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oStriated in appearance but is involuntary Muscle Innervation- is the stimulation of a muscle by an impulse transmitted by a motor nerve oMotor nerves enable the brain to stimulate a muscle to contract. When the stimulation stops, the muscle relaxes. Antagonistic Muscle Pairs Contraction- the tightening of a muscle. As is contracts, it becomes shorter and thicker causing the belly to enlarge Relaxation- occurs when a muscle returns to its original form. As the muscle relaxes it becomes longer and thinner, belly is no longer enlarged. Flexion- decreasing the angle Extension- increasing the angle Muscles named for their locationPectoalis major – anterior chest wall Lateralis- means toward the side Medialis- towards the midlineMuscles named for their direction
Oblique- slanted or at an angle Rectus- means in a straight alignment with the vertical axis of the body Sphincter –ring likeTransverse Muscles named for number of divisions Biceps brachiiTriceps brachiiMuscles names for their size or shapeGluteus Maximus- largest muscle of the butt Deltoid Muscle- shaped like an inverted triangle Muscles named for strange reasonsHamstring group- consist of 3 separate groups biceps femoris, semitendinosus, and semimembranosus muscles. Function- knee flexion and hip extensionHead Frontalis- in the forehead and raises and lowers the eyebrows Temporalis- moves the lower jaw up and back to close the mouth Masseter- which is one of the strongest in the body, moves the lower jaw up to close the mouth when chewing TrunkExternal and Internal Oblique-oExternal- flex and rotate the vertebral column; flex the torso and compress the abdomen. oInternal- flex the spine, support the abdominal contents, help breathe, and rotate the spine. Rectus Abdominis- helps flex the trunk, assists in breathing, and supports the spine Transverse Abdominis- located on the side of the abdomen. Engaged when a person laughs or coughs. Shoulders and Arms Deltiod- forms the muscular cap of the shoulder Trapezius- muscle moves the head and shoulder blade Biceps Brachii- located in the anterior upper arm, flexes the elbowTriceps Brachii- located in the posterior upper arm, extends the elbow
Muscles of the legs Rectus Femoris- extends the leg at the kneeQuadriceps femoris- made up of 4 muscles including vastus lateralis and vastus medialis, which flex and extend the leg at the knee Hamstring group- involved in knee flexion and hip extension Gastrocnemius- the calf muscle that flexes the knee and bends the foot downward. Muscle DisordersMyalgia- tenderness or pain in the muscles Myorrhexis- the rupture or tearing of a muscle Rhabdomyolysis- can result from a direct or indirect muscle injury. Death of muscle fibers releases their contents into the bloodstream, where they can lead to complications such as renal failure.