1. Chapter Outline I Functions and Divisions of the Nervous System A. Overall Function 1, 2, 3 … a, b, c … i), ii), iii) … B. Basic Processes Used C. Classification of Nervous System II Histology of Nervous System III Membrane Potentials IV Graded Potentials  V Action Potentials VI The Synapse VII Neurotransmitters and their Receptors VII The Basics of Neural Integration

2. V. Action Potentials (AP) A. Basic Conepts 1.Potential Change 2.Cells: 3.Initiated by: 4. Threshold– see next slide 5. All-or-None 6. Start & End Locations 7. Type of Gated Channel 8. Next step after AP 9. Unmyelinated and Myelinated SEE NEXT FIGURE

3. Action Potentials … 4. Threshold Threshold =  Membrane depolarized by 15 to 20 mV Subthreshold stimulus is not detected

4. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2010 Pearson Education, Inc. Non-Myelinated Axon Myelinated Axon

5. 8. OVERVIEW OF MECHANISMS  Depolarizing Graded Potential ON AXON  Depolarization  Repolarization  Hyperpolarization  Return to Resting State  Adjacent chunks of membrane stimulated one after another  When end is reached: Neurotransmitter carries message across to next neuron

6. GP AP

7. Action potential 1 2 3 4 Resting state Depolarization Repolarization Hyperpolarization The big picture 11 2 3 4 Time (ms) Threshold Membrane potential (mV) Figure 11.11 (1 of 5) Action Potentials …

8. Generation of an Action Potential

9. Action Potentials … Unmyelinated Axons … B. Types of Voltage-gated Channels  Na+ Channel has two Voltage gates  ACTIVATION  INACTIVATION  for Na+ to enter cell:  K+ Channel has one Voltage gate  is slow

10. C. Detailed Steps 1. Resting State: Na+ and K+ Channels are closed Na + Potassium channel Sodium channel 1 Resting state Activation gates Inactivation gate K+K+

11. Action Potentials … 2. Depolarizing Phase a. Caused by: b. Na + influx causes: c. At threshold (–55 to –50 mV): Na + 2 Depolarization K+K+

12. 3. Repolarizing Phase a.Na + channel: - Importance of inactivation gate b. Permeability to Na +: c. K + gates: d. Potential restored as: 3 Repolarization Na + K+K+

13. Action Potentials … 4. Hyperpolarization a. K + channels: b. Undershoot c. Sodium Channels: 4 Hyperpolarization Na + K+K+

14. Action Potentials … 5. Sodium-Potassium Pump a. Immediately after Repolarization, Na+ and K+: b. Pump restores:

15. Action potential Time (ms) 1 1 2 3 4 Na + permeability K + permeability The AP is caused by permeability changes in the plasma membrane Membrane potential (mV) Relative membrane permeability Figure 11.11 (2 of 5)

16. Generation of an Action Potential

17. 6. Propagation of an Action Potential– a. Nonmyelinated Axon 1.moves in one direction 2.Adjacent sections of membrane: 3. Positive Feedback Cycle

18. APs self-propagate – once started, all voltage channels open like dominoes (all or none) Voltage at 2 ms Voltage at 4 ms Voltage at 0 ms Recording electrode (a) Time = 0 ms. Action potential has not yet reached the recording electrode. (b) Time = 2 ms. Action potential peak is at the recording electrode. (c) Time = 4 ms. Action potential peak is past the recording electrode. Membrane at the recording electrode is still hyperpolarized. Resting potential Peak of action potential Hyperpolarization

19. Copyright © 2010 Pearson Education, Inc. Nerve Impulses– within and between neurons

20. Propagation of an Action Potential in Unmyelinated axons

21. Action Potentials … Propagation of an Action Potential … b. Myelinated Axon = Saltatory Conduction 1. Location of channels: 2. AP generate at: 3. leaps NEXT SLIDE

22. Voltage-gated ion channel Stimulus Myelin sheath Stimulus Node of Ranvier Myelin sheath U nmyelinated axon 1 mm saltatory conduction = jumps node to node, 30X FASTER!

