Lecture 3 Flashcards
Three ways discharge pattern can be altered that can affect force production:
- Double discharge
- Synchrony
- Fatigue compensation
What is discharge pattern?
Timing of APs discharged by either the same MU and different MUs
- Takes into account both recruitment and rate coding
What happens if a second discharge is injected after only 10ms (100Hz)?
A big jump in force production
Human MUs discharge ____Hz?
7-35 Hz with 140-30ms between APs
What is a second discharge injected called?
Double discharge
Pros and cons of double discharge:
Pro: Increase in the rate of force development
Con: Loss of fine motor control
Why is there more force with double discharge?
More calcium floods out onto the cell: Not enough time to all be resequestered and therefore more crossbridges can form
Cooperative recruitment: Where not all myosin heads have an affinity for actin at the start of a contraction, leading to an increase in activation of more myosin heads following a muscle contraction
What is synchrony?
The degree to which two different motor units fire simultaneously
When does synchrony occur?
- Large contractions
- Fatigue
- Coordination between muscles (i.e. right and left jaw muscles)
Synchrony generates _____ contractions:
Smooth
Is synchrony greater in dominant or non-dominant hand?
Non-dominant
Is synchrony greater in strength-trained or skill-trained individuals?
Greatest in strength-trained, lowest in skill-trained
Initial strength increases at 8-20 weeks are primarily due to what instead of increased muscle size?
Neural adaptations
- Increased coordination of agonists and synergists
- Increased double discharge
What happens at sustained submaximal contraction-fatigue?
- Increased duration of twitch (slow re-sequestering of Ca2+)
- Lower force (Less Ca2+ and less ATP cycling)
Tension builds during ___ phase and decreases during ____ phase:
Contraction, relaxation
