Lecture 9 Flashcards
What is a myofilamemt made of?
Thick myosin and thin actin.
What is the purpose of actin?
To be the structural stabilizing element that can acted upon. It gets pulled on by myosin when contracting.
What is the purpose of myosin?
It is a motor protein, and reaches out to pull on actin.
How does the cross-bridge cycle work in EC coupling? (PARCC)
- Attached state, the Ca2+ has left, but the actin and myosin are still in that cross-bridge state.
- Released state, ATP binds with myosin, causing it to release from actin.
- Cocked state, burns ATP to make energy, which is then stored in the myosin so that it is ready to pull on myosin again, but is currently prevented from doing so as it is blocked.
- Cross-bridge state, the Ca2+ is now present due to the excitation process, getting rid of the barrier, and the energized myosin then grabs onto the actin.
- Power stroke state, the myosin uses its energy to pull, causing the acting to slide, shortening the sarcomere and causing a contraction.
What 2 things does muscle tension depend on and why?
The number of fibres recruited and the rate that the muscles are stimulated. The more fibres recruited (activated), the more force is generated. The higher the frequency of the stimulation the more tension is created, until it reaches tetanus (maximum amount of stimulation). If in this state for too long, ATP depletes and will be fatigued, and muscle will not be able to stay contracted.
What is the difference between fast and slow fibres?
Fast fibres are used for quicker and more powerful movements, and are for shorter periods of time. Slow fibres are for support, and do not get tired easily. They have more blood vessels for energy flow and many mitochondria.
