(LE 3) Muscle Flashcards
Where are calcium ions stored in muscles?
in sarcoplasmic reticulum in terminal cisternae
Describe the sliding filament theory
Describe muscle relaxation
Action potentials stop. Calcium release channels close. Calcium ions are pumped back into the SR against their gradient Ca2+ ATPase pumps.
What is a muscle twitch?
single rapid contraction and relaxation of muscle fibers
What is the Treppe effect?
refers to the gradual increase in the force of contraction seen when a muscle is stimulated repeatedly with stimuli of the same strength, starting from a resting state.
What three factors influence the force of contraction?
- frequency of stimulation
- motor unit recruitment
- length of muscle fiber
What is creatine, how is it related to ATP, and how is it used?
Creatine is a compound produced by the liver that can be phosphorylated with Pi from ATP to phosphorylate it to ADP. It holds onto the Pi and serves as an energy reserve since ATP hydrolyzes easily.
How are skeletal muscle fibers categorized?
How they produce ATP
- Oxidative fibers: aerobic
- glycolytic fibers: anaerobic
How quick they contract
- slow twitch: low tension; weak force
- fast-twitch: high tension; strong force
What are Type I fibers?
slow twitch/ slow oxidative
- lots of myoglobin
What are Type II b fibers?
fast twitch/fast glycolytic
- large glycogen stores
- little myoglobin
What are Type II A fibers?
Intermediate twitch/fast oxidative
- adapted to contract fast using aerobic metabolism
What is muscle fatigue and how is it caused?
exercise induced reduction in ability to contract
- sustained contraction fatigue due to accumulation of extracellular K+ during AP
- slow-twitch fibers in moderate exercise deplete glycogen stores. fast twitch recruited, converting glucose to lactic acid, interfering with Ca2+ transport
- central fatigue caused by changes in CNS
