Exploring Action Potentials: Simulation and Key Factors

docx

School

Baylor University *

*We aren’t endorsed by this school

Course

4119

Subject

Chemistry

Date

Jun 10, 2024

Type

docx

Pages

Uploaded by MinisterNeutronQuail5

NSC 4119-02 January 31, 2022 Action Potential Lab Questions: 1. Producing an Action Potential Simulation: A. In this simulation, what stimulus strength does it it take to produce an action potential? At 1ms duration, the stimulus strength to produce an action potential was 20nA. B. More generally, what is the term for a depolarization large enough to generate an action potential? The term would be above the threshold value. 2. Exploring the Refractor Period: A. During the absolute refractor period, no additional action potentials are possible. B. However, during the relative refractory period, a second action potential can be generated under when: there’s a greater stimulus. 3. Encoding Stimulus Strength (1): A. How do different current intensities affect action potential firing? The different current intensities affects the frequency or quantity of the action potential firings at a time. B. What can we infer from increases in firing rate? We can infer that the size of that action potential does not become affected but influence the speed that the neuron could fire. 4. Encoding Stimulus Strength (2): A. How do different current durations affect action potential number? As the duration number increases at a longer period of time, the number of action potentials also increase as well. B. For a long duration stimuli, how does the inter-stimulus interval change over time? Over time, when action potentials had been firing, it eventually gets slowed down C. What is the term for this change? Spike rate adaption aka spike frequency adaptation.

5. Axon Diameter and Myelination: A. How does the axon diameter affect conduction velocity of action potential? When an axon has a larger diameter, the conduction velocity of the action potential is much quicker and the messages can be delivered faster. The reason is that there ion flow has less resistance and less probable that the incoming ions will collide causing it to be slowed down. B. How does myelination affect conduction velocity of action potential? Myelination speeds the conduction velocity of action potential because it functions as an electrical insulator. 6. Axon Diameter and Myelination (continued): A. In the "Axon Diameter" simulation, export the spreadsheet with the data you generated and use it to find the line of best fit for the non-myelinated and myelinated data (note that the non-myelinated data is not really linear, but for the purpose of this comparison the linear approximation is good enough). Based on the generated trendlines, what conduction velocity would you expect for a myelinated and unmyelinated 20 uM axon (Hint 1: solve the equation using Excel, so you don't have to complete by hand; Hint 2: 20 is your X-value in the generated equations)? 0 0.2 0.4 0.6 0.8 1 1.5 2 0 2 4 6 8 10 12 f(x) = 0.4 x − 0.04 f(x) = 1.43 x − 2.1 Conduction Velocity and Axon Diameter Non-myelinated Linear (Non-myelinated) Myelinated Linear (Myelinated) Axon diameter (µm) Conduction Velocity Non-myelinated: 7.97 µm Myelinated: 26.55 µm

B. Based on your calculations, is there a difference between how small and large diameter axons benefit from myelination? Why? Yes, there is a significant difference when it came for axons that were much thicker, there was a linear relation of the conduction velocity and axon diameter. There were more space to allow the information to travel freely. When the axon diameter smaller, there was also a reduction in the conduction velocity thus even with the insulation of myelin, there’s not enough space or room from hindering the conduction.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version