Download - Lecture Slides Week 8 Slides
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Bioelectricity Week 8
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Bioelectricity -- Week 8
Bioelectricity Week 8:
Stimulation
A) Galvanis observationsB) Spherical cellC) Cylindrical fiber, with timeD) Field stimulation
Train system: -- Control
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Bioelectricity Week 8_2
Stimulation Train system: Control!
1. Introduction to week 8
2. What is meant by stimulation?3. Why analyze stimulation?
4. Analyze Passive instead of Active?5. Single Spherical Cell.6. Strength-Duration Curves
7. Stimulation of a cylinder with cuff electrodes
8. Stimulation , the Tiger function9. Field stimulation, the field10. Field stimulation, the consequences
11. Week 8 in review
12. Good-bye and Special Thanks
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Stimulation
by Galvani
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Galvani experiment, more modern view
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In bioelectricity, stimulation means
The use of electrical currents to influence the action of
excitable tissue.
Often it is used to initiate action potentials.
On other occasions it is used to stop action potentials.
And it can be used to modify function, as done by Galvani.
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Bioelectricity Week 8_4
Stimulation Train system: Control!
1. Introduction to week 8
2. What is meant by stimulation?3. Why analyze stimulation?
4. Why Analyze Passive instead of Active?5. Single Spherical Cell.6. Strength-Duration Curves
7. Stimulation of a cylinder, Tiger function
8. Stimulation with cuff electrodes9. Field stimulation, the field10. Field stimulation, the consequences
11. Week 8 in review
12. Special Thanks
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LinearityIn the context of stimulation
Linearity means that the voltage changes produced by twosimultaneous stimuli are equal to the added results of each oneseparately.
In stimulation linearity cuts the analytical work in half, or more.
Thats because stimulation usually involves 2 or more electrodes, for example, source
and sink. Often linearity means that results from only one electrode have to be found.
The other can be handled with parameter changes, and then added.
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So we will analyze..
..several geometrical arrangements of stimulus electrode and
tissue.
The geometries are sphere, cylindrical cuff, and cylindrical field.
These are chosen to demonstrate different principles of
stimulation.
Each geometry gives insights useful in the others, and in realstimulation as well.
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Bioelectricity Week 8_5
Stimulation Train system: Control!
1. Introduction to week 8
2. What is meant by stimulation?3. Why analyze stimulation?
4. Analyze Passive instead of Active?5. Single Spherical Cell.6. Strength-Duration Curves
7. Stimulation of a cylinder, Tiger function
8. Stimulation with cuff electrodes9. Field stimulation, the field10. Field stimulation, the consequences
11. Week 8 in review
12. Special Thanks
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Bioelectricity Week 8_6
Stimulation Train system: Control!
1. Introduction to week 8
2. What is meant by stimulation?3. Why analyze stimulation?
4. Analyze Passive instead of Active?5. Single Spherical Cell.6. Strength-Duration Curves
7. Stimulation of a cylinder, Tiger function
8. Stimulation with cuff electrodes9. Field stimulation, the field10. Field stimulation, the consequences
11. Week 8 in review
12. Special Thanks
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Strength-duration
Io
Weiss-Lapicque equation
Re-arrange and divide by R.
T is the time required to reach the threshold vm .
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Strength-duration graph
Weiss-Lapicque equation
Ith is the current strength required to reachthreshold vm in stimulus duration T.
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Duke University Gardens
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Bioelectricity Week 8_7
Stimulation Train system: Control!
1. Introduction to week 8
2. What is meant by stimulation?
3. Why analyze stimulation?4. Analyze Passive instead of Active?5. Single Spherical Cell.6. Strength-Duration Curves
7. Stimulation of a cylinder, cuff electrodes
8. Stimulation, Tiger function9. Field stimulation, the field10. Field stimulation, the consequences
11. Week 8 in review
12. Special Thanks
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Stimulation of a cylindrical fiber
using a cuff electrode drawing of currentpattern
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Steady state vm what is the significance of
the minus sign?
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Duke University Gardens
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Bioelectricity Week 8_8
Stimulation Train system: Control!
