Nervous System Vertebrates Vs Invertebrates Physical Education Essay

The nervous system is an organ system composed of a net of cells called neurons in the brain that regulates the animal’s action and sends signals between from the brain to the rest of the body (Northcutt, 2000) . Vertebrates are part of the subphylum of Vertebrata. These animals possesses internal skeleton made of bone (spinal cord) (Northcutt, 2000). Invertebrates are animals without a backbone. A vertebrate nervous is by far more complex than that of an invertebrate. These two phyla of animals are as different as day and light but still possess similar characteristics pasted down by the early animals (invertebrates). The comparison of the nervous systems between these two phyla of animals can be done more intensely with the comparison of mammals and insects.

Invertebrates are animals that lack a spinal cord (backbone). Invertebrates include animals such as insects, worms, jellyfish, and spiders ect… Invertebrates’ nervous system exhibit cephalization which is an evolutionary process where nervous tissue and sensory structures are concentrated in the front end of the nerve cord (Freeman, 2005). Among the noncoelomate invertebrates, sponges are the only major phylum that lack nerves. The simplest nervous systems occur among cnidarians, in which all neurons are similar and linked to one another in a web, or nerve net. There is no associative activity, no control of complex actions, and little coordination.

The simplest animals with associative activity in the nervous system are the free-living flatworms, phylum Platyhelminthes. Running down the bodies of these flatworms are two nerve cords, from which peripheral nerves extend outward to the muscles of the body. The two nerves cords converge at the front end of the body, forming an enlarged mass of nervous tissues that also contains interneuron with synapses connecting neurons to one another. This primitive “brain” is a rudimentary central nervous system and permits a far more complex control of muscular responses than is possible in cnidarians (Freeman, 2005).

All of the consecutive evolutionary transformation in nervous systems can be considered as a series of amplification on the characteristics already present in flatworms. For example, among coelomate invertebrates, earthworms exhibit a central nervous system that is connected to all other parts of the body by peripheral nerves.

As animals became more complex, so did their nervous systems. The complex nervous system of vertebrate animals has a long evolutionary history. The origin and development of the vertebrate nervous system begins with the primitive brain of vertebrates (Northcutt, 2000). The lampreys and hagfishes are the most primitive living vertebrates. Their brains reveal the most basic and simple vertebrate brain pattern. The myelin sheath on the nerve fibers found in all higher vertebrates is not present in these animals (Northcutt, 2000) . They lack the complexity of the nervous connection of all the higher vertebrates. Although the early vertebrate brain was small it already had three divisions that characterize the brains of all contemporary vertebrates (Webster, 2004) . The Hindbrain or rhombencephalon is composed of the cerebellum and the medulla oblongata (passes thru the spinal cord) which regulate the animal’s balance and movement (Nathan, 1997). The midbrain or mesencephalon is situated behind the thalamus and regulate vision (Nathan, 1997). The forebrain or prosencephalon is the front part of the brain which deals with smell (Nathan, 1997).

The nervous system is the most complex system in the body. The nervous system is divided into the central nervous system and the peripheral nervous system. The brain and the spinal cord form the central nervous system of vertebrates while sensory and motor form the peripheral nervous system.

The central nervous system is the largest and the most complex part of the nervous system. It is the body’s command center. It works to align the activities of all the body parts. The central nervous system composed the brain and spinal cord is cavernous and alveolate and positioned above dorsal to the gut (Webster, 2004). The spinal cord is uniformly gray in color with the nerve cell bodies lying close to the central canal (Webster, 2004). It is responsible for receiving and interpreting signals from the peripheral nervous system and also sends out signals to it, either consciously or unconsciously. The peripheral nervous system (PNS) in vertebrates is divided into the somatic and the autonomic nervous system. Motor neurons that stimulate skeletal muscles to contract make up the somatic nervous system; those that regulate the activity of the smooth muscles, cardiac muscle, and glands compose the autonomic nervous system. The autonomic nervous system is further broken down into the sympathetic and parasympathetic divisions. These divisions counterbalance each other in the regulation of many organ systems.

The honey bee is an invertebrate (insect) which normally have a primitive nervous system (Blankenship and Houck, 2002). However the honey bee possesses a very developed nerve and sensory system. Their Central Nervous System is divided into a brain (in the head) which is located above the pharynx, and a ventral nerve cord (accumulation of nerves in the abdomen) stretching from the head to end of abdomen (Blankenship and Houck, 2002). The brain is the seat of all the mental faculties of a bee. The brain is the bee’s sensory center. A decapitated bee is deprived of any sensory stimuli and the ability to eat (Blankenship and Houck, 2002). However the bee still retains its motor competence which means it can still walk, fly and sting (Blankenship and Houck, 2002). Sensory information travels from the eyes and antennae which transmits the nervous impulses to the motor centers of the ventral nerve cord.

Just like Vertebrates, Invertebrate’s neurons work using an electrochemical process. The honey bee nervous system is similar to that of vertebrates Although Invertebrates nervous system functions basically the same way as that of vertebrates there structure are completely different.

The Honey Bee nervous system is less advanced and complex than humans. Their spineless feature is the main difference between theirs and Humans nervous system. The Honey Bee ‘s nervous system is distributed throughout the body, whereas Humans that have a spine have a central nervous system and a peripheral nervous system, or in other words a central control system and a sensory system. The division of Human’s nervous system into the central and peripheral nervous enhances the complexity of their system. The central nervous system (the brain and spinal cord), is hollow and situated above (dorsal to) the gut (Horstadius, 2006). This contrasts with the solid ventral nerve cord of the Honey Bee (Horstadius, 2006). Humans possess a highly developed and larger brain which gives them a more profound intelligence and thinking. With the help of specialized nerve fibers, they can react very quickly to changes in their surroundings, giving them a competitive edge. However unlike other invertebrate the Honey Bee brain is encased in a definite head just like humans.

The nervous systems in animals range from simple nerve nets to paired nerve cords with primitive brains to elaborate brains and sensory systems. Virtually all members of the animal kingdom have at least a rudimentary nervous system. Invertebrate animals show varying degrees of complexity in their nervous systems, but it is in the vertebrate that the system reaches its greatest complexity. The difference between the human and honey bee nervous system is greater than the similarities.

Work Cited

R. Glenn Northcutt, Charles Noback, Ruben Adler, Bengt Kallen, Leon S. Stone, (2000) “Nervous system (vertebrate)”, in [email protected], http://www.accessscience.com, DOI 10.1036/1097-8542.449300

James E. Blankenship, Becky Houck, (2002), “Nervous system (invertebrate)”, in [email protected], http://www.accessscience.com, DOI 10.1036/1097-8542.449210

Walter J. Freeman, (2005), “Brain”, in [email protected], http://www.accessscience.com, DOI 10.1036/1097-8542.093200

Douglas B. Webster, (2004) “Spinal cord”, in [email protected], http://www.accessscience.com, DOI 10.1036/1097-8542.645900

Sven Horstadius, (2006), “Neural crest”, in [email protected], http://www.accessscience.com, DOI 10.1036/1097-8542.449700

Peter Nathan, (1997), The Nervous system, London : Whurr Publishers, 1997