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Lecture 1

BIOB34H3 Lecture 1: 22

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University of Toronto Scarborough
Biological Sciences
Blake Richards

12202015 OneNote Online Lecture 22: Motor Control (Chapter 19 Text Book Notes) Saturday, December 19, 2015 6:27 PM Neural Control of Skeletal Muscle Is the Basis of Animal Behavior A Major function of an animals nervous system is to generate its behavior. Ways in which the coordinated motor output of a nervous system produces behavior may be as simple as the withdrawal of a limb in response to a painful stimulus, or the tailflip escape of a crayfish, or as complex as the mating behavior of a stickleback fish or of a songbird. Invertebrate neural circuits involve fewer neurons than vertebrate circuits Although qualitatively similar, vertebrate circuits always include many more neurons than invertebrates do. Similar inconsistencies in neuron number occur in the central nervous system, with vertebrates having 104 to 105 times as many neurons as invertebrates. This difference leads to two generalizations about invertebrate and vertebrate neural circuits: In many cases an invertebrate neuron may be a uniquely identified neuronthat is, a neuron whose structure, location, electrical activity, or other properties are sufficiently distinctive that the neuron can be recognized and studied in every individual of a species. In contrast, nearly all vertebrate neurons cannot be uniquely identified, but can be recognized only as members of a population. Single individual neurons play functional roles in invertebrate circuits, whereas many neurons participate in a particular function in vertebrate neural circuits. For example, a single arthropod neuron may act as a command neuron, a neuron whose activity is sufficient to command a particular element of behavior. For vertebrates, a larger number of neurons nearly always act together to provide such a command function. We have already described two simple invertebrate neural circuits, each mediating a reflex, which we can define as a simple, graded response to a specific stimulus. Several neural circuits of invertebrates, whether reflexive as in these examples or centrally programmed, are well understood because of the relatively small number of neurons they have. Vertebrate spinal reflexes compensate for circumstances, as well as initiate movements Spinal reflexes are mediated by the neural circuits of the vertebrate spinal cord. https:adminmailutorontomy.sharepoint.compersonalhema_potluri_mail_utoronto_ca_layouts15WopiFrame.aspx?guestaccesstoken=0NXnTejTLtMMJI 118
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