Chapter 41: The Nervous System

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Chapter 41 The Nervous System

• Matt Burgner
• Period 1
• Mrs. Walters

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Nervous system

• Communication among cells depends on chemical
  stimuli
• Cell converts stimuli into electrochemical
  symbols that are rapidly conducted through neuron
  itself
• Nervous system controls movement and reflexes of
  organisms

www.agen.ufl.edu/.../ lect/lect_20/nervsys.gif
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Evolution of Nervous system

• As species become larger, the need for a nervous
  system is greatened.

www.ama-assn.org/ ama/pub/category/7172.html
www.student.loretto.org/ zoology/chp2030/Flat...
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Organization of the Vertibrate Nervous System

• Primary central (brain and spinal cord)
• Secondary Peripheral Nervous system (the sensory
  and motor pathways that carry info. To and from
  CNS (central nervous system for rest of
  presentation)

http//environmentalet.hypermart.net/psy111/orgns.
gif
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Organization contd

• Motor
• Somatic (to skeletal muscles)
• Autonomic (to smooth muscles cardiac, muscle,
  glands)
• Autonomic sympathetic and parasympathetic

http//www.heartcareassociates.info/publications.a
sp
http//environmentalet.hypermart.net/psy111/orgns.
gif
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Neurons

• Functional unit neuron
• Surrouned by glia cells in CNS
• Peripheral surrounded by Schwann cells
• In clusters called ganglia in PNS and in CNS
  called Nuclei
• Axons (nerve fibers) in bundles called tracts
  (CNS) Nerves (PNS)
• Enveloped in insulating myelin cheaths

http//www.epub.org.br/cm/n14/mente/chaos.html
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The Central Nervous Syst.

• Links brain and rest of the body through spinal
  cord
• Spinal cord separated into inner gray matter and
  outer white matter
• Gray matter- mostly inter-neurons, the cell
  bodies of motor neurons and neurogla
• White matter- tracts of axons

http//www.nfra.net/CentSys.htm
Link to more on central nervous system
http//www.unm.edu/jimmy/spinal_notes.htm
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The CNS contd

• Contains brain stem
• Conducts signals to and from spinal cord and also
  cell bodies of the neurons who innervate the
  muscles and glands of the head
• Also control respiration and blood pressure

http//www.cis.rit.edu/htbooks/mri/chap-14/chap-14
-r.htm
http//137.222.110.150/calnet/Cereb/page2.htm
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Peripheral Nervous syst.

• Both motor and sensory (motormovement)(sensory
  carries signal)
• Bundle together called cranial nerves (directly
  to brain) and spinal nerves (connect to spinal
  cord)
• There is 31 pairs in humans
• Separate near spinal cord sensory neurons are in
  dorsal root ganglia, sensory feed into dorsal
  side of spinal cord
• Fibers from motor neurons emerge from spinal
  cordo on ventrical side

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PNS contd

• Four types
• Reflex arcs (sensory to central then back to
  motor)
• Ex hand touches stove, your hand will
  automatically withdraw from the stove

http//www.biosci.uga.edu/almanac/archive/1998/win
ter_98/cb_380/anatomy/Two-neuron-reflex.JPG
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Somatic vs. Autonomic

• Autonomic involuntary Nervous system
• Consist of nerves that control cardiac muscle,
  glands and smooth muscle
• Smooth muscle found in walls of blood vessels, in
  digestive, respiration, excretory and
  reproductive system
• People that do yoga can control their rates of
  heartbeat and contractions of some smooth muscle

• Somaticvoluntary Nervous system
• Controls skeletal muscles, able to move at will
• Skeletal musclces do move involuntary as well
• It is called a reflex

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Somatic vs. Autonomic contd

• Cell bodies of somatic motor cells in CNS w/o
  interruption to skeletal muscles
• Autonomic cell bodies from CNS do not go to place
  affected. Synapse w/ motor cells of somatic cells
• Sensory input comes from neurons examining
  environmental changes

http//starklab.slu.edu/neuro/Motor.htm
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Sympathetic vs. Parasympathetic

