Chapter 7 Muscular System Main Terms: Myology- Azygous- Bi, tri-, quadri - Externus- Gracilis- Latissimus- Longissimus, Longus- Medius- Orbicularis- Quadratus- Rectus- Rhomboideus- Scalenus- Serratus- Teres- Transversus- Vastus- Functions This system works with the skeletal system to create movement. The skeletal system provides the attachment for the muscles. It is also one half of the animal weight (varies from animal to animal) The muscles in addition to movement, support and maintain posture, and produce body heat. They help for internal organs such as heart, uterus, lungs, and intestines. There is never a time that the muscles are not working because the stomach, heart, intestine, and arteries move even when we are not aware. Allied Structures Tendons- strong, fibrous white bands which attach to bones. They enable movement. The phalanges of the foot are controlled by the muscles of the limb through their tendons. Aponeurosis- a flat and ribbon like tendon, attaches the muscles to the bone Tendon Sheath- surrounds the tendons when there is a long distance between the joint and the attachment Fascia- a sheet of fibrous membrane that encloses muscles and separates them into groups Ligament- strong band of fibrous tissue connecting bones or cartilage Origin- the less moveable of the two points of attachment Insertion- the point of attachment by a muscle Motor Nerve- causes muscle to move by stimulating a group of muscle fibers. Motor (neuromotor) unit- nerve cell and its group of muscle cells. Composition of Muscle Muscle cells are long and slender so they are called fibers. Sarcolemma- the plasma membrane of a muscle cell Sarcoplasm- the cytoplasm of a muscle cells Muscle cell contractions varies on the action needed. More rapid action is used to move a smaller size structure. An example would be the eye Many muscles are moved by a muscle group not just one muscle. Exercise does not increase muscle fibers, but the thickness of the muscle fiber. Classification of Muscles Skeletal Voluntary Striated These are attached to the skeleton. They are voluntary because they are controlled at will When muscles contract they become shorter and thicker. Smooth Nonstriated Involuntary Found in the stomach, intestines, uterus, blood vessels, and iris of the eye These muscles are involuntary and controlled by the autonomic nervous system Some muscles might be under the control of hormones Cardiac Striated Involuntary It is involuntary but shows striation Controlled by the autonomic nervous system Attachment of Muscles Muscles can be attached to many things in many different locations. Tendons extend into the phalanges not the muscles which reduces the bulk of the digits. Muscle usually attaches to the bone except for in the larynx and thorax where they are attached to cartilage. Some muscles are attached to skin like the cheek and mucous membranes like the tongue Movement of Muscles Prime movers- actively produce movement Antagonists- in oppositions to prime movers which relax as the prime movers contract Synergists- contract with the prime movers to help execute the movement or steady a part Naming Muscles Muscles may be named for their action. Example: Extensor carpi radialis Extends the carpus Muscles may be named for their origin and insertion Example: occipitofrontal Between the occipital and frontal skull bones Muscles maybe named for their location. Example: External Oblique muscle of the abdomen Muscles may be named for their shape or use Example pyramidal Shaped like a pyramid Muscles may be named for the direction of their fibers Example: Orbicular muscles of the eye Around the eye Muscles maybe named according to the number of their sections. Examples: Biceps Bi- two cep- means head