23. Action Potentials … D. Characteristics of Action Potentials  1. Refactory Period a. Absolute Refractory Period:  Stage o AP:  Na+ channels:  Another action potential possible? b. Relative Refractory Period:  Stage of AP:  Na+ Channels:  Another action Potential possible?  ** Diagram on next slide

24. Figure 11.14 Stimulus Absolute refractory period Relative refractory period Time (ms) Depolarization (Na + enters) Repolarization (K + leaves) After-hyperpolarization Nerve cannot fire, Na+ channels inactivated. Threshold elevated, only exceptionally strong stimuli cause APs

25. Action Potentials … 2. Coding for Stimulus Intensity  Strong stimuli generate APs more often than weaker stimuli  Intensity determined by: Stimulus Strength AP Frequency

26. Review Questions _______________ gates on Na+ channels help ensure 1-way flow of APs. The opening of slow ____ voltage channels allows the cell to repolarize. How is increased intensity of a stimulus coded by action potentials? What describes the magic minimum change for causing an AP? Inactivation K+ Increasing frequency of APs threshold

27. Action Potentials … 3. Conduction Velocity  Diameter of Axon:  Myelinated or not: Voltage-gated ion channel Stimulus Myelin sheath Stimulus Node of Ranvier Myelin sheath U nmyelinated axon M yelinated axon, APs generated only in nodes of Ranvier, jump rapidly from node to node. 1 mm saltatory conduction = jumps node to node, 30X FASTER!

28. Action Potentials … Diameter of axon … Nerve Fiber Classification  Group A fibers =  Group B fibers =  Group C fibers = Students Do Above

29. Action Potentials … E. Multiple Sclerosis (MS) STUDENTS DO Treated w/ immune suppressants

30. Table 11.2 (1 of 4) Summary of GP vs AP

31. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2010 Pearson Education, Inc. VI The Synapse =

32. The Synapse … A. Basic Concepts & Terms: 1.Synapse = 2.Function: 3. Presynaptic neuron & Postsynaptic neuron:

33. Figure 11.16 Dendrites Cell body Axon Axodendritic synapses Axosomatic synapses Cell body (soma) of postsynaptic neuron Axon (b) Axoaxonic synapses Axosomatic synapses (a) Not common or well understood Dendrodendritic and dendrosomatic, too 4. Part of Neuron involved in Synapse

34. 5. Types of Synapses  Electrical:  Chemical  Via Neurotransmitters

35. Figure 11.17, step 1 Action potential arrives at axon terminal. B. The Chemical Synapse … Mechanism Steps Ca 2+ Synaptic vesicles Axon terminal Mitochondrion Postsynaptic neuron Presynaptic neuron Synaptic cleft Ca 2+ Postsynaptic neuron 1

36. Figure 11.17, step 2 Action potential arrives at axon terminal. Voltage-gated Ca 2+ channels open and Ca 2+ enters axon terminal. Ca 2 + Synaptic vesicles Axon terminal Mitochondrion Postsynaptic neuron Presynaptic neuron Synaptic cleft Ca 2+ Postsynaptic neuron 1 2 The Chemical Synapse

37. Figure 11.17, step 3 Action potential arrives at axon terminal. Voltage-gated Ca 2+ channels open and Ca 2+ enters the axon terminal. Ca 2+ entry causes neurotransmitter- containing synaptic vesicles to release by exocytosis. Ca 2+ Axon terminal Mitochondrion Postsynaptic neuron Presynaptic neuron Synaptic cleft Ca 2+ Postsynaptic neuron 1 2 3 The Chemical Synapse Synaptic vesicles

38. Figure 11.17, step 4 Action potential arrives at axon terminal. Voltage-gated Ca 2+ channels open and Ca 2+ enters the axon terminal. Ca 2+ entry causes neurotransmitter- containing synaptic vesicles to release their contents by exocytosis. Ca 2+ Synaptic vesicles Axon terminal Mitochondrion Postsynaptic neuron Presynaptic neuron Synaptic cleft Ca 2+ Neurotransmitter diffuses across synaptic cleft, binds to receptors on postsynaptic membrane. Postsynaptic neuron 1 2 3 4 The Chemical Synapse

39. Figure 11.17, step 5 Graded potential along postsynaptic membrane Binding of neurotransmitter opens ion channels, resulting in graded potentials. 5 Bound Neurotransmitter

40. Figure 11.17, step 6 Reuptake Enzymatic degradation Diffusion away from synapse Neurotransmitter effects terminated by reuptake through transport proteins, enzymatic degradation, or diffusion away from synapse. 6

41. The Synapse … 2. Postsynaptic Potentials and Synaptic Integration  Graded Potentials  Strength of signal:  2 types: 1.EPSP 2.IPSP 1.Consider EPSP vs IPSP Are they graded or APs? What triggers them? How do they work?

