Unit 7,8

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Unit 7,8
2013-12-05 08:13:48

Unit 7,8
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  1. Unit 7 purpose
    determine the impact of (recruitment/frequency coding) in human adductor pollicis muscle
  2. Unit 7 Procedure -Recruitment
    • stim ulnar nerve once a sec at increasing stim volt at wrist
    • prevent frequency coding from interfering with data collected
  3. Unit 7 Procedure- Frequency Coding
    • supramaximal stimulus voltage to the ulnar nerve at increasing frequency
    • to keep all motor units active preventing recruitment interference
  4. Unit 7 Results -Recruitment
    • ** Dif motor neurons have dif activation thresholds
    • as ↑ Stim voltage, activation thresholds bypassed and more units activated  increasing muscle twitch force
    • When all units recruited, increase in stim volt does not increase total muscle force
  5. When Ca released from SR due to AP in t-tubular membrane…
    • binds to troponin creating cross bridges and force generation
    • reuptake by active membrane transport mechanism
  6. Unit 7 Results - Frequency Coding
    • **Sarcoplasmic levels of Ca and number of cross bridges formed
    • increase stim frequency, increase Ca released into Sarcoplasm, increase cross bridge formation, increasein force generation
    • plateaus when all cross bridges have been formed even with increase in frequency
  7. Unit 8 Procedure 1
    • Sustained, submax contraction at 2 target forces
    • 3 brief MVC  chose best
    • Target force levels (20%, 60%)  sustain 4 min, record force every 20 sec
  8. Unit 8, 1, Results
    • metabolic failure
    • loss of force generation at 60% level bc sustain contractions at mod to max force comprises blood flow to contracting muscle (blood vessels compressed)
    • ---leads to decrease iO2 delivery and metabolic waste removal
    • ---leads to use of anaerobic metabolism for ATP and increases lactate levels
    • ---causes decrease in muscle fiber pH, slowing the rate of enzyme function and therefore ATP generation
    • ---causing the supply to be less than the demand, leading to loss of sustained force
  9. Unit 8 Procedure 2
    • intermittent 0.6 duty cycle, submax contraction of target force w/ MVC every 3rd contraction
    • 3 Brief MVC  chose best
    • 60% target force
    • every third contraction, 2 sec MVC
    • ---Only record MVC
    • continue until MVC at target force
  10. Unit 8, Results 2
    • explain the loss of max force generating capacity
    • 4 sec of rest allowed restore of muscle blood flow providing O2 and removing waste
    • ---don’t need anaerobic CR
    • Repetitive stim of t tubular membrane result in K build up in t-tubular extracellular space
    • ---decreasing membrane excitability and amplitude of Aps
    • --decreases amount of Ca released from SR per impulse
    • --leads to less cross bridges formed
    • ---causes decrease in tension  decrease in MVC