8 October 2010 Lecturer Dr Kim Nguyen Today

8 October 2010 Lecturer Dr. Kim Nguyen Today: Two 1 QQs 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

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

1 QQ # 14 for 8: 30 class 1. The cell bodies of second order neurons in the pathway for pain and temperature a) Are located in the dorsal root ganglia b) Are located in the gray matter of the spinal cord c) Are located in the dorsal column nuclei d) Have axons that decussate e) Have axons that form synapses onto neurons in the thalamus 2. What would be the predicted deficits of a person whose entire thalamus on the right side of the brain was completely destroyed? a) No sense of pain or temperature in the right foot b) No sense of pain or temperature in the right hand c) No sense of pain or temperature in the left hand d) No sense of touch in the left hand

1 QQ # 13 for 9: 30 class 1. Compared to non-myelinated axons, myelinated axons a) Require less Na+ K+ ATPase b) Conduct action potentials faster c) Have lower thresholds d) Have more voltage-gated ion channels e) Release less neurotransmitters from their axon terminals 2. Muscarine a) Acts just like ACh on muscarinic ACh. Rs b) Acts just like ACh on nicotinic ACh. Rs c) Blocks m. ACh. Rs. d) Blocks n. ACh. Rs e) If tagged with a fluorescent label could be used to detect the presence and locations of inotropic and metabotropic ACh. Rs.

1 QQ # 14 for 9: 30 class 1. The cell bodies of second order neurons in the pathway for touch and proprioception a) Are located in the dorsal root ganglia b) Are located in the gray matter of the spinal cord c) Are located in the dorsal column nuclei d) Have axons that decussate e) Have axons that form synapses onto neurons in the thalamus 2. What would be the predicted deficits of a person whose entire thalamus on the left side of the brain was completely destroyed? a) No sense of pain or temperature in the right foot b) No sense of pain or temperature in the right hand c) No sense of pain or temperature in the left hand d) No sense of touch in the left hand

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. ACh. E and MAO) 3) Uptake by astrocytes 3) Reuptake into presynaptic terminal (e. g. SSR)

S 2 Figure 6. 28 EPSPs : which ion moving in which direction? Duration of PSP vs AP Synaptic delay Some ion Channels that allow flux of Na+ and K+ simultaneously e. g. nicotinic Acetylcholine Receptor (n. ACh. R)

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- = -70 m. V) or in cells that actively transport Cl- out. EK+

S 4 Figure 6. 31 Summation and Synaptic Integration Different times Different locations Each IPSP hyperpolarizes by 5 m. V. Each EPSP depolarizes by 5 m. V. If 4 inhibitory synapses are active at the same time, how many excitatory synapses must be active simultaneously to exceed threshold (-55 m. V) if the resting membrane potential is -70 m. V?

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

S 6 Presynaptic Facilitation Presynaptic Inhibition Mechanism: vary Ca++ entry in presynaptic terminal B. Size of PSP is Variable! Figure 6. 33 Who Cares?

S 7 Figure 6. 34

S 8 Figure 6. 27 Tetanus toxin & Botulinum toxin disrupt SNARE function.

S 9

S 10 ACh. E and MAOSSRIs: Lexapro, Prozac, & SSRI Paxil, Zoloft Figure 6. 34