B3.3 Muscle and Motility Flashcards
example of motile organism
bacteria
sessile organism example
Sponges, corals and anemones
Most fungi species
All plant species
what does each striated muscle fibre contain
organised arrangement of contractile proteins in the cytoplasm
Many nuclei
sarcoplasmic reticulum (SR) which stores calcium and conveys signals to all parts of the fibre at once using protein pumps in the membranes
what are myofibrils
bundles of actin and myosin filaments, which slide past each other during muscle contraction
when a muscle contacts what happens
the sarcomere shortens due to the sliding of actin and myosin filaments
simplified sliding filament model
myosin head binds to exposed binding site on actin molecule
myosin head moves by rowing action
ATP binds to myosin head so it separates from actin filament, ATP is now hydrolysed so moves myosin back to original position
cycle is repeated at a binding site further along actin molecule, closer to z disc
antagonistic muscle action
A muscle pulls in one direction at a joint and the other muscle pulls in the opposite direction
what is an isometric contraction
a muscle contraction without motion
what protein does muscle contraction and relaxation rely on
titin
what is titin
a large protein that joins the ends of the myosin filaments to the z-line
it has many folds which give it spring like properties for contraction
what happens when a muscle is relaxed
sarcomere lengthens and the titin is stretched out
when does a skeletal muscle contract
when it receives an impulse from a motor neurone via the neuromuscular junction
what does a motor unit of a skeletal muscle consist of
motor neurone,
muscle fibres, neuromuscular junctions
what polysaccharides made up exoskeletons
chitin
how are synovial joints chracterised
by a joint cavity filled with a lubricating synovial fluid which reduces friction which is produced by synovial membrane
