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Smooth muscle Contraction • Spindle Shaped • Central nuclei • Lack Striations, transverse tubules, and lack well developed sacroplasmic reticulum • Actin and myosin thin and randomly distributed • Multi-unit-Separate units » Muscle of iris and blood vessels • Visceral-Sheets of spindle cells » Respond as a single unit » Rhythmicity- spontaneous » peristalsis 1 • Internal organs• outer longitudinal • Inner circular Contraction Impulses travel across the membraneCalcium diffuses into the cell from the extracellular fluid. Calcium binds to a protein calmodulin-activating contraction. Nt- Ach and Norepi, stimulates/ inhibits contractions altering degrees of contraction. Smooth- slow and longer contraction 2 Terms • • • • • Origin Insertion Prime mover-Agonist Assist a prime mover-Synergists Antagonist- movement in the opposite direction or resist a prime mover, 3 Skeletal Muscle Actions • origin – immovable end • insertion – movable end • prime mover (agonist) – primarily responsible for movement • synergists – assist prime mover • antagonist – resist prime mover’s action and cause movement in the opposite direction 4 Muscular Tissue Three Types of Muscle Tissues Skeletal Muscle Cardiac Muscle • usually attached to bones • under conscious control Smooth Muscle • striated • walls of most viscera, blood vessels, skin • not under conscious control • not striated • wall of heart • not under conscious control • striated 5 6 Smooth Muscle Fibers Compared to skeletal muscle fibers • shorter • single nucleus • elongated with tapering ends • myofilaments randomly organized • no striations • lack transverse tubules • sarcoplasmic reticula not well developed 7 Cardiac Muscle • only in the heart • muscle fibers joined together by intercalated discs • fibers branch • network of fibers contracts as a unit • self-exciting and rhythmic • longer refractory period than skeletal muscle 8 Muscles of Facial Expression-CNVII • Orbicularis oculiblinking/closes eyelids • Orbicularis oris-closes lips/protrudes lips-kissing • Buccinator-compresses cheeks as in blowing air • Zygomaticus-raises corner of mouth/smiling • Platysma-pouting/draws mouth downward & elevates skin • Frontalis-elevates eyebrows & creases skin 9 10 Muscles of Mastication-CNV3 • Masseter-elevates mandible • Temporalis-elevates mandible • Pterygoid – Medial-elevates and moves it from side to side – Lateral-depresses and protracts 11 12 Muscles of Head and Vertebra • Paired muscles- flex, extend, and rotate the head and hold the torso erect. • Sternocleidomastoid-flex and rotates • Extend and rotate – Splenius capitis – Semispinalis capitis – Erector spinae 13 Muscle of the Pectoral Girdle • Trapezius- raises scapula and shoulders, elevates clavicle, extends neck and head • Serratus Anterior -pulls scapula forward and downward, used when pushing something. – Damage to the long thoracic nerve-results in winged scapula • Rhomboids-retracts, elevates, and rotates • Levator Scapula-elevates scapula • Pectoralis minor- pulls scapula in forward and downward, raise ribs in forceful inhalation 14 15 16 17 Muscles That Move the Arm • Flexors – Coracobrachialis – Pectoralis major- also adducts arm • Extensors – Teres Major – Latissimus dorsi- also adducts arm (swimmer muscle) • Abductors – Deltoid – most prominent muscle of the shoulder-axillary nerve-fracture to the neck of humerus-unable to abduct the arm – Supraspinatus • Rotators cuff muscles – – – – Subscapularis Infraspinatus Teres minor Supraspinatus 18 • • • • • Movement of Forearm Biceps brachii-flexes and laterally rotates elbow Brachialis- strongest flexor of elbow Brachioradialis-aids in flexing Triceps- opposes-extends elbow 19 Muscle of the Abdominal area • Compress the abdominal cavity and increases pressure, used during forceful exhalation or defecation • Rectus abdominis-six pack • External oblique-fibers runs downward to pelvic girdle • Internal oblique-fibers run upward to lower ribs • Transversus abnominis- deepest layer-runs horizontally across • Linea alba- connective tissue band that runs from xiphoid to symphysis pubis 20 21 22 Transversus abdnominis 23 Muscles of the Thigh • Anterior group- primary flexors of thigh – Psoas – iliacus • Posterior group- extends the thigh – Gluteus muscles- maximus-the largest muscle in the body – Tensor fasciae latae-extends from ilium to the iliotibial tract- abducts, rotates, and flexes • Adductors – Pectineus-flexes – Adductor brevis, longus, magnus-flex and rotate 24 – Gracilis- straplike band from the pubic bone to tibia 25 Pectineus 26 Gluteus Muscle 27 Quadriceps Femoris group Extensor • • • • • Extends leg at knee Rectus femoris Vastus lateralis Vastus medialis Vastus intermedius 28 Flexors of knee Hamstring Muscles • Biceps femoris • Semimembranosus • Semitendinosus • Sartorius-strap like that passes obliquely across the front of thigh- abducts and rotates laterally 29 • Semimembranosus • Semitendinosus 30 31