CORE-UA 306 Lecture Notes - Lecture 9: Notochord, Encephalization, Invertebrate
24 Mar 2020
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Most organisms in present & past have survived without nervous system: neurons & muscles, brain cells & muscles evolved first. Allowed animals to move: nerve net, consists entirely of neurons. Receive sensory info: connect directly to other neurons that move muscles. No structure to resembles brain/spinal cord: bilateral symmetry, nervous system on one side of animal mirrors that on the other side. Similar to human nervous system: segmentation, body of animals consists of series of similar muscular segments, nervous system has similar repeating segments. Contain similar repeating nervous system segments of spinal cord: ganglia, clusters of neurons. In more recently evolved invertebrate: resemble primitive brains, function somewhat like command centers. Octopuses: spinal cord, relatively highly evolved chordates have single nervous system, pathway connects brain w/ sensory receptors & muscles. Chordates: animals that have both brain & spinal cord. Notochord: flexible rod that runs length of back.
