{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

human phys lec 3

# human phys lec 3 - Biophysical ofcellsandtissues...

This preview shows pages 1–8. Sign up to view the full content.

Biophysical basis for electrical activity of cells and tissues

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Electricity review Opposite charges attract, same charges repel Separating opposite charges requires energy Moving like charges closer together requires energy Charged particles can move through materials called conductors , which gives rise to electric current. Charged particles do not move through materials called insulators (also known as dielectric materials). Main conductor in the body is H 2 O A phospholipid bilayer is an insulator (high dielectric constant)
Review of important equations in electricity I = V/R where I is current, V is voltage (potential), R is resistance (Ohm’s Law) I VG h G i d t (1/ R ) A th f f Oh ’ L = where is conductance (1/ ). Another form of Ohm’s Law For current flowing during the charging or discharging of a capacitor I C = C d V /d t

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Electrical units used in physiology Units of current are Amperes (A). In physiology we normally use nA or pA Units of voltage are Volts (V). In physiology we normally use mV Units of resistance are Ohms ( Ω ). In physiology we normally use M Ω Units of conductance are Siemens (S). In physiology we normally use pS Units of capacitance are Farads (F) In physiology we normally use pF Units of capacitance are Farads (F). Units of charge are Coulombs (C) (= the charge of 6.24×10 18 protons) Alessandro Volta, Professor of Physics and Physiology, University of Pavia, Italy from 1779 1804
It is possible to relate electrical charges (in Coulombs) to the number of ions in terms of chemical concentration. The charge of one mole of protons (or electrons) is ~ 96 485 coulombs The charge of one mole of protons (or electrons) is 96,485 coulombs. This number is known as the Faraday constant ( F ) Recall that one mole is ~6.022×10 23 (or Avogadro's number) A current of 1 A = 1 C/sec is equivalent to 6.24×10 18 electrons/sec

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Electrodiffusion refers to the diffusion of charged particles in a solution All particles in solution (including ions) diffuse according to J dif = D d c /d x (first law of diffusion). Charged particles in solution also influenced by electric fields. For example, negatively charged ions will move towards an positively charged electrode. Th l t i d ib d b J d V /d h i th bilit The later process is described by drift = ucz x where u is the mobility constant, c is the concentration of the charged particle, z is the charge on the particle, and d V /d x is the electric field (change of voltage with distance).
Na + (at high concentration) Na + (at low concentration) I i h h b i l l i bl N + Imagine that the membrane is completely impermeable to Na .

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 32

human phys lec 3 - Biophysical ofcellsandtissues...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online