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)