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Muscle Physiology. Muscle Cell Contraction. Parts of a Muscle Fiber. Sarcoplasm = cytoplasm Sarcolemma = cell membrane T tubules – extensions of sarcolemma into sarcoplasm Sarcoplasmic reticulum (SR) = smooth endoplasmic reticulum (SER) Contains CA 2+ ions
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Muscle Physiology Muscle Cell Contraction
Parts of a Muscle Fiber • Sarcoplasm = cytoplasm • Sarcolemma = cell membrane • T tubules – extensions of sarcolemma into sarcoplasm • Sarcoplasmic reticulum (SR) = smooth endoplasmic reticulum (SER) • Contains CA2+ ions • Surrounds myofibrils & T tubules
The Motor Unit • Motor unit = a motor neuron + all of its muscle fibers
The Neuromuscular Junction (NMJ) • Motor neuron • Multiple axon terminals – can connect to several muscle fibers • Axon terminals contain vesicles full of the neurotransmitter (NT) acetylcholine (ACh) • Muscle fiber • Synaptic cleft = space between neuron & muscle fiber • Sarcolemma is folded at NMJ to increase surface area & number of receptors