Muscle fibres and structures Flashcards
what are the functions of the muscular system?
maintain body's temperature movement support (maintain posture)
what is the breakdown of a muscle?
Epimysium fasciculi muscle cell fibre myofibril sarcomere
what is a fasciculi?
bundles of muscle fibres that make up muscle belly
what is Epimysium?
connective tissue that surrounds the muscle belly, fasciculi and muscle fibres respectively
what is actin?
the thin protein filament found in muscle cells that together with myosin form sarcomeres
what is myosin ?
the thick protein filament that together with actin form sarcomeres
what is a sarcomere?
the contractile units of skeletal muscle
what are the different types of muscle fibres?
type 1 slow
type 2 a fast
type 2 b fast
what are the characteristics of a type 1 slow twitch muscle?
red
high in everything
small fibre size
10-180 fibres/ motor neurons
what are the characteristics of a type 2 a fast twitch muscle?
pink
medium
300-800 fibres
what are the characteristics of a type 2b fast twitch muscle?
white
low
300-800
what are the effects of endurance training on muscle fibres?
capillary content increase
myoglobin content increase
increase resistance to fatigue
more efficient use of aerobic system
what are the effects of strength training on the muscle fibres?
increase force of contraction
increased size of muscle fibres
muscle mass increase
cap and myo don’t change
what is a motor unit?
is a motor neuron attached to a muscle fibre
what is a summary of the sliding filament theory?
during a contraction thin actin filaments slide inwards over thicker myosin filaments causing a shortening of each sarcomere along the entire length of the myofibril, this causing shortening over the muscle and the entire muscle
what happens at stage 1 ?
actin potential reaches the axon terminal and acetylcholine is released, this causes the depolarization of the motor end and is transmitted down the T tubules into the muscle fibres , choline is released
what happens at stage 2 ?
the actin filament has active sites surrounded by troponintropomyosin , the calcium ions bind to this, revealing active binding sites and myosin heads attach to the actin to form a cross bridge.
what happens at stage 3 ?
ATPase enzyme catalyzes the breakdown to ATP, energizing the myosin cross bridge , the myosin pulls the actin inwards , shortening the muscle
what happens at stage 4 ?
when an ATP molecule binds to its head, the myosin detaches from the actin, ATP can be broken down again and again as long as there are enough calcium ions
what happens at stage 5 ?
the impulse stops , calcium ions are pumped back into the sarcoplasmic reticulum , the myosin no longer pulls on the actin so it moves back to its position at rest and the muscle relaxes
what are calcium ions?
released from sarcoplasmic reticulum and binds to troponin
what is actin?
component of thin filament
what is myosin?
component of thick filament
what is troponin?
calcium ions bind to this to help move tropomyosin strands from the binding sites
what is tropomyosin ?
a protein molecule, part of the thin filament; covers binding sight
what is cross bridges ?
formed by myosin heads attaching to the actin
what is the ratchet mechanism?
alternate use of myosin cross bridges to produce a contraction
