The all-or-none principle states that

Answer 1

In the simplest sense, the all-or-none principle of neuronal firing means that a neuron will either fire or it won't, there is no "half" firing. When a neuron receives excitatory input, its sodium (Na) channels open and allow Na to flow into the cell, depolarizing it (a resting neuron has a membrane potential of -65mV relative to extracellular fluid outside the cell). Once the neuron has been sufficiently excited above some threshold (typically -55mV), the cell fires, or sends an action potential down its axon to its terminal button. This electrical signal causes a series of chemical actions within the cell which results in neurotransmitters being released from the cell, to be picked up by other neurons. As long as a neuron reaches the threshold, it will always result in a large influx of Na ions, bringing the membrane potential to about +40mV, which will propagate down the cell as an action potential. If the neuron does not reach this threshold, it will not depolarize or create an action potential.

Answer 2

The all-or-none principle states that once a nerve impulse reaches a certain threshold, it will always trigger an action potential without any decrease in strength. In other words, a stimulus must be strong enough to initiate an action potential, and once it does, the action potential will be of the same magnitude regardless of the strength of the stimulus. This principle is fundamental to understanding how nerve cells communicate and transmit signals.

Answer 3

The all-or-none principle states that if a stimulus surpasses threshold amount, the action potential is the same. It was created by the American physiologist Henry P. Bowditch in 1871.