Membrane-potential-activity

Membrane-potential-activity - Membrane Potential Discovery...

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Membrane Potential Discovery Activity Before starting, you should understand the following: ion cation anion concentration gradient simple diffusion What ions are the predominant ions of the extracellular fluid?_____________________ of the intracellular fluid? __________________________________________________ Membrane Potentials: This exercise is designed to help you understand the basis of resting membrane potentials, graded potentials, and action potentials in living cells. When we do this as a formal activity, we use different color poker chips to represent different ions (see supply list below). If you are doing it at home, you can use anything small and convenient, such as 4 different types of dried beans or pennies, nickels, dimes, and quarters. A piece of paper divided into two sections represents the intracellular (ICF) and extracellular (ECF) compartments. The two compartments are the same size. The dividing line between the compartments represents the cell membrane. Colored rectangles of paper are used to indicate ion channels. When the long axis of a channel is perpendicular to the membrane, the channel is open and ions can flow through it. (see figure below) SUPPLY LIST Paper into two compartments labeled ECF and ICF) One die ( 2 of a pair of dice) Small rectangles representing: K + leak channel Na + leak channel
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Membrane Potentials 1 gated Na + channel gated K + channel gated Cl channel Colored paper circle representing the Na + /K + -ATPase colored poker chips or other objects to represent chloride ions, Na + , protein anions, K + Electricity Review: Atoms, the smallest units of matter, are electrically neutral entities. They are composed of positively charged protons, negatively charged electrons, and uncharged neutrons, but in balanced proportions so that an atom is neither positive nor negative. The removal or addition of electrons to an atom creates a charged particle known as an ion . Positive ions, or cations , that are important in the human body include Na + , K + , and H + . For each of these positive ions, somewhere there is a matching electron, usually found as part of a negative ion, or anion . For example, when Na + in the body enters in the form of NaCl, the “missing” electron from Na can be found on the Cl - . The following principles are important to remember when dealing with electricity in physiological systems: (1) The Law of Conservation of Electric Charge states that the net amount of electric charge produced in any process is zero. This means that for every positive charge on an ion, there is an electron on another ion. Overall, the human body is electrically neutral. (2) Opposite charges (+/-) are attracted to each other, but two charges of the same type (+/+ or -/-) repel. With ions, the ion species does not matter: only the net charge on the ion is important. Thus a Cl - has one negative charge that is equal and opposite to one Na + or one K + . (3) To separate positive and negative charges, it is necessary to use energy. For example,
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This note was uploaded on 06/10/2011 for the course BIO 365S taught by Professor Silverthorn during the Spring '08 term at University of Texas.

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Membrane-potential-activity - Membrane Potential Discovery...

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