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47 Cards in this Set
- Front
- Back
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What are the 3 different types of muscle cells? |
Cardiac muscle Skeletal muscle Smooth muscle |
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What does cardiac muscle do? |
Contracts without conscious control. Only found in the heart |
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What can skeletal muscles also be called and what do they do? |
Striated/stripped/voluntary muscle Moves the skeleton |
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What do smooth muscles do? |
Contract without conscious control. Found in the wall of internal organs |
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What must happen to bring about movement? |
Two bones have to move in relation to one another about a joint. Skeletal muscles are attached to both bones and as the muscle contracts, the bones move about the joint |
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What do ligaments do? |
Attach bones together at a joint |
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What do tendons do? |
Attach muscles to bone |
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What are ligaments and tendons made up of? |
Collagen |
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What are some properties of ligaments and tendons? |
They're inelastic, flexible and don't snap when pulled. |
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What provides nutrients to cartilage and what does cartilage do? |
Synovial fluid from synovial membrane. Cartilage is the pads where bones meet to reduce friction when they move |
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What are muscles usually found in? |
Antagonistic pairs. One muscle contracts to bring about movement in one direction and its pair contracts to bring about movement in the opposite direction. |
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Why does this happen |
Muscles can only exert a force when they are contracting. They can only lengthen again when they're passively stretched by the action of an antagonistic muscle |
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What must happen to bend the elbow? |
The biceps muscle contracts, pulling the radius upwards and the triceps relaxes. The biceps is called a flexor muscle because it causes flexing of the muscle. |
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What happens to straighten the elbow? |
The biceps relaxes and the triceps contracts, pulling the ulna downwards. The biceps is passively stretched. The biceps is called an extensor muscle because it straightens the elbow. |
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What are muscles? |
Large bundles of multinucleate cells called muscle fibres |
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What are sarcolemma? |
Cell membranes of muscle fibre cells folded inwards into the cytoplasm |
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What do T tubules do? |
Help spread electrical impulses through the sarcoplasm so all parts of the muscle are reached |
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What does the sarcoplasmic reticulum do? |
Stores and releases Ca2+ ions |
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What does each muscle cell (fibre) contain? |
Myofibrils |
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What are myofibrils made of? |
Protein filaments which interlock in a regular way. The thin filaments are actin and the thick are myosin. |
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What do myofibrils do to the appearance of skeletal muscles? |
They give them a striated (striped) apearance |
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What model is used to demonstrate muscular contraction? |
The sliding filament model |
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What happens in the sliding filament model? |
When a muscle contracts, the actin filaments are drawn in between the myosin filaments thus shortening the sacromere; because each sacromere contracts, the whole myofibril contracts |
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What are the 2 strands of actin? |
F actin and G actin |
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What is the structure of actin filaments? |
Troponin, tropomyosin and G actin |
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What does tropomyosin do? |
Reinforces actin and blocks the binding site |
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What is the structure of myosin filaments? |
Thick myosin filaments and myosin heads |
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How does muscle contraction and stimulation occur? (Step 1) |
Action potential arrives at many neuromuscular junctions simultaneously. This causes Ca2+ protein channels to open and Ca2+ to diffuse into the synaptic knob. |
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How does muscle contraction and stimulation occur? (Steps 2-3)
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Ca2+ causes synaptic vesicles to fuse with the presynaptic membrane and release ACh int the synaptic gap. ACh diffuses across the synaptic cleft and binds with receptors on the muscle sarcolemma, causing depolarisation. |
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How does muscle contraction and stimulation occur? (Step 4) |
Action potential travels down the T tubule and causes Ca2+ to be released from the sarcoplasmic reticulum. |
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How does muscle contraction and stimulation occur? (Step 5)
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Ca2+ causes tropomyosin molecules that were blocking the binding site on the actin filament to pull away. This unblocks the binding site on the actin, allowing actin myosin cross bridge to form. |
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How does muscle contraction and stimulation occur? (Step 6)
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ADP molecules attached to the myosin head mean they're in a state to bind to the actin filament and form a cross bridge. |
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How does muscle contraction and stimulation occur? (Step 7)
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Once attached to the actin filament, the myosin heads change their angle, pulling the actin filament along as they do so, releasing ADP and Pi. This is called the power stroke |
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How does muscle contraction and stimulation occur? (Steps 8-9)
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An ATP molecule attaches to the myosin head, causing it to detach from the actin filament. The Ca2+ then activate ATPase, which hydrolyses the ATP to ADP and Pi. The hydrolysis provides the energy for the myosin head to return to it's original position. |
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How does muscle contraction and stimulation occur? (Step 10)
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The myosin head, once more with an attached ADP, then reattaches itself further along the actin filament and the cycle is repeated as long as the concentration of Ca2+ remains high. |
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How are myosin molecules joined? |
Tail to tail in 2 oppositely facing sets |
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What does this structure mean? |
The movement of one set of myosin heads is in the opposite direction to the other. This means the actin filaments move in opposite directions. This movement pulls the actin filaments towards each other and so, shortens the sacromere |
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What happens in muscle relaxation? |
When nervous stimulation stops, Ca2+ ions are actively transported back into the endoplasmic reticulum using energy from hydrolysing ATP. The re-absorption of Ca2+ allows tropomyosin to block the actin filament again. Myosin heads are no longer able o bind and contraction stops. The muscle relaxes and actin filaments slide back into their original position. |
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Why does energy need to be supplied in muscle contraction? |
There's very little ATP stored in a muscle, so as soon as contraction starts, more ATP has to be generated |
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What are the 3 ways in which this ATP can be generated? |
Aerobic respiration Anaerobic respiration Creatine phosphate |
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What is creatine phosphate and how can it be used to produce ATP? |
It's a molecule stored in the cytoplasm of muscle cells. The phosphate group can be used to phosphorylate ADP to ATP |
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Which enzyme catalyses this reaction? |
Creatine phosphate transferase |
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What are skeletal muscles made up of? |
2 muscle fibres, slow and fast twitch |
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What does a slow twitch muscle fibre do? |
It contracts slowly and can work for a long time without tiring. Energy is released slowly through aerobic respiration. |
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What do slow twitch muscle fibres have? |
Energy is released slowly through aerobic respiration so they have lots of mitochondria and a good blood supply. They're rich in myoglobin, a red protein which stores oxgyen so they're reddish in colour
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What does a fast twitch muscle fibre do? |
Contracts very quickly but tires easily. Energy released quickly through anaerobic respiration using glycogen in fast twitch muscle fibres. |
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What does a fast twitch muscle have? |
Stores of creatine phosphate. They have very few mitochondria and less myoglobin, so they're a whitish colour. |
