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

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