BIOL 1107 Lecture Notes - Lecture 14: Neuroglia, Midbrain, Dorsal Root Of Spinal Nerve
8 Dec 2017
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All animals have a nervous system except for sponges. Cnidarians (sea jellies, hydras, anemones: neurons connect to each other in a network, activation of neurons in one area leads to activation of all or most neurons. Slightly more complicated: nerve ring around mouth connected to larger radial nerves extending to arms, mouth and arms operate independently. Planaria: nerve cords extend length of animal connected by transverse nerves. Collection of neurons in head form cerebral ganglia. Perform basic integration of sensory input and motor output. Same basic structure: more neurons, ventral nerve cords have ganglia in each segment, rudimentary brain. Trend toward cephalization - increasingly complex brain in the head. Brain has several subdivisions with separate functions: advanced mollusks. Brains with well-developed subdivisions: all chordates have a cns (brain and spinal cord) and pns, organization shows similarities to segmented nervous system of. Entire nervous system develops from neural tube in embryo: hindbrain.
