L15. Skeletal Muscle 2 Flashcards
Contrast the duration of muscle action potential with the duration of muscle contraction, and explain the significance of this difference
Summation, Twitch, Tetanus:
Single Twitch: Muscle relaxes between action potential stimuli
Tetanus: When the frequency of muscle contraction is such that the maximal force is tension is generated without any relaxation of the muscle. summation: The occurrence of additional twitch contractions before the previous twitch has completely relaxed.
Two Types of Contraction:
Isometric: Same Length
Isotonic: Same Tension
Two Types of Isotonic Contraction:
Concentric Contraction: (C for Contracting)
Eccentric Contraction: (E for Extending)
Eccentric Contraction + DOMS:
Force-Length Relation:
At the molecular level, muscles are made up of protein filaments called actin and myosin. These filaments slide past each other to generate force and produce movement. When a muscle contracts, the actin and myosin filaments overlap more, allowing for more cross-bridges to form between them, which generates force.
When a muscle is at its optimal length, there’s an optimal overlap between the actin and myosin filaments, maximising the number of cross-bridges and thus the force-generating capacity of the muscle. This optimal length is often referred to as the “resting length” or “length at which maximal force can be generated.”
When a muscle is stretched beyond its optimal length, the overlap between actin and myosin decreases, reducing the number of cross-bridges and thus decreasing the force-generating capacity of the muscle. This is known as the “passive tension” phase. Similarly, when a muscle is shortened beyond its optimal length, the overlap between actin and myosin is also reduced, limiting the potential for cross-bridge formation and reducing force production. This is known as the “active tension” phase.
So, the force-length relationship of a muscle can be visualised as a bell-shaped curve, with force production being highest at the optimal length and decreasing as the muscle is stretched or shortened beyond that point. This relationship is crucial for understanding how muscles function in various physiological conditions and during movement.
Force-Velocity Relation:
When muscles contract slowly, they can generate more force. But when they contract quickly, they can’t generate as much force. It’s like trying to lift a heavy weight slowly versus trying to lift it quickly – you’ll have an easier time lifting it slowly because you can apply more force.
This relationship is important in understanding how muscles work during activities like sprinting, where muscles need to contract quickly but might sacrifice some force, or during activities like lifting heavy weights, where muscles contract slowly to generate maximum force.
3 Types of ATP Generation:
1)Creatine Phosphate Shuttle: Rapid, Up to 10 seconds
2)Glycolysis: Anaerobic Respiration (DOES NOT USE OXYGEN), Rapid up to a few minutes
3)Oxidative Phosphorylation: Aerobic Respiration (USES OXYGEN), Slow Sustained Longer than a few minutes
Different Skeletal Muscle Fibres:
Memorise first few lines ?
DOMS + Popping Sarcomere Theory:
2 Types of Muscle Fatigue:
Metabolic Accumulation Theory of Fatigue:
Ammonium (NH4), Pi (Inorganic Phosphate),
2 Clinical Applications:
