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THE MUSCULAR SYSTEM By: Jennifer De Dios Pd: 4th (MAJOR FUNCTIONS…
THE MUSCULAR SYSTEM
By: Jennifer De Dios
Pd: 4th
MAJOR MUSCLES
ANTERIOR VIEW
Trapezius
Sternoicleidomastoid
Deltoid
Pectoralis Major & Minor
Tricep & Bicep Brachii
Brachialis
Brachioradialis
Flexor Carpi Radialis
Serratus Anterior
Rectus Abdominus
External Oblique
Internal Oblique
Abductor Longus
Sartorius
Gracilis
Rectus Femoris
Vastus Lateralis
Vastus Medialis
Fibularis Longus
Gastrocnemius
Extensor Digitorum Longus
Tibialis Anterior
POSTERIOR VIEW
Trapezius
Deltoid
Triceps Brachii
Brachioradialis
Flexor Carpi Ulnaris
Extensor Digitorum
Latissimus Dorsi
Gracilis
Biceps Femoris
Semitendonosus
Semimembranosus
Gastrocnemius
Soleus
Fibularis Longus
MAJOR FUNCTIONS
☆MOVEMENT: Blood courses because beating cardiac muscle of heart and smooth in the walls of blood vessels --> maintains blood pressure --smooth muscle propels substances through organs and tract
☆POSTURE AND BODY POSITION: tiny adjustments to counteract downward pull of gravity
☆STABILIZE JOINTS: strengthen and stabilize
☆GENERATE HEAT: as they contract -- maintain body temperature
3 TYPES OF MUSCLE TISSUE
☆SKELETAL MUSCLE: Responsible for body mobility (contract, tires, rests)
--extremely adaptable
☆CARDIAC MUSCLE: Only in heart -- bulk of heart walls
--striated, not voluntary
--contract without stimulus by nervous system
☆SMOOTH MUSCLE: Walls of hollow visceral organs
--force fluids and substances through internal body channels
--forms valves to regulate, dilates and constricts pupils, forms arrector pili muscle
--no striations, not voluntary
BODY MOVEMENT TERMINOLOGY
GLIDING
☆Flat bone surface glides or slips over another without angulation or rotation
Example: Intercarpal and intertarsal joints
FLEXION
☆Bending movement that decreases the angle of the joint and brings the articulating bones closer together
Example: bending head forward on chest ornknee from a straight to angled
EXTENSION
☆Reverse of flexion--increases the angle between the articulating bones and typically straightens a flexed limb or body part
Example: straightening a flexed neck, body trunk, elbow
ABDUCTION
☆Movement of a limb away from midline or median plane of the body
Example: spreading fingers or toes
ADDUCTION
☆Opposite of abduction--movement of a limb toward body midline
CIRCUMDUCTION
☆Moving a limb so that it describes a cone in space, distal end of the limb moves in a circle while point of cone is more or less stationary
ROTATION
☆Turning a bone around it's own long axis
Example: Hip and first two cervical vertebrae
SUPINATION & PRONATION
☆Supination: turning backward
☆Pronation: turning forward
Example: rotating the forearm laterally
DORSIFLEXION & PLANTAR FLEXION
☆Up and down movements of the foot at the ankle
Example: lifting the foot
INVERSION & EVERSION
☆Special movements of the foot
Example: sole of foot turns medically or faces laterally
PROTRACTION & RETRACTION
☆Nonangular anterior and posterior movements in a transverse plane
Example: mandible is just out or retracted
ELEVATION & DEPRESSION
☆Elevation: lifting a body part superiorly
☆Depression: body part is moced inferiorly
Example: shrugging shoulders and chewing
OPPOSITION
☆Saddle joint between metacarpal I and trapezium
Example: touch thumb to the tips of the other fingers
STRUCTURE OF SKELETAL MUSCLE
MUSCLE (organ)
☆consists of hundreds to thousands of musc cells, plus connective tissue wrappings, blood vessels, and nerve fibers
--connective tissue wrappings covered externally by epimysium
FASCICLE (a portion of the muscle)
☆discrete bundle of musc cells, segregated from the rest of the musc by a connective tissue sheath
--surrounded by perimysium
MUSCLE FIBER (cell)
☆elongated multinucleate cell; has a banded (striated) appearance
--surrounded by endomysium
MYOFIBRIL (organelle composed of bundles of myofilaments)
☆rodlike contractile elements that occupy most of the musc cell volume
☆composed of sarcomeres arranged end to end, they appear banded, and bands of adjacent myofibrils are aligned
SARCOMERE (segment of myofibril)
☆contractile unit, composed of myofilaments made up of contractile proteins
MYOFILAMENT (extendes macromolecular structure)
☆THICK: bundled myosin molecules
☆THIN: contain actin molecules (plus other proteins)
--sliding of thin filaments past the thick filaments produces muscle shortening
SLIDING FILAMENT THEORY
☆Shortening occurs if cross bridges generate enough tension on thin filaments --> exceed forces that oppose shortening
--cross bridges become inactive, the tension declines, musc fiber releases
☆Nervous system stimulates musc fibers, myosin heads on thick filaments latch onto myosin-binding sites in thin filaments
☆Cross bridges form and break several times during a contraction acting like tiny ratchets to generate tension and propel the thin filaments toward sarcomeres
☆Musc cell shortens
DISORDERS
DUCHENNE MUSCLE DYSTROPHY
☆Almost only in males (diagnosed between 2 to 7 years old)
☆Progresses from the extremities upwards --> head and chest, cardiac
☆Caused by defective gene for dystrophin (cytoplasmic)
☆Fragile sarcolemma tears during contraction --> Ca2+ (damaging)
regenerative musc is lost --> apoptosis--> mass decrease
MYASTHENIA GRAVIS
☆Drooping upper eyelids, difficulty swallowing and talking, generalized musc weakness, shortage of ACh receptors
☆Autoimmune -- immune system destroys ACh receptors
RIGOR MORTIS
☆Cross bridge detachment is ATP driven
☆Musc stiffen 4 hours after death --> peak rigidity at 12 hours --> dissipates over next 48 to 60 hours
☆dying cells unable to exclude Ca
--Ca influx into musc cells promotes formation of myosin cross bridges
☆ATP synthesis ceases but continues to be consumed