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Muscle Naming, Contractions & Diseases. Anatomy & Physiology Mrs. Halkuff. Naming a Muscle. Location : External/Internal Shape : Deltoid (Triangle)/ Trapezius (Trapezoid) Size : Minimus / Maximus / Brevis / Longus Direction of Muscle Fibers : Rectus/Transverse/Oblique
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Muscle Naming, Contractions & Diseases Anatomy & Physiology Mrs. Halkuff
Naming a Muscle • Location: External/Internal • Shape: Deltoid (Triangle)/Trapezius (Trapezoid) • Size: Minimus/Maximus/Brevis/Longus • Direction of Muscle Fibers: Rectus/Transverse/Oblique • Number of Origins: Biceps/Triceps/Quadriceps • Location of Origins/Insertion: Sternocleidomastoid
Muscle Contractions • Skeletal muscle is made up of long fibrous cylinders called myofibrils that run the length of the muscle cell. • Muscle cells contract because myofibrils contract. • Each myofibril contains a lot of thick and thin filaments, which run parallel to the myofibril axis.
Actin: Protein made of thin filaments. • Myosin: Protein made of thick filaments. • Create an alternating light and dark banding pattern in the myofibrils that can be seen in the light microscope. • Myosin: Thick, dark bands called “A Bands” • Actin: Thin, light bands called “I Bands” • “Z Line” runs through the I band perpendicularly and connect neighboring myofibrils.
Sarcomere: Segment of the microfibril that runs between two adjacent Z lines. • When contracting, Actin moves past the Myosin causing the sarcomere to shorten. • When fully contracted, the Actin overlaps. • Actin & Myosin is always the same length. When relaxed, the distance between the two Z lines is great. • When contracted, the distance between the two Z lines is very small.
Thick filament (MYOSIN) Thin Filament (Actin) Thick filament (MYOSIN) Thin Filament (Actin)
Diseases Myopathies • Neuromuscular disorder • Muscle weakness due to dysfunction of muscle fiber. • Other symptoms: Muscle cramps, stiffness, & spasm • Fibromyalgia • Chronic muscle, ligament, tendon pain, fatigue, tender points • Rarely life-threatening, mostly pain management • Muscular Dystrophy • Progressive weakness & degeneration of skeletal muscles. • Wide spectrum: Some children die in infancy while others have mild symptoms into adulthood.