week 3-4 - Question from Practice Midterm What`s a way for...

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Question from Practice Midterm
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What`s a way for calculating the driving force? Ohm`s Law What`s a way for converting the electrical driving force to chemical driving force? Nernst Equation
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Question What if it transports 1 Ca++ and 2Na+ instead of 1 Na+ and 1 H+? What would be the chemical gradient established for Ca++
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Answer 10 fold
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Voltage Clamp Continued
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Drugs Tetrodotoxin (TTX) Blocks Na+ channels Reduce inward currents Tetraethylammonium (TEA) Blocks K+ channels Reduce outward currents
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Why would we want to add drugs to the solution while doing the voltage clamp experiment? The currents that we observe after voltage-clamping the squid axon are a combination of Na+ and K+ currents. Applying those drugs can help us to observe these two types of currents separately. After applying TTX---only K+ current would be observed After applying TEA---only Na+ current would be observed
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Voltage clamp after applying TTX The current observed is an outward potassium current. Which channels contribute to the potassium currents observed?
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Voltage clamp after applying TEA The current observed is an inward sodium current. Which channels contribute to the sodium currents observed? Adding the Na+ and K+ current together one can get the total current.
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Question What would happen to the K+ current during voltage clamp observed if one increases the extracellular K+ concentration?
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Answer Less outward K+ current + decreased amplitude Think of Ohm`s Law Magnitude of current is proportional to the driving force and conductance
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Question from practice midterm.
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What happens before an action potential is transmitted? Stimulants binding to receptors changes membrane permeability to certain ion species, resulting in changes in membrane potentials of afferent neurons.
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Signals integrate at trigger zone (axon hillock) What tells the difference between a strong stimulus and a weak stimulus?
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  • Fall '07
  • French
  • NMDA, frequency stimulus, Low frequency stimulus, high frequency stimulus

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