Topic 10: Skeletal Muscle Physiology - Muscle Tension - Fiber Length Flashcards
Which fiber length is optimum?
resting fiber length
Why is resting fiber length optimum? (2)
- allows for a maximum number of cross bridges formed upon stimulation
- which allows for max tension
What happens if you decrease tension to a short fiber length? (2)
- thin filaments overlap and interfere with cross bridge attachment
- min length is 70% optimal
What happens if you decrease tension to a longer/stretched fiber length? (2)
- not all myosin heads near actin binding sites
- max length is 130% optimal
Why does the size of fiber matter in relation to muscle tension? (2)
the thicker the fiber, the more myofibrils/fiber
- so more tension
How can we increase the size of fiber? (2)
- exercise, testosterone for males
What is muscle fatigue? (2)
- muscle does not contract well
- reduced maximum tension
What are the two fiber types in a muscle?
fast and slow
What is a fast muscle fiber? (2)
- contract and relax rapidly
- white (little myoglobin)
What is a slow muscle fiber? (2) (3)
- contract and relax slowly
- red (more myoglobin)
- ex. postural muscles
In a WHOLE muscle, what affects tension? (4)
- Number of fibers contracting
- number of fibers/motor units
- Muscle Size
- Fatigue
Why does the number of fibers contracting in a whole muscle affect tension? (2)
- more active motor units means increased tension
- small motor units recruited first, then larger ones added when more tension needed
Why does the number of fibers/motor units in a whole muscle affect tension? (3)
- more fibers/unit increases tension
- 1 neuron to 10 fibers is weak
- 1 neuron to 1000 fibers is strong
Why does whole muscle size affect tension?
- larger means more fibers
What is muscle tone? (2)
- low levels of tension in a few fibers that develops as different groups of motor units are alternately stimulated over time
- gives firmness to muscles
