Nervous system of invertebrates
It is said that invertebrates’ nervous system is completely different in comparison to vertebrates, however, the studies and data do not support this claim. (Murphey, 1986)
Observed conserved neuronal conjunctions in the invertebrates’ brain are useful for rebuilding the phylogenetic pathways. As an example, the study of midbrain and visual lobes of insects and crabs show that they are sister groups, that their optic chiasma and visual neurons are homoplastic. In a nematode, perception and identification of remarkable portion of ions takes place in the hemispheres and brain system. The lateralization is also seen which makes the worm able to distinguish different ions. In fruit flies (parasites) (insects) the developed brain parts have important role in their long-term memory. (Frasnelli 2013)
Invertebrates have varying degrees of brain analysis, such as escape and defense, and a variety of responses to the environment however; they do not have all the capabilities of vertebrates. (Broom 2013) Some invertebrates have significant brain systems; they have analogs with the brain cortex, although they differ widely in vertebrate brains. (Elwood 2011) Arthropods which have a number of specific neurons. In general, their nervous system differs substantially from that of the vertebrate nervous system but they also have many similarities. Their special nerve cells are present in certain parts of their body and from their accumulation ganglion is created. They also have a dorsal nerve cord. (Smarandache-Wellmann 2016)
The octopus’s nervous system is very complex. Its neurons are even more than some mammals such as rat. In the octopus brain, there are even visual lobes. (Hochner 2010) The complexity of the octopus’s nervous system extends to the arms. Octopus arms process the octopus’s sensory function to the environment. The nervous system of the arms consists of axial bumps in the nerve cord (ANC) . The ANC is composed of two axonal and cerebrobrachial tracts (CBT) and running dorsally along the ANC, and a medullary cord (MC) segments below. MC contains a cell cortex for neuronal monopolar cells. The CBT contains axons that transmit high-energy signals and information to the central nervous system and ganglia and makes communication. The octopus has more than 40,000,000 neurons per arm. A great deal of the information is processed in the neuronal system of the arms So axons control specific areas of the arms. (Zullo, Eichenstein et al. 2019)