<P> The neuromuscular junction differs from chemical synapses between neurons . Presynaptic motor axons stop 30 nanometers from the sarcolemma , the cell membrane of a muscle cell . This 30 - nanometer space forms the synaptic cleft through which signalling molecules are released . The sarcolemma has invaginations called postjunctional folds , which increase the surface area of the membrane exposed to the synaptic cleft . These postjunctional folds form what is referred to as the motor endplate , which possess nicotinic acetylcholine receptors ( nAChRs ) at a density of 10,000 receptors / micrometer in skeletal muscle . The presynaptic axons form bulges called terminal boutons ( or presynaptic terminals ) that project into the postjunctional folds of the sarcolemma . The presynaptic terminals have active zones that contain vesicles , also called quanta , full of acetylcholine molecules . These vesicles can fuse with the presynaptic membrane and release ACh molecules into the synaptic cleft via exocytosis after depolarization . AChRs are localized opposite the presynaptic terminals by protein scaffolds at the postjunctional folds of the sarcolemma . Dystrophin , a structural protein , connects the sarcomere , sarcolemma , and extracellular matrix components . Rapsyn is another protein that docks AChRs and structural proteins to the cytoskeleton . Also present is the receptor tyrosine kinase protein MuSK , a signaling protein involved in the development of the neuromuscular junction , which is also held in place by rapsyn . </P>
<P> The neuromuscular junction differs from chemical synapses between neurons . Presynaptic motor axons stop 30 nanometers from the sarcolemma , the cell membrane of a muscle cell . This 30 - nanometer space forms the synaptic cleft through which signalling molecules are released . The sarcolemma has invaginations called postjunctional folds , which increase the surface area of the membrane exposed to the synaptic cleft . These postjunctional folds form what is referred to as the motor endplate , which possess nicotinic acetylcholine receptors ( nAChRs ) at a density of 10,000 receptors / micrometer in skeletal muscle . The presynaptic axons form bulges called terminal boutons ( or presynaptic terminals ) that project into the postjunctional folds of the sarcolemma . The presynaptic terminals have active zones that contain vesicles , also called quanta , full of acetylcholine molecules . These vesicles can fuse with the presynaptic membrane and release ACh molecules into the synaptic cleft via exocytosis after depolarization . AChRs are localized opposite the presynaptic terminals by protein scaffolds at the postjunctional folds of the sarcolemma . Dystrophin , a structural protein , connects the sarcomere , sarcolemma , and extracellular matrix components . Rapsyn is another protein that docks AChRs and structural proteins to the cytoskeleton . Also present is the receptor tyrosine kinase protein MuSK , a signaling protein involved in the development of the neuromuscular junction , which is also held in place by rapsyn . </P>
which component of the neuromuscular ( myoneural ) junction is considered the presynaptic membrane
which component of the neuromuscular ( myoneural ) junction is considered the presynaptic membrane
the sarcolemma
the sarcolemma