 of glucorticosteroid activity) is
  released in response to stress. Release
  controlled by the hypothalamus increases
  metabolism, lowers inglammation, depresses immune
  response.

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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.

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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

• 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.)

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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.

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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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