BIOB32H3 Lecture Notes - Local Field Potential, Rigor Mortis, Sarcomere

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cerisealligator589

8 May 2012

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Review the goldman equation: combine all the ions together. In frog, pk is extremely larger than pna. Why? cuase the leak channel of k+ is open in resting axon main reason of the vm ( leak channel only refers to the k+) Pcl can be ignored m, since almost impermeable: compare with nernst equation. N only gives you ek , not thinking about permeability ,only concentration. While goldman, takes into account multiple ions. The intensity necessary to trigger at least one or a few axon to fire ap. Max stim: max # of axons fire max cap. Tm: the hodgkin cycle: positive feedback loo. Current applied from outside ( electrode stimulus on the neuron), to trigger just a few na+ channel to open, but not enough to trigger a all-or non-ap. Then more na+ channel( voltage-gated na+ cchannel, activated by depolarization open due to depolarization )

Related Questions

Why does changing concentrations of ions change equilibrium potential and changing permeability affect threshold? You might want to discuss the Nernst Equation vs the Goldman equation.

viridiantortoise718

In the cell, which of the following parameters is the easiest to change?
1. The charge of each ion
2. The permeability of each ion
3. The concentration difference of each ion
The answer is the second one (permeability of each ion). However I don't understand how you can change the permeability of an ion and how is it easier than changing the concentration difference of each ion?

Compare the intracellular and extracellularconcentrations for Na and K of a %u201Cgeneral%u201D mammalian cellto that in a squid which lives in the salty ocean. What are thevalues for Na and K out and in? (You can find values by going togoogle and typing in %u201Csquid axon ion concentrations%u201D orgoing to http://faculty.weber.edu/nokazaki/Comparative%20Animal%20Physiology/Tests/Chp%2011%20Essay%20questions.htm). Why are they different? Why is the voltage ofthe squid neuron so very similar to that of a %u201Cgeneral%u201Dmammalian cell (hint: is it the absolute concentrations of ionsthat are important or their ratios across the plasma membrane)?

You will be plotting the flowof ions -
which is an electrical current. When you make yourplots, the y axis
will be the amount of current flow. Make it sothat inward current
(that is, net flow of ions into the cell) isdownward (below zero), and
outward current (that is, the flow of ions out ofa cell) is positive.

Then, Use the Goldman equation and the Goldmanequation simulator to answer the following questions. Whenanswering "Why" questions, do so in one-two sentences.

Start with the default conditions in thesimulator.

PK = 100 Ko = 10mM Ki = 100

PNa =1 Nao =100 Nai = 1

PCl =10 Clo= 100 Cli = 10

What is the voltage of a cell that has thesevalues? Why

If the relative potassium permeability waschanged to 1, what would be the voltage of the cell? Why?

Change the permeability of K back to 100. Ifthe permeability to chloride is changed from 10 to 100, will therebe a voltage change? Why?

Change the permeability of chloride back to10. Now, change the extracellular concentration of potassium to 90mM. What is the voltage of the cell? Why?

Now change the extracellular concentration ofpotassium to 200. What is the voltage of the cell? Why? Now changethe permeability to potassium to 9999. Is there a further largechange in the voltage of the cell? Why?

amaranthjackal220

BIOB32H3 Lecture Notes - Local Field Potential, Rigor Mortis, Sarcomere

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