• Autonomic separated into two divisions
  sympathetic and parasympathetic
• Differences 1) axon of symp. originate
  in thoracic (chest) and lumbar (lower back)
  region of the spinal cord axons of psymp.
  emerges from cranial and sacral (tail) region

http//www.ortho-u.net/o11/27.htm
http//www.bartleby.com/107/22.html
http//www.courses.vcu.edu/DANC291-003/unit_5.htm
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Sympathetic vs. Parasympathetic

• Preganglionic both release acetylcholine as their
  neurotransmitters, post ganglionic utilize
  different neurotransmitters
• Sympathetic- noradrenaline
• Parasympathetic- Acetylcoline

http//www.buy-phentermine.biz/neurotransmitters.h
tml
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Pre and Post Ganglionic

• Neurons whose axons emerge from CNS and terminate
  in ganglia preganglionic
• Go to ganglia and terminate in effectors known as
  postganglionic
• Sympathetic Preganglionic axonsshort, post long
• Parasympathetic Preganglionic axons long and
  post short

http//www.arts.uwaterloo.ca/bfleming/psych261/le
c5se26.htm
Link to go look at pre and post gagnlionic nerves
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Homeostatic regulation
http//gcg.tran.wau.nl/haaker/s-drive/practicum/a
drenaline.htm

• Psymp. Involved primarily in restractive
  activities of body it slows down heartbeat,
  increases movement of smooth muscles
• Ex eating a heavy meal or following orgasm
• Symp. Attributes for preparing the body for
  action
• Causes adrenaline to pour out, fight or flight

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The Nerve Impulse

• Nerve conduction associated w/ electric phenomena
• Difference in amount of electrical change between
  and - electrical potential (in milivolts)
• Interior of membrane negatively charged is called
  resting potential
• When stimulated becomes positively charged and
  called action potential
• Action potential along the membrane nerve impulse

http//library.thinkquest.org/2935/Natures_Best/Na
t_Best_High_Level/Nervous_Net_pages/Nervous_title.
html
Link to Nervous system
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Ionic Basis of Action Potential

• Potassium ions (K) and sodium ions (Na)
  critical concentration differences
• Proteins that open and close ion channels called
  gated
• Resting state Na channels are closed and K are
  open at equilibrium the cell is negatively
  charged
• When stimulated the Na rush in giving the cell a
  more positive charge than outside action
  potential

http//users.rcn.com/jkimball.ma.ultranet/BiologyP
ages/E/ExcitableCells.html
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Propagation of an Impulse

• Reversal in polarity continues to move along the
  axon. This depolarization opens Na channels,
  said to be voltage-gated, and allows Na to rush
  in
• As the Na comes in, adjacent to that depolarizes
  so it opens its Na channels
• Only in one direction

http//cal.vet.upenn.edu/saortho/chapter_65/65mast
.htm
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Role of Myelin Sheath

• Most importatn feature is that it is interrupted
  at regular intervals by openings or nodes
• At nodes allows K and Na to come in and out of
  axon

http//www.mtsinai.on.ca/EBFFRC/MS/default.htm
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The Synapse

• A neuron junction, gap between 2 neurons
• In electrical synapse, nerve impulse goes from 1
  to the other
• Chemical synapse (neurons dont touch)
• 20 nanometer gap called synaptic cleft
• Neurotransmitters packaged in vesicles at axon
  terminal and are stored
• When action potential comes Ca ions flow in axon
  so vesicles get pushed out, a form of
  exocytosis into synaptic cleft

http//ifcsun1.ifisiol.unam.mx/Brain/synap.htm
http//ifcsun1.ifisiol.unam.mx/Brain/synap.htm
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The synapse continued

• Neurotransmitters picked up by receptors of the
  post-sympathetic cell which may or may not
  trigger a nerve impulse
• Some are removed or destroyed, control of nervous
  system NTs can be recycled too

http//www.driesen.com/neurotransmitter_processes.
htm
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Neurotransmitters

• Many types notably dopamine, serotonin, and
  gama-aminobutyric acid (GABA)
• Lack of dopanime Parkinsons disease

http//www.crocker.k12.mo.us/teacher/abran5b.html