Muscle physiology Flashcards
What is the first major event leading to contraction and relaxation?
Acetylcholine (ACh) binds to the ligand -gated channel. causes the release of NA+, which depolarizezs the motor end plate.
What is the 2nd major event of contraction and relaxation?
Exciation-contraction coupling: The action potential produces and propagates along the sarcolemma and then onto the T-tubles. The t-tubules have voltage gated channels and receptors that when they receive the signal, they cause the release of Ca2+ from the terminal cistertane. The Ca2+ then binds to troponin. This causes troponin to alter tropomyosin, exposing the active sites on actin
What is the 3rd event leading to contraction and relaxation?
The contraction cycle: The mysin head can now bind to the exposed actin site. This bond is called a crosslink and causes inorganic phosphate (Pi) to be released. This phosphate is from the previous cycle.The release of Pi is what starts the power stroke. The myosin head will then pivot and bend. This is causing the movement of actin to the m-line.
AS the mysoin head pivots and bends, ADP is released.
Once ATP binds to the myosin head, this breaks the crosslink bond and causes the release of myosin. The recovery stage happens when the ATP that is now bound to the released myosin hydrolysis. This is ADP and Pi. This energizes the mypsin head. This is repeated until ATP is finished or CA2+ is finished
WHat is the 4th event leading to contraction and relaxation?
Relaxation: NO more Ach is released. The remaining is broken down by AChE.
This means no AP is propagated to ultimately release CA2+. Any remaining Ca2+ in the sarcoplasm is reabsored by the Sarcoplasmic reticulum, including the one attached to troponin. This results in the covering of the active sites by tropomyosin. Muscle goes back to resting state
What is needed for contraction and relaxation?
ATP!!
What is a twitch?
muscle fiber responds to a single action potential
WHat are the phases of a twitch?
latent period, contraction phase. and relaxation phase
What is the latent period?
No tension: when muscle fiber is stimulated. the end is when there is pulling force. After a couple of pulling
What is the contraction phase?
the raising of tension
WHat is the relaxation phase?
the drop of tension
What is a treppe
an increase in peak tension with each successive stimilis delivered shortly after the completion of the relaxation phase of the preceding twitch
What is wave summation?
occurs when muscle fiber is stimulated again before it can completely relax form previous one
What is incomplete tetanus?
only parial relation before stimuli
