2. Nervous system in different organisms I

 

Is it possible to notice that different animals have the same type of neural system?

 

No, neurological systems differ in structure and complexity across the animal kingdom.

 

Invertebrates are animals that do not have a backbone (spinal column). Invertebrates include animals with no spines, such as insects, worms, jellyfish, and spiders, to name a few examples.

 

Invertebrates are helpful creatures to study because their neural systems are similar to those of vertebrates. Neurons in all animals use an electrochemical process to function. The function of invertebrates' more simple nervous systems is easier to learn.

 

We should understand certain terminology and their meanings before learning about the neurological systems of various invertebrates.

 

Let us now look at the neurological systems of several species using examples.

In comparison to other species, Porifera members lack a separate neurological system. They are devoid of brain and nerve cells. For oxygen intake, waste disposal, and digestion, they rely on water intake and output.

 

 

The only multicellular animal without a nervous system is sponges. They lack nerve and sensory cells. However, outside of a sponge, touch or pressure causes a local contraction of the sponge's body.

Cnidarians have a nerve net, a diffuse, non-centralised nervous system; this is the first species in which the neurological system predominantly controls muscular contraction. Cnidarians are hence known as ‘net nerve animals.

 

  

A nerve net characterizes the neurological system of the hydra. A nerve net is a cluster of neurons that are distinct but “connected.” Synapse connects neuron to neuron. At the synapse within a neural net, communication between neurons can happen in both directions. The nerve network is concentrated around the mouth. Unlike higher animals, the hydra does not contain nerve cell bodies that are clustered together. There are no ganglia in this area. Specific cells in the hydra handle touch and chemical detection.

A disorganised network of neurons exists in Ctenophora, which is similar to Cnidaria.  Each comb plate contains the core network of interconnecting nerve cells. When a nerve pulse is activated in one of them, it is communicated to all cells that communicate with it via synapses. From there to others, it results in imprecise reactions, such as "pulsating" movements in living water when swimming. The most primitive type of nervous system is known as the diffuse nervous system.

 

 

Jellies don't have brains; instead, they have a nervous system made up of a network of connecting nerve cells (a nerve net). The entire body of jellyfish is enclosed in a nerve net. In addition, certain jellyfish feature rhopalia, which are specialised structures. There are receptors for in these rhopalia.

The statocyst makes touch with the cilium when the animal moves and its body is tilted.  A nerve's action potentials are activated when the cilium bends. This gives you the information to move their muscles.

Platyhelminthes have a ladder-like nervous system. It consists of the brain and two main longitudinal nerve cords connected by transverse commissures at regular intervals.

 

 

The neural system of the flatworm differs from that of the invertebrates described previously. It does have a nerve net; however, it is connected by long nerve cords. These cords are linked to the cerebral ganglia, which are found in the brain. Because of the nerves that connect the nerve cords, the central nervous system has been described as ladder-like.

Aschelminthes nervous system comprises a circumpharyngeal ring that gives rise to nerves, forwards, and backwards.

 

 

Roundworms have a primitive brain and a simple nervous system. Four nerves connect the top to the bottom of the body and run the length of it. The nerves spread out from a circular ring that serves as the brain at the animal's front end (the head area).