EXAM 2 ANSWERS DOS

EXAM 2 ANSWERS DOS - 26 NEUROMUSCULAR JUNCTION =...

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26) NEUROMUSCULAR JUNCTION = specialized point of contact between motor neuron and skeletal muscle fiber. synaptic vesicles: contain Ach Acetylcholine = type of neurotransmitter CALCIUM: Concentration outside of cells vs. inside cells -calcium PROMOTES EXOCYTOSIS -in muscle cells, smooth ER is modified to store calcium Mitochondria OXIDATIVE NERVE IMPULSE steps: Ca^2+ influx from ECF by way of calcium channels into motor neuron cytoplasm. Ach exocytosis into synaptic cleft Ach binds to motor end plate ( Ach receptor) which is located on the sarcolemma ( cell membrane of skeletal muscle) = Motor end plate depolarization - region is highly folded= MORE SURFACE AREA for Ach depolarization nerve impulse CONDUCTION through T tubules this TRIGGERS SR calcium release into sarcoplasm cross-bridge formation sarcomere shortening muscle contraction! postsynaptic membrane= the surface of the cell on the opposite side of the synapse from the synaptic terminal of the stimulating neuron that contains receptor proteins and degradative enzymes for the neurotransmitter (dictionary def.) 27) SR (sarcoplasmic reticulum)= modified smooth ER -calcium storage tank - terminal cisterns associated with T tubule (“triad”) Triad= contains terminal cisterns & T tubule T tubule= Pipe, that wraps around muscle fibers, tells SR to release calcium . -Extracellular fluid stored here terminal cistern= SR tubule that forms larger, perpendicular cross-channels over the junction between each A band in a myofibril and it’s adjacent I bands (A-I junctions) -occur in pairs on either side of the T tubule. **DRAWING** (PG. 245 in textbook, B-34)
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28) Slow oxidative fibers ( SO fibers)= DARK fibers slow-twitch fibers slow to fatigue slow to contract -fatigue-resistant = HIGH ENDURANCE ex. chicken legs b/c walks all day -OXIDATIVE METABOLISM= AEROBIC (aerobic/endurance training targets SO fibers) -MAKE Mitochondria -MAKE myoglobin in cytoplasm (to store more oxygen in muscle cells) DARK STAINING Fast glycolytic fibers (FG fibers)= LIGHT fibers fatigue easily LOW ENDURANCE high velocity contracting -energy from stored glycogen= ANAEROBIC (anaerobic/strength training targets FG fibers) - Mitochondria - Myoglobin in cytoplasm LIGHT STAINING ANAEROBIC (strength) TRAINING: -muscular HYPERTROPHY= muscle mass GAIN increase in cell size b/c more
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muscle proteins added - # of MYOFIBRILS (MUSCLE ATROPHY= muscle mass LOSS decrease in size due to loss of muscle proteins) 29) isometric contractions= resistance (load) is GREATER> than muscular tension -muscle length CONSTANT -joint angle CONSTANT ex. holding arm up and leaving it there isotonic contractions= resistance (load) is LESSER < than muscular tension -muscle length CHANGES -joint angle CHANGES concentric= SHORTENING -muscle shortens -joint angle DECREASES ex. picking up a book, kicking a ball eccentric= LENGTHENING -muscle lengthens -joint angle increases -movements that are gravity resist ex. going down stairs, running downhill, landing from a jump
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