1. PowerPoint ® Lecture Slide Presentation by Patty Bostwick-Taylor, Florence-Darlington Technical College Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings PART A 7 The Nervous System

2. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Neurons  Neurons = nerve cells  Cells specialized to transmit messages  Major regions of neurons  Cell body—nucleus and metabolic center of the cell  Processes—fibers that extend from the cell body

3. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Neurons  Cell body  Nissl substance  Specialized rough endoplasmic reticulum  Neurofibrils  Intermediate cytoskeleton  Maintains cell shape

4. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Neurons Figure 7.4

5. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Neurons  Cell body  Nucleus  Large nucleolus  Processes outside the cell body  Dendrites—conduct impulses toward the cell body  Axons—conduct impulses away from the cell body

6. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Neurons Figure 7.4

7. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Neurons  Axons end in axonal terminals  Axonal terminals contain vesicles with neurotransmitters  Axonal terminals are separated from the next neuron by a gap  Synaptic cleft—gap between adjacent neurons  Synapse—junction between nerves

8. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Neurons  Myelin sheath—whitish, fatty material covering axons  Schwann cells—produce myelin sheaths in jelly roll–like fashion  Nodes of Ranvier—gaps in myelin sheath along the axon

9. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nervous Tissue: Neurons Figure 7.5

10. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Cell Body Location  Most neuron cell bodies are found in the central nervous system  Gray matter—cell bodies and unmyelinated fibers  Nuclei—clusters of cell bodies within the white matter of the central nervous system  Ganglia—collections of cell bodies outside the central nervous system

11. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Neuron Classification Figure 7.6

12. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.8a Structural Classification of Neurons  Multipolar neurons—many extensions from the cell body

13. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structural Classification of Neurons  Bipolar neurons—one axon and one dendrite Figure 7.8b

14. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Structural Classification of Neurons  Unipolar neurons—have a short single process leaving the cell body Figure 7.8c

15. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses  Resting neuron  The plasma membrane at rest is polarized  Fewer positive ions are inside the cell than outside the cell  Depolarization  A stimulus depolarizes the neuron’s membrane  A depolarized membrane allows sodium (Na+) to flow inside the membrane  The exchange of ions initiates an action potential in the neuron

16. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses Figure 7.9a–b

17. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses  Action potential  If the action potential (nerve impulse) starts, it is propagated over the entire axon  Impulses travel faster when fibers have a myelin sheath

18. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses Figure 7.9c–d

19. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses  Repolarization  Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane  The sodium-potassium pump, using ATP, restores the original configuration

20. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Nerve Impulses Figure 7.9e–f

21. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses  Impulses are able to cross the synapse to another nerve  Neurotransmitter is released from a nerve’s axon terminal  The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter  An action potential is started in the dendrite

22. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na + Neurotransmitter broken down and released Ion channel opensIon channel closes

23. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 1 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron

24. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 2 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Vesicle fuses with plasma membrane Synaptic cleft Ion channels Receiving neuron Transmitting neuron

25. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 3 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron

26. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 4 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron

27. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 5 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na + Ion channel opens

28. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 6 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na + Neurotransmitter broken down and released Ion channel opensIon channel closes

29. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of a Signal at Synapses Figure 7.10, step 7 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na + Neurotransmitter broken down and released Ion channel opensIon channel closes