Muscle Contraction

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What is a sarcomere?
The distance between adjacent Z lines
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How do slow twitch fibres differ from fast twitch fibres in the way they function?
Slow twitch - Contract more slowly and provide less powerful contractions over a longer period. Fast Twitch contact more rapidly, and produce more powerful contractions but for a short period.
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How are slow twitch fibres adapted for their function?
Large store of myoglobin to store large amounts of oxygen. Rich supply of blood vessels to deliver oxygen and glucose.. Lots of mitochondria to produce ATP. Adapted for aerobic respiration to avoid a build up of lactic acid.
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How are fast-twitch fibres adapted for their function?
Thicker and more numerous myosin filaments. High concentration of enzymes involved in anaerobic respiration. Store of phosphocreatine which generates ATP from ADP in anaerobic conditions. So adapted for anaerobic due to a build of lactic acid
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What is a neuromuscular junction?
Where a motor neurone meets a skeletal muscle fibre
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What changes occur to a sarcomere when a muscle contracts?
I band becomes narrower, Z lines move closer together (sarcomere shortens) H-zone becomes narrower.
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Describe the role of calcium ions in the contraction of a sarcomere
They interact with the tropomyosin molecule to reveal binding sites on actin allowing myosin heads to bind to exposed sites on actin filament, energy released from ATP moves myosin head back to its original position
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Explain the importance of ATPase during muscle contraction
Breaks down ATP yielding energy. Used to break actomyosin bridges.
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What are the two types of muscle that are used involuntary?
Cardiac muscle and smooth muscle.
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Why does the structure of muscle allow it to perform its function of contraction efficiently?
Separate muscle cells are fused into muscle fibres so there are no points of weakness
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Outline how a muscle relaxes
Nervous stimulation ceases; Calcium ions actively transported back into endoplasmic reticulum using energy from the hydrolysis of ATP; Absense of calcium ions allows tropomyosin to block binding sites on actin filaments ag
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Why is energy needed for muscle contraction?
Movement of myosin heads; Reabsorption of calcium ions into endoplasmic reticulum by active transport
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How is the shape of the myosin molecule adapted to its role in muscle contraction?
Fibrous protein long and thin; provides surface area for which actin can move along; Globular proteins form bulbous structures; Allows it to exactly fit the binding sites of the actin filament
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Trained sprinters have high levels of phosphocreatine in the muscles. Explain the advantage of this.
Phosphocreatine stores phosphate; Used to generate ATP from ADP in anaerobic conditions; Sprinter's muscles often work strenuously and so oxygen supply is short; Phosphocreatine allows for production of ATP to continue when anaerobic respiration is n
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Explain the advantage of marathon runners having a high proportion of slow muscle fibres in their muscles.
Can exercise for long periods of time. Respire aerobically - slow fibres adapted to aerobic, as they have many mitochondria which is the site of the Kreb's Cycle. Producing large amounts of ATP
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Explain the advantage of having the high glycogen content of fast muscle fibres
Glycogen broken down gives a lot of glucose for anaerobic reparation. Anaerobic is not very efficient.
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Explain the advantages of lots of capillaries supplying slow muscle fibres
Many capillaries give large surface area for oxygen diffusion. Allows high rate of aerobic reparation.
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Explain how a decrease in the availability of calcium ions could disrupt the contraction mechanism in muscles.
Cannot move tropomyosin from binding sites on actin therefore myosin heads do not bind.
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How is the shape of the myosin molecule adapted to its role in muscle contraction?
Fibrous protein long and thin; provides surface area for which actin can move along; Globular proteins form bulbous structures; Allows it to exactly fit the binding sites of the actin filament
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Describe the role of ATP and phosphocreatine in producing contraction of a muscle fibre.
ATP allows myosin to detach from actin; Phosphocreatine allows regeneration of ATP under anaerobic conditions; Phosphocreatine releases Pi to join ADP
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What evidence is there that muscle contraction is caused by actin and myosin filaments sliding past one another?
Changes seen in the band patterns on myofibrils
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Describe the two types of protein filaments.
Actin - thinner and consists of two strands twisted around one another Myosin - thicker and consists of long rod-shaped fibres with bulbous heads
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Card 2

Front

How do slow twitch fibres differ from fast twitch fibres in the way they function?

Back

Slow twitch - Contract more slowly and provide less powerful contractions over a longer period. Fast Twitch contact more rapidly, and produce more powerful contractions but for a short period.

Card 3

Front

How are slow twitch fibres adapted for their function?

Back

Preview of the front of card 3

Card 4

Front

How are fast-twitch fibres adapted for their function?

Back

Preview of the front of card 4

Card 5

Front

What is a neuromuscular junction?

Back

Preview of the front of card 5
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