BIOL 404-Exam 4-Muscle 5
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What happens when two stimuli are applied in a close time sequence?
- A twitch of higher tension
What happens when two stimuli are applied in an interspaced time sequence?
- A rise in tension with a second rise piggy backing on it
What protein is responsible for the passive elastic properties of relaxed muscle fibers?
What is Titin?
A protein that is responsible for the passive elastic properties of a relaxed muscle fiber
What is the "optimal length" LO for muscle fiber contraction?
The length at which the fiber develops the greatest isometric active tension
What is the term for the length at which the fiber develops the greatest isometric tension?
- L0 Optimal Length
When a muscle is shortened what kind of isometric contraction would you expect?
Poor due to excessive overlapping of filaments during contraction
When a muscle is lengthened, what kind of contraction would you expect?
Poor because not many cross-bridges can contact the myosin
What are the three ways that muscle fiber can form ATP?
- Phosphorylation of ADP by creatine phosphate
- Oxidative phosphorylation of ADP in the mitochondria
- Phosphorylation of ADP by the glycolytic pathway in the cytosol
What are the three mechanisms of muscle fatigue from short-duration, high intensity exercise?
- Conduction Failure
- Lactic acid build-up
- Inhibition of Cross-bridge cycling
Describe conduction failure:
The AP can fail to be conducted into the fiber
Why does Conduction failure occur?
- Buildup of K in the small volume in the T-tubule
- Results from repolarization of repeated APs
- Causes persistent depolarization of the T-tubule membrane and inability to conduct
What type of muscle failure is cause by a failure to produce action potentials in the T-tubular membrane?
Describe how Lactic Acid buildup causes muscle fatigue:
- Elevated [H ion] alters protein conformation and activity
- May alter muscle proteins involved in Ca release
- Effects C ATPases, imapiring relaxation of muscle
What type of Conduction failure alters protein conformation, particularly as it involved Ca release and impairs Ca ATPases?
Lactic Acid buildup
Describe how inhibition of cross-bridge cycling occurs:
The buildup of ADP and Pi directly inhibits cross-bridge detachment from actin and slows the rate of cycling
What type of conduction failure is due to buildup of ADP and Pi?
Inhibition of Cross-bridge cycling
What does Inhibition of Cross-bridge cycling lead to?
reduced shortening velocity and impaired relaxation
What type of muscle fatigue results in reduced shortening velocity and impaired relaxation?
Inhibition of Cross-Bridge Cycling
What is Central Command Fatigue?
When the cerebral cortex fails to send excitatory signals
What type of fatigue occurs when the cerebral cortex fails to send excitatory signals to the motor neurons?
Central Command Fatigue
Why might a person feel that they must stop exercising though their muscles are not fatigued?
Central Command Failure
What type of Fatigue is associated with the "will to win"?
Central Command Failure
How are fibers classified?
- By their Maximal Velocity
- The major way they form ATP
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