Anatomy ch 10

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Anatomy ch 10
2010-10-20 22:43:52
Anatomy Muscular tissue

Note and vocab form ch 10 muscle tissue
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  1. Types of Muscle tissue
    • 1. Skeletal - striated, voluntary - move bones of skeleton
    • 2. Cardiac - striated, involuntary - forms heart wall
    • autorhythmicity - built-in rhythem of the heart
    • 3. Smooth - nonstriated (smooth), involuntary - walls of hollow internal structures, such as blood vessels, airways, and most organs in the abdominopalvic cavity
  2. Functions of skeletal muscle
    • 1. produce body movement
    • 2. stabilizing body position
    • 3. storing and moving substances within the body
    • 4. Generating heat (thermogenesis)
  3. Properties of Muscle Tissue
    • 1. Electrical excitability - ability to respond to electrical stimuli
    • 2. Contractility: ability to contract fully when stimulated
    • 3. Extensibility: ability to stretch without being damaged
    • 4. Elasticity: ability to return to original shape after contraction or extension
  4. striated
    alternating light and dark protein bands are seen when the tissue is examined with a microscope
  5. muscle fiber
    a muscle cell - called muscle fibers because of their elongated shape
  6. Fascia
    • superficial fascia - separates muscles from skin - areolar CT and adipose tissue
    • Deep fascia - holds muscles with similar functions together - dense irregular CT
  7. 3 layers of CT that extend from the fascia to protect and strengthen skeletal muscle
    • Epimysium: surrounds whole muscle
    • perimysium: surrounds muscle bundles of 10 to 100 muscle fibers called fascicles
    • endomysium: surrounds individual muscle fiber (muscle cell)

    all three CT extend beyond the muscle fibers and form a tendon- dense irregular CT that attach muscle to the periostium of the bone

    tendon sheaths - certain tendons (esp wrist & ankle) are enclosed by tubes of fibrous CT
  8. aponeurosis
    tendon that extends off muscle tissue as a broad, flat layer

    ex. epocranial aponeurosis
  9. nerve and blood supply of skeletal muscles
    • somatic motor neuron - the nerve endings that supply each muscle fiber - connected at the neuromuscular joint
    • muscle tissue has high O2 requirements so is well supplied with arteries
    • 1 artery and 1 or more veins for each muscle
    • blood vessels and nerve fibers enter central part of muscle and branch
  10. hyperplasia
    satellite cells
    growth in muscle tissue by an increase in the number of fibers

    hypertrophy - an enlarging of existing muscle cells (growth in infancy)

