NMJ.pptx

NEUROMUSCULAR JUNCTION  NEUROMUSCULAR JUNCTION oMotor end plate oThe synapse between axons of motor neurons and skeletal muscle. oChemical synapse SYNAPSE TRANSMISSION  COMPONENTS OF NEUROMUSCULAR JUNCTION oSynaptic knobs oPresynaptic membrane oSynaptic cleft oPostsynaptic...

NEUROMUSCULAR JUNCTION  NEUROMUSCULAR JUNCTION oMotor end plate oThe synapse between axons of motor neurons and skeletal muscle. oChemical synapse SYNAPSE TRANSMISSION  COMPONENTS OF NEUROMUSCULAR JUNCTION oSynaptic knobs oPresynaptic membrane oSynaptic cleft oPostsynaptic membrane o Synaptic knobs: Mitochondria and acetylcholine vesicles o Presynaptic membrane: Synapsin proteins o Synaptic cleft: Extracellular fluid and acetylcholinesterase enzyme oPostsynaptic membrane: Subneural cleft Receptors  STEPS OF NEUROMUSCULAR TRANSMISSION erve impulse or action potential ning of voltage-gated calcium channels Influx of calcium ions inside the cell increases Opening/rupture of vesicle and release of acetylcholine tylcholine comes to the synaptic cleft  Acetylcholine binds with nicotinic receptors to form the acetylcholine- receptor complex Opening of ligand-gated sodium channels Influx of sodium ions inside the cell increases Development of endplate potential Generate muscle action potential Muscle contraction takes place  ENDPLATE POTENTIAL oRMP of postsynaptic membrane is -80 to -90 mV. oInflux of Na channels causes local positive potential change – END PLATE POTENTIAL. oIt’s localized, Non-Propogated, Does not obey All or None Law. o But when critical level of -60mv reached triggers action potential in muscle fibre in both direction.  MINIATURE ENDPLATE POTENTIAL oAt rest, small quantity of acetyl choline are released from nerve terminal. oEach vesicle release produces weak end plate potential about 0.5mv – Miniature End Plate Potential. AGENTS AFFECTING NMJ TRANSMISSION  Botulinus toxin: Blocks release of ACh from presynaptic terminal Curare: Competes with ACh for receptors on motor end plate Neostigmine: Inhibits acetylcholineesterase Hemicholinium: Blocks reuptake of choline into  DISEASES oMyasthenia Gravis oEaton Lambart Syndrome oMYASTHENIA GRAVIS: Autoimmune disorder presence of antibodies to the ACh receptor on the muscle end plate. o LAMBART EATON SYNDROME:  autoimmune disorder Antibodies against calcium channels in axon terminal