Topic 11.2 Flashcards
Exoskeletons
- External skeletons that surround and protect most of the body surface of animals
How do bones and exoskeletons facilitate movement
- Provide an anchorage for muscles
- Act as levers
Give one example of an antagonistic pairs and explain
- Biceps and triceps
- When biceps contracts, tricepts relaxes
- the arm bends
Name another animal that uses antagonistic pairs of muscles
- Grasshoppers use antagonistic pairs of muscles to produce a powerful jump
Annotate the following diagram of the human elbow
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Cartilage
- Tough, smooth tissue that covers the regions of bone in the joint
- Prevents contract between regions of bone that might otherwise rub together
- Prevents friction
- Absorbs shocks that might cause bones to fracture
Synovial fluid
- Fills the cavity in the joint between the cartilages on the ends of the bones
- Lubricates the joint
- Prevent the friction
Joint capsule
- Tough ligamentous covering to the joint
- Seals the joint and holds in the synovial fluid
- Prevent dislocation
Tendon
Connects muscle to bones
Ligaments
Connects bone to bone
Hinge joint
- ie. knee joint
- only allows two movements (flexion/bending and extension/straightening)
Ball and socket joint
- ie. the hip joint
- has greater range of movement
- can flex, extend, rotate and move sideways/back
Label abduction and adduction in the following diagram
Refer to picture
Label the following diagram of a muscle fibre
Refer to picture
Skeletal muscle
- multinucleate
- contain specialized endoplasmic reticulum
- called skeletal muscle because are attached to bones
- called striated muscle because when their structure is viewed using a microscope, stripes are visible
- composed of bundles of muscle cells known as muscle fibres
Muscle fibre
- makes up skeletal muscle
- although a single plasma membrane called the sarcolemma surrounds each muscle fibre, there are many nuclei present and muscle fibres are much longer than typical cells
- a modified version of the endoplasmic reticulum, called the sarcoplasmic reticulum, extends throughout the muscle fibre
- contains many myofibrils
- between myofibrils are large numbers of mitochondia which provide ATP for contraction
Sarcoplasmic reticulum
- extends throughout the muscle fibre
- wraps around every myofibril, conveying the signal to contract to all parts of the muscle fibre at once
- stores calcium
Myofibrils
- within each muscle fibre, there are many parallel, elongated structures called myofibrils
- have alternating light and dark bands, which give stiated muscle its stripes
- in the centre of each light band is a disc-shaped structure referred to as the Z-line
- made up of contractile sarcomeres
Sarcomere
- many sarcomeres makes up a myofibril
- consists of a regular arrangement of two types of protein filaments: thin actin filaments and thick myosin filaments
Draw a labelled draigram of the structure of a sarcomere
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Draw the structure of a sarcomere in relaxed muscle and the structure after the muslce contracts
Refer to picture
Identify the contracted and the relaxed sarcomere
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Explain how skeletal muscle contracts
- muscles/fibres/myofibrils contain (repeating) units called sarcomeres;
- muscle/sarcomeres contain actin filaments and myosin filaments;
- actin fibres are thin AND myosin fibres are thick;
- arriving action potential causes release of calcium ions;
- from sarcoplasmic/endoplasmic reticulum;
- calcium ion binds to troponin;
- causing troponin and tropomyosin to move (on actin);
- ATP binds to myosin heads releasing them/breaking cross bridges;
- ATP hydrolysed/split into ADP + Pi;
- ATP/energy causes myosin heads to change shape/swivel/become cocked;
- myosin heads bind/form cross-bridges to (exposed) actin binding sites;
- myosin heads swivel/move actin (releasing ADP + Pi);
- myosin filaments move actin filaments towards centre of sarcomere;
- sliding of filaments/actin and myosin shortens the sarcomere
