+ Muscular System

+ Muscle Tissue The job of muscle tissue is to CONTRACT It does this by responding to stimuli 3 types of muscle tissue Smooth Cardiac Skeletal

+ Characteristics of Smooth Muscle Has no striations Spindle-shaped cells Single Nucleus Involuntary—no conscious control Found mainly in the walls of hollow organs

+ Characteristics of Cardiac Muscle Has striations Usually has a single nucleus Involuntary Found only in the heart

+ Characteristics of Skeletal Muscle Most attach to bones by tendon Cells are multinucleate Striated—have visible binding Voluntary Cells surrounded & bundled by connective tissue

+ Physiological Properties of Muscle Tissue Contractibility Excitability/Irritability Elasticity Extensible

+ Skeletal Muscle Makes up roughly 40% of weight Striated and voluntary Made up of light and dark bands Actin (light and thin) Myosin (dark and thick)

+ Muscle fibers Skeletal muscle is made up of long thread-like cells called muscle fibers Muscle fibers: Made up of microfilaments called actin and myosin Muscle contraction occurs due to thick and thin filaments sliding and reacting with each other Muscle fiber= myofibril (myo=muscle) Filaments are arranged into sarcomeres

+ Sarcomeres Structural unit of a muscle fiber (myofibril) Composed of the two proteins (myosin & actin) Is responsible for contractile propertites

+ Structure of Sarcomere Sarcomeres are composed of the following: A-Band: consists of one end to another of the thick filament (myosin); also contains thin filaments (actin) H-Zone: found inside the A-Band; consists of only thick filaments M-Line: in between the H-Zone (goes straight down the center) I-Band: contains thin filaments only, found outside the A-band Z-Line: posts; it is where the sarcomere begins and ends

+ Sarcomere

+ Muscle Contraction When the muscle contracts, the myosin fibers do not move Myosin fibers pull the actin fibers in; creates a sliding process Closes the H-Zone

+ Organization of Muscle Tissue

+ Fascia Connective tissue that wraps and binds the muscles 2 types: Superficial Found in dermis Made of loose C.T. and areolar tissue Contains blood vessels and fat cells Found in scalp, palms, and soles Deep Separates and focuses on skeletal muscle Dense C.T. Forms cords or sheets past the muscle to form tendons

+ Deep Fascia Tissue 3 types of dense c.t. extend from the deep fascia to protect and strengthen the muscle Epimysium Outer layer, circles the whole muscle Perimysium Middle layer, surrounds muscle fibers Endomysium Inner layer, surrounds individual muscle fiber Egg crate analogy

+ Motor units In order for a muscle to contract, a motor neuron must send a signal to the muscle fiber Neurotransmitter: ACH (acetylcholine) Causes contraction Motor Unit: Number of muscles the neuron has Fingers: more neurons, less muscles Back: more muscles, less neurons

+ Muscle Fibers 3 types of skeletal fibers Red Fibers: slow twitch; lots of mitochondria & myoglobin White Fibers : fast twitch; less mitochondria & myoglobin Intermediate Fibers: combination Myoglobin: oxygen binding protein, that determines the type of fibers (more myoglobin=faster fiber) Light vs. Dark meat Depends on myoglobin present

+ Types of Muscle Contractions Isometric Muscle contracts, but no movement occurs Eccentric Muscle ‘contracts,’ but gets longer Concentric Normal muscle contraction

+ Attachment of Muscles Origin Part of the muscle that moves the least Insertion Part of the muscle that moves the most Belly Widest part of the muscle

+ Naming muscles Muscles are often named based on one of the following: Location Number of origins Direction of fibers Shape Size Action

+ Location Structure near which muscle is found FRONTALIS = near FRONTAL bone OCCIPITALIS = near OCCIPITAL bone

+ Number of origins Number of tendons of origin BICEPS = Two Biceps Brachii Biceps Femoris TRICEPS = Three Triceps Brachii QUADRICEPS = Four Quadriceps Femoris

+ Direction of fibers Relative to the Midline RECTUS = parallel to the midline Rectus Abdominus TRANSVERSE = perpendicular to midline Transverse Abdominus OBLIQUE = diagonal to midline External Oblique

+ Shape Relative Shape of the Muscle DELTOID = triangular shape Δ TRAPEZIUS = trapezoid shape  SERRATUS = saw- toothed ♒ RHOMBOIDEUS = rhomboid shape  TERES = round ○

+ Size Relative Size of Muscle MAXIMUS = largest Gluteus Maximus MEDIUS = middle Gluteus Medius MINIMUS = smallest Gluteus Minimus LONGUS = longest Fibularis Longus BREVIS = short Fibularis Brevis TERTIUS = shortest Fibularis Tertius

+ Action NAMEACTIONEXAMPLE FLEXOR Decrease angle at a joint Flexor Carpi Radialis EXTENSOR Increase angle at a joint Extensor Carpi Ulnaris ABDUCTOR Move bone away from midline Abductor Pollicis Longus ADDUCTOR Move bone toward midline Adductor Longus LEVATOR Produce upward movement Levator Scapulae DEPRESSOR Produce downward movement Depressor Labii Inferioris SUPINATOR Turn palm upward/anterior Supinator PRONATOR Turn palm downward/posterior Pronator Teres

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