1. POWERPOINT ® LECTURE SLIDE PRESENTATION by LYNN CIALDELLA, MA, MBA, The University of Texas at Austin Additional text by J Padilla exclusively for physiology at ECC Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings HUMAN PHYSIOLOGY AN INTEGRATED APPROACH FOURTH EDITION DEE UNGLAUB SILVERTHORN UNIT 2 PART A 8 Neurons: Cellular and Network Properties

2. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings About this Chapter  Organization of the nervous system  Electrical signals in neurons  Cell-to-cell communication in the nervous system  Integration of neural information transfer

3. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Nervous System Subdivisions

4. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Organization of the Nervous System Figure 8-1

5. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-2 Model Neuron Dendrites receive incoming signals; axons carry outgoing information

6. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cells of Nervous System (NS): Axons Transport  Slow axonal transport  Moves material by axoplasmic flow at 0.2–2.5 mm/day  Fast axonal transport  Moves organelles at rates of up to 400 mm/day  Forward transport: from cell body to axon terminal  Backward transport: from axon terminal to cell body

7. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cells of NS: Glial Cells and Their Function Figure 8-5 (1 of 2) Glial cells maintain an environment suitable for proper neuron function

8. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

9. Graded Potential  The cell body receives stimulus  The strength is determined by how much charge enters the cell  The strength of the graded potential diminishes over distance due to current leak and cytoplasmic resistance  The amplitude increases as more sodium enters, the higher the amplitude, the further the spread of the signal

10. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-8a Electrical Signals: Graded Potentials Subthreshold and suprathreshold graded potentials in a neuron If a graded potential does not go beyond the treshold at the trigger zone an action potential will not be generated

11. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Graded Potentials Figure 8-8b Depolarizing grading potential are excitatory Hyperpolarizing graded potentials are inhibitory Graded potential= short distance, lose strength as they travel, can initate an action potential Depolarizing grading potential are excitatory Hyperpolarizing graded potentials are inhibitory Graded potential= short distance, lose strength as they travel, can initate an action potential

12. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Trigger Zone  Graded potential enters trigger zone- summation brings it to a level above threshold  Voltage-gated Na + channels open and Na + enters axon – a segment of the membrane depolarizes  Positive charge spreads along adjacent sections of axon by local current flow – as the signal moves away the currently stimulated area returns to its resting potential  Local current flow causes new section of the membrane to depolarize – this new section is creating a new set of action potentials that will trigger the next area to be depolarized  The refractory period prevents backward conduction; loss of K + repolarizes the membrane – Once the Na+ close they will not open in response to backward conduction until they have reset to their resting position- ensures only one action potential is initiated at time.

13. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

14. Electrical Signals: Voltage-Gated Na + Channels Figure 8-10c Na+ channels have two gates: activation and inactivation gates

15. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5-37 Changes in Membrane Potential Terminology associated with changes in membrane potential (chpt 5 figure) Animation: Nervous I: The Membrane Potential PLAY

16. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Action Potentials Figure 8-9 (1 of 9) Cell is more positive outside than inside Rising phase

17. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Action Potentials Figure 8-9 (2 of 9) As ions move across the membrane the potential increases Rising phase

18. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Action Potentials Figure 8-9 (3 of 9) Graded potentials have brought the membrane potential up to threshold Rising phase

19. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Action Potentials Figure 8-9 (4 of 9) Beyond threshold potential the sodium gated channels allow the ion to move in, making the inside of the cell more positive Rising phase

20. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Action Potentials Figure 8-9 (5 of 9) Na+ continues to move into the cell until it reaches electrical equilibrium. At that point Na+ movement stops

21. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-9 (6 of 9) Electrical Signals: Action Potentials Falling phase K+ moves out of the cell along its gradient and the inside of the cell becomes more and more negative

22. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Action Potentials Figure 8-9 (7 of 9) Hyperpolarization (undershoot) occurs when the potential drops below resting; caused by the continuing movement of K+ out of the cell

23. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Action Potentials Figure 8-9 (8 of 9) Leaked Na+ & K+ in cell increases potential toward resting voltage

24. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-9 (9 of 9) Electrical Signals: Action Potentials Returns to its original state where the outside is more positive than the inside and the membrane potential is -70mv

25. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-11 Electrical Signals: Ion Movement During an Action Potential

26. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-9 Electrical Signals: Action Potentials

27. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-12 Electrical Signals: Refractory Period Action potentials will not fire during an absolute refractory period

28. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Action Potential Travel Down Axon Each region of the axon experiences a different phase of the action potential

29. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Myelinated Axons Saltatory conduction- signal seems to “jump” from node to node moving swiftly- compensates for smaller diameter. Demyelination slows down signal conduction because the current leaks. Sometimes conduction does not reach the next node and dies out. Saltatory conduction- signal seems to “jump” from node to node moving swiftly- compensates for smaller diameter. Demyelination slows down signal conduction because the current leaks. Sometimes conduction does not reach the next node and dies out.

30. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Speed of action potential  Speed of action potential in neurons is influenced by:  Diameter of axon  Larger axons are faster- less resistance to ion flow due to the larger diameter. Large diameter axons are only found in animals with small less complex nervous systems.  Resistance of axon membrane to ion leakage out of the cell  Myelinated axons are faster – the myelin sheath insulates the membrane allowing the action potential to pass along myelinated are sustaining conduction without slowing down by ion channels opening.

31. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-13b Electrical Signals: Coding for Stimulus Intensity Since all action potentials are identical, the strength of a stimulus is indicated by the defrequency of action potentials. Neurotransmitter amounts released are directly propertional to frequency as long as a sufficient supply is available

32. POWERPOINT ® LECTURE SLIDE PRESENTATION by LYNN CIALDELLA, MA, MBA, The University of Texas at Austin Additional text by J Padilla exclusively for physiology at ECC Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings HUMAN PHYSIOLOGY AN INTEGRATED APPROACH FOURTH EDITION DEE UNGLAUB SILVERTHORN UNIT 2 PART A 5 Membrane Dynamics

33. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electricity Review  Law of conservation of electrical charges- the net amount of electrical charge produced in any process is zero.  Opposite charges attract; like charges repel each other- happens with protons & electrons  Separating positive charges from negative charges requires energy – membrane pumps use active transport so separate ions  Conductor versus insulator – a conductor allows the charges to move towards each other and an insulator keeps them separate- does not carry current.

34. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5-32b Separation of Electrical Charges Resting membrane potential is the electrical gradient between ECF and ICF Inside of the cell is more negative than the outside Electrical gradient create the ability to do work just like concentration gradients Inside of the cell is more negative than the outside Electrical gradient create the ability to do work just like concentration gradients

35. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5-32c Separation of Electrical Charges Resting membrane potential is the electrical gradient between ECF and ICF. Resting membrane potential is due mostly to potassium- it is the equilibrium potential of K+ A relative scale shifts the charge to a -2

36. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Potassium Equilibrium Potential

37. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5-35 Sodium Equilibrium Potential Can be calculated using the Nernst Equation Concentration gradient is opposed by membrane potential

38. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Nernst Equation  Predicts membrane potential for single ion- membrane potentials result from an uneven distribution of ions across a membrane.  Membrane potential is influenced by :  Concentration gradient of ions – Na+, Cl-, & Ca2+ have higher [extracellular] and K+ has a higher [intracellular]  Membrane permeability to those ions - only K+ is allowed to move in so this ion contributes to the resting potential

39. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: GHK Equation  Predicts membrane potential using multiple ions- resting membrane potential= the contribution of all ions that cross the membrane X membrane permeability values. Ion contribution is proportional to membrane permeability for that ion. Potentials will be affected if ion concentrations change.  P=permeability value

40. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Electrical Signals: Ion Movement  Resting membrane potential determined by  K + concentration gradient  Cell’s resting permeability to K +, Na +, and Cl –  Gated channels control ion permeability  Mechanically gated – respond to physical forces (pressure)  Chemical gated - respond to ligands (neurotransmitter)  Voltage gated - respond to membrane potential changes  Threshold voltage varies from one channel type to another – the minimum stimulus required and the response speed varies for each type

41. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cell-to-Cell: Postsynaptic Response Fast and slow responses in postsynaptic cells involve ion channels and G-protein receptor Figure 8-23 Postsynaptic cell Presynaptic axon terminal G R Ion channels open More Na + in More K + out or Cl – in EPSP = excitatory depolarization IPSP = inhibitory hyperpolarization Ion channels close Less Na + in Less K + out EPSP = excitatory depolarization Alters open state of ion channels Activated second messenger pathway Inactive pathway Modifies existing proteins or regulates synthesis of new proteins Coordinated intracellular response Rapid, short-acting fast synaptic potential Neurotransmitter Slow synaptic potentials and long-term effects Chemically gated ion channel G protein– coupled receptor

42. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-20 Cell-to-Cell: Chemical Synapse Chemical synapses use neurotransmitters; electrical synapses pass electrical signals. Chemical synapses are most common. Electrical synapses are found in the CNS and other cells that use electrical signals (heart)

43. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-21 Cell-to-Cell: Calcium  Events at the synapse  Exocytosis: Classic versus kiss-and-run Voltage-gated Ca 2+ channel Postsynaptic cell Ca 2+ Docking protein Synaptic vesicle Action potential Axon terminal Receptor An action potential depolarizes the axon terminal. The depolarization opens voltage- gated Ca 2+ channels and Ca 2+ enters the cell. Calcium entry triggers exocytosis of synaptic vesicle contents. Neurotransmitter diffuses across the synaptic cleft and binds with receptors on the postsynaptic cell. Cell response Neurotransmitter binding initiates a response in the postsynaptic cell. 4 5 1 2 3 4 5 1 2 3

44. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-22 Cell-to-Cell: Acetylcholine Synthesis and recycling of acetylcholine at a synapse

45. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Integration: Long-Term Potentiation Figure 8-30 Long-term potentiation- mechanism used in learning and memory using Glutaminergic Receptors.

46. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 8-24 Cell-to-Cell: Inactivation of Neurotransmitters

47. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cell-to-Cell: Neurocrines  Seven classes by structure -  Acetylcholine –(Ach) neurotransmitter composed of choline and coenzyme A (acetyl CoA), binds to cholinergic receptors  Amines – neurotransmitter, derived from a single amino acid: Dopamine, Norepinephrine, Epinephrine, Serotonin, Histamine  Amino acids – an amino acid that functions as a neurotransmitter: Glutamate, Aspartate, Gamma-aminobutyric, Glycine  Purines –made from adenine  Gases – act as neurotransmitter, half-life of 2-30 sec.  Peptides -neurohoromones, neurotransmitters, and neuromodulator,  Lipids – eicosanoids

48. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cell-to-Cell: Amine  Derived from single amino acid  Tyrosine  Dopamine -neurotransmitter/neurhormone  Norepinephrine -tyrosine, neurotransmitter/neurhormone, secreted by noradrenogenic neurons,  Epinephrine - neurotransmitter/neurhormone, also called adrenaline, secreted by adrenogenic neurons  Others  Serotonin – neurotransmitter, is made from tryptophan  Histamine – neurotransmitter, is made from histadine

49. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cell-to-Cell: Amino Acids  Glutamate: primary excitatory  CNS  Aspartate: primary excitatory  brain (select regions)  Gamma-aminobutyric(GABA): Inhibitory  brain  Glycine  Inhibitory  spinal cord  May also be excitatory

50. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cell-to-Cell: Neurocrines  Peptides -involved in pain and pain relieve pathways  Substance P and opioid peptides  Purines- bind purinergic receptors  AMP and ATP  Gases- produced inside the body, function and mechanisms not totally understood  NO and CO  Lipids -bind cannabinoid receptors in brain and immune system cells  Eicosanoids

51. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cell-to-Cell: Receptors  Cholinergic receptors  Nicotinic on skeletal muscle, in PNS and CNS  Monovalent cation channels  Na + and K +  Muscarinic in CNS and PNS  Linked to G proteins  Adrenergic Receptors   and  - two classes  Linked to G proteins- initiate second messenger

52. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Integration: Injury to Neurons Figure 8-32 If the cell body is not damaged the neuron will most likely survive. Axon healing is similar to growth cone of a developing axon.