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Autonomic nervous system. Intro. Autonomic nervous system (ANS) Sympathetic nervous system (SNS) Fight or flight Major nerve : Sympathetic chain Major neurotransmitters : Epi, NE Bind to : α and β receptors Parasympathetic nervous system (PNS) Rest and digest Major nerve : Vagus

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  • Autonomic nervous system (ANS)
    • Sympathetic nervous system (SNS)
      • Fight or flight
        • Major nerve: Sympathetic chain
          • Major neurotransmitters: Epi, NE
          • Bind to: α and β receptors
    • Parasympathetic nervous system (PNS)
      • Rest and digest
        • Major nerve: Vagus
          • Major neurotransmitter: Ach
          • Binds to: Cholinergic receptors



Sympathetic chain

Cranial nerve X (Vagus n.)

autonomic response to exercise
Autonomic response to exercise
  • Epi, NE increase exponentially with ex intensity
  • Effects:
    • BP
      • increase
        • Vasoconstriction
        • Increased cardiac output
    • HR
      • increase
    • Activates glycolysis/lipolysis
training effects on autonomic nervous system
Training effects on autonomic nervous system
  • Submaximal exercise
    • Reduced catecholamine response
      • Reduced HR
      • Reduced blood pressure response
      • Reduced lactate?
      • Altered fuel use?
training effects on autonomic nervous system1
Training effects on autonomic nervous system


  • Maximal exercise
    • Maximal adrenergic activity is increased with training
  • Effects
    • Increased maximal hepatic glucose production
  • Also
    • Helps defend blood pressure
    • Helps maintain cardiac output
growth hormone
Growth hormone
  • Polypeptide hormone
    • anterior pituitary gland
      • Regulates
        • Growth (Anabolic)
          • Stimulates protein synthesis
        • Cell reproduction
        • Metabolism
          • Potent stimulator of lipolysis
      • Endocrine gland
        • Releases hormones into the blood
      • Released during
        • Fasting
        • Exercise
        • Sleep
  • Neuro-endocrine integration
    • Hypothalamic-pituitary axis
      • Hypothalamus regulates output from anterior Pituitary
        • Growth hormone releasing factor (GHRF)
growth hormone response during exercise
Growth hormone response during exercise
  • Lag of ~ 15 minutes before GH increases
  • Proposed metabolic effects of GH
    • Increases growth of all tissues
    • Increases lipolysis
    • Promotes gluconeogenesis
    • Reduces hepatic glucose uptake
cortisol and the pituitary adrenal axis
Cortisol and the pituitary-adrenal axis
  • Cortisol
    • Steroid hormone
      • Cholesterol
    • Glucocorticoid
      • Promotes glucose production
    • Stimulates AA release from muscle (catabolic)
    • stimulates gluconeogenesis
  • Hypothalamus
    • Releases corticotrophin releasing factor (CRF)
  • Anterior Pituitary
    • Adrenocorticotrophin (ACTH)
  • Adrenal cortex
    • cortisol

Anterior pituitary

  • Glucocorticoid
    • Cortisol/cortisone
      • Help to regulate blood glucose
      • Released during prolonged, exhaustive exercise
  • Mineralcorticoid
    • Aldosterone
      • Released from adrenal cortex
      • Works with renin/angiotensin system
      • Electrolyte homeostasis
        • Reabsorption of water and sodium, excretion of potassium
  • Note how cortisol changes throughout the day
    • also, rises to highest level at the end of exercise
    • Influenced by intensity and duration of exercise
thyroid hormone
Thyroid hormone
  • Triiodothyronine (T3) and thyroxine (T4)
  • T3 greatest biological activity
  • Thyroid stimulating hormone (TSH; anterior pituitary) stimulates thyroid to release thyroxine
  • Cells convert T4 to T3
  • Stimulates metabolism
  • “permissive” effect
    • Enhances the effects of other hormones
    • Perhaps through adenylate cyclase/cAMP effect
exercise responses
Exercise responses
  • What do these responses tell us?
  • Why measure
    • Lactate?
    • Lactate threshold?
    • Oxygen deficit?
    • Oxygen debt?
  • Quantify exercise intensity
exercise metabolism
Exercise metabolism
  • Oyxgen consumption
    • Principle measure of exercise intensity
    • Increases linearly with intensity
  • Blood lactate
    • Easy to measure
    • Fair index of intensity
lactate issues
Lactate issues
  • Blood lactate
    • Balance between rate of appearance (Ra) and disappearance (Rd)
    • Lactate used by other tissues as an energy source
    • Level in blood
      • Balance between Ra/Rd
      • Determined by fiber type and oxidative capacity of tissue
muscle consumer of lactate
Muscle: Consumer of lactate

