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The Muscular System

The Muscular System. Types of Muscle Tissue. Types of Muscle Tissues. Types of Muscle Tissue. All highly vascular for transport of oxygen, CO 2 , waste and sugars Human body has three types: Skeletal muscle: moves bones Smooth muscle: body functions that you do not control consciously

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The Muscular System

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  1. The Muscular System

  2. Types of Muscle Tissue

  3. Types of Muscle Tissues

  4. Types of Muscle Tissue • All highly vascular for transport of oxygen, CO2, waste and sugars • Human body has three types: • Skeletal muscle: moves bones • Smooth muscle: body functions that you do not control consciously • Cardiac muscle: found in heart, pumps blood

  5. Skeletal Muscle

  6. Skeletal Muscle • Made of elongated cells called muscle fibers • Each fiber has many nuclei and striations • Striations: alternating light and dark bands • Skeletal muscles are voluntary muscles and work in pairs • Called antagonistic because it pulls against another type of muscle and vice versa

  7. Function of Skeletal Muscles • Produce movement • Maintain posture and body position • Support soft tissue • Guard entrances and exits • Encircle openings to digestive and urinary tracts. Control swallowing, defecation and urination • Maintain body temperature

  8. Smooth Muscle

  9. Smooth Muscle • Forms the walls of the stomach, intestines, blood vessels, and internal organs • Individual cells are spindle shaped with one nucleus • No striations • Surrounded by connective tissue • Involuntary muscle

  10. Cardiac Muscle

  11. Cardiac Muscle • Makes up the walls of the heart • Cells are cigar shaped • Intercalated disc: a double membrane separating adjacent cells in cardiac muscle fibers • Shares characteristics with both other types of muscle: • Is striated • Is involuntary • Has one nucleus

  12. Muscle Structure

  13. Muscle Structure • From the outside in… • Epimysium: tough, fibrous connective tissue that surrounds and separates fasciculi • Fascicle: bundle of muscle fibers • Perimysium: connective tissues that surrounds and separates fasciculi • Muscle fiber: muscle cell, large, long, cylindrical, multinucleated and made mostly of microfilaments • Sarcolema • Sarcoplasma • Sarcosomes • Sarcoplasmic reticulum • Endomysium

  14. Muscle Structure • From the outside in continued… • Myofibrils – microfilaments (actin and myosin) that fill a muscle fiber • Actin: thinner protein made of two twisted filaments • Myosin: thicker protein, bigger molecule • These overlap, giving the striated appearance • Thin actin filaments are anchored to a structure called the Z line • Region from one Z line to the next is a sarcomere

  15. Four Functions

  16. Four Functions • Irritability • Responds to stimulation • Stimulation from nerves • Contractibility • Ability to shorten and move • Pulls on bones • Elasticity • Ability to resume original shape after contraction • Conductivity • Ability to carry an impulse • Causes contraction

  17. Muscular Contraction

  18. Muscular Contraction • Sliding Filament Theory (Huxley) • Need stimulus from motor neuron for muscle to contract • Calcium ions are stored in sarcoplasmic reticulum • Very few calcium ions are found in the sarcoplasm of relaxed muscle • Muscle cells produce ATP, which sits on myosin in relaxed muscle • Motor End Plate: Terminal end of motor neuron that sits in a depression • Close to sarcolema but does not touch it (Space is called the synapse) • Comes from a motor neuron or a neuron that stimulates muscles to contract • Carries impulse to muscle or innervates muscle

  19. Steps of Muscular Contraction • Action potential from the motor neuron moves down to terminal end and then calcium ions diffuse into the terminal • Calcium ions trigger the synaptic vesicles to release acetylcholine, a neurostransmitter • Acetylcholine diffuses across synaptic clef to a receptor site on the sarcolema • Acetylcholine cause new action potential to spread from nerve to muscle • Action potential spreads over the sarcolema until it finds an opening • It goes through the opening to the sarcoplasmic reticulum, where it triggers the release of calcium ions into the sarcoplasm • Calcium ions cause active sites on actin to be exposed • Myosin crossbridges can now link up with the active sites on actin • Actin moves inward, sarcomere shortens, muscle fibers contract and use a lot of ATP

  20. Stopping Muscular Contraction • Acetylcholinesterase is released as muscle contracts and neutralizes the acetylcholine • No more action potential Is traveling to muscle • Calcium does not tighten so the crossbridges on mysoin release • Muscles relax

  21. Moving Muscles • Muscles are attached to the outer layer of bone with a tough fibrous cord called a tendon • Origin: where muscle attaches to a relatively stationary position and anchors muscle • Insertion: where the muscle attaches to the moving bone • Action: result of muscle contraction; movement • Most muscles work in pairs; one contracts while one relaxes for smooth movement • Flexor: a muscle that bends a joint • Extensor: a muscle that straightens a joint

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