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Muscle System

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icer215's version from 2016-08-20 02:30

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Functions of muscle systemsupport, mobility
Supportmuscles maintain your posture when you sit/stand, muscles also stabilize joints, help prevent dislocations.
Mobility you move because of skeletal muscles. Your guts move because of smooth muscles. Your blood flow because of pumping action of the heart.
peripheral circulatory assistanceHeart is a muscle that pumps blood. Contraction of skeletal muscles around the deep veins help squeeze the blood through those veins. Diaphragm contraction (breathing) sucks blood into the chest cavity, and also squeezes on abdominal veins.
ThermoregulationMethod of keeping body temperature stable (homeostasis)
SweatingWhen the environment temperature is greater than the skin’s temperature. Method of heat loss
Shivering reflexIn response to cold, muscle generate heat by shivering. Contraction of muscles
Skeletal muscle striated, voluntary, shaped like long fibers, multinucleated.
Smooth musclenonstriated, involuntary, shaped like almonds (tapered ends), one nucleus per cell.
Cardiac musclestriated, involuntary, branched, shaped like fibers cross-linked to one another, typically one nucleus per cell.
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Striateddue to sarcomere structure (A bands dark, I bands light). Skeletal and cardiac muscles have sarcomeres.
Nonstriatedsmooth muscles don't have sarcomeres so they're not striated. They still have myosin, actin, and use the sliding filament mechanism. They just are not organized into sarcomeres.
Myofibrilslong cylindrical strand of contractile proteins
Sarcomerescontractile unit of a muscle. Composed of thick and thin filaments
Thick filamentslocated at the center of the sarcomere and overlap with the thin filaments. Comprised of myosin – elongated protein that forms cross bridge binding to the thin filament
Thin filamentsattached to Z disk and extend towards the center of the sarcomere. Comprised of actin and troponin
Troponinis binding site for calcium ions ➙ myosin head binds to the actin as a result
Z- diskdark strip at the ends of one sarcomere
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Muscle Fiber TypesSlow twitch (Type I) & Fast twitch (Type II)
Slow twitch (Type I)More efficient generating ATP by oxidative metabolism, Contains a lot of myoglobin, mitochondria, and blood capillaries, Fibers are red,For continuous muscle contraction over a long time, Fire slowly ➙ fatigues slower ,Great use for: endurance sports i.e. Marathons & Bicycling for hours
Fast twitch (Type II)Utilize anaerobic metabolism to generate ATP, For short strength or speed required movements of muscles, Fire quickly ➙ fatigues faster, Great use for: short bursts of activity i.e. Sprinter
IIA typesRed fibers, Hybrid of type I and type II fibers,Contains lots of myoglobin, mitochondria, and blood capillaries, Uses both aerobic and anaerobic metabolism,Very fast and strong contraction
IIB typesWhite fibers, Contains little myoglobin and mitochondria, ATP production is slower, Anaerobic metabolism, Resistance training can turn these types into type IIA
Force-velocity relationshipMuscle changes length affecting the force generation. Force decreases with increasing shortening velocity. Speed of muscle changing lengths during contraction
Vague nerveParasympathetic outflow to the heart ➙ slows the heart rate
AcetylcholineBinds to muscarinic cholinergic remember ➙ opens ligand-gated ion channels ➙ hyperpolarizes the membrane potential ➙ decreases heart rate
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Norepinephrine from sympathetic neurons & epinephrine from adrenal medullaBinds to beta-adrenergic receptors at the pacemaker tissue (myocardium) ➙ increase uptake of calcium ions ➙ the heart rate and contractility. Process involves increasing intracellular calcium level within cardiac myocytes
Calcium influxRegulate myocardial contractility. Increase calcium influx ➙ increase heart rate-Depolarization occurs
Oxygen DebtKnown as excess post-exercise oxygen consumption (EPOC). Increased intake of oxygen after strenuous activity
Oxygen supply is not producedfast enough for demand ➙ aerobic breakdown of pyruvic acid ➙ cannot produce all the ATP required for further energy demands
The body findsanother way to provide ATP ➙ through anaerobic pathways
Lactic acid pathwayProduction of ATP through anaerobic glycolysis. Pyruvic acid ➙ lactic acid
Most of lactic acidis transported to liver to convert back to glucose or glycogen
After exerciserecovery occurs
Lactic acidcarbon dioxide + H2O
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Requires extra oxygen forAbove catabolic reaction to occur. Replenish ATP, phosphocreatine and glycogen. Pay back all the oxygen borrowed from hemoglobin, myoglobin, air in the lungs, and body fluids
Depending on the intensity of exerciseEPOC takes from as short as 30 seconds to as long as more than 24 hours
Voluntary MusclesSkeletal muscles i.e. biceps, Contract consciously – can be controlled, Under the control of the somatic nervous system, Skeletal muscles are anchored to bones by tendons, Skeletal muscles are striated, Have multinucleated cells, Contraction is strong and forceful
Involuntary MusclesCardiac and smooth muscles i.e. heart, Contract unconsciously – cannot be controlled, Under the control of the autonomic nervous system (sympathetic and parasympathetic), Smooth muscles are found within the walls of organs and cardiac muscles are only found in the heart, Smooth muscles are non-striated while the cardiac muscles are striated, Smooth muscles have 1 nuclues/cell while cardiac muscle have 1-2 nuclei/cell, Smooth muscle contracts smoothly and continuously while cardiac muscle contracts strongly and forcefully
Red muscle cellsare rich in mitochondria and myoglobin. Also known as type I, slow twitch muscle.They can contract for a long period of time (long duration) with little force (low intensity)
Carry more oxygen (myoglobin)using fats and carbohydrates to fuel energy
Red muscle fibersundergo aerobic respiration
Myoglobingives the red color
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MitochondriaAlso known as power house in cells. Produce ATP (Adenosine triphosphate), source of energy unit in our body
Actin filamentThin filament, Contractile protein filament, Consists of troponin and tropomyosin
Tropomyosin blocks/unblockthe myosin head from forming cross bridge and functions to regulate the muscle contraction
Myosin filamentThick filament, Contractile protein filament, Consists of myosin head
Cross bridgeWhen myosin head binds to actin, a cross bridge is created
Sliding filament modelWhen cross bridge is crated, myosin head heads causing actin to slide in the direction of the stroke, toward the M line à muscle contracts. ATP hydrolysis is necessary to detach myosin head from actin
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I bandArea where only thin filaments are present, Thinnest structure of sarcomere, Located at the sides of the sarcomere
A bandConsists of both think and think filaments. Located at the middle (in H zone)
M lineLine of myosin at the middle of the sarcomere
Z lineZigzag line on the sides of the sarcomere. Connects the filament of adjacent sarcomeres
H zoneArea where only thick filaments are present
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