lecture 35 notes - Lecture 35: Movement and Its Control...

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Lecture 35: Movement and Its Control 1066…1105-1119 Knee-Jerk Reflex 1- the reflex is initiated artificially by tapping the tendon connected to the quad 2- sensors detect a sudden stretch in the quad 3- sensory neurons convey the info to the spinal cord 4- in response to signals from the sensory neurons, motor neurons convey signals to the quad, causing it to contract and jerking the lower leg forward 5- sensory neurons also communicate with interneurons in the spinal cord 6- the interneurons inhibit motor neurons that lead to the hamstring muscle. This inhibition prevents contraction of the hamstring which would resist the action of the quad 50.5 The Physical Interaction of Protein Filaments is Required for Muscle Function Vertebrate Skeletal Muscle -skeletal muscle : attached to the bones and is responsible for their movement -skeletal muscles consist of a bundle of long fibers running parallel to the length of the muscle and each fiber is a single cell with many nuclei, reflecting its formation by the fusion of many embryonic cells -a muscle fiber contains a bundle of smaller myofibrils arranged longitudinally -myofibrils composed of thin filaments and thick filaments - thin filaments : 2 strands of actin & 2 strands of a regulatory protein coiled around one another - thick filaments : staggered arrays of myosin molecules -skeletal muscle is also striated muscle because of the regular arrangement of the filaments creates a pattern of light and dark bands -each repeating unit is a sarcomere , the basic contractile unit of the muscle -in a muscle fiber at rest, thick and thin filaments only partially overalp The Sliding-Filament Model of Muscle Contraction -neither the thin filaments nor the thick filaments change in length when the sarcomere shortens; rather, the filaments slide past each other longitudinally, increasing the overlap of the thin and thick filaments -sliding of filaments based on the interaction between the myosin and actin molecules that make up the thick and thin filaments -each myosin molecule consists of a long tail region and a globular head region extending ot the side -the tail adheres to the tials of other myosin molecules that form the thick filament -head center that powers muscle contractions -it can bind ATP and hydrolize it into ADP and phosphate -hydrolysis of ATP converts myosin to a high-energy form that can bind to actin, form a cross-bridge, and pull the thin filament toward the center of the sarcomere -cross bridge is broken when a new molecule of ATP binds to the myosin head -in a prepeating cycle, the free head cleaves the new ATP and attaches to a new binding site on another actin molecule farther along the thin filament -a typical muscle fiber at rest contains only enough ATP for a few contractions…energy needed for repetitive contractions is stored in creatine phosphate and glycogen -creatine phosphate can transfer a phosphate group to ADP ATP -the resting supply of creatine phosphate is sufficient to sustain contractions for about 15
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This note was uploaded on 03/03/2010 for the course BIOG 1101 taught by Professor N/a during the Fall '10 term at Cornell University (Engineering School).

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lecture 35 notes - Lecture 35: Movement and Its Control...

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