SKELETAL MUSCLE CONTRACTION AND RELAXATION Flashcards
What is the axon terminal? and what does it contain?
End of motor neuron axon where the electrical signal is transmitted to a chemical signal. Contains voltage gated ca ion channels in the membrane and synaptic vessels filled with a neurotransmitter
What is the neurotransmitter in voltage gated ca ions
acetylycholine
What is the synaptic cleft
space between axon terminal and musclefibers
What is the motor end plate
Specialized region of the muscle fiber sarcolemma. it is a folded surface with high density of ligand gated Na channels
First step of excitation phase
an action potential arrives at the axon terminal and triggers ca channels in the axon terminal to open
Second step of excitation phase
ca entry triggers exocytosis of synaptic vessels
Third step of excitation phase
synaptic vessels release ACh into synpatic cleft
fourth step of excitation phase
ACh binds to ligand gated ion channels in the motor end plate
fifth step of excitation phase
ion channels open and na enters the muscle fibers
sixth step of excitation phase
entry of Na depolarizes the sarcolemma locally producing an end plate potential
what is excitation contraction coupling
the link between events at the neuromuscular junction and muscle contraction
first stage of excitation contraction coupling
end plate potential stimulates an action potential
second stage of excitation contraction coupling
The action potential is propagated down the T tubules
third stage of excitation contraction coupling
t tubule depolarization leads to the opening of ca channels in the SR and ca enters the cytosol
What happens during a skeletal muscle contraction
Ca is released from the SR at the terminal cisternae, binds troponin, troponin moves, myosin binding sites on actin become exposed
