NRSC 335 Lecture Notes - Lecture 4: Symmetry In Biology, Spinal Nerve, Cerebral Cortex
5 Feb 2017
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S ingle cell organisms have functions that nervous systems would accomplish: nervous systems differ (or ability to transduce info from outside. S ensory and locomotion world) widely across species. E xample: invertebrates (mollusca) vs vertebrates (c hordata) S low unmyelinated axons: g iant axons, monopolar neurons (limited arborization) E volution has retained some nervous system properties across phyla (neurons, action potentials: homology. In other cases, evolution has produced different solutions to similar problems (vision: nervous systems share many similarities, analogy, vertebrate brains. S egmentation (spinal nerve pairs: development from a neural tube, bilateral symmetry, hierarchical control (brain controls spinal cord) Localization of function: e laboration of existing structures -> evolution, not addition! Forebrain structures tend to get bigger: mammals have a big cerebral cortex, development of rostral structures -> evolution. E ncephalization factor: distance above/below the trend line: humans have the highest encephalization factor.
