Muscular System Pau Junyent & Aurora Nieto
Whatare muscles? I • contractile tissue found in animals • over 650 muscles • halftheweight of thehumanbody • producemovement & bodyheat • skeletal, smoothandcardiac • abilityto contractandconductelectricalimpulses • voluntary (biceps)or involuntary(lungs) • striatedor smooth
Whatare muscles? II • Rigor Mortis: stiffeningbodyafterdeath, causedbycalcium in themuscle • contract& relax; NOT stretch • madeup of elastictissue • need: Oxygen and Blood • Antagonist muscles: pair of muscles that do opposite things from one another • Elasticity: the ability to return to original shape • Flexion: ability to bend a joint
Differences • Differentfunctions • Appearance - skeletal muscle: striated(striped) - cardiac muscle: striatedbutstripesless organized. containbranches, allowrapid communication - smooth muscle: composed of cells withdarknuclei; notstriated
Smooth Muscle I • Involuntary muscle • Found in hollow parts of the body • Stimulated by the nervous system • Two groups: single-unit and multiunit • Single-unit: rapid and simple contractions • Multiunit: contractions depend on the nervous system • Found in: Walls, arteries, veins, urinary bladder, lymphatic vessels, uterus, respiratory tract, iris, etc… • Structure and function the same for every all organs • Said to be in charge of ‘housekeeping’ functions
SmoothMuscle II • Contracts everything at once • Cytoplasm is filled with myosin and actin molecules • Myosin: ATP-dependent motor protein • Actin: Protein found in all eukaryote cells • Contraction caused by sliding actin and myosin filaments
Skeletal Muscle I • Produce movement & supports the skeleton • Voluntary muscle • Controlled by the nervous system • Attached to bones by tendons • Made up of muscle fibers (myoblasts) • Cartilage: connectivetissuefound in joints
SkeletalMuscle II • Two groups: Type I and type II • Type I: red, presence of oxygen, for endurance and slow fatigue • Type II: white, absence of myoglobin, reliance on glycolytic enzymes, used shortly, use oxidative and anaerobic metabolism, fast fatigue
Skeletal Muscle III – Categorized I • Categorizednotonlyby color butbyarragement of fascicles • Parallel, convergent, pennate, sphinter • Parallel muscles: • fascicles runparallel to thedirection of the muscle • most skeletal muscle (triceps, biceps) • Convergent muscles: • Fiberscomeoutfrom a commonpoint. • Cover largessurfaces. • Allow a lot of movement(pectoralis major)
Skeletal Muscle III – Categorized II • Pennate muscles: • 1 or more tendons runthroughthemuscle • thefascicles forma slanted angle to thetendons • greateramount of muscle fibers = moretension (RectusFemoris) • Sphintermuscles (circular) : • arrangedaroundanopening • whenmuscle contracts, opening gets smaller. • attheentrancesandexits of passageways
Most Important Skeletal Muscles Pectoralis Major: • Thick, fan-shapedmuscle • At the front (chest) of humanbody • Flexeschestarea GluteusMaximus: • Largestand most superfcial of gluteal muscles • Shapeandappearance of buttocks • Flexesthighjoint
Differences (Tendon & Ligament) • Ligaments: • connectbone to bone • help to stabilizejoints • long, stringycollagen • Slightlyelastic • Stretched to graduallyincreaseflexibility. • Tendon: • connects muscle to bone • tough, flexible • attached to theskeletal muscles • intermediariesbetweenthe muscles
Cardiac Muscle I • Involuntary or voluntary muscle • Heart • Send blood to all the body by using contraction • Cardiomyocytes have 1-4 nuclei • Cordinated contractions • Blood is sent to clean body from waste products and keep the body active • Highly resistant to fatigue
CardiacMuscle II • Needs a lot of calcium • Largest number of mitochondria • Cardiac muscles contract to squeeze blood out • Relaxes to fill the heart with blood
Muscle Regeneration • Occurs when a muscle is stretched or torn (muscle strain) • Muscle breaks when the stress limit is trespassed • Provides more strength and larger size • Regenerates when the body rest • Regeneration will occur no matter how old • Satellite cells fuse with the broken fibers
Video • http://www.youtube.com/watch?v=ren_IQPOhJc
