muscle fibre structure + activity Flashcards
epimysium
layer of connective tissue wrapping around muscle
thickens to form tendon
perimysium
connective tissue between epimysium and fasciculi
fasciculi/fasciculus
bundle of muscle fibres
endomysium
connective tissue binding muscle fibres together to form bundles
sarcolemma
cell membrane of muscle fibres
sarcoplasm
gel-like fluid containing mitochondria, atp, myogoblin, enzymes, energy nutrients ,actin and myosin fillaments
myofibril
long strands in muscle fibre
sarcomeres
individual units responsible for contractions
contains protein myofilaments -> actin and myosin
how do sarcomeres contract
nerve impulse received -> calcium produced -> myosin attaches to actin through the breakdown of ATP (rows actin towards mysin)
steps of muscular activity initiation
brain innitiates message -> goes through spinal cord to motor nerve, to motor neuron -> message jumps neuromuscular junction with acetylcholine -> arrive at muscle fibres
number of fibres in motor unit
precise movemnts -> small motor units
gross movements -> large motor units
characteristics of small motor units
slow contraction
resistant to fatigue
easily recruited + excitable
for prolonged activities
characteristics of large motor units
fast contraction
rapidly fatigues
harder to be recruited + excitable
utilised for high force activities
henneman principle (size principle)
recruitment of motor units commences with smaller motor units then larger motor units
all or nothing principle
nerve impulse must reach a certain threshold in order for a muscle to contract
