Major Sections of the Course

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Bioelectricity: A Quantitative Approach

33 ratings

Duke University

Bioelectricity: A Quantitative Approach

33 ratings

Nerves, the heart, and the brain are electrical. How do these things work? This course presents fundamental principles, described quantitatively.

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Electricity in Solutions

This week's theme focuses on the foundations of bioelectricity including electricity in solutions. The learning objectives for this week are: (1) Explain the conflict between Galvani and Volta; (2) Interpret the polarity of Vm in terms of voltages inside as compared to outside cells; (3) Interpret the polarity of Im in terms of current flow into or out of a cell.; (4) Determine the energy in Joules of an ordinary battery, given its specifications; (5) State the “big 5” electrical field variables (potentials, field, force, current, sources) and be able to compute potentials from sources (the basis of extracellular bioelectric measurements such as the electrocardiogram) or find sources from potentials.

Introduction to Week 10:30

What is the Question5:35

About Bioelectricity5:14

Major Sections of the Course5:52

Rectification of Names10:11

Ions in Solution6:55

Core-Conductor Model of a Nerve Fiber9:02

Potential and Voltages in the Fiber5:31

Axial Currents in the Fiber5:08

Membrane Resistance3:53

Membrane Current, Failure & Mystery3:34

Week 1 in Review4:29

Conheça os instrutores

Dr. Roger Barr
Anderson-Rupp Professor of Biomedical Engineering and Associate Professor of Pediatrics
Biomedical Engineering, Pediatrics

So, hello again, this is Rodger Coatbar for the Bioelectricity course.

And I am talking about Section 1 -4 in which there is an overview

of all the different sections, and subsections of this course as a whole.

That's very important, because each thing relates to each of the other things.

We have to discuss them sequentially, but, it is not as though they are independent.

Section 1 which is our present section,

we discussed the background of Bioelectricity.

We talk about the questions we're working on.

And in a little bit, we'll discuss some of the characteristics of electricity,

when it's in salt water.

Section 2 is about Energy.

To make an electrical system work.

Of any kind, you have to have Energy.

In electrical systems, this may be said, you should have to get some voltage.

Voltage is energy for unit of charge.

So you have to get voltage from some place, and within an electrical system.

You have to create that in each segment of active fiber, quite different than in

systems designed by people who are dealing with radios or televisions.

In the course, I've used an analogy of the.

Biological system to railroads, and I've used that analogy because it helps keep

the different pieces in place, and gives a common framework of

reference to help one remember, how one thing relates to another.

So in Bioelectricity, our first task is to get Energy,

perhaps in organizing a train company, we'd need money.

So we'd want to sell some tickets in advance, so

as to build up our bank account.

Section 3 of the course, involves Pumps and Channels.

Pumps came up in the energy development, so here especially Channels.

Channels are specialized structures that, allow the Bioelectric

engine to run, so by analogy in the railroad, I show this train engine.

When you have pumps and channels and voltages.

You can create pulses and

these pulses in Bioelectric systems are called Action potentials.

That is to say Action potentials are pulses,

not all pulses are Action potentials, but Action potentials are pulses.

In this course we consider especially pulses created,

based on the understanding of Hodgkin and Huxley.

And mathematically as described with a Hodgkin-Huxley model.

To actually get an Action potential, you have to have different kind of Channels

in the right phase relationships cooperating and linking one to another.

So as to make it all happen.

So this composite unit, and Action potential

is taken as an analogy to train cars on the Railroad.

Now, no matter how fast our Railroads you have,

the train won't go anywhere if you don't have a Track.

So the Track is absolutely essential, to running trains back and forth.

Similarly, all electric systems have to,

have currents that move from one place to another.

And these currents are determined by the tissue structure.

The currents flow inside the fibers or cells.

Flow outside, and

they flow very importantly, through the electrically active membrane.

And finally, when you have all those things together,

you can make the train go.

So with the Bioelectric system, and finally.

What do we know about each, of the preceding sections?

We can put them together, and form an explanation of propagation.

The means by which action potentials carry information, from one place

to another, so if I put all these things down and one schematic.

See at the top, that my task is to make plans.

Figure out how to get Energy.

And then to understand three things, which are, in a way, independent.

What Channels are, and how they work?

How to put the Channels together, so as to create Action potentials, the pulses, and

then how to figure out and understand, how currents flow from one place to another,

the currents in the living structure.

Once I have all those three together, I can put them together, and

have propagation.

And down at the bottom, you see the same diagram listed by analogy for

the Railroad.

Here's a closeup picture, of the beautiful Duke chapel.

And with that picture, we close this subsection.

I will see you again, shortly for the next.

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