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Nervous System. Divisions Central nervous system (CNS). Brain and spinal cord. Both contain fluid-filled spaces which contain cerebrospinal fluid (CSF).

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Presentation on theme: "Nervous System. Divisions Central nervous system (CNS). Brain and spinal cord. Both contain fluid-filled spaces which contain cerebrospinal fluid (CSF)."— Presentation transcript:

1 Nervous System

2 Divisions Central nervous system (CNS). 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. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

3 PNS Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig

4 Neuron Anatomy

5 Membrane Potential Measuring Membrane Potentials. -70 mV is resting Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

6 Normal Levels Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.7

7 Hyperpolarization. Gated K + channels open K + diffuses out of the cell the membrane potential becomes more negative. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.8a

8 Depolarization Gated Na + channels open Na + diffuses into the cell the membrane potential becomes less negative. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.8b

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. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.8c

10 Step 1: Resting State. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.9

11 Step 2: Threshold. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.9

12 Step 3: Depolarization phase of the action potential. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.9

13 Step 4: Repolarizing phase of the action potential. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.9

14 Step 5: Undershoot. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.9

15 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig Moving Potential

16 Saltatory conduction In myelinated neurons only unmyelinated regions of the axon depolarize. Thus, the impulse moves faster than in unmyelinated neurons. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig

17 Synapses Electrical Synapses. Action potentials travels directly from the presynaptic to the postsynaptic cells via gap junctions. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

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. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

19 Fig

20 Routes of Nerve Transmission


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