Compare (consider both similarities and differences), contrast, and give the physiological significance of the following pairs of terms:  electrical and chemical synapses absolute refractory period vs. relative refractory period

Comparison between electrical and chemical synapses are:

1. Electrical synapses are direct connections between neurons, found in retina, olfactory bulb, cerebral cortex whereas Chemical synapses are small gaps present between neurons where chemicals are set to diffuse, found in synaptic junctions in the body.
2. Electrical synapses are found in higher vertebrates whereas Chemical synapses are found in lower vertebrates and invertebrates.
3. In case of electrical synapses, one way transmission of signals take place whereas in case of chemical synapses, two way transmission of signals take place.
4. Impulse is transmitted through gap junctions in electrical synapses whereas for transmission of impulse in chemical synapses, neurotransmitters are used.
5. Both electrical and chemical synapses are made of synaptic clefts.

Physiological significance of electrical synapses are:

1. Gap junction pores are large so that molecules such as ATP are allowed to diffuse between the cells and also allows electrical synapses to coordinate the intracellular signaling and metabolism of coupled neurons.
2. Fast transmission. Since passive current flow across the gap junction occurs instantly, thus communication is possible without the delay that is characteristic of chemical synapses.

Physiological significance of chemical synapses are:

1. Human brain has large number of chemical synapses. 
2. Helps in biological computations that underlie perception and thought.
3. Allows neurons that are present in central nervous system in formation of interconnected neural circuits.