Outline of Functional Organization of Nervous System
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Overview of the Nervous System -
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One One of the the bod body’ y’s s home homeos osta tati tic c cont contrrol systems Contai Contains ns sensor sensors, s, integ integrat rating ing center centers, s, and output pathways or ore int inter erne neur uron ons s in in a path pathwa way y! greater number of interconnections and ability to integrate info "#$%&&&&&&
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Cnidarians -
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ost ost nerv nervous ous system systems s are are org organi anized zed into into ' functional divisions( o )*erent sensory o +ntegrating o *erent motor Cnid Cnidar aria ians ns are are an ecep cepti tion on o Nervous system is interconnected interconnected web or nerve net o Neurons are not specialized into di*. divisions Neurons carry )/ in both directions o Neurons not speci0c sensory#motor
Nervous Systems )cross )nimal 4roups -
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Nervous System 1erms( -
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2undle 2und les s of myel myelin inat ated ed and and unm unmye yeli lina nate ted d aons nclo nclosed sed in severa severall laye layers rs of connec connectiv tive e tissue o ndoneurium 5raps each aon /erineurium o 5raps a bundle 6fascicle7 of aon o pineurium 5raps the entire nerve ied Nerves o Contain both a*erent and e*erent neurons ach neuron is either a*erent 6sensory7 or e*erent 6motor7
2ila 2ilate tera rall lly y symm symmet etri rica call o 3ight and left side are mirror images Cephalization Sense organs are concentrated at o anterior end 4anglia o 4roups of neuronal cell bodies Nuclei 4roups of neuronal cell bodies o within the brain 2rain o +ntegrating center made up of clusters of nuclei 1racts o 2unds of many aons within the CNS Nerve o 2undle of many aons outside of CNS
Structure Structure of a Nerve
Ceph Cephal aliz izat atio ion n Occu Occurs rs in mos mostt anim animal als s o Cnidarians and echinoderms lac8 cephalization Orga Organi nism sms s wit with h mor more comp comple le nerv nervou ous s systems have more neurons ! more more synapses o +ncreased 9 of synapses allow for more integration of info, and more comple behaviors o emories are stored in synapses, a comple nervous system also allows for a greater potential for learning
F+4:3 %.$&&&&&&&&&&&&&& 1he ;ertebrate ;ertebrate CNS -
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spinal cord7 /art art of Nerv Nervou ous s sys syste tem m et eten ends ds to periphery of body o /NS ! nerves outside CNS
Cranial ? Spinal Nerves Cranial Nerves -
it it dir directl ectly y from from s8u s8ull @' pairs Some Some a*er a*eren ent, t, some some mot motor or,, som some e mi mied ed
Spinal Nerves -
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2ranch from spinal cord nter and eit between adAacent vertebrae Named based on region of vertebral column from which they emerge Cervical, thoracic, lumbar, sacral o and coccygeal ied nerves
4ray and 5hite atter -
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2rain and spinal cord contain " types of tissues( o 4ray atter 6neuronal cell bodies7 5hite atter 6tracts of aons and o myelin sheaths7 Spinal cord white matter on surface, gray matter inside Cerebral Corte gray matter on surface, white matter inside
CNS is isolated and protected -
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eninges o Bayers of C1 surrounding brain > Spinal Cord o 9 of meninges vary across taa 6mammals have ' 0shes have @7 Cerebral Spinal Fluid 6CSF7 o Fills spaces within the CNS and acts as shoc8 absorber 2lood D brain barrier o 1ight Aunctions in brain capillary endothelium limit passage of solutes from bloodstream into CSF
1he ;ertebrate 2rain -
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2rain is an etension of SC o Nerve tracts etend between brain and SC Several cavities called ventricles containing CSF ' regions o 3hombencephalon 6hindbrain7 3eEees and involuntary behaviors esencephalon 6midbrain7 o Coordination of sensory info 3elay center in mammals o /rosencephalon 6forebrain7 +ntegration of olfactory info with other senses
3egulate body temp, reproduction, eating, emotion Bearning and memory in mammals
2rain Size and orphology -
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ost groups of verts have the same maAor brain structures although these structure vary in relative size uch of variation due to body size 2irds and mammals have larger brains than other verts )nimals with large brains have more neurons o ore comple integ centers and more behaviors
/arts of ammalian 2rain -
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Cerebrum -
Outer layer is corte ivided into " cerebral hemispheres Beft side ! controls right side of o body o 3ight side ! controls left side of body GGneurons pass between the " sides via corpus callosum
Bocated at base of forebrain :nder thalamus o
Bimbic System
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) networ8 of connected structures that lie between the corte and the rest of the brain +nEuences emotions, motivation, memory Sometimes called the emotional brain +ncludes hypothalamus and other parts o )mygdala
)ggression and fear responses
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1opology of the Cerebral Corte -
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)ssociation )reas of Cerebrum
1halamus -
Barge grouping of gray matter above hypothalamus /art of the reticular formation 3eceives input from limbic system and all senses HC/1 olfaction 3elays info to corte )cts as a 0lter by bloc8ing some a*erent signals
pithalamus -
