PMI

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Class Topics
Title Anat Phys 11/10/06
Objectives

• To learn about the nervous system.

• PMI
• Review Skeletal System Test
• Nervous System
• Do what you can, with what you have, where you
  are.
• Theodore Roosevelt

Friday, November 06, 2009 231 AM
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Class Assignments
By When
What

• Read 240-270 11/16/06
• Nervous System Test 11/16/06
• Due this class period
• Due next class period
• Due in the future

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Neuroglia (Figure 9-2)

• Oligodendrocytes - CNS - used to speed up action
  potentials
• Schwann cells - found in PNS - aids in conduction
  of action potential and helps large neurons

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Neuron Parts

• Cell body
• cytoplasm, nucleus (with nucleolus), and
  organelles
• organelles including Nissl bodies (like RER) and
  lacking mitotic spindles
• Dendrites
• numerous
• conduct action potential towards cell body
• Axon
• single
• conduct action potential away from cell body

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Resting Membrane Potential

• Difference in charge on inside and outside of
  plasma membrane
• unequal distribution of ions
• Ion channels
• integral proteins that regulate ion movement in
  cell membrane
• not only in nerve cells

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Resting Membrane Potential (cont.)

• Ions most often found
• Na, K
• More sodium outside and potassium inside
• this imbalance is kept by the sodium- potassium
  pump
• uses energy to move the ions out/in the cell

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Sodium-Potassium Pump

• Forces Na out and K in the cell
• Creates a concentration gradient
• Na diffuses in and K diffuses out
• Pump doesnt work evenly
• 3 Na for every 2 K
• Creates an electrical gradient with more positive
  charges on the outside
• K diffuses more readily than Na
• Increases the electrical gradient

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• Inside the cell
• Negatively charged
• Lack of positive ions and presence of Cl- ions
• Cell is at resting potential
• Ready to go at stimulus
• POLARIZED
• Voltage
• About 70 mV (millivolts)
• Very small amount
• A D battery has about 1.5 volts

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Action Potential

• Excitability
• Ability to respond to a stimulus
• A stimulus changes the permeability of the cell
  membrane
• Na ions are able to diffuse through the cell
  membrane (sodium ion channels)
• DEPOLARIZED
• Changes the electrical potential from 70mV to
  30 mV
• Changes the charge inside the cell from negative
  to positive

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Action Potential (cont)

• REPOLARIZED
• Sodium ion channels close
• Potassium ion channels open
• Diffusion of K ions begins
• Cell is back at resting potential
• Very small amount of ions moved
• Time taken is minimal (milliseconds)

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Conduction of a nerve impulse

• The action potential moves quickly along a nerve
  fiber
• Propagated by the electrical gradient
• Figure 9-8 (p. 248)

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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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Animations

• Action potential
• http//www.blackwellscience.com/matthews/actionp.h
  tml
• Channel gating
• http//www.blackwellscience.com/matthews/channel.h
  tml
• Other links
• http//www.psych.ufl.edu/rowland/neurochem12/sld
  031.htm
• http//bio.bio.rpi.edu/HB/Universal20Files/Lectur
  es/L40NerveAP/L40NerveAP.html