lab_2-skeletal_muscle_lecture

lab_2-skeletal_muscle_lecture - Properties of Skeletal...

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Properties of Skeletal Muscle Laboratory 2
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Purpose To analyze the effects of stimulus intensity and stimulus frequency on contraction To analyze the effects of acetylcholine (ACh) receptor blockade on muscle activity To see the effects of direct muscle stimulation
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Background: Skeletal Muscle is made up of muscle fibers (individual muscle cells) Muscle fibers contain many myofibrils Myofibrils are made of thick (myosin ) and thin (actin ) filaments
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Myofibrils are organized into arrays forming the sarcomere Sarcomere : contractile unit within the muscle fiber 1 sarcomere=area between 2 Z lines
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Motor neurons branch to innervate many individual muscle fibers A motor unit consists of the motor neuron and all the muscle fibers it innervates
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Small motor units allow for very fine muscle control (Ex. Muscle for eye movement) Large motor units are incapable of fine motor control but are able to create larger amounts of tension (Ex. Leg muscles) Muscles are often made up of different sized motor units, which can help control the force of muscle contraction Physiologically, motor units are activated from smallest to largest (Henneman Size Principal) Note: In lab, we will be directly stimulating the sciatic nerve. Direct stimulation causes the recruitment of motor neurons from largest to smallest, due to larger neurons having a lower threshold to direct electrical stimulation (have a lower resistance)
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Excitation-Contraction Coupling Neuromuscular Junction : Area where the motor neuron synapses with the muscle fiber Depolarization causes the release of Acetylcholine
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