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MUSCULAR SYSTEM. CHARACTERISTICS OF MUSCLE TISSUE  Irritability  Ability to respond to a stimulus (either external or internal)  Stimulation produces.

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Presentation on theme: "MUSCULAR SYSTEM. CHARACTERISTICS OF MUSCLE TISSUE  Irritability  Ability to respond to a stimulus (either external or internal)  Stimulation produces."— Presentation transcript:

1 MUSCULAR SYSTEM

2 CHARACTERISTICS OF MUSCLE TISSUE  Irritability  Ability to respond to a stimulus (either external or internal)  Stimulation produces a muscle contraction  Contractibility  Ability to shorten or contract  Extensibility  Ability to stretch or extend  Elasticity  Ability of muscle to return to its original shape after contraction or extension

3 TYPES OF MUSCLES  Skeletal – striated and voluntary  Smooth – involuntary  Cardiac – heart

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5 SKELETAL MUSCLE CHARACTERISTICS  Most attach to bones by tendon  Cells are multinucleate  Striated—have visible binding  Voluntary  Cells surrounded & bundled by connective tissue

6 SMOOTH MUSCLE CHARACTERISTICS  Has no striations  Spindle-shaped cells  Single Nucleus  Involuntary—no conscious control  Found mainly in the walls of hollow organs

7 CHARACTERISTICS OF CARDIAC MUSCLE  Has striations  Usually has a single nucleus  Joined to another cardiac muscle cell  Involuntary  Found only in the heart  Made to work continuously

8 MUSCLES AND MUSCLE FIBERS  Each muscle is an organ comprised of skeletal muscle tissue, connective tissues, nervous tissue, and blood  Muscles are composed of many fibers that are arranged into bundles called fascicles  Muscle fiber = muscle cell

9 CONNECTIVE TISSUE COVERINGS  Fascia – strong, dense connective tissue that surround and separates each muscle  Tendon – connective tissue that goes beyond the muscle to join with the periosteum of the bone  Aponeuroses – broad sheets of connective tissue

10 CONNECTIVE TISSUE COVERINGS  Epimysium – layer of connective tissue around each whole muscle  Perimysium – layer of connective tissue around each bundle of muscle fibers  Endomysium – layer of connective tissue around each muscle cell

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12 MUSCLE FIBERS  Each muscle fiber membrane is the sarcolemma; muscle cytoplasm is called sarcoplasm  Within the sarcoplasm are many fibers called myofibrils; myofibrils are individual muscle fibers made up of myofilaments  These filaments are found in two types: myosin (thick) and actin (thin). The organization of these filaments produces striations found in skeletal muscle

13 MUSCLE FIBERS  A bands (dark bands) are made up of overlapping thick and thin filaments. In the center of A bands is an H zone, consisting of myosin filaments only.  I bands (light bands) are made up of actin filaments anchored to Z lines  Sacromere – extends from Z line to Z line  Z lines – lines across the muscle fiber

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15  Transverse tubules – passageways for the nerve impulse to travel into the muscle fiber  Sacroplasmic reticulum – passageway that stores and releases Ca+  Calcium ions – Ca+ binds with troponin and tropomyosin which allows the actin and myosin to bind together

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17 IT IS IMPORTANT TO REMEMBER THE HEIRARCHY fasicles myofibrils myofilaments actin myosin

18 IT IS IMPORTANT TO REMEMBER THE HEIRARCHY fasicles myofibrils myofilaments actinmyosin

19 muscleepimysium myofibrilsmyofilament sarcomere muscle fiber

20 muscle epimysium myofibrils sarcomere muscle fiber myofilament

21 NEUROMUSCULAR JUNCTION  The site where the motor neuron and muscle fiber meet  Activates the muscle  Also called the motor unit

22 1. Neuron 2. Sarcolemma (or motor end plate) 3. Vesicle 4. Synapse 5. Mitochondria Motor Unit or Neuromuscular Junction

23 NEUROTRANSMITTERS  Acetylcholine – this neurotransmitter released from the end of the neuron which relays impulses to the muscle cell  Acetylcholinesterase – enzyme that quickly breaks down and removes acetylcholine

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25 SLIDING FILAMENT THEORY  The theory of how muscle contracts  The contraction of a muscle occurs as the thin filament slides past the thick filaments  Involves five different molecules plus calcium ions  Myosin  Actin  Tropomyosin  Troponin  ATP

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28  Video of sliding filament theory

29 OTHER TERMS  Threshold stimulus – minimal strength required to cause a contraction  All-or-None response – fibers do not contract partially, either they do or they don’t  Motor unit – the muscle fiber + the motor neuron  Recruitment – more and more fibers contract as the intensity of the stimulus increases  Muscle tone – sustained contraction of individual fibers, even when muscle is at rest  Hypertrophy – muscles enlarge  Atrophy – muscles become small and weak due to disuse  Muscle fatigue – muscle loses ability to contract after prolonged exercise or strain  Muscle cramp – a sustained involuntary contraction

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