KEY_Spring 2021 M4 Biol 316 core content assessment take home V1 1 Biol 316 CMN Spring 2021 Core content Assessment Due: Flexible but let’s shoot for Sunday April 25th by midnight Below is a diagram...

This is for my cell/molecular neuroscience class. the questions regard I/V plots and action potentials and synapses and questions about channels and ions


KEY_Spring 2021 M4 Biol 316 core content assessment take home V1 1 Biol 316 CMN Spring 2021 Core content Assessment Due: Flexible but let’s shoot for Sunday April 25th by midnight Below is a diagram of a somatosensory afferent system that responds to peripheral thermal stimulation. Under normal conditions the peripheral 1o afferent fiber encodes for increasing intensity of thermal stimulation in the range of 250C to 350C by increasing the frequency of AP firing from 1 AP/sec @ 250C to 10 AP/sec @ 300C to 100 AP/sec @ 350C. If the 1o afferent fiber was stimulated at different times with either a 250C, 300C, or 350C temperature probe, answer the following questions about the effect it would have at synapse A. Presynaptic plot Postsynaptic plot 1. Using the I/V plot above draw the predicted I/V relationships of a voltage-gated calcium channel VGCa++ in the presynaptic terminal at each temperature (you should have a I/V relationship (line) for each temperature). Give a brief explanation below for the relationships you predicted. (10 points) 2. Using the I/V plot above draw the predicted I/V relationships at each temperature for the ligand-gated AMPA channel in the postsynaptic neuron (you should have a I/V relationship for each temperature). Give a brief explanation below for the relationships you predicted. (10 points) 3. Briefly describe what affect the different temperatures would have on the size of the quanta and why. (10 points) 2 4. Briefly describe what affect the different temperatures would have on the quantal event size and why. (10 points) As indicated on the diagram below, Synapse B responds to the same temperature stimulation as Synapse A but has three different types of ion channels present on the postsynaptic membrane that open under varying conditions. The AMPA channel conducts Na+ and K+ when NT present; the NMDA channel conducts Na+, K+, and Ca++ but only when both NT is present and the Vm is @ - 40mV; the Voltage-gated Na+ channel (VGNa+) conducts Na+ but only when Vm is @ -35mV. Therefore the amount of current associated with Synapse B (IsynapseB) is dependent upon both the presence of NT and the membrane potential (Vm) and is equal to the sum of the individual currents for each channel (IAMPA + INMDA + IVGNa+) Given this information, answer the following questions: 5. Assuming an unlimited number of all channels at the synapse, what effect would the different temperatures have on the I/V relationship for Synapse B? Plot the predicted relationship of the graph below and give a brief explanation (10 points) 3 6. Would you predict Synapse B to produce a EPSP or IPSP at each of the different temperatures? And why? Use the I/V plot below to represent your answer of either an EPSP or IPSP for each temperature. (10 points) 7. Using your knowledge of what makes a synapse an EPSP or IPSP and your answer to the question above, propose a cellular/ molecular mechanism for how synapse B could change from either an EPSP or IPSP to the opposite in response to increasing temperature. Use the diagram and plots below to help in your answer. (10 points) 4 8. Increases in the efficacy of a synapse (synaptic plasticity) can occur as a consequence of short-term plasticity (STP) or long-term plasticity (LTP). Below is an illustration of a normal synapse containing pre-synaptic and post-synaptic terminals. For both STP and LTP, draw an example of a structure and/or mechanism that would be indicative of the possible changes that occur to produce plasticity at the synapse through metabotropic G-protein coupled reception (GPCR). In addition, using the I/V plots, predict the I/V relationships that would be indicative of your examples of STP and LTP. (10 points) 5 This is a new section and the reference to synapses in the questions below refer to the basal ganglia diagram below. Under normal conditions, both synapse 1 (Syn1) and synapse 2 (Syn2) above release the same type of NT which leads to an inhibitory post-synaptic potential (IPSP) in MSN2 cells but an excitatory post-synaptic potential (EPSP) in MSN1 cells. Based on your understanding of metabotropic g-protein coupled receptor (GPCR) signaling at these synapses answer the following: 9. For both synapse 1 and synapse 2, diagram the possible GPCR mediated signaling pathway that could explain the different functional changes (IPSP versus EPSP) in the MSN2 and MSN1 cells even though they both utilize the same type of NT. Your pathways should start from NT release at the respective synapses and go through GPCR activation that lead to changes in ionotropic receptors that lead to either EPSP or IPSP. (10 points) MSN2 MSN1SN SN Cortex Cortex Syn1 (IPSP) Syn2 (EPSP) Syn4 (EPSP) Syn3 (EPSP) Astrocyte Astrocyte Astrocyte Microglia 6 10. Under normal conditions, the simultaneous activation of synapse 1 and 4 (SN to MSN2 and Cortical to MSN2) can lead to a significant increase in the amount of available NT in synapse 4 compared to the amount of available NT after activation of synapse 4 alone. This increase in available NT can therefore lead to an increase in the magnitude (size) of the EPSP at synapse 4. Diagram a cell non-autonomous pathway that utilizes the cells of the tripartite synapse that could explain how the activation of synapse 1 could lead to changes in available NT at synapse 4 under normal conditions. There are multiple correct pathways but choose only 1. Your pathway should start with the release of NT at synapse 1 and end with the increased EPSP magnitude at synapse 4. It should also include the mechanism for the increased available synaptic NT, and the channel/ receptor types that would be activated in synapse 4 that leads to the increased EPSP. (10 points)