Energy for Muscle Contractions

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Energy for Muscle Contractions

• Anatomy Physiology
• Chapter 6

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Energy for Muscle Contractions

• Your muscles have various ways of providing the
  energy necessary to perform a muscle contraction.
• 4 possible ways to meet the energy needs of a
  muscle follow

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Plan A

• Immediate and direct source is on-site ATP
  molecules.
• Fibers contain enough ATP to sustain contractions
  for 5-6 seconds
• Chemical equation
• ATP ? ADP phosphate energy

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Plan A On-site ATP

• Involves breakdown of stored glycogen to glucose
  into pyruvate, which is then converted to lactic
  acid.
• However, if lactic acid accumulates, fatigue
  results

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Plan B

• Creatine Phosphate
• This is a high energy compound used to produce
  ATP
• Provides for about 15 seconds of maximal
  contraction
• Chemical equation
• Creatine phosphate ? creatine phosphate
  energy
• The energy created here is used to convert
• ADP phosphate ? ATP

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Plan C

• Glycogen
• On-site ATP and creatine phosphates have been
  exhausted.
• Stored glycogen ? ATP (thru glycolysis)
• Anaerobic process good for another 30-40 seconds
  of maximum muscular contractions
• Can go to aerobic respiration if enough oxygen is
  available (provides for even longer period of
  contractions)

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Plan C Glycogen Cellular Resp.

• Pyruvate turned into acetyl CoA, which then
  enters Krebs cycle. complete breakdown of the
  glucose molecule.
• Provides 20x more ATP than anaerobic respiration
• Useful during endurance exercise
• BUT
• Anaerobic is 2.5x faster than aerobic
• Note Activities requiring sudden surges of
  power (tennis, soccer) use aerobic anaerobic

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Plan D

• Alternate Metabolic Pathways
• As exercise intensity increases, and glycogen
  stores are depleted, alternate sources are
  converted to glucose (gluconeogenesis)
• Must be enough oxygen available to switch to
  these sources (aerobic)
• Start to metabolize lipids
• Start to metabolize proteins

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Aerobic vs. Anaerobic

• Aerobic means "with oxygen."
• Aerobic exercise is any large muscle activity
  that you can sustain for two to three minutes or
  longer, because exercising for prolonged periods
  requires a source of oxygen and its delivery to
  the muscles.
• Because aerobic exercise requires oxygen from the
  air to get to your muscles, the exercise can
  continue only when a source of oxygen is
  available.
• Your heart and lungs work together to supply
  oxygen to tissues in your body.

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Aerobic vs. Anaerobic

• The term "anaerobic" means "without air" or
  "without oxygen."
• Anaerobic exercise uses muscles at high intensity
  and a high rate of work for a short period of
  time.
• Anaerobic exercise helps us increase our muscle
  strength and stay ready for quick bursts of
  speed.

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Homeostasis of Muscle Tissues

• How do your muscle maintain homeostasis?

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Oxygen Debt

• Occurs when muscular exertion is so great that
  the cardiovasular system can not meet the muscle
  fibers oxygen needs.
• Anaerobic glycolysis produces the ATP
• Lactic acid is then produced when not enough O2
  is available

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Oxygen Debt

• Example
• You run the 100 meter dash in 12 seconds.
• This exercise requires 6 liters of oxygen for
  total aerobic respiration.
• Actual oxygen that can be delivered to muscles is
  only 1.2 liters.
• You now have an oxygen debt of 4.8 liters.

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Paying back the Debt

• Involves
• Converting lactic acid back into pyruvic acid
  (80 of this occurs in the liver causing an
  increase in blood pH)
• Replenishing ATP in muscle fiber
• Replenishing creatine phosphate
• Payback of oxygen borrowed from
• Hemoglobin
• Myoglobin
• Oxygen in lungs and other body fluids

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Maximal Oxygen Uptake

• The maximum capacity for oxygen consumption by
  the body during maximum exertion.
• OR
• How much oxygen your body can take in during
  exercise lasting over 1 minute.