Anatomy Physiology II Exam 1 Review Power Point 1 Muscular System and Review Objective 1 Define and identify the anatomy of skeletal muscle and explain the sliding filament theory leading to muscle contraction There are 660 skeletal muscles Muscles constitute approximately 45 of body weight The largest organ system important tissue for bioenergetic homeostasis during rest and exercise Major site of energy transduction and storage End organ for the primary support systems involved in exercise such as cardiovascular and pulmonary Composition of skeletal muscle o 75 water o 5 inorganic salts pigments and substrates o 20 a mixture of proteins Sliding Filament Theory o It is the shortening of sarcomeres that is responsible for the contraction of skeletal o In a sarcomere the actin and myosin slide past one another but remain the same length muscles as when the muscle is at rest o When the myofilaments slide past one another and the sarcomeres shorten the myofibrils also shorten because the myofibrils consist of sarcomeres joined end to end o The myofibrils extend the length of the muscle fibers and when they shorten the muscle fibers shorten o Muscle fibers like other cells of the body are electrically excitable so electrical signals action potentials travel from the brain or spinal cord along axons to muscle fibers and cause them to contract Objective 2 Define and distinguish between the types of muscle fibers and explain the possibilities or lack thereof of fiber type morphology 1 1 There are 2 major types of skeletal muscle fibers slow twitch and fast twitch o The myosin of slow twitch muscle fibers causes the fibers to contract more slowly and o The myosin of fast twitch muscle fibers causes the fibers to contract quickly and to to be more resistant to fatigue fatigue quickly Slow twitch oxidative SO muscle fibers type I fibers contract slower have a better developed blood supply have more mitochondria and are more fatigue resistant Fast twitch muscle fibers type II fibers respond rapidly to nervous stimulation contract rapidly for shorter periods of time and fatigue quickly Fast twitch fibers come in 2 forms o Type IIa or fast twitch oxidative glycolytic FOG fibers Relies on both anaerobic and aerobic ATP production o Type IIb or fast twitch glycolytic FG fibers Relies almost exclusively on anaerobic glycolysis for ATP production 3 types o Type I Slow o Type IIa Fast fatigue resistance o Type IIx or IIb Fast fatigable Sprinters have more fast twitch muscle fibers while long distance runners have more slow twitch muscle fibers Neither fast nor slow twitch muscle fibers can be easily converted into muscle fivers of te other type without training Intense exercise that requires anaerobit respiration such as weight lifting increases muscle strength and mass and causes fast twich muscle fibers to enlarge more than slow twitch muscle fibers Aerobic exercise increases the cascularity of muscle and causes slow twitch muscle fibers to enlarge more Weight training followed by period of rest can convert some muscle fibers from type IIa to type IIb However a type I muscle fiber cannot be converted to a type II fiber and vice versa 2 2 Objective 3 State the different types of skeletal muscle contraction and the functions and characteristics of skeletal muscle Types of skeletal muscle contraction o Isometric contractions the length of muscle does not change but the amount of tension increases during contraction Responsible for the constant length of the postural muscles of the body such as the muscles that hold the spine erect o Isotonic contractions the amount of tension produced by the muscle is constant during contraction but the length of muscle changes Movements of the fingers when typing is predominantly isotonic o Concentric contractions are isotonic contractions in which tension in the muscle is great enough to overcome the opposing resistance and the muscle shortens Such as lifting a backpack o Eccentric contractions isotonic contractions in which tension is maintained in a muscle but the opposing resistance is great enough to cause the muscle to increase in length When a person slowly lowers a heavy weight Muscle functions Functional characteristics o Produce movement o Maintain posture o Stabilize joints o Generate Heat o Excitability o Contractility o Extensibility be able to contract has been stretched o Elasticity the capacity of muscle to respond to a stimulus ability of muscle to shorten forcefully means a muscle can be stretched beyond its normal resting length and still stretching the ability of muscle to recoil to its original resting length after it Objective 4 What are the different types of fascicle arrangements Also what determines a muscle s power and Range of Motion ROM Fascicle arrangements bundles of fibers o Circular Fascicles arranged in rings Orbicularis Oris Eye o Convergent Broad Origin and fascicles converge toward insertion Pectoralis Major O sternum clavicle I tendon of humerus Converge toward humerus Converge toward humerus o Parallel Sartorius fascicles run parallel along the AXIS Longest Muscle o Fusiform Spindle Shaped o Pennate Attach obliquely to the Attach obliquely to the central tendon Featherlike Unipennate Extensor Digitorum Longus Multipennate Delts Bipennate Rectus Femoris 3 3 Fascicle Arrangement ROM Looks like feathers o Arrangement of fascicles determines that muscle s ROM and power o Parallel Fascicle arrangement Muscles that shorten the most o Muscles with the greatest numbers of fibers have most power i e Bipennate Rectus and multipennate Pound for Pound Strong Objective 5 Describe the 3 classes of levers and apply the knowledge to uses of mechanical advantage and muscle insertions to determine lever classes in the body Lever is a bar on a fixed point fulcrum You have the load and effort applied force So in your body o Bone Lever o Joint Fulcrum o Muscle Insertion point at Bone Effort o Bone and weight Load whatever you are trying to move A lever allows a given effort to move a load farther and faster than without lever load o Power Lever Load is close to fulcrum and the effort is far from fulcrum In this case a small effort over a large distance can move load Car Jack High mechanical advantage o Speed Lever Load is far from fulcrum and effort is close to fulcrum the effort must be greater mechanical disadvantage or low mechanical advantage Three classes of levers o First Class Lever Effort and load are on the ends and fulcrum is in the
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