Week 3- muscles Flashcards
Myosin
Thick protein filament
Point at which ATP is transferred ito energy
Myosin head pulls the actin the move
Sarcomere
Smallest part
Arranged in parallel
Thicker wider structure
Each sarcomere containing actin and myosin
Actin
Thin protein filament containing binding sites. On the binding sites are troponin which prevents the myosin from grabbing onto the actin
Troponin
A complex of 3 proteins, attached to tropomyosin
Tropomyosin
An actin binding protein which regulates muscle contracts. Holds troponin in place
Motor unit
Nerve/nerve impulse plus bunch of muscle fibres
Spatial summation
Changes in strength of contraction brought about by altering the number and size of motor units involved. Allow motor units to recover/avoid fatigue
Action potentials
In order for the skeletal muscles to contract, a message (Action potential) needs to be sent from the nervous system to the muscle fibres. This triggers release of calcium
The contractile mechanism process
A nervous impulse arrives at the neuromuscular junction which causes release of acetylcholine which causes calcium to be released from the sarcoplasmic reticulum . Calcium binds to troponin changing its shape and so moving tropomyosin from the active site. The myosin filaments can now attach to the actin forming a cross bridge. The breakdown of ATP releases energy which enables the myosin to pull the actin filaments inwards and so shortening the muscle. The myosin detaches from the actin and the cross badge is brokenn
Biopsy
Long hollow needle put into the muscle, pull a vacuum and you get a bulge of muscle tissue
Type 1 slow twitch
Fatigue resistant Many mitochondria High capillary density Slow contraction time Long distance running Red (myoglobin) Less fore and takes longer to produce
Type 2a fast twitch
Fast contration time
Fatigue resistant
Used mainly during short high intensity events such as 400m
Less red
Can produce the same amount of force but faster than slow twitch
Sometimes 10 times as much power
Type 2B fast twitch
Fatiguable Low oxidative capacity Short sprints High velocity contraction Few mitochondria High glycogen stores Low myoglobin content
biochemical characteristics
The maximum shortening velocity of a single fibre correlates with its maximum ATP utilisation. If can’t use ATP quickly, won’t contract quickly. Mean Vmax of type 2 is 10 times grater than type 1.
Myosin specialised heads
2 specialised binding sites
one is a binding site for actin
Second acts as an ATPase
