Question

What is the advantage of alternating between all or none and graded signals in a neural pathway.?

Answer 1

Q).What is the advantage of alternating between all or none and graded signals in a neural pathway?
Answer: Neurons does not evolve to "all-or-nothing" over "graded signalling" but spikes added to the neurons. Once spiking neurons emerged, they may have many advantages for increasing neural signals. Neural pathway of human still highly depends on "graded" signal for some reasons-
1. long-distance signal transmission - The original reason for spikes to evolve for supporting of long-distance signal propagation to sensory neurons. Non spiking neurons can not transmit electrical signal more than 1 mm and they are slow and decayed during travelling. Whereas spiking neutrons can transmit electrical signal upto 1 m.
2. Fast and consistence synaptic signal transmission - Spikes provides more precious, fast signal to peripheral terminal of axons. Moreover spikes transmitted same electrical signal to the all axon terminal. This may be important for the synaptic plasticity.
3. Temporal precision - Spikes allow temporal information to be processed at a precise timescale.
For example auditory neurons emit spikes that are precisely times relative to auditory events at 10 milliseconds scale.
4. Introducing non-linearities - Spikes are a "decision" by the neuron, and decisions introduce "non-linearities" which may be required for computation.

Fig: Transmission of electrical signal in neural pathway

Dendrites Graded Potentials Action Potentials um Triggen Lone