Muscular System About 650 skeletal muscles in the human body 17 muscles to smile…42 muscles to frown Largest muscle = gluteus maximus Longest muscle = sartorius Smallest muscle = stapedius (inner ear) Takes >200 muscles to walk

-mysium=CT membrane and tendon sheath Myofilaments

Types of Muscle Skeletal Striated Voluntary Multinucleated Smooth Nonstriated Involuntary Cardiac Intercalated disks ~ 50% of body weight Work in groups to perform a function

General Functions of Muscular System Movement Skeletal muscle contractions move body in whole or part Heat Production Muscle cells produce heat via catabolism to maintain temperature homeostasis 85% of body heat comes from muscle contractions Posture Continued partial contraction of muscle in order to perform many functions

Characteristics of all Muscle Excitability Respond to stimuli Contractility Actively shorten to exert a pull Tension that can be harnessed by CT Extensibility Continue to contract over range of resting lengths Ex: smooth muscle can be stretched to several times its original length and still contract on stimulation Elasticity Return to original length after contraction

Muscle Fiber Arrangement Parallel Convergent Pennate Bipennate Sphincter

Muscle Attachment Does NOT move when muscle contracts Does move when

Naming Muscles Location Function Shape Fiber direction Number of heads/divisions Points of attachment Muscle size

Location Function Fiber Direction Shape Frontalis Frontal bone Femoris Femur Gluteus Posterior of hip/thigh Oculi Eye Oris Mouth Radialis Radius Ulnaris Ulna Brachialis Arm Abductor Moves part away from body Adductor Moves part toward body Depressor Lowers a part Extensor Extends a part Flexor Flexes a part Levator Elevates a part Rotator Rotates a part Fiber Direction Shape Oblique Diagonal to midline Rectus Parallel to midline Sphincter Circling an opening Transversus Right angle to midline Deltoid Shaped like delta ∆ Orbicularis Circular Platy Flattened; platelike Quadratus Square Rhomboideus Diamond-shaped Trapezius Trapezoidal

Number of divisions Size Bicep Two heads Tricep Three heads Quadricep Four heads Size Brevis Short Longus Long Magnus Large Maximus Largest Medius Moderately sized Minimus Smaller

Raises eyebrows Frowning Mastication Blinking Laughing Whistling, smiling Puckering Mastication Flexes head

Moves head Moves head Flexes head

Superficial Back Muscles Large, fan-shaped muscles provide force in a wide range of body positions -EX: leaning back to straight vertical and all points in between. Shrugging, pulling scapulas together and down Rotator cuff muscles Stabilize shoulder joint, pull arm back Shoulder movement Pull the arm down, Stabilize torso during many movements (EX: bench press)

Trunk Muscles - Thorax Elevate ribs

Trunk Muscles Abdomen Flexes trunk Stabilizes Lower back Compresses

Upper Arm Flexes Upper arm Extends forearm

Flexors

Extensors

Upper Leg Deep muscle Vastus intermedius Longest muscle Biceps femoris Semimembranosus Quadricep Femoris Semitendinosus

Lower Leg Plantar flexion

Foot

Posture Good Posture – body alignment that favors function with least work Standing Position Head and chest held high Chin, abdomen, buttocks pulled in Knees slightly bent Feet firmly on ground 6 in. apart Poor Posture - puts abnormal strain on ligaments and bones Maintenance Tonicity (muscle tone): muscles exert a pull against gravity Continuous and passive partial contraction of muscles

Classification of Muscle Group Actions Agonist (Prime Mover) Muscle most responsible for movement Antagonist Opposes prime mover Provides precision and control during prime mover contraction Relaxes when prime mover contracts Synergist Aid prime mover Contract at same time as prime mover Fixator Joint stabilizer Maintains posture/balance during prime mover contraction