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UAB BY 116 - Skeletal Muscle Contraction
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By 116 1st Edition Lecture 15 Outline of Last Lecture D. Sympathetic SystemParasympathetic systemVI. Smooth muscleCommon Smooth musclesSpecialized smooth musclesPhysiological typesD. Features of all muscle Outline of Current Lecture VII. Voluntary Skeletal muscle 3 muscles that are involvedSkeletal muscleFunctional Characteristics of muscleContractionMuscle fiber types Current LectureVoluntary Muscle Physiology – somatic motor activity3 muscles that are involved Primary movers- Skeletal muscle Postural muscles- deep muscleMuscles of ventilation- intercostals muscles, diaphragm- movement of the thoracic cage sizeSkeletal muscleHeat producers- thermoregulationPumps around the blood vessels, some control over blood; assists the return of blood to the heart. Veins are controlled by skeletal muscle though venous valves Thoracic pump- have inferior vena cava making a sort of vacuum, negative pressure that will suck the blood to the heart.Creatinin (waste product of muscle work) is filtered through the kidney and used to see if they are healthy contributes to acid control/base regulation because they will not be breaking down lactic acid Structureorigin- on immovable skeletal bone, closest to the middline, insertion- on the movable bone thickest portion of muscle is muscle body- shortens toward the body muscle facet= bundle of muscle fibers, they give us the different shapes These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.muscle fiber is a bundle of myofibrils, wrapped around these is a sarcoplasmic reticulum, and tubulin (network of tubes that transverse across the muscle fibers and are the conductors in thecell) myofibrils – give us contractilitythin filaments- actinthick filaments- myosincalcium diffuses to the myofibrils from the t-tubuoles to the myofibrils the t- tubuloles and SR is conductivity of electrical impulse sarcolemma= membrane of muscle cell where excitability happens endomesium, perimesium, epimesium important to extensibility and elasticity striation- repeated pattern of light and dark band (thin and thick)sarcomere- repeating pattern of actin and myosin Z-lines- define one sarcomeric unit (distance of sarcomereM-line- mid-line of sarcomere and myosin extends off it in either direction, making up the A-bandA- band – consists of the m-line and the overlap region, it covers all of the myosinH-zone – part of A-band that only contains myosin fibers, none of the overlap with actinI-band – contains acting and hits the front end of the Aband all the way to the next A-bandFunctional characteristics of muscles Excitability – receive and respond to stimuliConductivity – receive stimulus and transmit a wave of excitation Contractility – ability to shorten forcibly when stimulated Extensibility- stretched and extended Elasticity – can bounce back to original lengthContraction- tension and force is generated Overall There is a Neutral, Tension and then Satiety period. Neutral is the latent period, beginning toneTension is the contraction phase where muscle is shortening Satiety is the relaxation phase where elongation happensExcitation begins in brainhave sensory info, congnitive brain info and homeostatic brain info (blood pressure) – all of them funnel into the prefrontal cortex From the prefrontal cortex, this info is relayed to the premotor cortex- which receives other info about the body’s equilibrium and proprioceptioncerebellum contains past motor movement memoryBrain then gives the plan for movement to the primary motor cortexinfo is then sent down the upper motor neuron in the CNS and synapses in the spinal nerve which passes movement to the lower motor neuronCoticospinal tract- deals with motor neurons, exits on anterior/ ventral horn of spinal cord Motor Unit- 1 motor neuron and ALL the muscle fibers it controlsshorten every sarcomere towards M-line during contraction sarcomere is the shortest unit that we see shorteningA-band never changes sizesize of overlap increases I band shortenslever movement form insertion to origin or stabilizes joint Procedural steps of contractionMuscle responds to neural inhibition Ach is released destroyed at motor end plate by Acholinesterase causing an action impulse conducted down the T-tubules AP activates the DHP gate that opens Ca channels Calcium is pumped into the Sarcomplasmic reticulum Calcium binds to troponin, which moves myosin away from blocking the binding sitesCalcium is the key to coupling excitation to contractionMyosin and actin is uncoupled and unblocked Actin and Myosin Cross bridge cyclemyosin goes through a change in energy status (from high to low) which causes movement couples( extends ( attaches ( relaxsarcomere elongates and afferent spinal frequency is slower because of this sarcolemma returns to resting potential Fatigue- happens when use up all ATP, lose yourenergy source, or when you run out of calcium or many other reasonsmuscle cramping occurs when calcium levels are low Satiety and Muscle RelaxationSatiety= satisfied with original task of Muscle Muscle fiber types Type I- oxidative slow twitch –slow and is a red muscle fiber that is the most used muscle typeslowest development time , smallest diameter, and longest contraction durationLong endurance, essentially fatigue resistantuses: postureType IIa – oxidative fast twitch- red musclehas intermediate tension, and a medium diameter as well as a short contraction timethis is also fatigue resistantuses- standing, walkingTypr IIb- fast twitch glycolytic – white muscle and this is the least used fiber fastest development time, largest diameter , and short contraction time this is easily fatiguedused in jumping Adaptations to resistance and aerobic trainingHyperplasia- increase in muscle cell numberHypertrophy- increase in myofiber diameter can fiber types twitch?Intermediate Type IIa fibers can adapt to exercise- it either becomes more like slow or fast


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