You are recording from a cell with a restingmembrane potential of -65 mV. You inject 100pA of current, resulting 58.7 mV.What is the value of tau? With this in mind, whatis the capacitance of the cell? Please providerelevant equations to illustrate your thoughtprocess.When you terminate the current injection, howlong do you expect for it to take for the cell torepolarize to -63 mV?

Electrophysiology of the cell -- Electrophysiology explains ,cell as electrical equivalent circuits…

Answered: You are recording from a cell with a…

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter4: Principles Of Neural And Hormonal Communication

Section: Chapter Questions

Problem 3SQE

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One of the important uses of the Nernst equation is in describing the flow of ions across plasma membranes. Ions move under the influence of two forces: the concentration gradient (given in electrical units by the Nernst equation) and the electrical gradient (given by the membrane voltage). This is summarized by Ohms law: Ix=Gx(VmEx) which describes the movement of ion x across the membrane. I is the current in amperes (A); G is the conductance, a measure of the permeability of x, in Siemens (S), which is I/V;Vm is the membrane voltage; and Ex is the equilibrium potential of ion x. Not only does this equation tell how large the current is, but it also tells what direction the current is flowing. By convention, a negative value of the current represents either a positive ion entering the cell or a negative ion leaving the cell. The opposite is true of a positive value of the current. a. Using the following information, calculate the magnitude of Na [ Na+ ]0=145mM,[ Na+ ]i=15mM,Gna+=1nS,Vm=70mV b. Is Na+ entering or leaving the cell? c. Is Na+ moving with or against the concentration gradient? Is it moving with or against the electrical gradient?
Patch clamp recording of a single ion channel yields the following results: Holding Potential (mV) Measured Current (pA) -100 -1.0 -50 0.0 0 +1.0 +50 +2.0 +100 +3.0 part a.) Calculate the membrane potential at the instant when a neuron has the following relative permeabilities: PK+ = 1.0, PNa+ = 1.0, PCl- = 1.0. Use the ionic concentration values in the picture included. a.) -12 mv b.) -35mv c.) -60 mv d.) +20 mv e.) 0 mv part b.) What would be the equilibrium potential for K+ in neurons under such circumstances? a.) -11 mv b.) +30 mv c.) +75 mv d.) -35 mv e.) 0 mv part c.) What would be the new resting potential, discounting the effects of non-gated chloride channels (just give an approximate value – no calculation is necessary)? a.) about +20 to +25 mV b.) about -30 to -40 mV c.) about +1 to +5 mV d.) close to ENa+ e.) about -10 to -15 mV
when calculating the Resting membrance potential using the goldman equation it is usally out, out , in / in, in, out. the cl- is switched so does that mean that when writing the in and out cellular concentartion should we still add negative sign in front of the value or since it is flipped we shouldnt?.
Calculate the free energy of transport for the movement of potassium by the sodium/potassium pump under normal physiological conditions: 4 mM serum potassium, 135 mM intracellular potassium, 37.1 °C, and resting potential -82 mV. Express your answer in kJ/mol. Show all work. Calculate the free energy of transport for the movement of potassium by the sodium/potassium pump under disturbed conditions of 2 mM serum potassium. Assume all other parameters remain the same. Express your answer in kJ/mol. Show all work. What factors could limit the continued action of the sodium/potassium pump when only 2 mM potassium is present in the blood plasma? Note that under normal physiological conditions, the cell interior contains 11 mM sodium and the blood contains 140 mM sodium.
At the peak of the action potential, Vm is approximately -65 mV. Assuming normal intracellular and extracellular K+ concentrations (refer to the table), (1) calculate the driving force (in mV) that acts on K+ ions and (2) use the information obtained in part 1 to determine the direction in which K+ ions will flow (i.e., into the cell or out of cell)
What is the intracellular voltage for Cl- if the intracellular concentration was 5 mM and the extracellular concentration was 130 mM. Write the voltage as a number in mV inside the cell relative to that outside, eg. -72 or + 90. Question 2. What is the intracellular voltage for Ca++ if the intracellular concentration was 0.0008 mM and the extracellular concentration was 0.6 mM. Write the voltage as a number in mV inside the cell relative to that outside, eg. -72 or +90. Round to the nearest milli Volt.
The typical distribution of K+ and Na+ ions inside and outside the cell is: [K+]in = 150 mM; [K+]out = 5 mM; [Na+]in = 10 mM; [Na+]out = 150 mM What are reversal potentials for Na+ and K+ at 25oC ? What should be the ratios of PNa/PK at (i) rest (-60 mV) and (ii) during the action potential (+20 mV) to generate a spike from -60 to +20 mV. Use the short form of Goldman equation.
Calculate the equilibrium membrane potentials to be expected across a membrane at 37 ∘C, with a NaCl concentration of 0.50M on the "right side" and 0.08 M on the "left side", given the following conditions. In each case, state which side is (+) and which is (−). (a)Membrane permeable only to Na+.
Separately, draw a table using arrows to depict the appropriate magnitude and direction of the forces and ion fluxes at different membrane potentials for a ligand-gated channel that is equally permeable to both ion X+ and ion Y+. The equilibrium potential for ion X+ is -60 mV, and the equilibrium potential for ion Y+ is -20 mV. Which item best represents the forces and fluxes for a membrane potential of -40 mV?
Separately, draw a table using arrows to depict the appropriate magnitude and direction of the forces and ion fluxes at different membrane potentials for a ligand-gated channel that is equally permeable to both ion X+ and ion Y+. The equilibrium potential for ion X+ is -60 mV, and the equilibrium potential for ion Y+ is -20 mV. Which item best represents the forces and fluxes for a membrane potential of -40 mV (a, b, c, or d)? Upwards arrows means outward direction and downwards arrow means inward direction. The length of the arrow determines the magnitude.
The ion flows across neuronal membranes at rest and duringan action potential do not significantly change bulk ionconcentrations, except for that of Ca2+ ions. Resting Ca2+ ionconcentrations in cells are usually about 10–7 M, and Ca2+ ionsexert physiological effects at concentrations of perhaps 10–5 M.Explain why relative changes of intracellular [Ca2+] are muchgreater than for, say, [Na+] (12–50 mM).
If a particular neuron has an intracellular Chloride concentration of 154.3 mM, an extracellular Chloride concentration of 163.2 mM, and a membrane potential of -54.1, what is the net driving force (in mV) acting upon Chloride?

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