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Matthew Hernandez Per3 Muscular - Coggle Diagram
Matthew Hernandez Per3 Muscular
Major Functions of Muscular System
Produce Movement- responsible for manipulation & locomotion EX: walking
When contracting, generates heat
Maintain posture & body position
Stabilize joints
3 Types of Muscles & their Functions
-Skeletal -Cardiac -Smooth
-Skeletal is attached to bones or skin, it is cylindrical, multi-nucleate cells w obvious striations, nerve & blood supply, CT coverings, attachments, moves the body & maintains posture, voluntary control
-Cardiac are the walls of the heart, striations, uni or bimucleate, pumps blood throughout body, involuntary control
-Smooth unitary muscle in walls of hollow visceral organs(not heart), multi unit in eyes, airways, large arteries, no striations, spindle shape, uni-nucleate, propels contents through internal organs and vessels, involuntary control
Muscle Coverings
-Skeletal muscle & muscle fibers covered in connective tissue, from external to internal
-reinforce whole muscle, support cells
-Epimysium: dense irreg CT surrounding entire muscle, may blend with fascia, outermost layer, supports and protects the muscle,
-Perimysium: fibrous CT surround fascicles(group of muscle fibers), middle layer, organizes fascicles, arrangement allows the nervous system to activate specific groups of muscle fibers for targeted movements,
-Endomysium: fine areolar CT surround each tissue, innermost layer, crucial role in transferring the force generated by the fibers to the tendon, hold fibers in place
Disorders Associated with Muscular System
-Myasthenia Gravis: neuromuscular disorder blocks neurotransmitters, causes can be age, possible tumor, autoimmune,
-Duchenne Muscular Dystrophy
(DMD), most common & serious form of muscle dystrophies, start from extremeties up, sarcolemma tear easily excess calcium enters, drop in muscle mass
-Cerebral palsy spastic paralysis causing muscle weakness
-Myositis inflammation of muscle
-Muscular Dystrophy muscle weakness & atrophy
-Fibromyalgia muscle pain
Neuromuscular Junction
6 Events
AP travels thru axon of motor neuron to axon terminal
Voltage-gated calcium channels open, calcium enters motor neuron and diffuses into terminal
Calcium entry causes synaptic vesicles to release ACh cuz of exocytosis
ACh diffuses across synaptic cleft, binds to ACh receptors, which contain ligand-gated cation ions
Ligan-gated cation ions open, sodium enters resulting in end plate potential
Sodium ions enter muscle fiber, potassium ions exit muscle fiber, Acetylcholinesterase degrades ACh
Sliding Filament Theory of Muscle Contraction
-Contraction is the activation of cross bridges to generate force
-shortening happens when tension gene. by cross bridges on actin exceed forces that oppose shortening
-when cross bridges inactive then contraction ends
-During contraction, thin filaments(actin) slide past thick filaments(myosin), overlapping
-As nerv sys stimulates muscle fiber, myosin heads allowed to bind actin, forms cross bridges, causing contraction(sliding) to commence
-Cross bridge attachments form and break several times, each time pulling thin filaments
a little closer toward center of sarcome in a ratcheting action, cause shortening of muscle fiber
-Z discs pulled towards M line
-I bands shorten
-Z disc become closer
-H zones disappear
-A bands move closer to each other
Action Potential in Muscle Fiber
-Resting sarcolemma is polarized, so a voltage exist across membrane
-Action potential caused by changes in electrical charges
3 Steps: 1. Generation of end plate potential 2. Depolarization 3. Repolarization
End Plate Potential: Motor neuron release ACh then binds to ACh receptors on sarcolemma -causes chemically gated ion channels on sarc to open -Na+ diffuse into muscle fiber, causes interior of sarcolemma becomes more negative -Results in local depolarization called end plate potential
Depolarization: generation and propagation of action potential -If end plate pot causes enough change in membrane voltage to reach critical level(threshold), in membrane voltage gated Na+ channels open -large entry of Na+ thru channels into cell triggers unstoppable AP lead to muscle fiber contraction -AP spread across sarcolemma from one voltage-gated Na+ to next, cause area to depolarize
Repolarization: restoration of resting conditions -Na+ voltage close, K+ close -K+ efflux out of cell brings cell back to initial resting membrane voltage -Refractory Period: muscle fiber cant be stimed for specific amount of time, untill repo complete
Sarcomere
-Smallest contractile unit of muscle fiber
-Contains A band with half of an I band on each end
Individual sarcomeres align align end to end along myofibril
Skeletal Muscles