PhET-Simulations-for-Biology/C3/Neuron/English-timed

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Time Narration
00:01 Welcome to this spoken tutorial on Neuron PhET simulation.
00:07 In this tutorial we will, Demonstrate Neuron, PhET simulation.
00:14 Here I am using, Ubuntu Linux OS version 14.04
00:20 Java version 1.7.0
00:25 Firefox Web Browser version 53.02.2
00:31 To follow this tutorial, Learner should be familiar with topics in high school biology.
00:39 Using this simulation we will learn about, Movement of ions across the membranes when the neuron is stimulated or at rest.
00:51 Function of leak and gated channels
00:54 Membrane permeability.
00:58 Sequence of events that generates an action potential
01:03 Use the given link to download the simulation.
01:08 I have already downloaded Neuron simulation to my Downloads folder.
01:14 To open the simulation, right click on Neuron_en.html file.
01:19 Select Open With Firefox Web Browser option.
01:24 Simulation opens in the browser.
01:27 The simulation window shows a cross-section of an axon.
01:32 The nerve fibre or axon is like a cylinder.
01:36 The interior of axon is filled with axoplasm.
01:41 Exterior is covered with a thin axon membrane.
01:45 Different types of ion channels are present on axon membrane.
01:50 On the top-left corner of the screen, we have a zoom slider.
01:55 This helps to see the close-up view of the membrane.
02:00 On the right-side of the interface, you will see a Legend box and Show box.
02:06 Legend box shows ions and channels.
02:12 In the Show box, we have check boxes to show, All Ions ,Charges ,Concentrations Potential chart .
02:23 At the bottom of the screen we have, a box with Fast Forward, Normal and Slow Motion radio buttons.
02:33 Rewind, Play/Pause and Step buttons
02:39 Stimulate Neuron button and Reset button
02:45 In this simulation, we will see the movement of, sodium and potassium ions across the axon membrane.
02:55 About Neuron :Neurons are highly specialized cells in nervous system.
03:02 They can detect, receive and transmit different kinds of stimuli.
03:09 Drag the zoom slider, to zoom-in the axon membrane.
03:14 The ion channels are selectively permeable to different ions.
03:20 Here, 2 different types of ion channels are shown.
03:25 Leak Channel and Gated Channel.
03:29 For reference please refer to the Legend panel on the right-side of the screen.
03:35 There are sodium and potassium, Gated and Leak channels in the Legend panel.
03:42 Leak ion channels are always open.
03:46 They are responsible for the resting membrane potential.
03:50 Gated Channels open or close in response to a stimulus.
03:57 To observe the exchange of ions properly, keep the simulation speed slow.
04:03 Click on Slow Motion radio button at the bottom of the screen.
04:08 Sodium and potassium ions are seen continuously moving in and out of the membrane.
04:15 They move through the respective leak channels.
04:19 In the Show box, check against Charges and Concentrations check-boxes.
04:28 Note the concentrations of potassium and sodium ions, outside and inside the membrane.
04:36 Axoplasm will contain high concentration of potassium ions and low concentration of sodium ions.
04:45 The fluid outside the axon contains low concentration of potassium ions and high concentration of sodium ions.
04:55 This forms a concentration gradient across the membrane.
05:00 As a result, outer surface of the membrane is positively charged.
05:06 While its inner surface becomes negatively charged.
05:11 Therefore the membrane is polarised.
05:16 Resting Potential.
05:19 The electrical potential difference across the axon membrane is called Resting Potential.
05:28 In the Show box, check the check-box for Potential Chart.
05:33 To stimulate the neuron, click on Stimulate Neuron button.
05:40 Notice that Sodium ions move inside and potassium ions move outside.
05:46 During the exchange of ions charges get exchanged.
05:51 Notice the change in polarity across the axon membrane.
05:56 At this stage the nerve fibre is said to be in action potential or depolarized.
06:03 This movement of ions happen through gated channels.
06:09 Pause the simulation briefly.
06:13 Observe the increase in the membrane potential in the potential chart.
06:18 Action potentials in neuron are known as nerve impulses.
06:23 Click on Play button to start the simulation.
06:27 After a period of action potential, again reversal of the process takes place.
06:34 During this process the sodium and potassium ions move in and out.
06:41 This restores the resting potential of the membrane.
06:45 This process is called repolarization.
06:49 Now the fibre is ready to receive responsive stimulations.
06:58 Let us summarize.
07:01 In this tutorial we have demonstrated, How to use, Neuron PhET simulation.
07:09 Using this simulation we have learnt about, Movement of ions across the membranes when the neuron is stimulated or at rest.
07:20 Function of leak and gated channels.
07:24 Membrane permeability.
07:27 Sequence of events that generates an action potential.
07:32 As an Assignment : Observe, the difference between a gated channel and a leak channel
07:41 the sequence in which ion channels open or close to propagate an action potential.
07:50 The video at the following link summarizes the Spoken Tutorial project.
07:56 Please download and watch it.
07:59 The Spoken Tutorial Project team: conducts workshops using spoken tutorials and gives certificates on passing online tests.
08:09 For more details, please write to us.
08:13 Please post your timed queries on this forum.
08:17 This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching.
08:26 The Spoken Tutorial Project is funded by NMEICT, MHRD Government of India.
08:34 More information on this Mission is available at this link.
08:39 This tutorial is contributed by Snehalatha Kaliappan and Meenal Ghoderao from IIT Bombay.
08:46 Thank you for joining.

Contributors and Content Editors

Karwanjehimanshi95, Nancyvarkey