The Comparison of Nervous Systems in Humans, Cnidarians, Flatworms, and Annelids

1671 WordsApr 21, 20137 Pages
Biology II 30 March 2012 The Comparison of Nervous Systems in Humans, Cnidarians, Flatworms, and Annelids The nervous system is one of the most important organ systems in the body. It is in charge of all of the things that happen within the body. Being responsible for receiving sensory input from internal and external stimuli, integrating and processing information, and generating output, it would be hard to survive without a nervous system; however, there are different types of nervous systems in various organisms. Humans, cnidarians, flatworms, and annelids all have very diverse nervous systems. There are similarities and differences in each of these beings. Of the fours organisms listed, the nervous systems in humans in the most…show more content…
The brain then will send motor neurons to the correct affecter in muscles and glands (Understanding the Basic Anatomy and Physiology of the Human Body). The nervous system of cnidarians is called a nerve net. This is the simplest nervous system found in any organism (The Nervous System: Organization). It is called a nerve net because there is no center point of the system, and the nerve cells are spread throughout the body in a net like system (The Nervous System: Organization). Within the nerve net of cnidarians you will find sensory neurons, motor neurons, and intermediate neurons. The intermediate neurons carry messages from the sensory neurons to the motor neurons, and some of these could possibly be organized into ganglia. In the body there are two layers of cells: nerve cells and body cells. The nerve cells help to coordinate the actions of some body cells that are within the net. For instance, if the body is touched, the whole body will react (Cnidarians). Flatworms, which have bilateral symmetry, have a nervous system that is arranged like a ladder that includes two nerve cords and a brain at the head end. The nerve cords, which are a simple peripheral nervous system, have commissural nerve fibers that make the rungs of the ladder. The brain, which is the central nervous system, is not truly a brain, but is more a collection of two ganglia that acts like one. The ganglia integrate signals from the

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