muscle flashcards.txt

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muscle flashcards.txt
2010-11-03 02:31:36

ch 10
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  1. muscle functions
    • 1. body movement
    • ie walking, running
    • 2. stabilizing body position
    • ie posture
    • 3. moving substances within body
    • ie heart pumping blood, moving substances in GI tract, soleus
    • 4. generating HEAT
    • ie contracting muscle, shivering
  2. properties of muscle
    • 1. excitability - ability to respond to stimuli (ie action potential)
    • 2. contractility - contract when stimulated (by action potential)
    • 3. extensibility - ability to STRETCH without damage
    • 4. elasticity - ability to return to ORIGINal length
  3. satellite cells
    cells that have capacity to regenerate damaged muscle fibers
  4. number of skeletal muscle fibers in body
    set before birth and most last a lifetime
  5. T-tubules
    tunnels in from plastma membrane, where action potential travels through
  6. Sarcoplasm
    • cytoplasm of muscle fiber
    • includes GLYCOGEN (used for ATP synthesis) and MYOGLOBIN (red colored protein w/oxygen bound - releases oxygen for ATP production)
  7. Sarcomeres
    Basic functional unit of a myofibril
  8. Types of muscle proteins
    • 1. Contractile
    • 2. Regulatory
    • 3. Structural
  9. Contractile Proteins
    • actin: thin filament
    • myosin: thick filament
  10. Regulatory Proteins
    • troponin: moves tropomyosin away from myosin-binding sites
    • tropomyosin: blocking myosin-binding site, therefore blocks contraction
  11. Structural Protein
    Titin: stabilizes position of myosin, accounts for much of the ELASTICITY and EXTENSIBILITY of myofibrils
  12. Steps of a contraction cycle
    • 1. ATP hydrolysis: reorients and energizes the myosin head
    • 2. Formation of cross-bridges: myosin head attaches to myosin-binding site on actin
    • 3. Power stroke: during the power stroke the crossbridge rotates, sliding the filaments
    • 4. Detachment of myosin from actin: as the next ATP binds to the myosin-head, the myosin head detaches from actin
  13. Production of ATP in Muscle Fibers
    • ATP needed to power contraction cycle and to pump Ca++ into SR
    • ATP inside muscle fibers will power contraction for only a FEW SECONDS
    • ATP must be produced by muscle fiber after reserves used up
    • 3 ways to produce ATP: creatine phosphate, anaerobic respiration and aerobic respiration
  14. Creatine Phosphate
    • 1st way of getting energy
    • -creatine phosphate transfers its phosphate group to ADP to regenerate new ATP
    • -excess ATP is used to synthesize creatine phosphate
    • -Provides enough energy for about 15 SECONDS
  15. Anaerobic Respiration
    • -Do not require Oxygen, instead GLUCOSE is used to generate ATP once creatine phosphate is depleted
    • -glucose comes from the blood and from the glycogen stored in muscle fibers
    • -Glycolysis breaks down glucose into molecules of pyruvic acid and 2 ATP�if oxygen present, pyruvic acid enters aerobic respiration and produces a lot of ATP
    • -if oxygen is LOW, pyruvic acid is converted to lactic acid, which is carried away by the blood (occurs as a 'burn,' or fatigue during a workout)
  16. Aerobic Respiration
    • if activity lasts longer than 30-40 seconds, need aerobic respiration
    • -pyruvic acid gets oxidized and generates a lot of ATP
    • -each glucose generates 36 molecules of ATP
  17. Sources of oxygen for muscle tissue
    • from the blood, through hemoglobin (is plentiful due to respiration, get more oxygen thru breathing)
    • from the muscles, through myoglobin - usually used up 1st
  18. Types of ATP production and when used during what type of muscle activity
    • Creatine phosphate: provides enough energy for the first 15 seconds
    • Anaerobic respiration: provides enough energy for about 30-40 seconds of Muscle activity
    • Aerobic respiration: provides over 90% of the ATP needed in activities lasting longer than 10 MIN
  19. Muscle Fatigue
    • due to the following
    • 1. Depletion of Creatine Phosphate
    • 2. Insufficient Oxygen
    • 3. Build up of lactic acid and ADP
    • 4. Depletion of Glycogen and other nutrients
    • 5. Inadequate release of Calcium from the SR
    • 6. Failure of motor neuron to release enough acetylcholine (ie ulner nerve damage)
  20. Oxygen Consumption after Exercise
    • added oxygen helps to restore muscle cells to their resting levels by the following:
    • 1. replace the oxygen removed from myoglobin
    • 2. synthesize creatine phosphate and ATP
    • 3. convert lactic acid into GLYCOGEN
  21. Maximum Tension (force)
    • Dependcent on:
