Physiology 206 Lecture 11 Outline of Last Lecture I. MuscleII. Thick filamentsIII. Thin filamentsIV. ContractionV. Types of contractionOutline of Current Lecture I. TetanyII. Motor neuronsIII. Motor unitsIV. Muscle fiber typesV. Muscle typesCurrent Lecture2/10/14Tetany-Muscle contracts and stays contracted-Tetanic stimuli - sensation that leads to tetanyo50-55 stimulations per second in human skeletal muscleoElectric current in US: 60 stimulations per second-Will deliver tetanic stimuli-Accidental electrocution-Reason why you can't let go; muscles clenchoIncandescent light flickers, but we can't see it.-US adapted to 60-Rest of the world is 55These 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.-Motor neurons fire tetanic stimuli to cause muscle contractionoHow we can vary the length of contractionoVarying strength-Caused by increasing or decreasing number of motor neurons firing contraction-Motor UnitoOne motor neuron and all of the muscles it innervatesoMuscle cells are innervated by only 1 neuronoSmall motor units allow for finer, graded contractions-Muscle MetabolismoIn lack oxygen, metabolites do not have enough substrates to metabolize all the way to carbon dioxideoInstead, it only metabolized to lactic acid, which is more acidic and causes pain are sustained use-Muscle fiber typesoRed muscle-Slow fatigue-Slow twitch (doesn't contract as rapidly)Myoglobin takes up more spaceLess space for actin and myosin-Operates for much longer-Has more myoglobin, a red proteinRelated to hemoglobinAlso binds to oxygenCarry around a reservoir of oxygen-Allows for oxygen to be used even when oxygen intake is decreasedoWhite muscle-Fast fatigueOnce enough oxygen cannot be gained to produce ATP, lactic acid is made instead-Fast twitch Smooth Muscle-Actin and myosin are not arranged in paralleloSkeletal only shortens in the long directionoSmooth can shorten in every direction Cardiac Muscle-StraitedoActin and myosin are arranged in parallel like in skeletaloHOWEVER they can send action potential to all neighboring cells like smooth muscle-Have unstable resting potentials -Atrial muscleoOnly 1 action potential every 150 mmsecoCan contract twice as frequently as ventricular muscle-Ventricular muscleoOnly 1 action potential every 300 mmsecoTherefore, only about 200 contractions per minute-Conducting
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