Endocrine%20System

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Endocrine System
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MajorHormone Secreting Structures
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General Information

• Integrates and coordinates activities of body
  cells.
• Maintains homeostasis by regulating
• 1. metabolism and energy balance
• 2. water, electrolyte nutrient balance
• 3. reproduction, growth and development
• 4. mobilization of body against stressors
• Hormones are secreted into interstitial fluid
  diffusing into blood or lymph fluid.
• Hormones act upon specific target cells.

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Regulation Communication

• Two systems for regulation
• endocrine system
• ductless glandular epithelium
• secrete hormones directly into blood
• chemical travels to target tissue
• target cells have receptor proteins
• slow, long-lasting response
• nervous system
• system of neurons
• transmits electrical signal release
  neurotransmitters to target tissue
• fast, short-lasting response

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Regulation by chemical messengers

• Neurotransmitters released by neurons
• Hormones release by endocrine glands

endocrine gland
neurotransmitter
axon
hormone carried by blood
receptor proteins
receptor proteins
Lock Keysystem
target cell
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Classes of Hormones

• Protein-based hormones
• polypeptides
• small proteins insulin, ADH
• glycoproteins
• large proteins carbohydrate FSH, LH
• amines
• modified amino acids epinephrine, melatonin
• Lipid-based hormones
• steroids
• modified cholesterol sex hormones, aldosterone

insulin
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Steroid Hormones

• Lipid soluble (hydrophobic)
• Synthesized from cholesterol
• Transported by a protein in bloodstream.
• Diffuses inside, binds with DNA to transcribe
  gene.
• Full effect could be minutes to days.

Animation Intracellular Receptor Model
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Protein Hormones

• Water soluble (hydrophilic)
• Binds to receptors on target cell membranes. No
  diffusion!
• Causes second messengers (cAMP) to be activated
  inside cell.
• Cascading effect a single molecule can activate
  hundreds of second messengers each which
  activates thousands of reactions.
• Rapid response
• Multiplier effect!

Animation Second Messenger cAMP
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Benefits of a 2 messenger system
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signal
Activated adenylyl cyclase
receptor protein
Not yet activated
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amplification
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amplification
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cAMP
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amplification
GTP
G protein
protein kinase
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amplification

• Amplification!

enzyme
Cascade multiplier!
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amplification
FAST response!
product
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Specificity of Hormones

• Target cells only respond to a specific hormone
  by having a unique receptor just for that
  hormone.
• EX Insulin receptors only respond to insulin not
  thyroxine.

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Control of Hormone Secretion
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Hormone Regulation

• Hormone secretion is controlled by
• 1. Neural stimuli
• 2. Humoral stimuli (blood chemistry)
• 3. Hormonal stimuli
• Process used to regulate
• FEEDBACK LOOPS!

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Homeostasis of Blood Glucose
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Regulation of Blood Sugar
Endocrine System Control
Feedback
islets of Langerhans beta islet cells
insulin
body cells takeup sugar from blood
liver storesglycogen
reducesappetite
blood sugar level (90mg/100ml)
liver releasesglucose
triggershunger
islets of Langerhansalpha islet cells
glucagon
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Gland A secretes a hormone that stimulates gland
B to increase secretion of another hormone. The
hormone from gland B alters its target cells and
inhibits activity of gland A.
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Target Cells

• Responsiveness can depend on
• 1. Hormone concentration
• 2. Amount of receptors
• a. up-regulation (increasing of receptors)
• b. down-regulation (decreasing of
  receptors)
• 3. Influence of other hormones
• Synergistic effect vs. Antagonistic effect

(Glucagon epinephrine)
(Insulin and Glucagon)
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Nervous Endocrine systems linked

• Hypothalamus master nerve control center
• nervous system
• receives information from nerves around body
  about internal conditions
• releasing hormones regulates release of hormones
  from pituitary
• Pituitary gland master gland
• endocrine system
• secretes broad rangeof tropic hormones
  regulating other glands in body

hypothalamus
posterior
pituitary
anterior
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Hormone Disorders

• Most involve the HYPOSECRETION or HYPERSECRETION
  of a hormone.
• Hypersecretion most likely due to a tumor on the
  gland.
• Few cases involve faulty hormone receptors or
  reduction of receptors.

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Graves Disease
Hyperthyroidism Symptoms Intolerance to
heat Heart palpitations Sensitivity to
light Weight loss Appetite increase Easily
agitated Protruding eyes
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Hypothyroidism or Myxedema
Early symptoms Being more sensitive to cold
Constipation Depression Fatigue or feeling
slowed down Heavier menstrual periods Joint or
muscle pain Paleness or dry skin Thin, brittle
hair or fingernails Weakness Weight gain
(unintentional) Late symptoms, if left
untreated Decreased taste and smell Hoarseness
Puffy face, hands, and feet Slow speech
Thickening of the skin Thinning of eyebrows
Cretinism lack of thyroxine during fetal life
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Goiter

• Iodine deficiency causes thyroid to enlarge as it
  tries to produce thyroxine

?
tyrosine iodine
?
thyroxines
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Acromegaly

• hypersecretion of GH during adulthood, usually a
  pituitary tumor.

Only certain bony regions in face, feet and hands
are affected by excessive bone deposition.
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Gigantism

• Hypersecretion of GH during childhood
• If left untreated, acromegaly will occur.

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Pituitary Dwarfism

• Hyposecretion of GH, can be corrected by giving
  GH hormone
• Must be diagnosed before growth plates have
  closed.
• Can be tumor related

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Gigantism vs. Dwarfism
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Adrenal Gland Disorders

• Cushings
• Excess Cortisol
• Weight gain
• Rounded moon face
• Fatty hump on back
• Fatigue

• Addisons
• Hyposecretion of glucocorticoids and
  mineralcorticoids
• Mouth lesions
• Hypoglycemia
• Strange skin pigmentation
• Salt craving

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Diabetes

• D. Insipidus
• tasteless
• Hyposecretion of ADH
• Extreme thirst
• Dehydration
• Excessive urination

• D. Mellitus
• Sweet tasting
• Hyposecretion of insulin (type 1)
• Blood glucose build up
• Weight loss
• Excessive urination
• Sweet smelling breath

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Adipose and Leptin

• Leptin is hormone that causes you to feel full.
• Obesity may be due to no leptin or not enough or
  hypothalamus becomes leptin resistant.