    • 1. rate at which nerve impulse arrives
    • 2. amount of stretch before contraction
    • 3. nutrient and oxygen availability
    • 4. size of motor unit
  22. Strength of contraction depends on??
    • depends on the size of the motor units and number that are activated
    • ie the more complex the muscles, the more muscle fibers used, such as more used in arm & leg (2000-3000) vs. in the eye (10-20) and voice (2-3)
  23. Muscle twitch contraction
    • brief contraction of muscle fibers in response to action potential
    • Latent period: 2msec
    • -brief delay b/w stimulus and muscular contraction
    • -action potential sweeps over the sarcolemma and Ca++ is released from SR
    • Contraction Period: 10-100msec
    • -Ca++ binds to troponin
    • -myosin binding sites on actin exposed
    • -Cross-bridges form (myosin head attaches to myosin binding site on actin)
    • Relaxation Period: 10-100msec
    • -Ca++ is transported back to SR
    • -myosin bindings sites covered by tropomyosin
    • -myosin heads detach from actin
    • (less complex the muscle, the less their contraction periods are)
  24. Types of Contractions
    • Isotonic Contraction: tension developed remains constant while muscle CHANGES LENGTH (ie picking book up off a table)
    • Isometric Contraction: tension generated is not enough for object to be moved and muscle does NOT CHANGE LENGTH (ie holding a book with an outstretched arm)
  25. Myoglobin content in different skeletal muscle fibers
    • Red muscle fibers: high myoglobin content (dark meat)
    • White muscle fibers: low myoglobin content (light meat)
  26. 3 Main Types of Skeletal Muscle Fibers
    • 1. Slow Oxidative Fibers (SO fibers)
    • 2. Fast Oxidative-glocolytic Fibers (FOG fibers)
    • 3. Fast glycolytic Fibers (FG fibers)
  27. Slow Oxidative Fibers (SO)
    • -smallest in diameter
    • -appear dark red (more myoglobin)
    • -SLOW speed of contraction
    • -ATP generated by AEROBIC respiration
    • -Very resistant to fatigue
    • -Maintaining posture for aerobic endurance activity, such as running a marathon
  28. Fast Oxidative-Glycolytic Fibers (FOG fibers)
    • -medium in diameter
    • -dark red (lots of myoglobin)
    • -ATP generated by Aerobic Respiration
    • -High resistance to fatigue
    • -Speed of contraction is FASTER
    • -contributes to activities such as walking and Sprinting
  29. Fast Glycolytic Fibers (FG fibers)
    • -Largest diameter
    • -most powerful contractions
    • -low myoglobin content, so low mitochondria and few blood capillaries
    • -ATP generated by GLYCOLYSIS
    • -Contraction strongly and quickly
    • -Fatigue VERY FAST
    • -used for intense aerobic movements lasting a short time, such as weight lifting or throwing a ball
  30. Distribution and recruitment of types of muscle fibers
    • -most are a mix of all 3 types
    • -neck, back and legs have high SO
    • -arms and shoulders have high FG
    • -legs have large SO and FOG
  31. Rations of fast glycolytic (FG) and slow oxidative fibers (SO)
    • These ratios are GENETICALLY determined
    • -ppl with high FG fiber proportions excel in intense activities (ie sprinting, weight lifting)
    • -ppl with high SO fiber proportions excel in endurance activities (ie marathon running)
  32. Types of exercise and its effect on muscle fibers
    • -Aerobic exercise transforms some FG fibers into FOG fibers, since endurance activities do NOT increase muscle mass
    • -Exercise that requires short bursts of strength increase size of FG fibers, hence when you weight lift your muscle get BIGGER (Hypertrophy)
  33. Cardiac Muscle Tissue
    • -Intercalated discs connect fibers
    • -contracts when stimulated by its own autorhythmic muscle fibers
    • -has the same arrangement of actin/myosin as skeletal fibers
    • -Many Mitochondria
    • -Needs AEROBIC respiration for ATP generation, and can use Lactic Acid produced by skeletal muscle to generate ATP
  34. Smooth Muscle Tissue
    • -Action potentials are spread through fibers via GAP JXNS
    • -Fibers stimulated by neurotransmitter, hormone or autorhythmic signals
  35. Anatomy of Smooth Muscle
    • -NOT arranged in orderly sarcomeres
    • -SMALL amounts of Ca++ stored
    • -Filaments attach to dense bodies and stretch from one dense body to the other (same way as Z discs)
  36. Physiology of Smooth Muscle
    • Can contract or relax in response to:
    • -Action potentials from the AUTONOMIC nervous system
    • -In response to stretching (ie when food enters digestive tract and intenstines stretches)
    • -Hormones (ie epinephrine causes relaxation of smooth muscles in air-ways and blood vessel walls)
  37. Aging related to Muscle Tissue
    • Results in:
    • progressive loss of skeletal muscle MASS
    • decrease in maximal strength
    • slowing of muscle reflexes
    • loss of flexibility