Bioelectricity: A Quantitative Approach

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

Created by:  Duke University

• Taught by:  Dr. Roger Barr, Anderson-Rupp Professor of Biomedical Engineering and Associate Professor of Pediatrics

  Biomedical Engineering, Pediatrics

Level Intermediate Language English How To Pass Pass all graded assignments to complete the course. User Ratings 4.7 stars Average User Rating 4.7See what learners said Coursework

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Syllabus


WEEK 1


Electricity in Solutions



This week's theme focuses on the foundations of bioelectricity including electricity in solutions. <p>The learning objectives for this week are:</p><p>• Explain the conflict between Galvani and Volta</p><p>• Interpret the polarity of Vm in terms of voltages inside as compared to outside cells</p><p>• Interpret the polarity of Im in terms of current flow into or out of a cell.</p><p>• Determine the energy in Joules of an ordinary battery, given its specifications.</p><p>• 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.</p>


12 videos, 5 readings expand

1. Reading: Welcome to the Course
2. Reading: Assessments, Grading and Certificates
3. Reading: Course Lecture Slides
4. Reading: Discussion Forums
5. Reading: Reference Text
6. Video: Introduction to Week 1
7. Video: What is the Question
8. Video: About Bioelectricity
9. Video: Major Sections of the Course
10. Video: Rectification of Names
11. Video: Ions in Solution
12. Video: Core-Conductor Model of a Nerve Fiber
13. Video: Potential and Voltages in the Fiber
14. Video: Axial Currents in the Fiber
15. Video: Membrane Resistance
16. Video: Membrane Current, Failure & Mystery
17. Video: Week 1 in Review

Graded: Quiz 1A
Graded: Quiz 1B

WEEK 2


Energy into Voltage



This week we will examine energy, by which pumps and channels allow membranes to "charge their batteries" and thereby have a non-zero voltage across their membranes at rest. <p>The learning objectives for this week are:</p> <ul><li> Describe the function of the sodium-potassium pump</li><li> State from memory an approximate value for RT/F</li><li>Be able to find the equilibrium potential from ionic concentrations and relative permeabilities</li><li> Explain the mechanism by which membranes use salt water to create negative or positive trans-membrane voltages</li></ul>


12 videos expand

1. Video: Introduction to Week 2
2. Video: A Membrane Patch; the Idea of It
3. Video: Energy as Trans-membrane Voltage Vm
4. Video: Sodium-potassium Pumps
5. Video: Ionic equilibrium
6. Video: Battery lifetime
7. Video: Problem session 1
8. Video: Membrane Resistance Rm
9. Video: Membrane capacitance Cm
10. Video: Why is Cm so big?
11. Video: Problem session, R and C
12. Video: Week 2 summary

Graded: Quiz 2A
Graded: Quiz 2B

WEEK 3


Passive and Active Resonses, Channels



This week we'll be discussing channels and the remarkable experimental findings on how membranes allow ions to pass through specialized pores in the membrane wall. <p>The learning objectives for this week are:</p><ul><li>Describe the passive as compared to active responses to stimulation</li><li>Describe the opening and closing of a channel in terms of probabilities</li><li>Given the rate constants alpha and beta at a fixed Vm, determine the channel probabilities</li><li>Compute how the channel probabilities change when voltage Vm changes.</li></ul>


12 videos, 1 reading expand

1. Video: Introduction to Active Response
2. Video: Why are passive and active so different?
3. Video: The simulation set-up
4. Video: The passive simulation
5. Video: The active simulation
6. Video: Where does the active response come from?
7. Video: Problem session, passive v active
8. Video: Channels: Experimental isolation of a channel
9. Video: Channels: Observed currents, voltage step
10. Video: Channels: Probability of being open
11. Video: Problem session, Channel probabilities
12. Video: Week 3 Conclusions
13. Reading: Alpha Beta Programming Assignment Instructions

