lecture 9= contraction of skeletal muscle Flashcards
What are the two key protiens that make up myofilaments?
Actin= thin filament
Myosin= thick filament
At what point in the bridge cycle does the myofilament slide?
The powerstrike stage where the myosin uses its stored energy to pull, causing the actin filament to slide.
What event has to happen for the cross bridge to form?
When calcium is present and bound to the myofilament the energised myosin head can now bind to actin, forming a cross bridge
What event has to happen for the cross bridge to be released?
released state- when an ATP binds to the myosin head it causes it to release the actin, therefore there is no more cross bridge.
What are the two determinants of skeletal muscle force generation?
Muscle fibre recruitment, and the frequency of stimulation.
How does recruitment work?
The size of a muscle contraction is dependent on how many nerves the brain activates. Small number of active neurons= low force
large number of active neurons= larger force
How does frequency of stimulation work?
A single signal from a nerve results in a pulse of calcium and a short period of muscle contraction ( a twitch), if there are many signals sent in a rapid sequence there is a sustained release of Ca which means there is a sustained period of contraction.
What is the maximum signaling and contraction capability of a muscle
this is tetanus, a point where force platueaus as the muscle cannot contract any more.
What are fast muscle fibres ?
Fast muscle fibres have a large diametre with a lower capillary and mitochondria supply, this means that they do not take long to get fatigued but they work fast to generate lots of force.
What are slow muscle fibres?
Slow muscle fibres are smaller cells that do not act fast and produce lots of force. They have large amounts of blood vessels and mitochondria as they constantly need to be sourcing their own energy to ensure muscles can continue working.
