BIO 203 Lecture Notes - Lecture 12: Cell Membrane, Extracellular Fluid, Neuromuscular Junction
8 Dec 2017
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Force length relationship: muscle is held at one length, which is varied between trails. Isomeric contraction: a muscle generates force but does not shorten. Isotonic contraction: a muscle generates constant force and shortens. Motor unit: made up of motor neurons & skeletal muscle fibers. Functional nerve- muscle group: motor units: neuron + muscle fibers. Coupled events: nerve action potential, transmission across neuromuscular junction, muscle action potential, intracellular messenger (ca2+) signal, mechanical contraction. Myofibrils: bundles of actin(thin) and myosin filaments (thick) Myosin head binds to actin: can bind & hydrolyze atp. This causes change in the head, releasing actin & return to position. Action potential spreads throughout muscle fiber via t tubules. Triggers release of ca2+ from the sarcoplasmic reticulum. Rapid delivery of multiple stimuli results in mechanical summation: delivery of subsequent stimulus before relaxation of previous contraction= increased contractile response, tetanus=mechanical summation response. Curare: isoquinoline alkaloid, post synaptic receptor toxin, competes at nicotinic receptor of nmj.