    satellite cells - cells that retain the capacity to fuse with one another or with damaged muscle fibers to regenerate functional muscle fibers
  11. fibrosis
    the replacement of muscle fibers by fibrous scar tissue due to skeletal muscle damage or degeneration
  12. sarcolemma
    transverse (T) tubules
    • the plasma membrane of the muscle cell
    • T tubules - tunnel in from the surface toward the center ir each muscle fiber (open to the outside of the fiber and are filled with interstitial fluid)
    • sarcoplasm - cytoplasm of a muscle fiber
    • Myoglobin - red-colored protein in the sarcoplasm - found only in muscle cells - binds O2 that diffuse into the muscle fiber from interstitial fluid
  13. myofibrils
    • contractile organelles of skeletal muscle - in the sarcoplasm
  14. sarcoplamsic reticulum (SR)
    terminal cisterns
    • SR - fluid-filled system of membranous sacs that encircle each myofibril
    • terminal cisterns - end sacs of the SR that butt against the T tubules from both sides
    • triad - a T tubule and two terminal cisterns on either side of it
  15. Word roots for Muscle
    • myo
    • sarco
  16. Filaments
    • short protein structures arranged into sarcomeres (short sections)
    • Two types:
    • Actin - thin filaments
    • Myosin - thick filaments
  17. Sarcomere
    • Functional - Contractile - units of skeletal muscle - short sections of filaments
    • Z disks: separate one sarcomere from the next
    • A bands: appear dArd - runs entire length of thick filament (thick and thin) in three zones
    • 1) H Zone: (Heavy) thick but no thin filaments
    • 2) Zone of Overlap - both thick and thin
    • 3) M line - in middle of sarcomere
    • I bands: appear lIght - contains only thin filaments - extends across Z disk from A band of one sarcomere to A band of next sarcomere
  18. Thick filaments
    • contain mostly Myosin - Have head (crossbridges) and tails - two gold clubs
    • Functions as a Motor protein - drives the action of cells
  19. Thin filaments
    • mostly Actin - have myosin binding sites - concave area on actin where myosin binds to it
    • Tropomyosin - covers binding site when muscle is relazed
    • Troponin - holds tropomyosin in place
  20. Proteins of muscle
    1. Contractile Proteins
    2. Regulatory Proteins
    3. Structural Proteins
    • Contractile proteins
    • Myosin - think filaments
    • Actin - thin filaments
    • Regulatory Proteins
    • Tropomyosin - when skeletal muscle is relaxed tropomyosin covers myosin binding site on actin
    • Troponin - when Ca2+ (calcium ion) bind to troponin it changes shape and pulls propomyosin away from myosin binding site - uncovers it
    • Structural proteins
    • Titin - connects to the Z disk and M line of a sarcomere- helps to stabilize the position of the thick filament - accounts for elasticity and extensibility of the myofibrils
    • Nebulin - wraps around length of each thin filament - helps anchor thin filament to Z disks
    • Myomesin - forms the M line of the sarcomere
    • Dystrophin - links thin filaments of the sarcomere to integral proteins of the sarcolemma
  21. The contraction cycle
    • 1. ATP hydrolysis - ATP that is bound to myosin head and is hydrolized into ADP - causes tropomyosin to move leaving binding site open
    • 2. Attachement of myosin to actin to form crossbridges
    • 3. Power stroke - ADP is released crossbridges act like tiny ratchets to propel thin filament towards center of sarcomere - each crossbridge attaches and detaches several times during contraction
    • 4. Detachment of myosin form actin - APT binds to myosin head causing it to detatch from actin
  22. Sliding filament mechanism
    muscle contracion occurs becuase myosin heads attach to and walk along the thin filaments at both ends of a sarcomere - pulling the thin filaments toward the M line - Z disks come closer together and sarcomere shortens - length of individual thick and thin filaments does not change
  23. Excitation-Contraction Coupling
    the events involved from excitation (receiving and propagating a stimulus) to contraction (actual sliding of the filaments)
  24. Ca2+ release channels
    • channels in the SR that open and let Ca2+ flow out into cytosol around the thick and thin filaments
    • calsequestrin - calcium-binding protein that enables calcium to be stored withing the SR
  25. Length-tension relationships
    Tension depends on the degree of overlap of thin and thick myofilaments

    • Lots of overlap = little tension
    • some overlap = allows for maximum tension - most binding available
    • little overlap = little tension - little possibility of binding
    • no overlap = no tension - muscle streatched out - muscle failure
  26. Neuromuscular joint - NMJ
    Neuromuscular Junctions
    • muscle contractions are controlled by the nervous system via the NMJ
    • Neuromuscular Junctions - area of contact between neuron and sarcolemma
    • Synapse - Regions where nerve cell communicates with other cell through the release of neurotransmitters called Acetylcholine (ACh)
    • Synaptic gap: space between the synaptic terminal and the sarcolemma
    • synaptic end bulbs:expanded ends of neuron
    • Motor End Plate: area on the sarcolemma where Ach receptors are found - every place you have a NMJ you have a motor end plate
  27. Activity of NMJ (Neuromuscular Junction)
    • 1. Release of acetylcholine (ACh):
    • --nerve impulses from the axon release ACh via exocytosis into the synaptic cleft
    • -- ACh diffuses across synaptic cleft and binds to receptors on sarcolemma - concentration gradient
    • 2. Activation of ACh receptors and production of muscle action potential
    • -- ACh binding opens sodium ion channels and causes an influx of sodium ions into the sarcoplasm
    • --This brings on an ACTION POTENTIAL that spreads all over via T tubules
    • -- Sarcoplasmic reticulum releases calcium ions
    • --calcium ions bind with troponin and expose myosin binding site
    • --Muscle fibers then contract
    • 3. Termination of ACh activity and subsequent relaxation of skeletal muscle fibers
    • --Release of ACh stops- causes release of calcium to stop
    • --Calcium pumped back into SR via active transport
    • -- Calcium ions detach from troponin
    • --Tropomyosin covers up myosin binding site - crossbridge cant attach - contraction stops
  28. Production of ATP in muscles:
    • 1. Excess ATP temporarily converted to and stored as Creatine Phosphate- a high energy molecule that is used to regenerate ATP to supply quick energy bursts
    • 2. Anaerobic Cellular Respiration - No oxygen - short burst of energy
    • --occurs in sarcoplasm - lactic acid byproduct- small amount of ATP
    • 3. Aerobic cellular respiration
    • -- occurs in mitochondria - large ATP - provides most of energy for activities that last more than 10 mins
  29. Muscle fatigue
    Motor Unit Recruitment
    • psysiological inability to contract - spirit is will but the flesh is not
    • - caused by insufficient oxygen or calcium
    • Motor Unit Recruitment:
    • adding motor units as we need more strength
    • process in which the number of active motor units increases
    • delays onset of muscle fatigue
  30. Oxygen consumption after exercise
    • 1. Oxygen debt is paid - extra oxygen needed for restoration
    • 2, Recovery Oxygen Uptake- better term than oxygen debt
    • a. lactic acid removed and recycled (converted to pyruvic acid to be used by mitochondria)
    • b. elevated body temp increases rate of chemical reactions
    • c. heart and respitory muscles work harder
    • d. tissue repair is ongoing
  31. Motor Unit
    • single neuron and all the muscles fibers it innervates
    • -can handle hundreds of muscle fibers
    • - each muscle has multiple motor units
    • - smaller motor units in muscles for fine movement
    • - not all motor units active at same time
    • - Recruitment- increasing tension through an increase in active motor units
  32. Muscle twitch
    Muscle twitch is the response of a muscle to a single brief threshold stimulus.

