ECEN 43415341 Currents and Voltages in the Body

ECEN 4341/5341 Currents and Voltages in the Body Lecture 5. 1/25/2019 1

Assignment 1 Read Chapters 2 and 3 2. Read two papers and write a 1 page summary on each. One paper should be on exposures from external sources of electric or magnetic fields or on internally generated fields from within the body. 2

Electrical Voltages and Currents In the Body 1. The Body is an Electro Chemical System A. Basic Sources of Energy are the Metabolic Processes in the mitochondria which supply about 95% of the energy for the cell by combining O 2 with glucose to form ATP. This in turn supplies the energy for the pumps that maintain the ion gradients across membranes and generate the electric potentials of -50 to -100 m. V between the outside and the inside of a cell. This leads to trans membrane fields on the order of 107 V/m B. There also endogenous electric fields in the extracellular fluids in the range of 10 to 100 V/m 3

Cell Models

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Source of Electric Fields 1. Plasma membrane that defines the cell boundary and the voltage is negative on the inside. 2. The Epithelium that surrounds every organ and the skin. This leads to the Transepithelial Potential, TEP, which is positive on the inside. 3. The TEP fields move ions and molecules around are the driving force for the growth of embryos and wound healing etc. 6

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A Cell Membrane Cartoon Voltage inside - 50 to -100 m. V about 1 charge per atoms 9

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Transepithelial Potential 1. Note separation of the Na and K channels 15 -60 m. V 11

Current Densities 1. 2. 3. Currents across cell membranes 1 μA/cm 2 to 10 μA/cm 2 the interior of the cell is negative. The Transepithelial Potential (TEP) is positive at the inside of the skin. Current densities from 10 μA /cm 2 to 100 μA /cm 2 Shocks at approximately 10 m. A 12

Lecture 6 Monday 28 2019 13

Chick Embryos 14

Effects are Time Dependent Applied external currents can cause abnormalities in the neural-stage embryo stage and not Gastrula-stage At 25 -75 m. V/mm leads to abnormalities 15

Measurements Around an Chick Embryo 16

Currents As Function of Position 17

Voltage Gradients 18

Planarian Regeneration 19

Growth of Planarian Flatworm In an Electric Field. Wendy Beane In vivo studies show that electric fields have a lot to do in controlling the size and shape of the growth. 20

Limb Currents • Amputated Limbs 10 to 100μA/cm 2 out of the cut. 60 m. V/mm to start and down to 25 m. V/mm within 6 hr (Note in other units these are Volts/meter) • Growth occurs toward negative electrode. Used to guide direction of nerve growth. • The currents during growth in a root or other cell can flow in one end and back into the side of the cell. • We have seen effects as low as 0. 2 m. V across a membrane in changing the oscillation of pacemaker cells or fields of 0. 01 V/m • Electroporation 1. 5 to 3 V/cell 21

Currents Near Wounds 22

Current Flow at a Cut 23

Electric Fields Near a Cut 24

Equivalent Circuit Model 25