Lec 5 Skeletal Muscle & Contraction Flashcards
What are the main functions of skeletal muscle?
Generate force production for posture and locomotion and heat production (i.e. shivering (and homeostasis when exercising))
What is the function of the sarcoplasmic reticulum?
REGULATOR of Ca2+ storage and releases (e.g. skeletal muscle homeostasis maintenance) during and after muscle contraction.
- When the SR releases Ca2+, it releases it INTO the sarcolemma.
- Ca2+ interacts with contractile proteins.
What does the sarcolemma (aka the plasma membrane) do?
It acts as a barrier between intracellular and extracelluar compartments.
Its the site where calcium enters and leaves the cell.
Why does fiber orientation/angle affect force production, velocity and ROM?
Bc the fiber orientation affects the line of pull (@ the longitudinal axis); the line of pull affects velocity & ROM capacity.
(e.g. parallel fibers vs pennate fiber arrangements)
T-tubles do what ?
Carries the AP signal from the membrane to each of the SR surrounding each of the myofibryils.
What is tropomyosin and what does it do when at rest?
Its a regulatory protein in actin and it blocks the (myosin) bindng site ON actin for myosin when at rest.
What is the sliding filament theory?
It explains how teh thick and thin filaments, which are of fixed length, move in relation to each other. This results in a change in sarcomere and muscle length.
When is the crossbridge/linkage between myosin and actin broken?
When the ATP binds to myosin.
*Once disassociated (actin and myosin), the ATP that is bound to myosin in then hydrolyzed. If calcium remains bound to troponin, the cycle then continues bc the attachment site is still exposed. (If at rest however, this can;t happen bc myosin and actin can’t interact bc of tropomyosin; teh binding blocker.
Disassociation of myosin and actin requires what?
The presence of ATP.
It must bind to myosin
What are the layers of muscle connective tissue?
Epimysium - outer most superficial layer
Perimysium - surrounds fascicles
Endomysium - surrounds individual muscle fibers/cell
What is the length-tension relationship in skeletal muscle?
The relationship between muscle length at the sarcomere and the force it can produce at that length.
The more cross-bridges between A&M, the > the force production. If two short, no tension or binding of A to M can be produced
If overstretched, the force production/contraction is reduced, bc not enough tension due to fewer crossbridges.
What is the stretch shortening cycle?
When active muscel lengthening is immediately followed by active muscle shortening
What are the the different contractile properties?
- Length-tension relationship
- Stretch shortening cycle
- Force velocity relationship
NOTE: Lengthening is eccentric (“elongate”); shortening is concentric
Describer the force velocity relationship
Force x Velocity = power
As load increases, velocity decreases
What do costameres do?
CONNECT sarcomeres (contractile uits) to the sarcolemma
