1. Nervous System

2. Divisions Central nervous system (CNS). Peripheral nervous system.
Brain and spinal cord.
Both contain fluid-filled spaces which contain cerebrospinal fluid (CSF).
The central canal of the spinal cord is continuous with the ventricles of the brain.
White matter is composed of bundles of myelinated axons
Gray matter consists of unmyelinated axons, nuclei, and dendrites.
Peripheral nervous system.
Everything outside the CNS.
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3. PNS
Fig
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4. Neuron Anatomy

5. Membrane Potential Measuring Membrane Potentials. -70 mV is resting
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6. Normal Levels
Fig. 48.7
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7. Hyperpolarization.
Gated K+ channels open  K+ diffuses out of the cell  the membrane potential becomes more negative.
Fig. 48.8a
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8. Depolarization
Gated Na+ channels open  Na+ diffuses into the cell  the membrane potential becomes less negative.
Fig. 48.8b
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9. Action Potential The Action Potential: All or Nothing Depolarization.
If graded potentials sum to -55mV a threshold potential is achieved.
This triggers an action potential.
Axons only.
Fig. 48.8c
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10. Step 1: Resting State. Fig. 48.9
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11. Step 2: Threshold.
Fig. 48.9
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12. Step 3: Depolarization phase of the action potential.
Fig. 48.9
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13. Step 4: Repolarizing phase of the action potential.
Fig. 48.9
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14. Step 5: Undershoot.
Fig. 48.9
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15. Moving Potential
Fig
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16. Saltatory conduction
In myelinated neurons only unmyelinated regions of the axon depolarize.
Thus, the impulse moves faster than in unmyelinated neurons.
Fig
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17. Synapses Electrical Synapses.
Action potentials travels directly from the presynaptic to the postsynaptic cells via gap junctions.
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18. Chemical Synapses More common than electrical synapses.
Postsynaptic chemically-gated channels exist for ions such as Na+, K+, and Cl-.
Depending on which gates open the postsynaptic neuron can depolarize or hyperpolarize.
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19. Fig
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20. Routes of Nerve Transmission