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19 Cards in this Set
- Front
- Back
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What did Luigi Galvani discover
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He discovered the electrophysiology of the brain
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What is an ion, what is a cation and what is an anion
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An ion is a charged atom; a cation is a positively charged atom; an anion is a negatively charged atom
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List three ways electricity in the nervous system differs from electricity in wires.
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Conducted by charged atoms rather than electrons; current flows across membranes rather than along wires; Almost all of the electrical signaling in the nervous system is related to changes n the membrane potential/transmembrane potential
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What is a lipid bilayer composed of and how are these molecules arranged?
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Composed of phospholipids with hydrophilic phosphate facing the outside; hydrophobic nonpolar tail of hydrocarbon on the interior
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What are ion selective channels and briefly, what do they do?
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Openings in the membrane that serve as pores through which ions can passed; regulate concentration of ions inside and out
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How does water associate with cations and anions in solution?
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Water is polar, so negatively charged anions are attracted to the H and positively charged cations are attracted to the O
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Why might the size of a potassium-selective channel be able to exclude sodium even though sodium ions are smaller than potassium ions?
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Large ions like K+ have fewer bound molecules than smaller ions like Na+ due to its less localized charge field ~ membrane could exclude Na+, but not K+
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If a membrane of a cell is permeable to all ions, is there a point when ions finally stop flowing across the membrane? Why (in 2 sentences or less)?
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Yes, once concentration gradient reaches equilibrium
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What is the meaning of a concentration gradient across a membrane? How do ions behave in such a gradient?
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The relation of two given areas, where the concentration of a particular substance differs between those areas. Diffusion will result in this substance moving along a concentration Gradient until the concentration of the two areas becomes equal.
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How do impermeable anions and ion-selective channels lead to a membrane potential?
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There is a higher concentration of K+ inside, so there is also a greater concentration of negative charge inside; eventually the K+ leave due to the concentration gradient, leaving the negative charge
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Why is a cell membrane like a capacitor?
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Opposite charges attract so they line up on either side of the membrane ~ bulk solution on either side is electroneutral. It can store charge.
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What two gradients are in balance when an ion is said to be at its equilibrium potential?
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Concentration and electrical
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Write the Nernst potential equation. Be able to solve it for common cations and anions.
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Eion = 2.303RT/zF log{[ion]out/[ion]¬in}; 2.3RT/F = 60mV
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List the inside and outside concentrations for Na+ and K+ for a typical cell.
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Na+ = 15mM inside & 150mM outside (Eq. Potential = 62 mV)
K+ = 100 mM inside & 5 mM outside (Eq. Potential = -80 mV) |
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What does depolarize mean? What does hyperpolarize mean?
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Means that the gradient is altered such that the membrane potential equals 0; hyperpolarize means the membrane potential becomes very negative
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Why is the GHK useful?
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Useful, because in order to calculate the resting potential in a neuron we need to account for the roles of multiple ions that have permeabilities
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What is the difference between an equilibrium and steady state?
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In equilibrium, all chemical potential gradients are zero and the rate in equals the rate out; at steady state, concentration is not changing
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Why is a Na+/K+ pump required in a neuron?
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Alters membrane permeability to change membrane potential to allow current to flow down axon
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What does electrogenic mean when talking about a pump?
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It sends 3 Na+ out for 2K+ in ~ it tends to make the inside more negative, while maintaining the concentration gradient
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