Skeletal Muscle Contraction
1. Neurotransmitter must stimulate muscle.
This happens at the neuromuscular junction.
Axon of neuron,
‘Synaptic bulb’
AcH
Muscle
Formed by
Muscle fiber
membrane
Contain
AcH
The space = synapse, synaptic
cleft
Neurotransmitter = Acethylcholine. Stored in vesicles on the distal
end of the axon.
1. A nerve impulse/action potential reaches the synaptic bulb
2. Calcium ions diffuse into the terminal.
3. This causes the vesicles to move to the cell membrane, fuse with it
and release AcH into the synaptic cleft.
4. AcH binds to receptor proteins on the muscle side of the junction.
5. This causes an impulse in the muscle that travels along and around
the muscle.
Motor end
plate =
membrane
of muscle
fiber.
Receptor
proteins
Depolarizes = becomes less negative
6. This muscle impulse/action potential moves along the
sarcolemma, into transverse tubules and into the sarcoplasmic
reticulum.
Action potential =
A spike of
electrical
discharge that
travels along
the membrane
of a cell
7. Calcium ions are released into sarcoplasmic reticulum
8. Calcium ions expose binding sites on actin.
9. Myosin heads bind to the binding sites and form cross bridges.
10. Myosin heads lose ADP and P, change shape and pull actin to the
center of the sarcomere… this results in the contraction of the
muscle.
11. ATP forms, binds to myosin head, cross bridges break and muscle
relaxes
Muscle relaxes
Muscle contracts
http://www.wiley.com/college/pratt/0471393878/student/animations/actin_
myosin/actin_myosin.swf
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__breakdown_of_atp_and_crossbridge_movement_during_muscle_contraction.html
http://www.dnatube.com/video/5034/Contraction-of-muscle-function-ofneuromuscular-junction
http://highered.mheducation.com/sites/0072495855/student_view0/chapter10/a
nimation__action_potentials_and_muscle_contraction.html
http://www.sumanasinc.com/webcontent/animations/content/muscle.html