Cnidarian Nervous System

Both of these groups have an external radial symmetry. Cnidarians have a single opening that acts as both mouth and anus and is generally surrounded by nematocyte-bearing tentacles (Steele and Technau; 2011).

An integration center in the reflex arc is a neuropathway that creates a reflex action to activating neurons to skip the spinal cord and protect your brain. The nerve cells can be categorized by their connections, structure, and neurotransmitters. The structural classification is depending on shape and size of the cell body, its dendritic tree, axon length, and the nature of the connections it makes. The neurons with one, two, or more than two neurites, are unipolar, bipolar, and multipolar respectively. Most of neurons in vertebrate nervous systems are multipolar, but there are significant exceptions. For illustration, bipolar neurons in the retina synapse with sensory neurons, and photoreceptors in the dorsal root ganglion are explained as pseudo-unipolar as they begin life as bipolar cells but their two neurites fuse. The unipolar neurons dominate in invertebrates. Collaterals a small side branch, as of a blood vessel or nerve. A neuronal pool is a group of interconnected neurons with specific functions. A pool may be diffuse, involving neurons in several regions of the brain, or localized, with neurons restricted to one specific location in the brain or spinal cord. However, the proper function of the circuit of the stretch reflex also relies on convergence and divergence. A single sensory has multiple branches that diverge and make synaptic connections with many individual motor neurons. Therefore, when the muscle contracts as a result of the neurologist’s tapper, it

The nervous system is made up of basic units called neurons. The main role of the neurons is to receive, integrate and transmit information throughout the body. There are some neuroglial cells found in nervous system aswell which provide support to the neurons by giving protection and nourishment Neurons have nerve processes that looks like finger like projections extended from the nerve cell body. They also contain axons and dendrites which enable them to transmit signals throughout the body. Normally, axon carry signals away from the cell body and dendrites carry signals toward the cell body according to Regina Bailey (2013). Neurons have three different shapes: bipolar, unipolar and multipolar where bipolar has two neuronal processes coming out of the cell body, unipolar has only one neuronal process coming out of the cell body and multipolar has many neuronal processes coming out of the cell body.

Neurons, nerve cells, have three basic parts: the cell body, dendrites, and axon. Neurons transmit signals to other nerve cells and throughout the body. They are simple components in the nervous system. The cell body includes the nucleus, which is the control center of the neuron. The dendrite branches off the cell body and receives information. The axon is attached to the cell body and sends information away from the cell body to other cells. When the axon goes through myelination, the axon part of the neuron becomes covered and insulated with fat cells, myelin sheath. This increases the speed and efficiency of information processing in the nervous system. Synapse are gaps between neurons, this is where connections between the axons and dendrites.

Neurons are information- processing units in the central nervous system that receive and transmit information. It is made up of an axon, dendrites and a cell body. The nucleus and cytoplasm are contained in the cell body. The axon starts from the cell body, dividing into smaller branches and then ends at the nerve terminals. The dendrites also branch from the cell body, receiving information from the other neurons. Axons from other neurons forms

* Interneurons or Pseudopolare (Spelling) cells form all the neural wiring within the CNS. These have two axons (instead of an axon and a dendrite). One axon communicates with the spinal cord; one with either the skin or muscle. These neurons have two processes. (Examples are dorsal root ganglia cells.)

Crayfish have an open circulatory system that pumps blood into a sinus-like hemocoel with the blood diffusing back to the circulatory system between cells. Blood is pumped by a heart into the sinuses, where tissues are surrounded by the blood. Adult crayfish possess a neurogenic heart which is modulated via inputs from the central nervous system, which act on the cardiac ganglion or directly on the myocardium. The crustacean cardiac ganglion (CG) is a cluster of neurons on the heart wall and produces rhythmic motor output for the heartbeat.

The Central nervous systems include the brain and spinal cord which transfers voluntary nerve impulse to skeletal muscles, skin, muscles, and glands.

The planarian is the first organism ever to have a fully productive synaptic nervous system (Mueller 2002). The synaptic nervous system contains nerve cells and it is when a neuron sends a signal, either electric or chemical, to another neuron and that signal contains information to be passed on or acted on (Mueller 2002). With the neural genes that are in planaria, they are able to build another fully function central nervous system, or CNS, without any of the old CNS (Cebria 2002). The CNS of a planarian is consisted of a brain in the head region and two ventral nerve cords that run down the body (Cerbria 2002).

The anatomical and functional divisions of the nervous system are divided into two categories the central nervous system (CNS) and the peripheral nervous system (PNS).

The central nervous system (CNS) is one of the two major parts of the nervous system. The CNS includes the brain, brain stem, and spinal cord, which together include the body's main control and data centre. Together with the peripheral nervous system (PNS), the CNS performs important functions.

Cnidarians were the first animals to have a mouth and a stomach, and as a result, they became the first active carnivorous predators (but not hunters, they catch prey that encounters their tentacles). Their mouths also act as their anus, as it expels waste after digestion.

Micronuclei are very carefully copied and moved so that each daughter cell gets one, but once division is complete usually new macronuclei will be produced from each cell's micronucleus, so careful shepherding of the macronucleus is not necessary. Sexual reproduction in ciliates is called conjugation. During conjugation, there is a transfer of genetic material via cell-to-cell contact by a bridge-like connection. The last system, which can be replaced by an organelle in the protozoa, is the nervous system. The function of the nervous system is to regulate and correlate body activities through conduction within and between individual cells or neurons, which eventually cause a response in some other system. In the paramecium, the macro and micronuclei are responsible for the functions of the nervous system. The nucleus is the control center of the cell and it contains the genetic info needed to copy to make new cells. Just as the brain, nerves and spinal cord would work; the micronucleus and macronucleus control the activities of the cell.

Despite its apparent lack of a central coordinating nervous system (no brain), Pycnopodia has a repertoire of sensory systems to locate and capture its prey. Its simple nervous system takes the form of a central ring, with radial nerves extending into each of its rays. Each ray is covered with thousands of tiny tubed feet that provide tactile information such as touch, temperature and body position. At the end of each ray are specialized tube feet filled with sensory cells that detect chemical cues and trigger sensations of taste and smell. Light sensory organs (red spots or eye spots) at the tip of each ray detect light and dark (direction, presence of large objects).

According to (Miller and Harley, 2016, p157) many cnidarians have two body forms, namely polyp and medusa. Polyps are usually sessile, they attach to substrates like rocks at their aboral end (the end furthest form the mouth). They have a cylindrical body shape, they do not possess gonads, while cnidarians are in