1. Do what you can, with what you have, where you are.
9/21/2018
Title: Anat & Phys 11/10/06
Objectives:
To learn about the nervous system.
Class Topics
PMI
Review Skeletal System Test
Nervous System
Do what you can, with what you have, where you are.
Theodore Roosevelt
Friday, September 21, :11 PM

2. Class Assignments Read 240-270 11/16/06 Nervous System Test 11/16/06
9/21/2018
Class Assignments
What
By When
Read /16/06
Nervous System Test 11/16/06
Due this class period
Due next class period
Due in the future

3. 9/21/2018
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

4. Neuron Parts Cell body Dendrites Axon
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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
Neuron Parts

5. 9/21/2018

6. Resting Membrane Potential
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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

7. Resting Membrane Potential (cont.)
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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

8. Sodium-Potassium Pump
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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 doesn’t 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

9. Cell is at resting potential
9/21/2018
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

10. Action Potential Excitability
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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

11. Action Potential (cont)
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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)

12. Conduction of a nerve impulse
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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)

13. 9/21/2018

14. 9/21/2018
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

15. Animations Action potential Channel gating Other links
9/21/2018
Animations
Action potential
Channel gating
Other links