Graded: Quiz 3A
Graded: Quiz 3B
Graded: Alpha Beta Programming Assignment

WEEK 4


Hodgkin-Huxley Membrane Models



This week we will examine the Hodgkin-Huxley model, the Nobel-prize winning set of ideas describing how membranes generate action potentials by sequentially allowing ions of sodium and potassium to flow.<p>The learning objectives for this week are:</p><ul><li>Describe the purpose of each of the 4 model levels (1) alpha/beta (2)probabilities (3) ionic currents (4) trans-membrane voltage</li><li>Estimate changes in each probability over a small interval $$\Delta t$$</li><li>Compute the ionic current of potassium, sodium, and chloride from the state variables</li><li>Estimate the change in trans-membrane potential over a short interval $$\Delta t$$</li><li>State which ionic current is dominant during different phases of the action potential -- excitation, plateau, recovery</li></ul>


12 videos, 1 reading expand

1. Video: Introduction to Action Potential
2. Video: What is the Problem
3. Video: HH replacement for Rm
4. Video: The equation for each pathway
5. Video: Changes in n, m, h
6. Video: Equations for alphas and betas
7. Video: Problem session, I_Na
8. Video: Putting it all together
9. Video: Changes in n, m, h, and Vm
10. Video: Numerical calculations, time and space
11. Video: Problem session, a Vm step
12. Video: Week 4 conclusions
13. Reading: Action Potential Programming Assignment

Graded: Quiz 4A
Graded: Quiz 4B
Graded: Action Potential Programming Assignment

WEEK 5


Axial and Membrane Current in the Core-Conductor Model



This week we will examine axial and transmembrane currents within and around the tissue structure: including how these currents are determined by transmembrane voltages from site to site within the tissue, at each moment. <p>The learning objectives for this week are:</p><ul><li>Select the characteristics that distinguish core-conductor from other models.</li><li>Identify the differences between axial and trans-membrane currents</li><li>Given a list of trans-membrane potentials, decide where axial andtrans-menbrane currents can be found.</li><li>Compute axial currents in multiple fiber sigments from trans-membrane potentials and fiber parameters</li><li>Compute membrane currents at multiple sites from trans-mebrane potentials</li></ul>


12 videos expand

1. Video: Introduction to Currents in Structure
2. Video: And now for something a little different
3. Video: Alternative tissue structures
4. Video: A 1D uniform cable model
5. Video: Grid divisions of a 1D model
6. Video: The local current loop
7. Video: Problem session, around the loop
8. Video: Determining axial current
9. Video: Determining trans-membrane current
10. Video: How does one know, without I_ion?
11. Video: Problem session, getting Ia and Im
12. Video: Week 5 in review

Graded: Quiz 5A
Graded: Quiz 5B

WEEK 6


Propagation



this week we will examine how action potentials in one region normally produce action potentials in adjacent regions, so that there is a sequence of action potentials, an excitation wave. the learning objectives for this week are: </p><ul><li>Identify the differences between the propagation pattern following sub-threshold versus threshold stimuli</li><li>Compute the changes in transmembrane potentials and currents from one time to a short time laterIdentify the outcome of stimulating a fiber at both ends</li><li>Quantify the interval after propagation following one stimulus to the time when there will be another excitation wave following a 2nd stimulus</li><li>Explain why "propagation" is different from "movement"</li></ul>


12 videos, 1 reading expand

1. Video: 6-1: Introduction to Propagation
2. Video: 6-2: Sub-threshold Stimulation
3. Video: 6-3: Threshold stimulation, time
4. Video: 6-4: Threshold stimulation, space
5. Video: 6-5: Stimulation at both ends
6. Video: 6-6: S1-S2 stimulation, varying interval
7. Video: 6-7: Problem session, excitation waves
8. Video: 6-8: Propagation, not movement
9. Video: 6-9: Axial currents as stimulus currents
10. Video: 6-10: The equation for velocity changes
11. Video: 6-11: Problem session, change in velocity
12. Video: 6-12: Week 6 in review
13. Reading: Propagation Programming Assignment Instructions

Graded: Quiz 6A
Graded: Quiz 6B
Graded: Propagation Programming Assignment Quiz

WEEK 7


Course Conclusion and Final Exam
In Week 7, we will briefly review the course, take a quick look at the next course at the second course in the series and complete the final exam. Good luck and thank you for joining me in the course. rcb.


2 videos expand

1. Video: 7-1: Course Review and a Look Forward
2. Video: 7-2: Good-bye and special thanks

Graded: Final Exam A
Graded: Final Exam B