Lactate concentration

  • Blood lactate increases during exercise above lactate threshold (>45-50% Vo2max)
    • Release from tissue (muscle) greater than uptake (less active tissues)
    • Release from muscle is quite high initially, then falls
    • Some subjects actually switch to net uptake

Net Lactate release

fate of lactate after exercise
Fate of lactate after exercise
  • Following exercise blood lactate levels fall
  • The vast majority of the Carbon from lactate (C3H5O3) shows up as expired CO2
    • Oxidized
    • C3H5O3 + H+ 3CO2 + 3H2O
  • Lactate may also be
    • Incorporated into Bicarbonate
    • Converted to glycogen
    • Converted to glucose
    • Incorporated into proteins









Expired CO2

Expired CO2

Expired CO2

lactate turnover during exercise
Lactate turnover during exercise
  • Turnover
    • Balance between production and removal
  • Rest
    • Balance between production and removal
      • Blood lactate low
  • Exercise
    • Production greater than removal at all intensities above lactate threshold (45-50% of Vo2max)
lactate turnover
Lactate turnover
  • Blood concentration (1) is dependent upon the balance between
    • Clearance (2)
    • Rate of appearance (3)
  • Note how trained lactate concentration is lower due to reduced rate of appearance and increased clearance rate




endurance exercise and lactate
Endurance exercise and lactate
  • Turnover
    • Measure used when metabolite is infused
    • Turnover is then based on infusion rate/amount in blood
      • Greater clearance from blood necessitates greater infusion rate to maintain a certain level
      • Lactate turnover is increased with endurance training
  • Metabolic clearance
    • Measure of rate of disappearance from blood
    • Also increased with endurance training
causes of the lactate threshold
Causes of the Lactate Threshold
  • Lactate threshold
    • Point where blood lactate starts to accumulate in the blood
    • Balance between Ra and Rd changes
    • MCR reaches a maximum
    • Greater recruitment of fast-twitch fibers
    • SNS?
      • Shunts blood flow away from inactive tissues
      • May reduce uptake
oxygen deficit
Oxygen deficit
  • Oxygen deficit
    • Difference between O2 demand and O2 consumption
      • O2 demand = ATP requirement
      • O2consumption = mitochondrial ATP production
    • Energy deficit supplemented by ATP-PCr and anaerobic metabolism
    • Typically used during >LT to maximal work
    • Tough to determine during “supra-maximal” exercise, where the O2 requirement is not known
    • Component of fatigue
oxygen debt
“Oxygen debt”
  • O2 consumption should fall back to resting levels immediately once the exercise ceases
    • This DOES NOT happen
    • Originally thought that O2 debt equal to the O2 deficit
      • Extra O2 consumption during recovery to “pay back” the debt
      • Thought to be completely due to non-aerobic metabolism (ATP-PCr and anaerobic metabolism)
  • Currently: Known that other factors help determine the size of the oxygen debt
    • Name changed to Excess post exercise oxygen consumption (EPOC)

STILL above resting

  • O2 consumption follows exponential decrease to resting levels
  • Time course can be quite prolonged (vs short time course of O2 deficit)
  • Temperature, catecholamines and pH impact EPOC, but have little or no effect on O2 deficit
  • So, some of the EPOC is due to oxidation of lactate/regeneration of glycogen and PCr but not a 1:1 relationship
  • Causes of excess post exercise VO2
    • Temperature
      • Heat production and muscle temperature increase dramatically during exercise
        • Muscle temperature can get as high as 40°C
      • High temperature can “loosen” the coupling between oxidation and phosphorylation
epoc and mitochondrial uncoupling
EPOC and mitochondrial uncoupling
  • Fatty acids and ions
    • Fatty acids may be involved in “uncoupling” of oxidative and phosphorylation
      • brown adipose tissue of rats
      • So, heat is produced, but ATP is not
    • May also impact the permeability of Na+ and K+ across the mitochondrial memebranes

This “linkage” is affected

epoc and mitochondrial uncoupling1
EPOC and mitochondrial uncoupling
  • Calcium
  • Increases oxygen consumption
    • Mitochondria sequester Ca2+
      • Energy dependent
    • Ca2+ uncouples oxidation and phosphorylation
epoc and mitochondrial uncoupling2
EPOC and mitochondrial uncoupling
  • Epinephrine and Nor-epinephrine
    • Take some time to be cleared from the blood following exercise
  • pH
    • Inhibits PCr recovery
    • May make mitochondrial membrane “leakier”