42. Postsynaptic Potentials … a. Excitatory Synapses and EPSPs—cause:  Neurotransmitter binds to:  Na + influx versus K + efflux  More Na+ in  causing depolarization  Result = ______ Time (ms) Threshold Stimulus Membrane potential (mV) (a) Excitatory postsynaptic potential (IPSP)

43. Postsynaptic Potentials … b. Inhibitory Synapses and IPSPs  Neurotransmitter binds to:  Ion movement:  Result = ___________ Time (ms) Threshold Stimulus Membrane potential (mV) (b) Inhibitory postsynaptic potential (IPSP)

44. Postsynaptic Potentials … 3. Integration and Modification of Synaptic a. Summation by the Postsynaptic Neuron ==  Types i) Spatial summation = ii) Temporal =  Interaction of IPSPs and EPSPs E 1 + E 2 I1I1 E 1 + I 1 E1E1 E1E1 1 1

45. VII Neurotransmitter (N) and Their Receptors  # of N per neuron:  Classification:structure and function  Acytelcholine  Serotonin  Dopamine  Norepineprine  Receptors on Dendrites and Cell Body

46. Classification of Neurotransmitters by Function = Mechanism of receptor stimulation by neurotransmitter 1.Channel-linked receptors Ion flow blocked Closed ion channel (a) Channel-linked receptors open in response to binding of ligand (ACh in this case). Ions flow Ligand Open ion channel

47. Neurotransmitters and Their Receptors … Classification of Neurotransmitters by Function … 2. G Protein-Linked Receptors: Mechanism  Neurotransmitter binds to:  G-protein:  “ Produces:  Activates: 1 Neurotransmitter (1st messenger) binds and activates receptor. Receptor G protein Closed ion channel Adenylate cyclase Open ion channel 2 Receptor activates G protein. 3 G protein activates adenylate cyclase. 4 Adenylate cyclase converts ATP to cAMP (2nd messenger). cAMP changes membrane permeability by opening or closing ion channels. 5b cAMP activates enzymes. 5c cAMP activates specific genes. Active enzyme GDP 5a (b) G-protein linked receptors cause formation of an intracellular second messenger (cyclic AMP in this case) that brings about the cell’s response. Nucleus

48. Figure 11.17b, step 1 (b) G-protein linked receptors cause formation of an intracellular second messenger (cyclic AMP in this case) that brings about the cell’s response. Receptor Neurotransmitter (1st messenger) binds and activates receptor. 1 G G Protein-linked Receptor-Mechanism Diagram has been modified from Textbook Diagram 1

49. Figure 11.17b, step 2 (b) G-protein linked receptors cause formation of an intracellular second messenger (cyclic AMP in this case) that brings about the cell’s response. Receptor G protein GTP Neurotransmitter (1st messenger) binds and activates receptor. Receptor activates G protein. Nucleus 1 2 Diagram has been modified from Textbook Diagram 2

50. Figure 11.17b, step 4 (b) G-protein linked receptors cause formation of an intracellular second messenger (cyclic AMP in this case) that brings about the cell’s response. Receptor G protein Adenylate cyclase ATP cAMP Neurotransmitter (1st messenger) binds and activates receptor. Receptor activates G protein. G protein activates adenylate cyclase. Converts to cAMP (2nd messenger). Nucleus 1 23 3

51. Figure 11.17b, step 5a (b) G-protein linked receptors cause formation of an intracellular second messenger (cyclic AMP in this case) that brings about the cell’s response. Receptor G protein Closed ion channelAdenylate cyclaseOpen ion channel ATP cAMP Neurotransmitter (1st messenger) binds and activates receptor. Receptor activates G protein. Converts to cAMP (2nd messenger). cAMP changes membrane by opening and closing ion channels. Nucleus 1 2 3 4a 4

52. VIII Basic concepts of Neural Integration : Organization of Neurons: Neuronal Pools  Functional groups of neurons  Integrate:  Forward it:

53. Patterns of Neural Processing  Serial processing  Example: reflexes 1 2 3 4 5 Receptor Sensory neuron Integration center Motor neuron Effector Stimulus Response Spinal cord (CNS) Interneuron

54. Patterns of Neural Processing …  Parallel processing  One stimulus  numerous responses  Importance:  Example

55. END REVIEW QUESTIONS: Next Slide

56. Review Questions _____________ synapses are rare and are possible thru gap junctions. ______________ synapses are by far the most common and require the diffusion of ____________________ across the synaptic ___________. What does Ca2+ cause synaptic vesicles to do? Electrical Chemical neurotransmitters cleft Empty into synaptic cleft via exocytosis

57. Review Questions _____________ facilitate AP generation but must be summed spatially and or _____________ to actually generate an AP. ____________ graded potentials decrease the likelihood of an AP. What type of receptors stimulate prolonged and often times multiple effects on the post-synaptic cell? EPSPs temporally IPSP G protein - linked