Nervous System

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Class Topics
Title Anat Phys 11/16/06
Objectives

• To learn about the nervous system.

• Nervous System
• Review
• "Honor is like an island, rugged and without a
  beach once we have left it, we can never
  return."
• Nicholas Boileau Despreaux

Thursday, March 31, 2016 1140 PM
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Class Assignments
By When
What

• Read 240-270 11/16/06
• Nervous system test 11/20/06
• Due this class period
• Due next class period
• Due in the future

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Review
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Animations

• Action potential
• http//www.blackwellpublishing.com/matthews/action
  p.html
• Channel gating
• http//www.blackwellpublishing.com/matthews/channe
  l.html

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Saltatory Conduction

• Movement of action potential along myelinated
  fibers
• Impulse moves from node of Ranvier to node of
  Ranvier
• Moves much faster due to the fact that the
  impulse jumps over the myelinated areas
• Can jump up to 3 mm sections
• 130 m per second compared to 10 m per second for
  unmyelinated

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Problems

• Speed Distance/time
• Myelinated fibers can carry an action potential
  150 m/s
• Unmyelinated fibers can carry an action potential
  10 m/s
• How long does it take for an action potential to
  travel from the toe to the brain of a 1.8 m
  individual for each fiber?

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All-none-response

• If a stimulus causes an action potential it will
  be sent the length of the neuron at maximum speed
• threshold stimulus
• minimum stimulus needed to send an action
  potential
• Summation
• a series of subthreshold stimuli that eventually
  add up to a stimulus

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Synapse (a coming together)

• Junction between neurons
• nerve impulse must move from one neuron to the
  other
• always from presynaptic neuron to postsynaptic
  neuron

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Anatomy of a synapse

• Presynaptic neuron
• Synaptic end bulb
• Synaptic vesicles
• Contain neurotransmitters
• Chemicals released to relay impulse
• Postsynaptic neuron
• Concave surface
• Synaptic cleft
• Space between the two neurons

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Physiology of a synapse

• Nerve impulse enters synaptic end bulb
• Ca2 ions enter bulb from outside
• Synaptic vesicles fuse with cell membrane
• Exocytosis of neurotransmitters
• Chemicals diffuse between cells
• Contact postsynaptic neuron (receptor protein)
• Can excite neuron or inhibit neuron
• Depends on what neurotransmitter is released
• Excited neurons open Na ion channels
• Neurotransmitter is immediately inactivated
• By enzymes (ex. acetylcholinesterase)

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Neurotransmitters

• Acetylcholine (Ach)
• neuromuscular junction
• prominent in PNS
• Dopamine
• brain processes that control movement, emotional
  response, and ability to experience pleasure and
  pain.
• Norepinephrine Epinephrine
• also called adrenaline
• sympathetic branch of autonomic system

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Neurotransmitters

• Serotonin
• found in brain
• Melatonin
• brain - used in sleep
• Endorphins
• inhibit the transfer of pain impulses
• opiates bond to same receptors
• morphine, heroin, codeine

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Neurotransmitter actions

• Inhibitory
• hyperpolarizes the cell membrane
• below resting potential
• unable to conduct an action potential
• Excitatory
• depolarizes the cell membrane
• action potential is sent to next neuron

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Good Links

• http//www.zerobio.com/central/actionpotential.htm
  
• http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
  BioBookNERV.html
• http//emile-21.com/VRML/membPotMain.html
• http//www.accessexcellence.org/RC/VL/GG/ecb/propa
  gation_action_potential.html
• http//www.ship.edu/cgboeree/theneuron.html
• http//www.dls.ym.edu.tw/ol_biology2/ultranet/Exci
  tableCells.html
• http//web.lemoyne.edu/hevern/psy340/lectures/psy
  340.02.2a.neur.impulse.html
• http//www.ucl.ac.uk/sjjgsca/NerveRestingPot.html
  
• http//www.columbia.edu/cu/psychology/courses/1010
  /mangels/neuro/neurosignaling/neurosignaling.html
• http//academic.kellogg.cc.mi.us/vrugginkf/biol202
  /bio202obj/nervous_system.htm
• http//www.cptc.ctc.edu/library/Bio2011820Lectur
  e20Notes20Rev200105.htm
• http//trc.ucdavis.edu/biosci10v/bis10v/week10/06p
  otential.html