Exercise physiology

From Iusmphysiology

Revision as of 01:04, 20 April 2011

• started here on 04/11/11.

Exercise physiology

Objectives

• The student will be able to describe the 3 metabolic systems that supply energy during exercise and relate exercise conditions with nutrient fuel use.
• The student will understand how oxygen consumption varies with exercise intensity.
• The student will be able to describe the 2 stages of oxygen recovery.
• The student will be able to describe respiratory changes during exercise.
• The student will be able to describe chemical and neural mechanisms stimulating ventilation during exercise.
• The student will be able to describe the dynamic relationship between changes in stroke volume and heart rate during exercise.
• The student will be able to describe the redistribution of blood flow to muscles and other organs during exercise.
• The student will understand the unique regulation of temperature during exercise.
• The student will understand the effect of training on cardiovascular, respiratory and metabolic function.

Metabolic aspects of exercise

• Exercise requires lots of ATP for all the work the muscle is doing.
• ATP can be generated in three ways: the phosphagen system, the glycogen-lactic acid system, or the aerobic system.
  • The phosphagen system uses creatine kinase to move the phosphate group off of creatine to ADP, generating ATP.
    • The phosphagen system (and the resident ATP) covers the energy for the 0-60 seconds of vigorous exercise.
  • The glycogen-lactic acid system runs glycogen through glycolysis to generate lactic acid.
    • The glycogen-lactic acid system covers the energy for the 1-4 minutes of vigorous activity.
  • The aerobic system uses the electron transport chain to generate ATP from glucose, fatty acids, and amino acids.
    • Aerobic oxidation of muscle glycogen, plasma glucose, and liver glycogen cover the energy for minutes 4-200 (and then tapers off).
    • Aerobic oxidation of plasma FFA (free fatty acids) and adipose tissue TAGs (triacylglycerides) cover the energy for minutes 45 and beyond.

Energy conversion in skeletal muscle

• Recall that glycolysis takes glucose to two pyruvate molecules, generating 6 ATP and 2 NADH.
• Recall that bursts of heavy activity utilize the phosphagen system and the glycogen-lactic acid systems for production of ATP.

Energy suply to muscle during exercise

• During exercise, epinephrine is elevated which signals to the liver, skeletal muscle, and adipose tissue.

• Epinephrine at the liver:
  • Epinephrine causes the liver to increase glycogenolysis and gluconeogenesis.
  • Epi--like glucagon--binds to a receptor that elevates cAMP levels and thus triggers activation of appropriate enzymes.
  • Note that gluconeogenesis can use lactic acid as a precursor to be converted into glucose.

• Epinephrine at the muscle:
  • Epinephrine at the skeletal muscle signals for the use of glycolysis (the anaerobic burning of glucose).
  • Epinephrine binds to a cAMP elevating receptor on skeletal muscle which leads to activation of appropriate enzymes for converting glucose into ATP and aerobic intermiediates (think NADH and pyruvate).
  • Glucose converted to pyruvate too quickly to be used in the (limited capacity citric acid cycle--oxphos) can be converted to lactic acid and secreted into the blood to be used in gluconeogenesis at the liver.
    • Recall that this loop (glucose -> pyruvate (to get the ATP and NADH) -> lactic acid -> liver -> glucose -> muscle -> pyruvate...) is called the cori cycle.

• Epinephrine at the adipose tissue:
  • Epinephrine at the adipose tissue causes TAG breakdown into FFAs for secretion into the blood.
  • Epinephrine binds to a receptor that activates the hormone-sensitive lipase.

Oxygen consumption during exercise

• The basal rate of oxygen consumption is about 0.25 L / minute.
• Light exercise can elevate oxygen consumption 3-fold to about 1 liter.
• Heavy exercise can elevate oxygen consumption 8-10 fold to nearly 3.5 liters.

V_O2: Maxiumum O₂ consumption

• stopped here on 04/11/11.
• started here on 04/12/11.

Objectives

• The student will be able to describe the 3 metabolic systems that supply energy during exercise and relate exercise conditions with nutrient fuel use.
• The student will understand how oxygen consumption varies with exercise intensity.
• The student will be able to describe the 2 stages of oxygen recovery.
• The student will be able to describe respiratory changes during exercise.
• The student will be able to describe chemical and neural mechanisms stimulating ventilation during exercise.
• The student will be able to describe the dynamic relationship between changes in stroke volume and heart rate during exercise.
• The student will be able to describe the redistribution of blood flow to muscles and other organs during exercise.
• The student will understand the unique regulation of temperature during exercise.
• The student will understand the effect of training on cardiovascular, respiratory and metabolic function.

• stopped here on 04/12/11.