Download Energy for Muscle Contractions

Energy for Muscle Contractions
Anatomy & Physiology
Chapter 6
Energy for Muscle Contractions
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
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:
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
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
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
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)
Plan C: Glycogen – Cellular Resp.


Pyruvate turned into acetyl CoA, which then
enters Kreb’s cycle. – complete breakdown of
the glucose molecule.
Provides 20x more ATP than anaerobic
respiration
–
Useful during endurance exercise
 BUT…
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Anaerobic is 2.5x faster than aerobic
Note: Activities requiring sudden surges of
power (tennis, soccer) use aerobic + anaerobic
Plan D:
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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)

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Start to metabolize lipids
Start to metabolize proteins
Aerobic vs. Anaerobic
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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.
Aerobic vs. Anaerobic

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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.
Homeostasis of Muscle Tissues

How do your muscle maintain homeostasis?
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
Oxygen Debt

Example:
–
You run the 100 meter dash in 12 seconds.

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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.
Paying back the Debt

Involves:
–
–
–
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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:

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Hemoglobin
Myoglobin
Oxygen in lungs and other body fluids
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.”