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Chapter 37 bio.docx - Chapter 37: Neurons and Nervous...

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Chapter 37: Neurons and Nervous Systems37.1 Evolution of the Nervous System-monitors internal and external conditions-homeostasisInvertebrate Nervous System OrganizationSimple multicellular- sponges – lack neurons- no nervous system.-can respond to environment-can communicate with each other-releases calcium or other ions-closure of osculum (central opening) in response to various stimuliHYDRAS: Cnidarians-Radial symmetry- nerve net (composed of neurons in contact w/ one another and with contractile cells in bodywall.- Jelly fish- 2 nerve nets- fast for major, slow for delicate movements.Planarians (Flatworms)1. Bilateral symmetry2.Ladder like system3.2 ventrally located lateral or longitudinal nerve cords (bundles of nerves)-extend from cerebral ganglia to posterior end of body.4.Transverse nerves- connect nerve cords and cerebral ganglia to eyespots.5.Cephalization – concentration of nervous tissue in the anterior or headregion.6.Ganglion-cluster of neuron cell bodies7.Anterior cerebral ganglia-receive sensory cells in the auricles.
8.2 lateral nerve cords-allow rapid transfer of info from the cerebral ganglia tothe posterior end.9.Transverse nerves between the nerve cords keep the movement of the twosides coordinated.10.Bilateral + cephalization = 2 significant organizational trendsAnnelids (Earthworms)& Anthropods (crab):-Complex-Brain-Ventral nerve cord has a ganglion in each segment.-Brain-receives sensory info.-Brain controls activity of ganglia and assorted nerves-Muscle activity of entire animal is coordinated.Cephalopods: Group of Molluscs: Squid-marked cephalization-anterior end has a well-defined brain and well-developed SENSE organs- Such as EYES- most intelligent invertebrates-highly social-collect, transport, assemble coconut shells for shelter use.Vertebrate Nervous System Organization:-more neurons than invertebrates-Brain controls nervous system.Vertebrate brain division:1.Hindbrain-ancient-regulates motor activity below level of consciousness.Example: lungs and heart function even during sleep.2.midbrain3.forebrain
-medulla oblongata- contains control centers for breathing and heart rate.-Cerebrum- coordination of motor activity (limb movement), posture, balancecentered here.Paired Sensory receptors: Gather information from environment:-anterior-1stencounters new environments.EyesEarsOlfactory structuresOptic lobes-midbrain-coordinating reflexes involving ears and eyes.Sense of smell- forebrainThalamus-receives sensory input from the midbrain and the hindbrain passes to cerebrum(anterior part of forebrain.)In the forebrain-hypothalamus is concerned with homeostasis.-Hypothalamus communicates with medulla oblongata and pituitary gland.Central Nervous System: CNS-brain-spinal cordPeripheral Nervous System: PNS-nerves and ganglia that lie outside the CNSThe Mammalian Nervous System:- forebrain = enlarged- outermost layer called neocortex-only in mammals-number of crevices and folds -increase surface area and numbers of connections betweenregions

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