What is the approximate membrane potential (mV) when the neuron is ready to be "fired"?

Write a question about the electrical action potential of the human nervous system in terms of physics.

Assume a length of axon membrane of about 0.10 m is excited by an action potential (length excited = nerve speed x pulse duration equal and opposite charge of negative organic ions, as shown in the figure below. Model the axon as a parallel-plate capacitor and take C = K² A/d and Q radius r = 1.6 × 10¹ μm, and cell-wall dielectric constant x = 2.9. = Positive charge layer Negative charge layer + External fluid Axon wall membrane No Axon radius = r + Internal fluid + How many sodium ions (Na+) is this? Na+ ions d + (a) Calculate the positive charge on the outside of a 0.10-m piece of axon when it is not conducting an electric pulse. (Assume an initial potential difference of 7.0 × 10-² V.) -2 9.03E-10 C How many K+ ions are on the outside of the axon assuming an initial potential difference of 7.0 × 10-² V? 5.639E9 K+ ions = 50.0 m/s X 0.0020 s = 0.10 m). In the resting state, the outer surface of the axon wall is charged positively with K+ ions and the inner wall CAV to investigate the…

3 Nernst Potential A cell memberane is selectively permeable: some ions can flow through it, and others cannot. When ions diffuse acros the membrane, the difference in concentration creates an electric potential difference and an electric field. The difference in concentration of potassium ions inside and outside of the cell is the main contribution to the "resting potential" of a сross neuron. The Nernst potential is the potential difference across a cell membrane due to the diffusion of ions through it: kgT In AV = Ze Co kg = 1.38 x 10-23 J/K is Boltzmann's constant, T is the temperature in degrees kelvin (K), e is the proton charge, Z is the ionic charge, c, is the molar concentration inside the membrane, and c, is the molar concentration outside the membrane. For a singly ionized molecule – like sodium (Na*) or potassium (K+) ions – we have Z = 1. (a) Suppose that the extracellular fluid of a cell – the fluid outside the cell memberane – has a potassium ion con- centration of…

Voltage across the resting membrane potential…A) Can be described by the Nernst equation.B) Is established by a difference in charges across the cell membrane, with the outside more negative than the inside.C) Defines the driving force for flow of a particular ion across the cell membrane, given its equilibrium potentialD) Is equally dependent on the flow of potassium and sodium ions through leak channels across the cell membrane.E) Stays the same during an action potential.

Assume a length of axon membrane of about 0.10 m is excited by an action potential (length excited = nerve speed pulse duration = 50.0 m/s 2.0 103 s = 0.10 m). In the resting state, the outer surface of the axon wall is charged positively with K+ ions and the inner wall has an equal and opposite charge of negative organic ions, as shown in Figure P18.43. Model the axon as a parallel-plate capacitor and take C = 0A/d and Q = C V to investigate the charge as follows. Use typical values for a cylindrical axon of cell wall thickness d = 1.0 108 m, axon radius r = 1.0 101 m, and cell-wall dielectric constant = 3.0. (a) Calculate the positive charge on the outside of a 0.10-m piece of axon when it is not conducting an electric pulse. How many K+ ions are on the outside of the axon assuming an initial potential difference of 7.0 102 V? Is this a large charge per unit area? Hint: Calculate the charge per unit area in terms of electronic charge e per squared (2). An atom has a cross section of about 1 2 (1 = 1010 m). (b) How much positive charge must flow through the cell membrane to reach the excited state of + 3.0 102 V from the resting state of 7.0 102 V? How many sodium ions (Na+) is this? (c) If it takes 2.0 ms for the Na+ ions to enter the axon, what is the average current in the axon wall in this process? (d) How much energy does it take to raise the potential of the inner axon wall to + 3.0 102 V, starting from the resting potential of 7.0 102 V? Figure P18.43 Problem 43 and 44.

6. The giant axon of a squid is 0.5 mm in diameter, 10 cm long, and not myelinated. Unmycli- nated cell membranes behave as capacitors with 1 μF of capacitance per square centimeter of membrane area. When the axon is charged to the -70 mV resting potential, what is the energy stored in this capacitance?

To measure signal propagation in a nerve in the arm, the nerve is triggered near the armpit. The peak of the action potential is measured at the elbow and then, 4.0 ms later, 24 cm away from the elbow at the wrist.a. What is the speed of propagation along this nerve?b. A determination of the speed made by measuring the time between the application of a stimulus at the armpit and the peak of an action potential at the elbow or the wrist would be inaccurate. Explain the problem with this approach, and why the noted technique is preferable.

3. Living cells "pump" singly ionized sodium ions, Na+, from the inside of the cell to the outside across the membrane potential AVmembrane = Vin - Vout= -70 mV. It is called pumping because work must be done to move a positive ion from the negative inside of the cell to the positive outside, and it must go on continuously because sodium ions "leak" back through the cell wall by diffusion. a. How much work must be done to move one sodium ion from the inside of the cell to the outside? b. At rest, the human body uses energy at the rate of approximately 100 W to maintain basic metabolic functions. It has been estimated that 20% of this energy is used to operate the sodium pumps of the body. Estimate to one significant figure the number of sodium ions pumped per second.

Please help. The nonpolar core of the membrane of a muscle cell has a thickness d = 4nm and a dielectric constancy k = 20. (a) What is the surface capacity of the membrane? Express your response in microcoulombs per square centimeter. (b) During muscle contraction, the internal potential of the cell increases by about 100 mV. For 1 cm2 of membrane, how many Na+ ions must have entered the cell for this purpose? (c) The medium outside the cell initially contains 0.150 mol / L of Na + ions in solution. Considering that it extends to 1 µm from the cell, what is the decrease in Na+ concentration immediately after the change in potential? (d) Estimate the number of times the process can be repeated before the Na+ ion reserve is exhausted. Please show formulas ans steps for my own understanding