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Chpt 12 Muscle

M lines structural proteins that anchor myosin during contraction
Titin elastic protein attaching myosin to Z disc that contributes to elastic recoil of muscle
A band dark,contains thick filaments (mostly myosin)
H band light,center of A band, no overlap of actin and myosin
I band light contains think filaments (mostly actin)
Z line/disc
Sarcomere contraction actin myosin filament side by side, actin is pulled toward the center H zones disappear and I band becomes very narrow
Cross bridges sliding filament theory, myosin head contains an ATP-binding site which functions as an ATPase, converts ATP into ADP + Pi (Relax, Attachment ATP, rachets & slides actin, ADP + Pi)
Power stroke conformational change which exerts force on actin
Tropomyosin filament in grove between double row of G-actins
Troponin complex is attached to tropomyosin at intervals of every 7 actins [I-inhibitor of myosin,M-tropomyosin association,C-calcium binding >10^-6M]
Sarcoplasmic reticulum calcium reservoir in muscle
Terminal cisternae where most of the calcium is in the sarcoplasmic reticulum
T tubules run along terminal cisternae
Ideal resting length is that which can generate maximum force; strength of muscle contraction influenced by: frequency of stimulation, thickness of each muscle fiber, initial length of muscle fiber
Optimal overlap too close or too far apart, less tension bc fewer cross bridges can form
Twitch single rapid contraction and relaxation of muscle fibers
Summation 2nd stimulus occurs before muscle relaxes from 1st, the 2nd twitch will be greater
Complete tetanus, tetany freq so fast no relaxation occurs, a smooth sustained contraction
Isotonic contraction force remains constant throughout shortening process
Isometric contraction exerted force does not cause load to move and length of fibers remain constant
Eccentric contraction load is greater than exerted force and fibers lengthen
Maximum oxygen uptake(aerobic capacity) max rate of oxygen consumption V02 Max
Lactate (anaerobic) threshold is % of max O2 uptake at which there is significant rise in blood lactate levels ~ 50-70& V02 max
Intensity of exercise mild plasma, free fatty acids; moderate exercise, muscle glycogen-plasma free fatty acids; heavy exercise, muscle glycogen
Oxygen Debt accumulates during exercise withdrawn from hemoglobin and myoglobin, bc O2 is required for metabolism of lactic acid produced by anaerobic respiration
Phosphocreatine (creatine phosphate) source of high energy Ps to regenerate ATP from ADP; 3X ATP levels
Slow-twich Type I fibers slow fatigue, slow oxidative
Fast-twich Type IIA(fast oxidative,aerobic) and IIX (fast glycolytic,anaerobic) fibers, fast fatigue
Satellite cells fuse with existing cells
Central fatigue occurs as brain is less able to
Upper motor system plan and rehearse,remember practiced,coordinate complex (Primary motor cortex, akin to sensory motor cortex)
Lower motor neurons,final common pathway motor neuron cell bodies are in ventral horn of spinal cord; axons leave in ventral root
Upper motor neurons facilitory and inhibitory activity influenced by sensory feed back from muscles and tendons
Cerebellum receives sensory input from spindles, Golgi tendon organs, and areas of corex devoted to vision, hearing and equilbrium [No descending tracts, influence motor activity indirectly, all output inhibitory, aids motor coordination]
Basal ganglia
Relationship UMN LMW MUSCLE
Motor unit includes each motor neuron and all fibers it innervates
Innervation ratio #of motor neurons:muscle fibers [1:100 fine control,less fibers to 1:200]{when a motor neuron is activated, all muscle fibers in its motor units contract
Recruitment how do skeletal muscles perform smooth movements?
Neuromuscular junction specialized region on myocyte
Action Potential terminal buton Ach Nicotinic receptors Na+ ions move depolarize from motor end-plate out to the sarcolema; V-G ch AP myocyte-tubules[Excitation-contraction coupling]
Tension information from golgi tendon organs
Length muscle spindle apparatus
Intrafusal fibers modified thin muscle cells; tell brain muscle bed is changing size; Nuclear bag fibers-loose aggregate:primary annulospiral sensory endings; Nuclear chain fibers-have nuclei in rows:secondary, flower-spray endings
Extrafusal fibers regular muscle fibers
Coactivation two class of neurons, alphas(muscle contraction and shortening-length); gammas(cause intrafusal to take up slack)
Knee-jerk reflex tap,intrafusal fibers, base of spinal cord, alpha motorneuron, stimulates extrafusal muscle fiber to contract
Golgi tendon organ reflex disynaptic reflex;3tension on tendons activates sensory neuron & 4tension on tendon is reduced
Reciprocal innervation 1muscle stretch activates spindle apparatus 2agonist muscle contracts in stretch reflex 3antagonist muscle relaxes
Crossed-Extensor Reflex get-back phenomenon heat glass nail involves double reciprocal innervation;affects contralateral side of cord
Created by: 100001194417609



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