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-No quiz this week; will be handed out next week (lectures 10-13)

-No quiz this week; will be handed out next week (lectures 10-13) -Quizzes are now take-home for 1 week (handed out/in at recitations) -Curve will be 5 points (average= 79) -Think about topics for a final research presentation -Study groups/partners.

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-No quiz this week; will be handed out next week (lectures 10-13)

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  1. -No quiz this week; will be handed out next week (lectures 10-13) -Quizzes are now take-home for 1 week (handed out/in at recitations) -Curve will be 5 points (average= 79) -Think about topics for a final research presentation -Study groups/partners

  2. Optional short presentations in class April 24th & April 29th (also May 6th during finals week) -research a human neurological disorder or injury and discuss in the context of developmental neurobiology -give a short 5-10 min slide presentation OR -write a 5-page report on how altered neural development may contribute/contributes to the disease, and which form of therapy you would recommend Examples: -Huntington’s chorea -Alzheimer’s disease -Major depressive disorder -Schizophrenia -Traumatic brain injury

  3. Highly-ordered projections from eye to tectum: D  L, V  M, N  C, & T  R *NT= nasal-temporal axis

  4. Removing half of the tectum does not permanently alter retinal map

  5. Removing half of retina does not destroy retinotectal map

  6. Retina expands its circumference; tectum grows posteriorly

  7. In vitro assay determined selective growth of temporal axons post. tectum: PI-linked repulsive cue

  8. Membrane-bound factor repulses temporal axons at posterior

  9. EphrinA ligands activate EphA receptors, & EphrinBs activate EphB receptors

  10. Temporal axons express EphA3, & posterior tectum expresses Ephrin-A2 & A5 EphA ligand gradient

  11. Repulsive EphA signals guide retina N-T, tectum A-P axon mapping; attractive EphB signals guide D-V, D-V axon mapping

  12. Retinal cell outgrowth on tectal membranes expressing EphrinA ligands: no temporal growth

  13. EphrinA2-/-; EphrinA5-/- RGCs randomly project to tectum; extra EphA3 R causes anterior shift of projections blue: extra EphA3

  14. Gradients of both ligand (tectum) and receptor (axon) establish map

  15. Retinal axon outgrowth is promoted at low levels of Ephrin-A2

  16. Repulsive EphA signals guide retina N-T, tectum A-P axon mapping; attractive EphB signals guide D-V, D-V axon mapping Xenopus laevis (frog)

  17. EphrinA ligands activate EphA receptors, & EphrinBs activate EphB receptors

  18. High EphA (T ret) low EphrinA (A tect); high EphB (V ret) high EphrinB1 (M tect)

  19. EphrinB-EphB forward & reverse signaling in D-V retinotectal map *RGC w/ EphR: forward signaling

  20. Olfactory receptor neurons synapse with 2nd order neurons in the glomerulus

  21. Each glomerulus in the olfactory bulb receives neurons of only one subtype Brain  Nose 

  22. Topographic map in the olfactory epithelium is random (grouped by odorant)

  23. Genetic labeling of an olfactory receptor revealed convergence on one glomerulus P2 receptor+ cells= blue Receptors: 7 transmembrane domains, G-protein coupled

  24. Olfactory receptors are expressed on both dendrites and axons olfactory epithelium olfactory bulb (brain) Odorant receptor protein is expressed on both dendrites and axons of olfactory sensory neurons. A and B. Staining of mouse olfactory epithelium with antibodies to two different particular odorant receptors (one labelled in red, the other in green). C. and D. Staining of mouse olfactory bulb with the same antibodies. Scale bars, 10mm. (From Barnea et al., 2004)

  25. No defined regional specificity in the nasal epithelium for olfactory neuron subclasses

  26. The olfactory neuron subtype & glomerular target is defined by its receptor

  27. P2 receptor deletion causes loss of glomerular targeting

  28. Swapping M71 in place of the P2 receptor leads to glomerulus “X” targeting

  29. Other guidance factors are needed for precise glomerular targeting

  30. Fine-tuning synaptic connectivity: A) reducing # afferents/ arborization to multiple target cells

  31. Fine-tuning neural connectivity: B) removing redundant inputs (afferents) to the same target cell

  32. In maturing neural circuits: C) remove excess synapses on same neuron

  33. Synaptic maturation also involves altering # synapses from a specific presynaptic neuron (afferent projection)

  34. Dual innervation of muscle by motor neurons is lost postnatally

  35. Multiple innervations at the immature neuromuscular junction

  36. EPSP: Voltage change in postsynaptic cell that increases the likelihood of firing an action potential (depolarizing) EPSP w/o action potential EPSPs generating an action potential EPSP: + charged ion influx (eg. Ca2+, Na+) IPSP: - charged ion influx (eg. Cl-), or + ion efflux

  37. Electrophysiological test for number of convergent inputs *quantal increases in PSP amplitude  estimate of input #

  38. The number of convergent innervations decreases with maturity

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