IMG_NEW_0014

IMG_NEW_0014 - resPonses). PNS: several components that are...

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b Evolutionary trends in nervous system design I tt't.tt 'i"HHm"e diffuse nerve net or interconnected nerve cells' Fig' 49'2 (al ' in more comPlex animals axons of multiPle nerve cells are bundled together forming nerves (b-h) ' cephalisation = ctffiing of neurons at anterior (head) end = "brain" (c) Evolutionary trends in nervous system design ll (Fig. as.2) ' small brain and longitudinal nerve cords = simplest cpntral nervous system (CNS) . in vertebrates, brain + spinal cord = CNS; nerves + ganglia = PeriPheral nervous sYstem (PNS) see Fig' 49'4 . slow, *rffirfl have simprer NS than active, prq1filf%ffi (s) Most bilaterally symmetricaianimals have a PNS and CNS (brain plus one or more nerve chords). Remember: nervoqi;yttsm complexity has much to Oo witnifrffiy' habitat and natural history. E.g. Why should a sessile clam have much cePhalization? 2l brain (integratlon or comPrex
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Unformatted text preview: resPonses). PNS: several components that are different in organization & function cranial nerves and sPinal nerves' The motor (efferent)division is divided in the autonomic and somatic nervous systems' a?-The autonomlc system is 'involuntary' and conveys signals that regulate the internal environment, e.g. cardiac muscle rn" ,o#tic nervous system sends signals to skeletal muscle,'voluntaq/ mainly in response to external stimuli. Parasympathetic: e n ha nces activiti es wh ich ga i n and conserve E: e.g. slows heart, increase activity of intestines Sympathetic: E expenditures and prepare individual for action: e.g. accelerates heart, dilat:e gupils' decrease activity of gut- 4q' wv' 9. Central nervous system has a high degree of cePhalization Regional speation in motor and surface area devoted t rb...
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