15.8 Contraction Of Skeletal Muscle Flashcards
Explain what is meant by antagonist muscles?
Muscles work in opposite directions
How do antagonist muscles work?
Pairs pull in opposite directions and when one is contracted the other is relaxed
what is the sliding filament mechanism
Process that involves the actin and myosin filaments sliding past one another
What changes to the sarcomere occurs when a muscle contracts?
- I band becomes narrower
- sarcomere shortens (z-line moves closer)
- H- zone becomes narrower
- A band remains the same
What discounts the theory that muscle contraction is due to filaments themselves shortening?
A bands remain the same which is determined by myosin length
What 2 types of protein make up myosin?
- the tail (fibrous)
- the head (globular)
The tail of myosin structure
A fibrous protein arranged into a filament made up of several hundred molecules
The head of myosin structure
A globular protein formed into 2 bulbous structures at one end
Why type of protein is actin?
Globular
What forms between bulbous heads of myosin and actin
Bulbous heads of the myosin filaments form cross- bridges with the actin filament
How is the muscle stimulated?
- ca^2+ channels open
- Ca^2+ diffuse into synaptic knob
- causes synaptic vesicles to fuse with presynaptic membrane
- acetylcholine released into cleft
- binds with receptors on muscle cell membrane
- Na+ channels open
- Na+ enter muscle causing depolarisation
role of phosphocreatine
- ATP is formed
- without respiration
muscle relaxation
- Ca2+ are actively transported back into the endoplasmic reticulum using energy from the hydrolysis of ATP
- reabsorption of Ca2+ allows tropomyosin to block the actin filament again
- myosin heads are now unable to bond to actin filaments and contraction ceases
role in ATP
- energy source
- detachment of myosin head
role of Ca2+
- cause movement of tropomyosin
- uncovering binding site on actin
