summation and tetanus

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I am learning myology and encountered 2 problems in tetanus and summation:

1. Unfused tetanus is just a continual summation of twitches if I am not mistaken. However, is it a MUST for summation / unfused tetanus to constantly increasing muscle tension from the photo (the graph) i.e. is this the definition?

Since we are in unfused tetanus when we hold something, and I can’t feel my biceps are constantly increasing in contraction / tension. (to my understanding, complete tetanus is when we are lifting up very heavy things only as it utilizes too much ATP) 

2. Can I say the muscles are in tetanus during contracting (lifting), and also in tetanus during constantly contracted state (keep the thing holding up) Since tetanus is just a frequent action of sliding filaments, which is common in both actions?

Also, during tetanus, I don’t need to shorten my muscles anymore (just holding something still), but myosin heads are still power-stroking to shorten the sarcomere/muscle, may I ask how to explain this?

Thank you very much.

[ahmet]

hi, this is presumably different than my prediction but I shall ask though.

are you asking about IPSP and EPSP?

as I remember summation was a different subject or I might have confused.

I think that tetanus might be also different in comparison all of these. 

because in tetanus , when I pay attention to description of the illness, the contractile case is (presumably) continuous. 

Thus action potentials are also continuous. 

according to my knowledge an action potential definitely exists or does not exist. But not between these two probabilities.(I mean its existence was certain)

on the other hand yes summation is also a case, but how,I do not remember very well

Edited October 18, 2020 by ahmet