sarcomere and length tension relashionship Flashcards
what is a sarcomere?
A sarcomere is the contractile unit of a muscle. Sarcomeres are responsible for muscle contraction and are the basic building blocks of muscle tissue.
What are the components of a sarcomere?
Z-Lines (Z-Discs)
A-Bands and I-Bands:
H-Zone:
M-Line:
Explainer the structure of the sarcomere? From the inner part going outwards
sarcomere
M- line runs N to S
H-zone
A-Band
I-Band
Z-line
What part contains actin?
I-band
What part contains myosin?
H- band and M-line
What part contains both actin and myosin?
Outer a band
Which Parts shorten sarcomere?
H zone and I band
what occurs at A band?
Actin and Myosin crossbridge or over lap of the protein filaments
Which 3 components shorten sarcomere or move closer together ?
1) Z line and move sarcomere closer together
2) I bands located on either side of A band which narrow when actin moves over myosin
3) The H-zone shortens due to the overlap of actin and myosin
which components don’t change length?
1) M-line
2) A-band (contains the entire length of myosin filament
describe the sliding filament theory?
the siding filament theory is when muscle contracts but more specifically the thin actin filaments slide past the thick- myosin filaments. This causes the sarcomere to shorten. The myosin heads on the thick filaments interact with actin on the thin filaments, forming cross-bridges. These cross-bridges cycle through binding and releasing, causing the filaments to slide past each other. Myosin heads attach to the open sites on actin to “pull” fiber shorter
describe actin=myosin complex?
1) Cross-Bridge Formation: (at rest)
The process of contraction begins when an action potential (nerve signal) arrives at the muscle cell, SERCA pump vomits from the sarcoplasmic reticulum
2)Binding of Calcium Ions:
Calcium ions bind to the regulatory protein troponin, which is associated with the thin (actin) filaments.
This binding causes a conformational change in troponin, which in turn shifts the position of tropomyosin, exposing the active binding sites on actin (where myosin attaches)
3)Cross-Bridge Formation: contraction
Myosin heads (thick filaments) have ATP (adenosine triphosphate) bound to them.
ATP is hydrolyzed into ADP (adenosine diphosphate) and inorganic phosphate (Pi) as the myosin head “cocks” into a high-energy state this breakdown enables myosin to bind to open site on actin where the heads pull actin
4) power stroke when pulling actin
5) detachment myosin heads DE attach from actin breaking the cross bridge
6)ATP Hydrolysis and Re-Cocking:
Once detached from actin, the myosin head hydrolyzes ATP into ADP and Pi.
This energy is used to “cock” the myosin head back into its high-energy state, ready for the next cross-bridge cycle.
process occurs as long as their is ATP
what shape is tropomyosin?
ribbon or helix like surrounds actin it also covers the binding sites “when muscle is relaxed”
what does troponin look like?
it has 2actin spherical molecules arraigned that are twisted containing the binding sites for myosin heads
what is happening when a muscle is relaxed?
Tropomyosin is covering the actin binding sites so myosin cannot attach
when a muscle contracts?
1)The calcium is released from SERCA Pump which floods the cytosol
2) The calcium binds to troponin pulling tropomyosin away from actin “occupied sites” which now expose them for the heads to attach.
3) myosin heads completes the power stroke
4) actin slides along myosin
what distinguishes actin and myosin under a Xray?
white is the actin filament
When a muscle contracts what are the black and white colour’s?
Black disappears due to actin sliding over it. white increases while black gets smaller
How is force linked to overlap?
More force is produced when their is greater overlap due to the powerstroke cycles.
less overlap means their is less myosin heads attaching and pulling actin
What is the relationship between force and overlap?
it is proportion
describe graph points a-e
A) when muscle is fully elongated and their is no tension no overlap so zero force
B) Maximin tension or force due to the complete overlap of actin-myosin
C) reached then end point of actin
D) complete overlap no longer can produce force due to no myosin not being able to pull any more actin e.g. think biceps curl at top range zero force
E) Force decreases end range
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