5.1 It is a complete muscle if the epimysium is present.
5.2 Sacoplasm is the cytoplasm of a muscle fiber.
5.3 In proper order:
b. Ca(2)+ binds to troponin, exposing the active sites on the actin, allowing the myosin heads to grab onto the actin.
d. The power stroke.
a. ATP binds to the myosin heads, making them release the active sites on the actin.
c. The return stroke.
5.4 This is the return stroke.
5.5 The muscle has finished contracting.
5.6 In proper order:
b. An action potential travels down the axon of a motor neuron.
e. ACh is released from the presynaptic terminal.
f. ACh travels across the synaptic cleft.
c. ACh interacts with the muscle fiber membrane to create a muscle action potential.
d. The action potential travels down a T-tubule.
a. Calcium ions are released from the sarcoplasmic reticulum.
g. Calcium ions bind to the troponin in an actin filament.
5.7 The Ca(2)+ ions move through the membrane of the sarcoplasmic reticulum via diffusion. this is passive transport.
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