Hormonal control and responses

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Hormonal control and responses
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Types of Hormones

• Amino acid derivatives
• epinephrine, serotonin, melotonin
• Protein
• insulin, parathyroid hormone, growth hormone
• Steroids
• derived from cholesterol
• sex hormones, mineralocorticoids, prostaglandins

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Hormone-receptor interaction

• Some hormones circulate to all tissues, but only
  act on some
• receptor must be present for effect to occur
• eg thyroid stimulating hormone only exerts an
  effect on the thyroid
• conversely some hormones work on virtually all
  tissues (insulin)

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Blood Hormone Concentration

• the effect of a hormone related to concentration
  in blood (to a point)
• Concentration affected by 4 factors
• rate of hormone secretion
• rate of metabolism or excretion
• transport proteins
• plasma volume (affected by exercise)

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Control of Hormone Secretion

• Rate of insulin secretion from the pancreas is
  dependent on
• Magnitude of input
• Stimulatory vs. inhibitory

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Factors That Influence the Secretion of Hormones
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Mechanisms of Hormone Action

• alteration of membrane transport (insulin)
• stimulation of DNA synthesis (testosterone,
  estrogen)
• activation of second messengers
• hormone doesnt enter the cell

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Relationship of Hypothalamus, Pituitary and
Target Glands
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The Hypothalamus is the Master Gland

• the hypothalamus controls the pituitary in two
  ways
• the hypothalamus can release releasing hormones
• releasing hormones act on anterior pituitary
  (TSH, ACTH, GH)
• neurons originating in the hypothalamus act on
  posterior pituitary (ADH)

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Positive and Negative Input to the Hypothalamus
(Growth Hormone)
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Growth Hormone

• uptake of amino acids and protein synthesis
• opposes insulin
• reduces use of plasma glucose
• increases gluconeogenesis
• mobilizes FFA

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Antidiuretic Hormone (ADH)

• causes resorbtion of H2O to maintain fluid
• stimulated by two factors
• high plasma osmolality (sweating)
• low plasma volume (loss of blood, exercise)

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Intensity vs. Plasma ADH
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The Adrenal Glands

• Medulla
• secretes epinephrine (E) and norepinephrine (NE)
• Cortex
• secretes mineralocorticoids, glucocorticoids

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Response to Catecholamines Role of Receptor Type
Receptor Type Effect of E/NE Membrane-bound enzyme Intracellular mediator Effects on Various Tissues
?1 ENE Adenylate cyclase ? cAMP ? Heart rate ? Glycogenolysis ? Lipolysis
?2 EgtgtgtNE Adenylate cyclase ? cAMP ? Bronchodilation ? Vasodilation
?1 E?NE Phospholipase C ? Ca ? Phosphodiesterase ? Vasoconstriction
?2 E?NE Adenylate cyclase ?cAMP Opposes action of ?1 ?2 receptors
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Aldosterone (Mineralocorticoid)

• regulates K and Na concentrations
• controls resorbtion in the kidney
• involved in thirst response

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Intensity vs. Mineralocorticoid Response
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Cortisol

• Actions
• promotes breakdown of tissue protein (inhibits
  protein synthesis)
• mobilizes FFA from adipose
• stimulates gluconeogenesis
• blocks entry of glucose into tissues (increases
  fat utilization)
• Involved in adaptation response to stress
  (exercise)

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Control of Cortisol Secretion
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Pancreas

• Insulin
• aids in transport of glucose into cells
• stimulated when blood sugar increases (storage of
  glucose, amino acids and fat)
• inhibited during exercise
• Glucagon
• opposite effect of insulin
• stimulated by low blood glucose
• mobilizes glucose and fatty acids

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Sex Hormones

• testosterone
• elevated during short-term high intensity
  exercise
• levels typically lower in endurance trained
  individuals

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Estrogen

• promotes higher levels of fat metabolism ?
• chronic endurance training may suppress E2
  (amenorrhea)

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Muscle Glycogen Utilization

• glycogen metabolism controlled by epinephrine
  (cAMP) and intracellular Ca (calmodulin) from
  sarcoplasmic reticulum
• epinephrine increases rapidly with intense
  exercise
• adrenergic blockade
• glycogen depleted only in exercising muscles
• Ca faster than cAMP and more specific

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Blood Glucose Homeostasis During Exercise

• mobilization of glucose from liver glycogen
  stores
• mobilization of plasma FFA from adipose tissue to
  spare plasma glucose
• synthesis of new glucose in the liver
  (gluconeogenesis) from AA, La, and glycerol
• blocking of glucose entry into cells to force the
  substitution of FFA as a fuel

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Slow Acting Hormones

• Thyroxine
• allows other hormones (eg epinephrine) to exert
  effect
• Cortisol
• GH

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Cortisol and Maintenance of Plasma Glucose
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At low intensity, cortisol decreases- at high
intensity it increases
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Growth Hormone Effects During Exercise
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Growth Hormone During Exercise

• Combine amino acids and glycerol to make glucose
  in the liver
• Breaks down triglycerides (fat) in the adipose
  tissue to make FFA available
• Blocks entry of glucose into the cell
• All of these go to maintain blood glucose

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Plasma GH Response vs. Intensity
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GH Response in Runners vs. Controls (Runners have
improved response)
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Fast Acting Hormones

• catecholamines (epinephrine and norepinephrine)
• N primarily neurotransmitter at synapse
• E primarily plasma hormone
• insulin
• glucagon

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Effects of Catecholamines during Exercise
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Catecholamines (adrenergic) During Exercise

• Break down glycogen in liver to free glucose
  available
• Break down triglycerides in the adipose tissue to
  make FFA available
• Block entry of glucose into the cell

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Catecholamine Response during Prolonged Exercise
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Insulin (storage) vs. Glucagon (mobilization)
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Insulin Levels Reduced during Moderate to Intense
Exercise
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Endurance Training Attenuates Insulin Response at
Given Workload
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Reduced Glucagon Response after Endurance Training
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Take home

• Almost all of the hormonal responses will be
  attenuated with endurance training
• Exception-growth hormone

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Glucagon Response Reduced after Endurance
Training Because

• increased utilization of FFA as fuel substrate
• decreased reliance on plasma glucose
• therefore decreased reliance on liver glycogen

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Remember

• ?-adrenergic inhibition
• ?-adrenergic excitation

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Adrenergic Control of Pancreatic Hormones
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Effect of Increased Sympathetic Activity on Fuel
Utilization
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Glucose Uptake by Cells can Increase 7-25 Fold
During Exercise. How?

• increased blood flow to exercising tissues
• increased metabolism causes gradient (diabetics)
• increased s of glucose transporter at membrane
  (diabetics)

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General Hormonal Responses to Graded or Prolonged
Exercise
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Lactic Acid Inhibits FFA Release from Adipose
Tissue (Means?)
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