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What is oxygen debt?
The extra oxygen needed after exercise for recovery processes.
Name four things that must occur for a muscle to return to resting state.
Replenish O₂, convert lactic acid to pyruvic acid, restore glycogen, resynthesize ATP and creatine phosphate.
What happens to lactic acid after exercise?
It's converted back into pyruvic acid in the liver.
Why do muscles need more oxygen after intense exercise?
To repay oxygen debt and restore normal metabolic conditions.
What molecule must be resynthesized using oxygen after exercise?
ATP.
Where is glycogen stored in the body?
In muscle fibers and the liver.
What percent of energy from muscle activity is used for work?
About 40%.
What percent of muscle activity energy is released as heat?
About 60%.
How does the body prevent overheating during exercise?
Heat is lost through skin radiation and sweating.
What is the main reason body temperature rises during physical activity?
Inefficiency of ATP use—most energy becomes heat.
What factors affect the force of muscle contraction?
Number of fibers activated, muscle size, and stretch length.
How does muscle fiber stretch affect contraction strength?
Optimal strength occurs at 80–120% of resting length.
What effect does increased muscle fiber recruitment have?
Stronger contraction.
How does muscle size influence contraction force?
Larger muscles produce more force.
Why does overstretching a muscle reduce contraction force?
Myofilaments overlap less, reducing crossbridge formation.
What determines a fiber’s speed of contraction?
The speed at which ATPase enzymes split ATP.
What are the two main factors used to classify muscle fibers?
Contraction speed and ATP-forming pathway.
What are the three types of muscle fibers?
Slow oxidative, fast oxidative, and fast glycolytic.
What is a characteristic of slow oxidative fibers?
Fatigue-resistant, contract slowly.
Which fibers have high myoglobin and many mitochondria?
Slow oxidative fibers.
What type of respiration do oxidative fibers use?
Aerobic respiration.
Which muscle fiber type is best for endurance activities?
Slow oxidative fibers.
Which fibers are moderately fatigue-resistant?
Fast oxidative fibers.
What kind of activities use fast oxidative fibers?
Sprinting and walking.
What characterizes fast glycolytic fibers?
Quick contractions and easy fatigue.
Which fibers have few mitochondria and little myoglobin?
Fast glycolytic fibers.
What energy system do fast glycolytic fibers primarily use?
Anaerobic glycolysis.
What does aerobic exercise do to capillaries?
Increases the number around muscle fibers.
How does aerobic exercise affect mitochondria?
Increases their number.
What is the effect of aerobic exercise on myoglobin?
Increases its content in muscle cells.
What performance benefit does aerobic exercise give?
Increases endurance and resistance to fatigue.
Does aerobic training significantly increase muscle size?
No, there's little hypertrophy.
What is muscle hypertrophy?
Increase in muscle size.
What causes hypertrophy during resistance exercise?
Enlargement of existing fibers, not increased fiber number.
What cellular components increase in hypertrophied muscles?
Myofibrils, mitochondria, myoglobin, and glycogen stores.
What happens to connective tissue in hypertrophied muscle?
It increases.
What type of exercise leads to hypertrophy?
Resistance training (e.g., weight lifting).
Does resistance training affect fiber number?
No, it affects size only.
What is the shape of smooth muscle cells?
Spindle-shaped.
Do smooth muscles have striations?
No, they are non-striated.
Where is smooth muscle found?
In walls of hollow organs (except the heart).
What connective tissue is found in smooth muscle?
Endomysium only.
What are the two layers of smooth muscle?
Longitudinal and circular。
What are the two types of smooth muscle?
Single-unit (visceral) and multiunit.
Where is single-unit smooth muscle found?
In hollow organs and small blood vessels.
What type of smooth muscle is autorhythmic and has gap junctions?
Single-unit smooth muscle.
What does single-unit smooth muscle do?
Contracts as a unit, often rhythmically.
Where is multiunit smooth muscle found?
Large arteries, airways, arrector pili muscles, and eyes.
Does multiunit smooth muscle contract as a unit?
No, individual fibers contract independently.
How are multiunit smooth muscle fibers activated?
Each fiber has its own motor neuron ending.