Energy Systems And Skeletal Muscle Plasticity Flashcards
What is the primary energy source for skeletal muscle contraction?
Adenosine triphosphate (ATP)
ATP serves as both an energy receiver and donor
What are the three metabolic energy systems in skeletal muscle?
- Immediate Energy System
- Lactic Acid System
- Oxidative System
What characterizes the Immediate Energy System?
Anaerobic and alactic; relies on ATP and creatine phosphate
Depletes energy yield after approximately 10 seconds of high-intensity exercise
What is the primary substrate for ATP generation in the Lactic Acid System?
Carbohydrate (glucose)
This system is active during short-duration, high-intensity exercise lasting 2 to 4 minutes
During which type of exercise is the Oxidative Energy System primarily used?
Lower intensity, sustained exercise
ATP is produced by mitochondrial respiration utilizing oxygen
What is the contractile unit within each muscle fiber called?
Sarcomere
Contains myosin and actin proteins
What is the role of myosin ATPase in muscle contraction?
Provides energy for myosin and actin to slide across one another
This interaction allows for muscle contraction
What is a motor unit?
A motor neuron and the muscle fibers it innervates
It is the functional unit of the neuromuscular system
What are the three primary classes of muscle fiber types?
- Type I (slow-twitch)
- Type IIa (fast-twitch intermediate)
- Type IIb (fast-twitch)
Which muscle fiber type is known for having a high anaerobic capacity?
Type IIb fibers
They are suited for high-intensity, rapid contractions but fatigue quickly
What adaptation occurs in Type II fibers with endurance training?
Decrease in Type IIb fibers and increase in Type IIa fibers
Type I fibers become faster with endurance training
What is the effect of heavy resistance training on muscle fiber type?
Increases MHC IIa and decreases MHC IIx
Hypertrophy plays a role in strength gains
How does endurance training affect glycogen stores in muscle fibers?
Increases intramuscular glycogen stores
Results in a glycogen-sparing effect and increased free fatty acid metabolism
What is the myonuclear domain concept?
Each myonucleus controls a finite volume of sarcoplasm
The amount of myonuclei increases during hypertrophy to maintain this domain
What are satellite cells?
Muscle stem cells activated during exercise
They contribute additional myonuclei during hypertrophy
What are the four myogenic regulatory factors (MRFs)?
- Myo-D
- Myogenin
- MRF-4
- myf5
True or False: Muscle fiber hypertrophy requires a decrease in myonuclear domain.
False
Moderate hypertrophy can occur without decreasing the myonuclear domain
What is required to produce myogenically-induced muscle hypertrophy?
Satellite cell activation
Satellite cell activation is crucial for muscle growth.
How long after heavy resistance training does satellite cell activation occur?
4 weeks
Satellite cell activation can remain elevated for up to 16 weeks.
What is associated with satellite cell activation during resistance training?
Increases in muscle fiber cross-sectional area
This indicates muscle growth.
What significant increase occurs when muscle fiber hypertrophy exceeds 26%?
Myonuclear number
This indicates a physiological response to significant muscle growth.
Does muscle fiber hypertrophy always depend on a decrease in the myonuclear domain?
No
Moderate muscle fiber hypertrophy can occur without new myonuclei.
How long after resistance training does satellite cell activation begin?
30 days
This activation can be maintained for up to 90 days.
What is the peak increase in the cross-sectional area of muscle fibers after 90 days of training?
17%
This indicates a gradual increase in muscle size.
What happens to muscle damage in response to heavy resistance training?
Release of growth factors
These growth factors help regulate satellite cell population during regeneration.
How quickly can satellite cells become activated after muscle damage?
Within 6 hours
This rapid response is critical for muscle repair.
Within how many days do satellite cells proliferate extensively after damage?
2-3 days
This is in response to growth factors released from damaged myotubes.
What happens approximately 5 days after muscle damage?
Satellite cells withdraw from the cell cycle
They may self-renew or form differentiated myotubes.
How long does it take for the architecture of damaged muscle to be largely restored?
10 days
This indicates effective recovery processes.
Is lighter intensity resistance training as effective as higher intensity for myogenic activation?
Yes
Both intensities can increase satellite cell numbers.
After how many weeks of resistance training can an increase in satellite cells be observed?
12 weeks
Both lighter and heavier training intensities show similar increases.
What new aspect of myogenic precursor cell activation was revealed by 12 weeks of lighter-intensity resistance training?
Increased number of satellite cells
This indicates that lighter resistance training can also promote muscle adaptation.
What role do satellite cells appear to play in skeletal muscle adaptation?
A broad physiological range
This suggests that their function is more versatile than previously thought.
