types of muscle contraction Flashcards
what are the 4 types muscle contraction
sliding filament mechanisms
- actin moving relative to myosin shortening muscle
cross-bridge cycle
- how myosin attaches to actin = movement
neuromuscular junction
- connection between NS and skeletal muscle
excitation-contraction coupling
- taking AP for NS and turn it into muscle contraction
what is the sliding filament mechanism?
like explain it at relaxed, contracted and maximal muscle contraction
relaxed muscle:
actin myofilaments attached to z disks and m line holds. some overlap in myosin and actin
contracted muscle:
myosin is in the middle of the sarcomere but the heads pull the actin closer to the m-line
maximal muscle contraction:
actin overlaps the sarcomere = no h zone or i band. the syosin heads reach the z disks.
what shortens during muscle contraction?
i band
h zone
what band never changes in size?
a band
what is the cross bridge cycle (contraction cycle)
- during contraction of a muscle calcium binds to troponin, –> causing exposure of active sites on actin myofilaments
- myosin heads bind to actin forming a cross bridges and phosphate is released from the myosin head
- myosin cross bridges rotate towards the center of sarcomere
- power stroke - ADP detaches - as myosin heads bind ATP, the cross-bridges detach from actin
- myosin heads hydrolyze ATP and become reoriented and energized
what are skeletal muscle electrical properties?
resting membrane potential:
- high [potassium] inside the cell
- low [sodium] outside of the cell
- depolarization causes muscle action potential
neuromuscular junction (NMJ)
- nerve impulse is comes from the spinal cord and moves along axon
- reaches synaptic bulb, it hits those voltage gated calcium channels
- voltage gated calcium channel opens and the calcium rushes into the cell
- calcium stimulates synaptic vesicles and move to synaptic cleft where acetylcoline is released
- acetylcholine diffuses across synaptic cleft and binds onto ligand-gates ion channels on the sarcolemma or the motor end plate of muscle
what happens during excitation-contraction couping?
- MAP propagated along sarcolemma and into T-tubules
- calcium channel in the SR open and calcium is released into the sarcoplasm
- calcium binds to troponin –> moves tropomyosin off myosin binding site
- heads of myosin bind onto active site and form a cross bridge