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4 functions of the muscular system
1. produce movement
2. maintain posture
3. stabilize joints
4. generate heat
• surrounds each myofibril and stores calcium
• calcium is released when the muscle fiber is stimulated to contract
What produces striations in skeletal muscle?
the precise arrangement of the myofilaments (thick & thin) in the myofibril
What is tetanic contraction? (tetanus)
• muscle doesn't completely return to resting state
• contraction is immediately followed by another very rapidly
• myofilaments are able to slide past each other during contractions
• muscle shortens
ex: bicep curl
• tension in the muscles increases
• the muscle is unable to shorten
ex: carrying an object in front of you
• some fibers are contracted even in a released muscle
• different fibers stimulated at different times by nervous system during muscle tone
• the process of stimulating various fibers is under involuntary control
• muscle remains firing, healthy, and ready for action
• common reason for muscle fatigue
• oxygen is reauired to get rid of accumulated lactic acid
• located in muscle cells
• high energy molecule
• CP transfers a phosphate to regenerate ATP
• CP supplies are exhausted in 20 sec
How are muscles named?
• direction of muscle fibers (rectus)
• relative size of the muscle (maximus)
• location of the muscle (temporalis)
• number of orgins (triceps)
• shape of the muscle (deltoid)
• action of the muscle (flexor)
• location of orgin & insertion (sterno)
• series of metabolic pathways taht occur in the mitochondria
• glucose is broken down to carbon dioxide & water releasing energy
• slower reactions that requires continuous oxygen
• 95% comes from this one
Series of reactions in anaerobic glycolysis
reaction that breaks down glucose w/out oxygen
glucose is broken down to pyruvic acid to produce some ATP → pyruvic acid is converted to lactic acid which produces muscle fatigue and cramps → 2 ATP/glucose produced
What are 2 reasons that the degree of shortening in a muscle might vary?
1) by changing the frequency of muscle stimulation
2) by changing the number of muscle cells being stimulated
What is the purpose of myosin cross bridges?
• generates the tension debeloped by a muscle cell when it contracts
• cross bridges attach to active sites on the actin sub units of thin filaments
• link thick and thin filaments together
What happens to Ca 2+ after skeletal muscle contraction?
Ca 2+ is reabsorbed into the SR and proteins block the myosin binging sites on the actin
Order of events in skeletal muscle contraction
1. neurotransmitter chemical stored and released by a nerver (at the axonal terminal of a motor neuron) upon arrival of nerve impulse (terminal = ending)
2. neurotransmitter attaches to receptors on the sarcolema which opens the sodium channels
3. the sarcolemma becomes temporarily permeable to sodium
4. sodium rushing into the cell generates an action positive (an excess of postitive ions generates an electrical current aka action potential)
5. once started, muscle contraction can't be stopped- it travels down the entire muscle cell
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