Movements of the body Contraction of skeletal muscles is responsible for the overall movements of the body Maintenance of posture Skeletal muscle constantly maintain tone, which keep us sitting or standing erect Respiration Muscles of the thorax carry out breathing movements Production of body heat When skeletal muscle contract, heat is given off as by product. The released heat is critical to the maintenance of body temperature Communication Skeletal muscles are involved in all aspect’s communications, including speaking, writing, typing, sign language and facial expressions Constrictions of organs and vessels Digestive system for digestion Blood vessels for blood circulation Contraction of the heart Contraction of cardiac muscle causes the heart to pump and to propel blood in all parts of the body Muscle has 5 principal characteristics that enables it to carry out its functions, thus contributes to homeostasis. 1. Excitability/Irritability • ability to respond to certain stimuli 2. Conductivity • ability to transmit impulses 3. Contractility • ability to shorten and thicken to generate to do work 4. Extensibility • ability to be stretched without damaging the tissue 5. Elasticity • ability to return to its original form and shaped after contraction A. Point of attachments 1. Point of origin – fixed and proximal in position 2. Point of insertion – movable and distal in position Heads – muscles that may have more than 1 pt of origin Slips – muscles that may have more than 1 pt of insertion B. Belly – the thickest and fleshy portion of a muscle SLIDE NO. 7 To pull on a bone, that is, to change the angle at its synovial joint, which essentially moves the skeleton, a skeletal muscle must also be attached to a fixed part of the skeleton. • The moveable end of the muscle that attaches to the bone being pulled is called the muscle’s insertion, and • the end of the muscle attached to a fixed (stabilized) bone is called the origin. • During forearm flexion—bending the elbow—the brachioradialis assists the brachialis SLIDE NO. 9 Connective tissue which surrounds and protects the muscle tissue. Fascia - a large sheet-like connective tissue that covers the entire muscle. a. Superficial fascia (subcutaneous layer/hypodermis) – found deep to the skin and surface of the muscle b. Deep fascia – found inside the muscle and separating them into functional group. SLIDE NO. 10 a. Sarcolemma • Cell membrane T tubules (transverse tubules) • Tube-like invaginations, along the surface of the sarcolemma and associated with smooth endoplasmic reticulum (sarcoplasmic reticulum) b. Sarcoplasm • Cytoplasm Contains Myofibrils - (Any of the elongated contractile threads found in striated muscle cells.) myofibrils constitute the sarcomere (contractile unit of muscle contraction) a. actin – blue line b. myosin – red line SLIDE NO. 11 • The movement of skeletal muscles is explained by the sliding filament theory. • Skeletal muscle cells are made up of fibers, which in turn are composed of tiny filaments. Blue line – thin filament (actin) Red line - thick filament (myosin) • When the muscle is stimulated by a nerve impulse, the filaments slide past each other and the muscle shortens. SLIDE NO. 12 Muscle groups according to their primary actions Prime movers • Orbicularis oculi – prime mover in closing the eye • Biceps brachii • Triceps brachii Antagonists • A muscle with an opposite action of the prime mover • Levator palpebrae superioris to orbicularis oculi Synergists • A synergist can also be a fixator that stabilizes the bone that is the attachment for the prime mover’s origin. • . Extensor muscles of the wrist as synergist; flexor muscles of the fingers as prime movers • The biceps brachii flex the lower arm. The brachoradialis, in the forearm, and brachialis, located deep to the biceps in the upper arm, are both synergists that aid in this motion Fixator or postural muscles • The function of a fixator muscle is to stabilize the origin of the agonist muscle so that it can move efficiently. • Examples: • The trapezius muscle can act as a fixator when the biceps is flexing the elbow joint. • The abdominals can act as fixators to stabilise the body for hip and knee movements. SLIDE NO. 13 • • There are about 600+ muscles in the body, which make up the muscular system The names of a muscle generally tells something about its structure, location, or function Shape • Trapezius, rhomboideus, deltoid, quadratus Size • Maximus, minimus, major, minor Location • Frontalis, occipitalis, brachii, femoris, abdominis Direction of fibers • Rectus, oblique, transversus Point of attachment • Origin and insertion • Sternocleidomastoid • Hyoglossus Position • Superior, inferior, external, internal Action • Flexor, extensor, supinator, pronator Structure • Semitendinosus • Semimembranosus Number of bellies • Digastric Miscellaneous • Sartorius – tailor’s muscle Combination • A combination of bases of names • External oblique muscle (position and direction of fibers • Tibialis anterior (location and position)
