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Muscular System

Muscular System. Anatomy of a Muscle. Major Functions of the Muscular System. Produce Movement Heat production Maintain Posture. Skeletal Muscle-Voluntary Muscle Threadlike cells that have multiple nuclei Many cross striations (stripes)

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Muscular System

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  1. Muscular System

  2. Anatomy of a Muscle

  3. Major Functions of the Muscular System • Produce Movement • Heat production • Maintain Posture

  4. Skeletal Muscle-Voluntary Muscle Threadlike cells that have multiple nuclei Many cross striations (stripes) Attached to bones to produce body movement or facial expressions Smooth Muscle-Involuntary MuscleElongated narrow cells with single nucleus No cross striations Found in the walls of hollow organs to propel food through them byperistalsis Cardiac Muscle-Also involuntary Found only in the heart Branching cells joined by intercalated disks with gap junctions that allow ions to pass freely from cell to cell=rapid conduction of electrical impulse.

  5. The functional unit of a muscle

  6. Striated Muscle Multinucleated Striations are visible Caused by the sarcomeres.

  7. Terms Sarcomere, Sarcolemma-cell membrane Sarcoplasmic Reticulum- like an endoplasmic reticulum of any cell.

  8. Physiology of Muscles contractionWhat Happens and Why? 1. A nerve impulse reaches the end of a motor neuron – releases acetylcholine • Acetylcholine diffuses across the gap of the neuromuscular junction and binds to receptors on the motor endplate of the muscle fiber. • Impulse travels along the sarcolemma, to the T tubules to sacs of the SR.

  9. THEN What HAPPENS? • Ca++ is released from the SR into the sarcoplasm, where it binds to troponin mlcs in the thin myofilaments. 5. Tropomyosin mlcs in the myofilaments shift, exposing actin’s active sites. • Energized myosin cross bridges of the thick myofilaments bind to actin and pull the thin myofilaments together. • Muscles Shortens.

  10. Sarcomere structure Actin Myosin

  11. Sliding Filament Theory

  12. Types of Muscle contractions • Isotonic –muscle shortens and movement occurs. • Isometric- muscle does not shorten but tension increases.

  13. Twitch contraction • Threshold stimulus – electrical stimulus of sufficient intensity must be applied to the muscle. • A single brief threshold stimulus produces a quick jerk of the muscle. 2msec 25msec 15msec

  14. Treppe: A Staircase phenomenon • A gradual step-like increase in the strength of contraction that can be observed in a series of twitch contractions that occur about 1 second apart. • Muscle Fatigue - Repeated stimulation of muscle in time lessens its excitability and contractility.

  15. TetanusSmooth sustained contractions • Stimuli comes in rapid succession the muscle does not have time to relax completely before the next contraction. • Normal skeletal muscles exhibit this most of the time. Rapid repeated Twitch contractions Looks like one continuous contraction

  16. Muscle Tone--tonic contractionsA continual partial contraction. • Maintaining posture – sitting or standing • When you pass out/faint muscle tone is lost • Muscles with Less tone are flaccid. • Muscles with More tone are spastic. • Tone is maintained by a negative feedback mechanisms centered in the nervous system (in spinal cord)

  17. Muscle Problems • Cramps-painful muscle spasms (involuntary twitches) caused by any irritation or ion and water imbalance • Convulsions-uncoordinated tetanic contractions of varying groups of muscles. May result from a disturbance in the brain or seizure. AP along motor nerve increases and becomes disorganized

  18. Fibrillation – abnormal contraction in which individual fibers contract out of sync.(asynchronously) instead of at the same time.

  19. Muscular Disorders • Sprains – Joint and ligament damage • Myalgia – Muscle pain • Contusions – bruises – localized bleeding • Poliomyelitis – Viral infection of the nerves that control skeletal muscles. • Muscular Dystrophy – A group of Genetic Disease characterized by atrophy of skeletal muscle tissues. Some forms Fatal

  20. Myasthenia Gravis – Autoimmune disease in which the immune system attacks muscle cells at the neuromuscular junction So nerve impulses are unable to fully stimulate the affected muscle. • Hernias – Weakness of abdominal muscles can lead to protrusion of an abdominal organ. • Strangulated Hernia – Cuts off blood supply to an organ which can lead to gangrene – death of the organ or individual – Requires emergency surgery.

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