ORTCITIAEE: Muscle contraction Flashcards
Myofibrils contain many thread-like structures called ______ filaments.
Protein
What are the two types of protein filaments?
- Thin filaments (actin)
- Thick filaments (myosin)
How many actin filaments are wrapped around each other in a thin filament?
2
Within a thin filament, wrapped around the actin filaments is another protein chain called _________.
tropomyosin
How many myosin filaments are wrapped around each other in a thick filament?
2
Thick filaments are made up of a protein called ______.
myosin
Thin filaments are made up of a protein called _____.
Actin
What does a sarcomere look like?
AT LEAST
1 myosin filament (in the middle)
4 actin filaments (in each corner of the myosin)
Myofibrils are made up of many repeating ______.
Sarcomeres
What is the middle of a sarcomere called?
M-line
(literally the middle line)
What is the middle of 2 sarcomeres OR/AND the middle of an actin filament called?
Z-line
(2 different sarcomeres that are connected by their actin filaments- it is in the middle of their shared actin filaments OR just in the middle of 1 sarcomeres actin filamets- this is confusing look it up)
Under a light microscope what are actin filaments described as?
Light bands (I bands)
Under a light microscope what are myosin filaments described as?
Dark bands (A bands)
Actin filaments can be described as _____/__ bands.
Light/I
Myosin filaments can be described as _____/__ bands.
Dark/A
The A-band contains overlapping _____ and _____ filaments
Thin
Thick
Why is the H-Zone lighter than the A-band?
Only contains thick filaments
No overlapping thick and thin filaments
What is the area between 2 M-lines called?
Z-line
What causes the movement of actin and myosin?
An action potential that is triggered inside a muscle fibre of a neuromuscular junction.
Where do the calcium ions come from?
Action potential inside muscle fibre causes the sarcoplasmic reticulum to release calcium ions into the myofibrils.
What do the calcium ions do?
They trigger tropomyosin to change shape and move away from the binding site, so the myosin heads are able to bind to them.
Where in the muscle fibre are calcium ions released from?
Sarcoplasmic reticulum
Myosin heads have an active site for ____.
ATP
A myosin head that is attached to an actin forms a _______ _____.
Actinomyosin crossbridge
Myosin heads hydrolyse ATP into ADP + Pi. What do they use this energy for?
Allows the myosin head to take its starting position
Myosin heads hydrolyse ATP. This makes them _____.
ATPases
What do calcium ions do?
Trigger tropomyosin to move away from the binding site.
Explain the sliding filament theory:
- Calcium ions trigger tropomyosin to move away from the binding site.
- Myosin head attaches to a binding site on actin to form an actinomyosin cross bridge.
- ADP + Pi are released from the myosin head- the power stroke.
- ATP binds to the myosin head and the myosin head detaches from actin.
- The myosin head hydrolyses ATP, which releases energy and allows for the myosin head to return to its starting position.
How does the sliding filament theory actually allow for muscle contraction?
- Actin contracts within sarcomeres.
- Many sarcomeres contracting allows for larger muscle contraction.
How is the power stroke triggered?
ADP and Pi are released.
What happens to the band/zones during muscle contraction?
Z-lines move closer to eachother
H-bands contract
A-band and M-line stay thesame
