Physiology of a muscle contraction Flashcards
thin filament slide inward past thick myosin filament
Sliding Filament mechanism
convert nervous signal to a muscle signal
Excitation
muscle action potential spreads through the T-Tubules into sarcoplasm
Excitation-Contraction Coupling
get calcium out of Sarcoplasm back into SR
Relaxation
Synapitc Knob stops releasing acetylcholine
Relaxation
sarcomere shortens but neither thin or thick filament change length
Sliding Filament Mechanism
nervouse signal arrives at a synaptic knob
Excitation
When nerve signals no longer arrive at the neuromuscular junctions
Relaxation
Calcium release channels into ST open
Excitation-Contraction coupling
ATP attach to ATP binding site on myosin head
Sliding filament mechanism
causes channels to open, allows calcium ions to enter synaptic knob
Excitation
nerve signals are no longer transferred to the motor end plate
relaxation
Calcium ions diffuse into sarcoplasm within one millisecond
Excitation contraction coupling
ATP splits by myosin ATPase and energizes their myosin head
sliding filament mechanism
triggers exocytosis of synapitc vesicles release acetylchonline diffuses the synaptic cleft
excitation
calcium channels close
Relaxation
Calcium ion bind to troponin molecules on thin filaments causing them to change shape
excitation contraction coupling
energizes myosin head attaches to an actin binding site to form across bridge.
sliding filament mechanism
acetylcholinesterase enzyme breaks acetylcholine molecule into fragments that are absorbed into the synaptic knob
Relaxation
acetylcholine binds to receptors on the motor neuron and plate, causes them to change shape.
excitation
myosin head swivels toward the center of the sacromere
sliding filament mechanism
troponin-tropomyosin complex shift to new position
excitation contraction coupling
Calcium ions transport out the sarcoplasm and break into SR using ATP energy
relaxation
Calcium ions bind to protein calsequestrin
Relaxation
Ion channels open and sodium ions enter muscle fiber while potassium ions leave muscle fiber
Excitation
Calcium ions dissociates from troponin and troponin-tropomyosin complex moves back to original postition
relaxation
exposes the myosin-binding sites on the actin filament so cross-bridge might form
excitation contraction coupling
myosin head draws the thin filament past the thick filament to generate power-stroke
sliding filament mechanism
move ions across sarcolemma creates muscle action potential excites muscle fiber
excitation
2nd molecule of ATP attaches to the ATP binding site on the myosin head and allows ATP to detach the actin filament
sliding filament mechanism
calcium concentration in sarcoplasm kept low unless contraction muscle fiber
relaxation.
new cross bridge forms along the thin filament and generates another power stroke.
sliding filament mechanism.
Free phosphate group immediately bind with calcium ion in sarcoplasm
relaxation
repeat as long as ATP and calcium present
sliding filament mechanism
