Muscle Tissue Cont.
Muscle
Metabolism
Chapter 10
Skeletal Muscle Metabolism
3 ways to replenish ATP:
1. Creatine phosphate energy storage system
2. Aerobic respiration
3. Anaerobic respiration = lactic acid system
1. Creatine Phosphate (CP)
• CP = high energy compound which can be used to
make ATP
• Duration of energy: 15 seconds; only small
amount available
CP + ADP ↔ creatine + ATP
2. Aerobic Respiration
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Uses oxygen for ATP production
Uses many substrates: carbohydrates,
lipids, proteins
Good for long term exercise
Duration of energy: hours
3. Anaerobic Respiration
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When O2 is unavailable
Very inefficient, does not create much
ATP
Produces lactic acid as a by-product –
ouch!
Duration of energy: 30 – 60 seconds
Summary of Muscle Metabolism
Muscle Tone
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Regular small contractions caused by spinal reflexes
These contractions do not produce movement
Provide constant tension development – muscles are firm
Example: neck, back and leg muscles – maintain posture
poor muscle tone
Other Muscle Terminology
• Muscle fatigue = muscle can no longer contract
despite neural stimulation
• Muscle hypertrophy = enlargement of muscle
due to repeated stimulation; muscle fibers develop
more mitochondria, more enzymes for aerobic
respiration, more glycogen reserves & grow in
size
• Muscle atrophy = loss of muscle tone & mass
due to lack of stimulation
Types of Muscle Fibers
• Fast fibers = white muscles; most skeletal fibers;
can contract in 0.01 sec or less after stimulation
• Slow fibers = red muscles; take three times as
long to contract after stimulation; contain lots of
myoglobin
• Intermediate fibers
• It is genetically determined which types of fiber
you have (exercise can change it somewhat)