Muscle Tension Flashcards
What does a muscle action potential trigger?
The release of calcium ions from the sarcoplasmic reticulum
How does the action potential reach the sarcoplasmic reticulum?
Via the transverse tubules which extend from the surface membrane deeper into the cell.
Describe what happens when an AP triggers the sarcoplasmic reticulum
- AP travels down transverse tubules and triggers sarcoplasmic reticulum
- Sarcoplasmic reticulum releases calcium ions
- calcium concentration inside cell increases
- calcium ions diffuse into muscle filaments
- calcium ions bind to troponin
What is a single muscle contraction generated by a single AP called?
A muscle twitch
How long does a muscle twitch last?
50-100 milli seconds
What does a muscle twitch do?
Results in an increase of muscle tension (force)
What are the three periods of a muscle twitch?
Latent period (where slack is taken up)
Contraction Period
Relaxation Period
What occurs when there are multiple AP’s?
The twitches summate and so more force is generated
Describe unfused and fused tetanus?
With several AP’s muscle tension increases, levels off and each AP is visible.
With an even greater frequency of AP’s the same occurs but each individual AP is not visible
-At increased frequencies more muscle tension is generated and tetanus becomes more fused
High level of fused muscle contractions rarely occur because?
Instead higher levels of force are generated by recruiting more muscle fibres into the contraction
Describe the Length tension relationship
At short length = low tension
intermediate length = high tension
long length = low tension
Explain the length tension relationship?
At intermediate length the overlap arrangement of action and myosin filaments is at an optimum allowing for best cross bridge formation and maximum force generation
- with long length = not enough overlap
- with short length = to much overlaps
