Muscle contraction

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What are the three types of muscle fibres?
Smooth muscle, cardiac muscle and skeletal muscle
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What is smooth muscle?
Muscles which contract without conscious control such as stomach, intestines and blood vessels
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What is a cardiac muscle?
Muscles which contract without conscious control but only found in heart
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What is skeletal muscle made up of?
Large bundles of long cells called muscle fibres
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What is the cell membrane of a muscle fibre called?
The sarcolemma
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What is the cytoplasm of a muscle fribre called?
Sarcoplasm
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What are the fold in the sarcolemma called?
T-tubules (transverse tubules)
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What is the purpose of t-tubules?
To spread electrical impulse throughout the sarcoplasm so they reach all parts of muscle fibre
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What are the networks of internal membranes called?
Sarcoplasmic reticulum
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What is the job of the sarcoplasmic reticulum?
Stores calcium ions for muscle contraction
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What is the meaning of multinucleate?
Having many nuclei
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What are the long cylindrical organelles in the muscle called?
Myofibrils
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what is the purpose of myofibrils?
They contain thin and thick myofilaments that move past each other to cause a contraction
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What are the thick myofilaments in myofibrils made up of?
Myosin
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What are the thin myofilaments made up of?
Actin
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Under a microscope, which band appears dark?
A-band
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What does the A-band contain?
Myosin filaments which some overlapping actin filaments
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Under a microscope, what band appears light?
I-band
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What does the I-band contain?
Actin filaments
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What are the short units of a myofibril called?
Sacromere
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What marks the end of each sarcomere?
The Z-line
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What is the middle of each sarcomere?
The M-line
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What does the H-zone consist of?
Only of myosin filaments
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What is the sliding filament theory?
Myosin and actin filaments slide over each other to make sarcomere contract, myofibrils themselves do not contract
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What happens do the bands when sacromeres contract?
A-band stays the same, I-band gets shorter, H-zone gets shorter
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what are the stages of muscle contraction?
Arrival of an action potential, movement of the actin filament, breaking of cross bridge, return to resting state
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What happens in the arrival of an action potential stage of muscle contraction?
Action potential depolarises sarcolemma, moves down t-tubules to sarcoplasmic reticulum, releases Ca2+ ions, ions bind to troponin to change its shape, this pulls out tropomyosin, actin-myosin cross bridge formed
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What happens in the movement of the actin filament stage of muscle contraction?
Ca2+ ions also activate ATPase to break down ATP for energy for muscle contraction, energy allows myosin globular head to preform power stroke
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What happens in the breaking of cross bridge stage of muscle contraction?
ATP provides energy to break cross bridge, myosin head removed from binding site and returns to starting position and reattaches to another binding site, cycle repeated.
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What happens in the return to resting state stage of muscle contraction?
When stimulation stops, Ca2+ ions leave their troponin binding site and go back to sarcoplasmic reticulum (needs ATP), troponin goes back to normal shape, tropomyosin blocks actin-myosin binding site
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How do the muscles get energy from ATP-phosphocreatine system (PCr)?
PCr joins to ADP to make ATP, PCr stored in cells, PCr system is very quick, PCr runs out very quick
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Other cards in this set

Card 2

Front

What is smooth muscle?

Back

Muscles which contract without conscious control such as stomach, intestines and blood vessels

Card 3

Front

What is a cardiac muscle?

Back

Preview of the front of card 3

Card 4

Front

What is skeletal muscle made up of?

Back

Preview of the front of card 4

Card 5

Front

What is the cell membrane of a muscle fibre called?

Back

Preview of the front of card 5
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