Lab 3 - skeletal muscle contraction Flashcards
How does the twitch amplitude change when increasing stimulus voltage ?
The twitch amplitude increases
How does the twitch amplitude change as voltage increases?
As voltage increases and the stimulus is greater, it is able to bring more muscle fibres to threshold.
How does twitching big muscles in the experiment differ from the process which occurs in the body?
In the experiment, the big muscle we stimulated has a low internal resistance, and so it was easily activated. However, in the body the small motor units are activated first. small motor units have small axon hillocks, so they are easy to being to threshold. In the body, the amplitude of the twitch would have been smaller, due to the activation of small, and not large, motor units.
Why do latency and duration differ for EDL and soleus?
In the EDL, there are mostly fast twitch fibres. therefore, latency is quick (fast ATPase) and duration is short (fast SERCA). In the soleus, there are mostly slow twitch fibres. therefore, latency is slow (slow ATPase) and duration is long (slow SERCA).
Why is a tetanic force greater than a twitch?
Continuous stimulation of the motor unit generates multiple twitches. there is an accumulation of Ca+ avaliable, so more cross-bridges form, and more force is generated.
What occurs to a muscle twitch as the length of the muscle increases?
As the length of the muscle increases, so does the passive tension. The degree of potential overlap increases, and so the twitch got weaker.
Length - tension relationship!
What is the optimal resting length of muscle?
70-130g
What happens to an MG patient when given a repetitive nerve stimulation test?
The twitch amplitude decreases with successive stimulation
What is the effect of administering a MG patient AchE blockers?
Blocking AchE means Ach is not broken down. there is more avaliable Ach, so muscle twitch can remain without change in amplitude. It relieves the patient of MG symptoms, but only temporarily.
