What is the all or non principle of muscle contraction?

Question

its for an assignment. i think it has something to do with isotonic contractions (concentric, eccentric)......yes /no??

Answer 1

my take on this question is....

smooth muscle (aka skeletal muscle/cardiac muscle) have things called "gap junctions" between the cells.  These gap junctions have ion-gated channels that allow an action potential to cross.  Therefore, you cannot have half a muscle contraction and it is an all or nothing type response.

Answer 2

The all or nothing principle has nothing to do with the type of contrationa muscle makes. It states that a muscle will either contract completely or not at all.  there needs to be enough Acetylcholine neurotransmitter to reach the threshold stimulus or else the muscle will not be stimulated and therefore will not contract.

Answer 3

firstly, lets assume that we are talking about skeletal voluntary muscle.  You send an impulse via nerve to the motor endplate, where the neurons meets up with the skeletal muscle fiber.  If this excitation (via release of ACh) is enough to cross the threshold in the postsynaptic cell (the motor fiber).   If this stimuli is strong enough, it will cause a depolarization of the muscle, which causes the sarcoplasmic reticulum to release calcium and cause a series of reactions within the muscle to make it contract.  Thusly, if a muscle fiber is activated with a strong enough impulse, it will contract.  This contraction is the same strength regardless of the intensity of the neuronal signaling (after it has crossed the threshold for excitation), so the fiber contracts.  Your muscle fibers only have one strength, on or off.  To vary your lifting, say a heavy object versus a lighter one, you recruit fewer muscle fiber bundles, rather than have all of the muscle fibers contract at  a lesser intensity.  they can't contract at a lesser intensity, so it is said to be all or none.  it has nothing to do with isotonic contractions.