In a simple model of an axon
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- The velocity of spike propagation is proportional to the following combination of factors: 1 a C, V R„R, m Where a is the radius of the axon, Rm and R; are specific resistances of the membrane and the internal buffer, respectively. If we double the radius and simultaneously increase the concentration of salt inside the axon twice (i.e. R; decreases two times), by how many fold will the velocity change?arrow_forwardAssume 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 × 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 has an 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 = ke,A/d and Q = CAV to investigate the charge as follows. Use typical values for a cylindrical axon of cell wall thickness d = 1.4 x 10-8 m, axon radius r = 1.4 x 101 um, and cell-wall dielectric constant k = 2.2.arrow_forwardWhat is the magnitude of the electric field in unite of N/C across an axon membrane (1.00x10^0)x10-8 m thick if the resting potential is -(7.400x10^1) mV?arrow_forward
- 12. (a) Using Eq. AQ=CAV and the data in the Table, calculate the number of ions entering the axon during the action potential, per meter of nonmyelinated axon length. (The charge on the ion is 1.6 x 10-19 coulomb.) (b) During the resting state of the axon, typical concentrations of sodium and potassium ions inside the axon are 15 and 150 millimole/liter, respectively. From the data in the Table, calculate the number of ions per meter length of the axon. Table 13.1 Properties of Sample Axons Hint: 1 F (farad) = 1coulomb/1 volt Property Nonmyelinated axon Myelinated axon Axon radius 5 x 10-m 5 x 10-6 m 1 mole /liter = 6.02 x 1020 particles (ions, atoms, etc. ) Resistance per unit length of fluid cm 6.37 x 10°2/m 6.37 x 10°2/m both inside and outside axon (r) Conductivity per unit length of axon membrane (gm) 1.25 x 10-4 mho/m In the resting state, the axon voltage is -70mV. During the pulse, the voltage changes to about +30mV, resulting in a net voltage change across the membrane of 100…arrow_forwardAssume a length of axon membrane of about 0.10 m is excited by an action potential (length excited = nerve speed x pulse duration = 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 has an 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 = CAV to investigate the charge as follows. Use typical values for a cylindrical axon of cell wall thickness d = 2.0 x 10-8 m, axon radius r = 1.6 x 10¹ μm, and cell-wall dielectric constant k = 2.9. Positive charge layer Negative charge layer External fluid Axon wall membrane Internal fluid - Axon radius= d -2 (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 x 10-² v.) 9.03E-10 C How many K+ ions are on the outside of the axon assuming an…arrow_forwardAssume a length of axon membrane of about 0.10 m is excited by an action potential (length excited = nerve speed x pulse duration = 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 has an 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 = KE A/d and Q = CAV to investigate the charge as follows. Use typical values for a cylindrical axon of cell wall thickness d = 1.8 x 10-8 m, axon radius r = 1.4 × 10¹ μm, and cell-wall dielectric constant x = 2.0. Positive charge layer Negative charge layer 1+ External fluid + + + Axon wall membrane + Internal fluid Axon radius = r + + + 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 x 10-² V.) How many K+ ions are on the outside of the axon assuming…arrow_forward
- Assume a length of axon membrane of about 0.10 m is excited by an action potential (length excited = nerve speed x pulse duration = 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 has an 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 = ke A/d and Q = CAV to investigate the charge as follows. Use typical values for a cylindrical axon of cell wall thickness d = 2.0 × 10-8 m, axon 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 Internal fluid Axon radius = r No + (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 x 10-² v.) d Your response differs significantly from the correct answer. Rework your…arrow_forwardAssume a length of axon membrane of about 0.10 m is excited by an action potential (length excited = nerve speed x pulse duration = 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 has an 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 = KE A/d and Q = CAV to investigate the charge as follows. Use typical values for a cylindrical axon of cell wall thickness d = 1.3 x 10-8 m, axon radius r = 1.3 × 10¹ μm, and cell-wall dielectric constant x = 2.1. Positive charge layer Negative charge layer External fluid + Axon wall membrane Internal fluid Axon radius = r + + How many sodium ions (Na+) is this? Na+ ions + (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 x 10-² V.) C How many K+ ions are on…arrow_forwardTwo resistors R1 = 3000 ohms and R2 = 4000 ohms are joined in series and connected to a 120-volt supply. The voltage drop across R1 and R2 are measured successively by a voltmeter having a resistance of 50,000 ohms. What is the sum of the readings?arrow_forward
- please helparrow_forwardTwo heaters A and B are in parallel across supply voltage V. Heater A produces 757 kcal in 20 min and B produces 1252 kcal in 10 min. The resistance of A is 10 ohm. What is the resistance of B in kiloohms? If the same heaters are connected in series across the voltage V, how much heat would be produced in calories in 5 minutes?arrow_forwardAssume 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 × 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 has an 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 = ??0A/d and Q = CΔV to investigate the charge as follows. Use typical values for a cylindrical axon of cell wall thickness d = 1.6 ✕ 10−8 m, axon radius r = 1.9 ✕ 101 ?m, and cell-wall dielectric constant ? = 2.6. (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.)?CHow many K+ ions are on the outside of the axon assuming an initial potential difference of 7.0 ✕ 10−2 V??K+ ions (b) How much positive charge must flow through the cell membrane to reach…arrow_forward
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