Lecture 5 Skeletal Muscle 3 Flashcards
What are the different muscle fibre types?
.There are two types of skeletal muscle fibers, fast-twitch and slow-twitch
Describe and explain the force-length relationship for skeletal muscle.
.The force -length relationship indicates that muscles generate the greatest force when at their resting (ideal) length, and the least amount of force when shortened or stretched relative to the resting length.
Describe and explain the force-velocity relationship for skeletal muscle
.The force-velocity relationship in muscle relates the speed at which a muscle changes length with the force of this contraction and the resultant power output (force x velocity = power).
What are the two types of forces occurring at the same time during muscle contraction?
Insertional or muscle force
External load/force
If muscle force is smaller than load force, will the muscle lengthen or shorten?
It will increase in length
If the muscle force is equal to the load force what will happen to the muscle?
The muscle will not move and remain at constant length
What contraction occurs when a muscle increases in length
Eccentric contraction
What contraction occurs when a muscle stays the same length when activated
Isometric contraction
If the muscle force is greater to the load force what will happen to the muscle?
The muscle will shorten in length
What contraction occurs when a muscle shortens in length when activated
Concentric contraction
What happens if external load is more than myosin force?
Sarcomere lengthens away from the centre.
What happens if external load is less than myosin force?
Sarcomere shortens towards the centre
What happens if external load is equal to the myosin force?
Sarcomere remains at a constant length
Does the cross-bridge cycle still occur during an isometric contraction?
Yes, all 4 phases of the cycle proceed normally.
What are two other types of contractions that start with Iso
Isotonic and Isokinetic
How does summed myosin force vary with changes in thick and thin filament overlap?
Once all the myosin heads attach to their counter-part actin there is no more myosin heads to attach to actin and therefore a plateau occurs. Shortening any further will result in the currently attached myosin heads to be detached due to the other end of actin now pushing their way through to the other side which decreases the force admitted. It further decreases once the myosin filament is squished against the Z-discs.
