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Muscular System

Muscular System. Key Concepts and Vocabulary Words. The muscular system produces movement and maintains posture. There are three kinds of muscles: skeletal , cardiac , and smooth . Muscles are excitable , contractile , extensible , and elastic .

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Muscular System

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  1. Muscular System

  2. Key Concepts andVocabulary Words • The muscular system produces movement and maintains posture. • There are three kinds of muscles: skeletal, cardiac, and smooth. • Muscles are excitable, contractile, extensible, and elastic. • Muscles are attached to bone by tendons and are arranged in opposing or antagonistic pairs. • Sarcomeresare the contractile units of muscle. • Muscle striations are caused by the arrangement of myofibrils within the muscle cell. Each myofibril contains groups of myofilaments composed of actin and myosin proteins.

  3. Key Concepts andVocabulary Words • A muscle contracts when myosin binds to actin causing the filaments to slide past one another. • Contraction is powered by ATP and controlled by two regulatory proteins and calcium ions (sliding filament theory). • Nerves stimulate muscle contraction at the neuromuscular junction. • Acetylcholine, released from the motor neuron, causes a change in muscle cell permeability resulting in the release of calcium ions and contraction. • A motor neuron and all the muscle cells it stimulates are called a motor unit.

  4. Key Concepts andVocabulary Words • A muscle twitch is the contraction caused by a stimulus to the muscle. • The ATP required for muscle contraction comes from creatine phosphate, aerobic respiration, and lactic acid fermentation. • Slow-twitch muscles, found in the abdomen and back, contract slowly, powerfully, and with endurance. • Fast-twitch muscles, found in the arms and legs, contract rapidly and powerfully, but with less endurance. • Aerobic exercise increases endurance while resistance exercise builds muscle mass.

  5. Characteristics of muscle tissue • Excitability – receive and respond to stimuli • Contractility – shorten and thicken • Extensibility – stretch and extend • Elasticity – return to original shape after contraction or extension

  6. Functions • Motion • Maintenance of posture • Heat production • Protection of internal organs

  7. Origin of muscle tissue • Forms from the mesoderm germ layer • Triploblasts simplest: flatworms • Segmentation  annelids, arthropods, vertebrates

  8. Types of muscle tissue • Skeletal • Attached to bones • Striated and voluntary • Cardiac • Heart wall • Striated and involuntary • Smooth • Walls of hollow internal structures • Nonstriated and involuntary • Striated • Voluntary movements • Longitudinal or circular in shape • Smooth • Involuntary movements Vertebrate muscles Invertebrate muscles

  9. Muscle action • Motion produced by action of muscles on bones  levers • Tendons attach muscles to bones (e.g. Achilles tendon) • 1 fixed point of attachment (origin) and 1 moving point of attachment (insertion) • Fascia sheets that cover muscles • Muscles work in antagonistic or opposing pairs

  10. Muscle movement • Adduction • Abduction • Flexion • Extension • Rotation • Sphincters • Levators • Depressors • Supination • Pronation

  11. Human skeletal muscle groups

  12. Anatomy of skeletal muscles epimysium tendon perimysium Muscle Fascicle Surrounded byperimysium endomysium Skeletal muscle Skeletal muscle fiber (cell) Surrounded by epimysium Surrounded by endomysium

  13. Organization of skeletal muscles

  14. Overview of the Sliding Filament Theory The muscle fiber is stimulated. Ca2+ ions are released. Thin filaments move to middle of sarcomere. Muscle fiber contracts. Muscle tension increases.

  15. Muscle twitch • Cycle of contraction and relaxation generated from one stimulus • Force Summation • Increasing # and size of fibers contracting • Increasing frequency at which action potentials are sent to muscle fibers • Types of Twitches • Slow Twitch • More ATP from aerobic respiration • Continuous extended contractions over time • Fast Twitch • Anaerobic metabolism (creatine phosphate and lactic acid fermentation) • Short bursts of speed • Fatigue quickly

  16. Aerobic vs anaerobic exercise • Aerobic exercise • Moderate intensity • Extended periods of time • Anaerobic exercise • High intensity • Shorter periods of time

  17. Cramps • Painful sensations caused by contraction/ overshortening of muscles • Causes • Hyperflexion • Inadequate oxygenation • Changes in temperature • Dehydration • Low amount of electrolytes in blood • Treatment • Correct breathing • Increasing intake of water and electrolytes

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