Muscle Tissue & Organization Sports Medicine Unit 3

MUSCULAR SYSTEM Muscle Functions Body Movement Maintenance of Posture Temperature Regulation – muscle contraction generates 85% of the body’s heat Storage and Movement of Materials Support

Characteristics of Muscle Tissue Excitability- receive and respond to stimuli Contractility- ability to shorten and thicken Extensibility- ability to stretch Elasticity- ability to return to its original shape after contraction or extension

Types of Muscle

Microscopic Anatomy of Skeletal Muscle Each muscle- has thousands of muscle fibers in a bundle running from origin to insertion bound together by connective tissue through which run blood vessels and nerves. Each muscle fiber - contains many nuclei, an extensive endoplasmic reticulum or sarcoplasmic reticulum, many thick and thin myofibrils running lengthwise the entire length of the fiber, and many mitochondria for energy

Sacromere Sacromere -The basic functional unit of the muscle fiber consists of the array of thick and thin filaments between two Z disks. Thick filaments - with myosin (protein) molecules Thin filaments - with actin (protein) molecules plus smaller amounts of troponin and tropomysin (also proteins). Striations -of dark A bands and light I bands. A bands- are bisected by the H zone with the M line or band running through the center of this H zone. I bands- are bisected by the Z disk or line.

Muscle Contraction As the muscle contracts - the width of the I bands and H zones decrease causing the Z disks to come closer together, but there is no change in the width of the A band because the thick filaments do not move. As the muscle relaxes or stretches - the width of the I bands separate as the thin filaments move apart but the thick filaments still do not move.

Skeletal Fiber Organization Circular Muscles Convergent Muscles Parallel Muscles Pennate Muscles

Circular Muscles Fibers arranged concentrically around an opening Functions as a sphincter to close a passageway or opening Example: Orbicularis oris (around mouth)

Convergent Muscles Triangular muscle with common attachment site Direction of pull of muscle can be changed Does not pull as hard as equal-sized parallel muscle Example: pectoralis major

Parallel Muscles Fascicles are parallel to the long axis of the muscle Body of muscle increases in diameter with contraction High endurance, but not very strong Example: rectus abdominis or sartorius

Pennate Muscles Muscle body has one or more tendons Fascicles at oblique angle to tendon Pulls harder than a parallel muscle of equal size Unipennate: all muscle fibers on the same side of the tendon (example: extensor digitorum) Bipennate: muscle fibers on both sides of the tendon (example: Interosseous) Multipennate: tendon branches within the muscle (example: deltoid)

Skeletal Muscles Origin - Attachment to the more stationary bone by tendon closest to the body or muscle head or proximal (head) Insertion - attachment to the more moveable bone by tendon at the distal end During movement, the origin remains stationary and the insertion moves. The force producing the bending is always a pull of contraction. Reversing the direction is produced by the contraction of a different set of muscles. As one group of muscles contracts, the other group stretches and then they reverse actions.

Naming of Skeletal Muscles Muscles are named according to a variety of features: Muscle action Specific body region Muscle attachments Orientation of muscle fibers Muscle shape and size Muscle heads/tendons of origin

Naming of Skeletal Muscles Muscle Action: Adductor Abductor Flexor Extensor

Naming of Skeletal Muscles Specific Body Regions: Oris (mouth) Cervicis (neck) Brachial (arm) Carpi (wrist) Pollicis (thumb) Gluteal (buttocks) Femoris (thigh) Hallus (great toe) Anterior (toward front) Posterior (toward back) Superior Inferior Superficialis (superficial) Profundus (deep)

Naming of Skeletal Muscles Muscle Attachments Sternum and clavical (cleido) Between the ribs (intercostal) Subscapular fossa (Subscapularis) Fibula (fibularis longus) Zygomatic bone (zygomaticus major)

Naming of Skeletal Muscle Orientation of muscle fibers Rectus (straight) Oblique (angled) Orbicularis (circular)

Naming of Skeletal Muscles Muscle shape and size Deltoid (triangular) Quadratus (rectangular) Trapezius (trapezoidal) Longus (long) Brevis (short) Major (larger of two muscles) Minor (smaller of two muscles) Maximus (largest) Medius (medium sized) Minimus (smallest)

Naming of Skeletal Muscles Muscle heads/tendons of origin Biceps (two heads) Triceps (three heads) Quadriceps (four heads)

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