    • Phases
    • 1). Latent Period - Muscle tension is beginning.
    • 2). Period of Contraction - Muscle fibers shorten.
    • 3). Period of Relaxation - Ca++ renters the sarcoplasmic reticulum
    • 4) refractory period - if you send another electrical signal muscle wont respond - cant contract agian yet
  33. Frequency of stimulation
    • i).Wave Summation - If 2 stimuli are delivered in rapid succession the second twitch will be greater than the first - increasing intensity
    • . ii).Unfused Tetanus- The amount of Ca++ increases in the cytoplasm results in a quivering response- PARTIAL relaxation -
    • iii). Fused Tetanus - Stimuli arrice very close - NO RELAXATION possible - occurs in most muscle contractions
  34. Muscle Tone
    • resting tension on a skeletal muscle
    • Poor - flaxxid, limp
    • Good - firm, solid
  35. Isotonic contractions
    Concentric isotonic contraction
    Eccentric isotonic contraction
    • The muscle changes length and moves a load
    • .Isotonic contractions- the thin actin filaments are sliding across the myosin
    • Concentric isotonic contraction- muscle shortens as tension exceeds resistance
    • Eccentric isotonic contraction- muscle lengthens as tension exceeds resistance
  36. Isometric contractions
    • Tension in the muscle increases but the muscle neither shortens or lengthens.
    • Isometric contractions the cross bridges are forming and pulling but the actin filament is not moving
  37. Types of muscle fibers
    • 1. Slow oxidative fibers - dont contract quickly\
    • - hydrolisys of ATP takes longer
    • - areobic respiration
    • - Takes 3 times as long to contract as fast fibers
    • - Dont fatigue easily - endurance activities
    • - lots of mitochondria, capillaries and myoglobin - appear red
    • 2. Fast Oxidative-Glycolytic fibers
    • - Gen ATP via aerobic AND anaerobic cellular respiration
    • - lots of capillaries and myoglobin
    • - aerobic endurance
    • 3. Fast Glycolytic Fibers
    • - anaerobic respiration
    • - contract quick and strong
    • - large diameter- lots of myofibrils
    • - few mitochondria & capillaries & myoglobin
    • - fatigue easily - good for weight lifting
  38. Motor Unit Recruitment
    • adding motor units as we need more strength
    • process in which the number of active motor units increases
    • delays onset of muscle fatigue
  39. Distribution and recruitment of different types of fibers
    • All three types of fibers are present in most muscles - slow oxidative, fast oxidative-glycolytic, and fast glycolitic fibers
    • relative proportions differ depending on the action of the muscle, fitness level, and genetics
    • distribution of muscle fiber types is genetically determined
    • Endurance exercieses can transform some fast glycolytic into fast oxidative-glycolitic
    • exercises that focus on guick and strong contractions can increase size and strength of fast glycolitic fibers - more thick than thin - results in hypertrophy
  40. White muscle fibers
    red muscle fibers
    • white - low myglogin - appear lighter
    • red - high myglobin - appear red - high mitochondria and more blood capillaries