BIOL 1000 Lecture Notes - Lecture 22: Cnidaria, Axon, Nerve Net
15 Sep 2016
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All animals have a nervous system except for sponges: nerve net. Neurons connect to each other in a network. Activation of neurons in one area leads to activation of all or most neurons. Cnidaria and ctenophora: neurons in this system connect to each other in a network called a nerve net. When one neuron is activated, all other neurons in the network as also activated. Platyhelminthes: groups of neurons called ganglia are present in each segment of these organisms. Annelida: two nerve cords extend length of animal connected by transverse nerves. A collection of neurons in the head form the cerebral ganglia that performs basic integration of sensory input and motor output: ventral nerve cords have ganglia in each segment, rudimentary brain. Arthropoda: the brains of these organisms have several subdivisions, each with a separate function. Groups of neurons called ganglia are present in each segment. Chordata: the brains of these organisms have many subdivisions, each with separate functions.
