Muscle IV Flashcards
Force generated by a muscle is called […]
Tension
The tension exerted by a whole muscle is controlled by […] and […]
Recruitment, summation
What is recruitment?
An increase in the number of active muscle fibers to generate muscle tension.
What is summation?
It is the additive effects of several closely spaced twitches to generate muscle tension.
Explain summation in the muscle fiber when it gets stimulated at a regular, relatively large interval.
Unfused tetanus occurs - each stimulation will cause a twitch, and the twitches will build on each other such that the fiber will reach a steady state of oscillation between contraction and relaxation.
Explain summation in the muscle fiber when it gets stimulated repeatedly at a very short interval.
Fused tetanus occurs - each stimulation will cause a twitch, and the twitches are so close together that the muscle fiber will just remain contracted.
Tetanus is defined as […]
The sustained contraction of the muscle fiber.
Compare the amount of tension generated by a twitch to the tension generated by unfused tetanus.
The peaks of the unfused tenanus consist of twice as much force as a twitch.
Compare the amount of tension generated by a twitch to the tension generated by fused tetanus.
The tension of fused tetanus is three times the tension of a twitch.
Describe how recruitment works (in general) in the generation of muscle force.
To increase the amount of force being generated by a single muscle, the number of muscle fibers that contract can be increased according to the motor unit of the muscle group.
Explain how the motor unit of the muscle group affects recruitment.
The motor unit, which can be small for something like the eye or large for something like the leg, determines the steps by which recruitment can occur. So a smaller motor unit means more fine-tuned adjustments, while a larger motor unit means more large-scale adjustments.
What is the main energy source for skeletal muscle metabolism?
ATP
Explain the first step of skeletal muscle metabolism.
The muscle has a stock of ATP, which gets converted into ADP when used. But since ATP concentrations have to remain high for the muscle to contract, the existing ATP is just enough to give the muscle time to start generating more elsewhere.
Explain the second step of skeletal muscle metabolism.
The muscle has a stock of creatine phosphate, which can take its phosphate and attach it to the ADP from step 1 to make more ATP using the enzyme creatine kinase. This converts the creatine phosphate to creatine and gives the muscle enough time for other energy-generating mechanisms to come in.
What are the two possible forms of ATP production in skeletal muscle excluding creatine phosphate?
Glycolysis and oxidative phosphorylation
How does glycolysis work in muscle cells?
Muscles can use either glucose from the blood or glycogen from the muscle itself to generate ATP (and pyruvate + lactic acid).
How does oxidative phosphorylation work in muscle cells?
The pyruvate producted by glycolysis can be used to produce more energy.
What are the 3 types of skeletal muscle fibers?
Fast glycolytic fibers, slow oxidative fibers, and fast oxidative fibers.
Describe the characteristics of fast glycolytic fibers in terms of ATPase activity, myoglobin/colour, and amount of force/unit time
High ATPase activity, no myoglobin (white muscle), generates large force over short time period.