1. Introduction to week 8
2. What is meant by stimulation?3. Why analyze stimulation?
4. Analyze Passive instead of Active?5. Single Spherical Cell6. Strength-Duration Curves
7. Stimulation with cuff electrodes
8. Stimulation, the Tiger function9. Field stimulation, the field10. Field stimulation, the consequences
11. Week 8 in review
12. Special Thanks
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Stimulation of a cylindrical fiber
using cuff electrodes steady state vm, no time in the equation here.(This is what we showed before.)
So how long does it take to get to the time when this equation is right?
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Stimulation of a cylindrical fiber
using cuff electrodes vm as function of time aswell as distance.
Your instructor calls thisequation the Tiger function.Other people do not use thisname.
Tiger function:
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Graphs of vm with time in it
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Field stimulation, the ideathat is, where current is going, as a picture
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Field stimulation, the beginning1st imagine the activating function established by the electrode
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Note proportionality between vm change with
time and activating function
Rate of change with time,
at the start of excitation,for a fiber at rest.
Activating function (named by Rattay)
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Duke University Gardens
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Bioelectricity Week 8_10
Stimulation Train system: Control!
1. Introduction to week 8
2. What is meant by stimulation?3. Why analyze stimulation?
4. Analyze Passive instead of Active?5. Single Spherical Cell.6. Strength-Duration Curves
7. Stimulation of a cylinder, Tiger function
8. Stimulation with cuff electrodes9. Field stimulation, the field10. Field stimulation, the consequences
11. Week 8 in review
12. Special Thanks
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Field stimulation, where it goes, convolution
The response depends on the activation function convolved with the Tigerfunction
Here f() is the activating function,and G() is the Tiger function.
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Field stimulation, where it goes, drawing
Here f() is the activating function, and G() is theTiger function.
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Stimulation
by Galvani
Creating an activation function andconvolving it with the Tiger function
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Duke University Gardens
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Bioelectricity Week 8_11
Stimulation Train system: Control!
1. Introduction to week 8
2. What is meant by stimulation?3. Why analyze stimulation?
4. Analyze Passive instead of Active?5. Single Spherical Cell.6. Strength-Duration Curves
7. Stimulation of a cylinder, Tiger function
8. Stimulation with cuff electrodes9. Field stimulation, the field10.Field stimulation, the consequences
11. Week 8 in review
12. Special Thanks.
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Week 8 in Review - 1
We know now that the stimulation creates action potentials, and the actionpotentials propagate, release calcium ions, and the muscle contracts
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Week 8 in Review -2
With a spherical cell model one knows that strength and duration interact toreach a vm level sufficient to initiate action potentials.
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Reviewing the course
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The train
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Bioelectricity Week 8_12
Stimulation Train system: Control!
1. Introduction to week 8
2. What is meant by stimulation?3. Why analyze stimulation?
4. Analyze Passive instead of Active?5. Single Spherical Cell.6. Strength-Duration Curves
7. Stimulation of a cylinder, Tiger function
8. Stimulation with cuff electrodes9. Field stimulation, the field10. Field stimulation, the consequences
11. Week 8 in review
12. Special Thanks
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Bioelectricity extends Special Thanks
To you, in this first offering of the online course.
Thank you for your patience, perseverance, andgood humor throughout the weeks of study of a
complex subject.
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Roger Coke Barr extends Special Thanks
To you, as a student in the first offering of this online
course.
Thank you for your patience, perseverance, and
good humor throughout the 8 weeks of study of thisfascinating but complex subject.
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Roger Coke Barr also extends Special Thanks
To Robert Plonsey, Emeritus Professor of Biomedical Engineering at Duke.Professor Plonsey is the senior author of the Bioelectricity AQA text on which this
course is based. His precise presentation of fundamental principles in
mathematical form has served to provide a foundation to the whole field of study.
To Madison S. Spach, Emeritus Professor of Pediatrics and Physiology at Duke.Professor Spachs leadership of research in cardiac electrophysiology and originalinsights in electrophysiological theory and experiment have energized all the
faculty and students around him.
To Andrew E. Pollard, Professor of Biomedical Engineering at the University ofAlabama at Birmingham, whose boundless good humor, original thinking, and
systematic development serve as a continuous stimulation to keep thinking and
keep having fun.
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Sarah Duke Garden, Duke University