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ach region of corte corresponds to a speci0c part of the body that it controls by motor output or from which it receives sensory input Size of brain region devoted to di*. parts of body varies widely
Bocated above the thalamus
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3eceives info from adAacent areas and further process and integrate info Size of areas is larger in animals with more comple behaviors
/NS +;+SONS&&& F+4:3 J.@I&&&&&&&&&&&&&& )utonomic Nervous System D +nvoluntary Nervous System -
+nvolved in
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aintaining
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Cortical Bayers -
I Bayers i*ers in shape and density of neurons ;ariable number of connections within each layer
Cortical Bobes -
Bobes named according to their function or overlying bones of the s8ull
2alancing of sympathetic and parasympathetic systems ' mechanisms for regulating autonomic function o ual innervations ost organs receive input from bothsystems o )ntagonistic )ction One system stimulates while the other inhibits o 2asal 1one :nder resting conditions )utonomic neurons carry )/s F+4:3 %.@J&&&&&&&&&&&
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)ntagonistic )ction 1able %.'&&&&&&&&&&&&&&&&
Similarities in )utonomic /athways -
/athways contain " neurons in series o /reganglionic ay synapse with many postganglionic neurons and instrinsic neurons o /ostganglionic Neurotransmitter is released at e*ector organ from varicosities /re ? post neurons synapse with each other in the autonomic ganglia
)utonomic 3eEe )rcs -
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Somatic otor /athways D ;oluntary Nervous System -
i*erences in )utonomic /athways -
i*erences between the Sympathetic 6S7 and /arasympathetic 6/S7 branches o /reganglionic Cell body Bocations S D thoracic and lumbar regions of spinal cord /S D hind brain and sacral region of spinal cord o 4anglia location S D chain that runs close to spinal cord /S D close to e*ector Number of postganglionic neurons that synapse with a single preganglionic neuron
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ost autonomic changes occur via simple neural circuits that do not involve conscious centers of the brain Figure %.""&&&&&&&&&&&&&&&&&&
Control only @ type of e*ector s8eletal muscles :sually under conscious control o Cerebrum Cell bodies of motor neurons are located in the CNS onosynaptic o )ons are very long, and etend all the way muscle )on splits into a cluster of aon terminals at the NM release acetylcholine Synaptic cleft between motor neuron and the muscle is very narrow *ect on the muscle cell always ecitatory o g. Causes depolarization and contraction Some pathways are not under conscious control o g. Knee D Aer8 reEe
)nimal 2ehaviors -
Only Sympathetic +nnervation
' Categories 3eEe behaviors o +nvoluntary and simple o 3hythmic behaviors :nderlie locomotion, breathing and the fn of the heart o ;oluntary behaviors ost comple and diverse
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Some e*ectors receive only sympathetic innervations o )drenal medulla Collection of modi0ed postganglionic neurons o Sweat 4lands o )rrector pili muscles in the s8in o Kidneys o 2lood vessels o F+4:3 %."L
3eEe )rcs -
Sympathetic vs /arasympathetic Systems 1)2B %.$&&&&&&&&&&&&&& 3egulation of the )utonomic System Figure %."@&&&&&
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Beast comple integrated responses Can involve as few as " neurons 6monosynaptic7 or more than " 6polysynaptic7 Figure %."'&&&&
Convergence and ivergence in 3eEe )rcs -
Neurons in reEe arcs arranged in " ways(
Convergence )llows spatial summation o ivergence )mplify signals Some reEe arcs have both convergence and divergence F+4:3 %."$&&&&&&&&&&
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3hythmic 2ehaviors -
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4overned by pattern generators o 4roups of neurons that produce self D sustaining rhtymic depolarizations " types of pattern generators o /ace ma8er cell ) cell generates spontaneous depolarizations that control the 0ring of all the cells in the networ8
+nvertebrate Bearning and emory -
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mergent property of the networ8 3hythmic depolarization occurs because of the organization of neurons in the networ8
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Swimming 2ehavior of Beech
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+nvolves pattern generators and reEees o 2rainstem initiates the process and regulates speed o 1he spinal cord acts as a pattern generator o )*erent signals are sent bac8 to CNS o Corte is involved with guiding locomotion in comple envi o Cerebellum coordinates locomotion
;oluntary movements&&&&& F+4:3 %."% Bearning and emory -
ost animals can learn and form memories due to the plasticity of the nervous system o Bearning /rocess of ac=uiring new info o emory
+nvolves a secondary circuit Serotonin released by facilitating interneuron binds to receptors )ctivation of 4 proteins +nactivation of K channels, )/ duration Ca"> inEu neurotransmitter release by sensory neuron •
1etrapod Bocomotion -
5ell studied in sea slug 6)plysia7 channels Neurotransmitter release Sensitization o +ncrease in response to gentle stimulus after eposure to a strong stimulus Caused by changes in presynaptic o aon terminal
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3etention and retrieval of info /lasticity Changes in synaptic and neuronal function in response to stimuli
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echanism of Serotonin’s e*ects -
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emory in ammals -
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Bong term potentiation 6B1/7 o 3epetitive stimulation of hippocampal tissue leads to an
increase in the response of the postsynaptic neuron
