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8 October 2010 Lecturer Dr. Kim Nguyen

8 October 2010 Lecturer Dr. Kim Nguyen. Today: Two 1QQs Chapter 6 Section C Synapses p. 160-171 Monday lecture Chapter 6 D Structure of Nervous System special emphasis on Fig 6-44 p. 181 Lab Next Week Sensory Physiology: Data Collection for Abstracts

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8 October 2010 Lecturer Dr. Kim Nguyen

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  1. 8 October 2010Lecturer Dr. Kim Nguyen Today: Two 1QQs Chapter 6 Section C Synapses p. 160-171 Monday lecture Chapter 6 D Structure of Nervous System special emphasis on Fig 6-44 p. 181 Lab Next Week Sensory Physiology: Data Collection for Abstracts Visual System: Textbook p. 208-216

  2. 1QQ # 13 for 8:30 class • Compared to non-myelinated axons, myelinated axons • Require more Na+ K+ ATPase • Conduct action potentials slower • Have higher thresholds • Have fewer voltage-gated ion channels • Release more neurotransmitters from their axon terminals • Nicotine • Acts just like Ach on muscarinic AChRs • Acts just like Ach on nicotinic AChRs • Blocks mAChRs. • Blocks nAChRs • If tagged with a fluorescent label could be used to detect the presence and locations of nicotinic AChRs.

  3. 1QQ # 14 for 8:30 class • The cell bodies of second order neurons in the pathway for pain and temperature • Are located in the dorsal root ganglia • Are located in the gray matter of the spinal cord • Are located in the dorsal column nuclei • Have axons that decussate • Have axons that form synapses onto neurons in the thalamus • What would be the predicted deficits of a person whose entire thalamus on the right side of the brain was completely destroyed? • No sense of pain or temperature in the right foot • No sense of pain or temperature in the right hand • No sense of pain or temperature in the left hand • No sense of touch in the left hand • No sense of touch in the right hand.

  4. 1QQ # 13 for 9:30 class • Compared to non-myelinated axons, myelinated axons • Require less Na+ K+ ATPase • Conduct action potentials faster • Have lower thresholds • Have more voltage-gated ion channels • Release less neurotransmitters from their axon terminals • Muscarine • Acts just like ACh on muscarinic AChRs • Acts just like ACh on nicotinic AChRs • Blocks mAChRs. • Blocks nAChRs • If tagged with a fluorescent label could be used to detect the presence and locations of inotropic and metabotropic AChRs.

  5. 1QQ # 14 for 9:30 class • The cell bodies of second order neurons in the pathway for touch and proprioception • Are located in the dorsal root ganglia • Are located in the gray matter of the spinal cord • Are located in the dorsal column nuclei • Have axons that decussate • Have axons that form synapses onto neurons in the thalamus • What would be the predicted deficits of a person whose entire thalamus on the left side of the brain was completely destroyed? • No sense of pain or temperature in the right foot • No sense of pain or temperature in the right hand • No sense of pain or temperature in the left hand • No sense of touch in the left hand • No sense of touch in the right hand.

  6. S 1 Figure 6.27 Most neurotransmitters are synthesized in the axon terminal. Exceptions: Peptide NTs originate in cell body, move in vesicles by fast orthograde axonal transport to axon terminal. Vesicle release proportional to Ca++ influx (High f AP leads to residual Ca++ in terminal) Fates of neurotransmitters: 1) Diffusion away from synapse, 2) Enzymatic degradation (e.g. AChE and MAO) 3) Uptake by astrocytes 3) Reuptake into presynaptic terminal (e.g. SSR)

  7. S 2 Figure 6.28 Some ion Channels that allow flux of Na+ and K+ simultaneously e.g. nicotinic Acetylcholine Receptor (nAChR) EPSPs :which ion moving in which direction? Duration of PSP vs AP Synaptic delay

  8. S 3 Figure 6.29 IPSPs :which ion moving in which direction? Some IPSPs result in no change in membrane potential by opening Chloride channels that stabilize membrane potential at resting value (Nernst Potential for Cl- = -70mV) or in cells that actively transport Cl- out. EK+

  9. S 4 Figure 6.31 Summation and Synaptic Integration Different times Different locations Each IPSP hyperpolarizes by 5 mV. Each EPSP depolarizes by 5 mV. If 4 inhibitory synapses are active at the same time, how many excitatory synapses must be active simultaneously to exceed threshold (-55 mV) if the resting membrane potential is -70mV?

  10. S 5 Priority by proximity To axon hillock! Diagram on Board: Degree of depolarization above threshold is proportional to frequency of action potentials.

  11. Size of PSP is Variable! S 6 Figure 6.33 Who Cares? Presynaptic Facilitation Presynaptic Inhibition Mechanism: vary Ca++ entry in presynaptic terminal B.

  12. S 7 Figure 6.34

  13. S 8 Figure 6.27 Tetanus toxin & Botulinum toxin disrupt SNARE function.

  14. S 9

  15. S 10 Figure 6.34 AChE and MAO & SSRI SSRIs:Lexapro, Prozac,Paxil,Zoloft

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