BIO 3303 Lecture Notes - Lecture 12: Axon Hillock, Sea Slug, Efferent Nerve Fiber
15 Mar 2018
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Na+ channel opens, na+ other door closes, k+ opens. Convergence, multiple sensory afferent to one efferent neuron, maybe need 3 for threshold. Eg construction noises on campus, stimulus no longer elicits same magnitude of response. Interneurons already exist but need to be turned on, start making neurotransmitter so it"s very close to threshold. Eg sensitized by a big scary noise at night. Not only serotonin, but most often it is, and in this example with the slug it is. Trend toward cephalization in elaboration of neural networks. Radially symmetric animals like cnidarians, jellyfish, hydra, anemones. Each can be a sensory, interneuron or efferent. No obvious integrating centres but have complex behaviour (eg anemone somersault, swimming) Clusters of neuronal cells, small independent integrating centres. Ganglia at the head where there"s lots of sensory to integrate. Connections between ganglia are very fast, axons elongating, start of directionality. Does all the integration of all the sensory.
