General Physics, 2nd Edition
2nd Edition
ISBN: 9780471522782
Author: Morton M. Sternheim
Publisher: WILEY
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Chapter 18, Problem 6RQ
To determine
The potential difference change when an axon subjected to a weak stimulus.
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An unmyelinated segment of the axon has a radius of r=2 pm and a
length of L=7 cm. what is its membrane capacitance (Farad) ?. (The
%3D
capacitance per unit area, Cm = 0.01 F/m2).
%3D
A. 0.000000008792
B. None,
C. 0.00000002638
D. 0.00000003517
E. 0.00000001758
a) What was the smallest voltage required to produce a contraction (the threshold voltage)? What proportion of the fibers in the muscle do you think were contracting to produce this small response?
b) What was the smallest voltage required to produce the maximum (largest) contraction? What proportion of the fibers in the muscle do you think were contracting to produce this maximal response?
What is the magnitude of the electric field across an axon membrane 1.2×10−8 m thick if the resting potential is -70 mV ?
Chapter 18 Solutions
General Physics, 2nd Edition
Ch. 18 - Prob. 1RQCh. 18 - Prob. 2RQCh. 18 - Prob. 3RQCh. 18 - Prob. 4RQCh. 18 - Prob. 5RQCh. 18 - Prob. 6RQCh. 18 - Prob. 7RQCh. 18 - Prob. 8RQCh. 18 - Prob. 9RQCh. 18 - Prob. 10RQ
Ch. 18 - Prob. 1ECh. 18 - Prob. 2ECh. 18 - Prob. 3ECh. 18 - Prob. 4ECh. 18 - Prob. 5ECh. 18 - Prob. 6ECh. 18 - Prob. 7ECh. 18 - Prob. 8ECh. 18 - Prob. 9ECh. 18 - Prob. 10ECh. 18 - Prob. 11ECh. 18 - Prob. 12ECh. 18 - Prob. 13ECh. 18 - Prob. 14ECh. 18 - Prob. 15ECh. 18 - Prob. 16ECh. 18 - Prob. 17ECh. 18 - Prob. 18ECh. 18 - Prob. 20ECh. 18 - Prob. 21ECh. 18 - Prob. 24ECh. 18 - Prob. 25ECh. 18 - Prob. 26E
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- Assume the length of an axon membrane of about 0.10 cm is excited by an action potential (length excited = nerve speed ✕ pulse duration = 50 m/s ✕ 2.0 ms = 10 cm). 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 = ??oA/d and Q = CΔV to investigate the charge as follows. Use typical values for a cylindrical axon of cell thickness d = 1.6 ✕ 10−8 m, axon radius r = 1.2 ✕ 101 ?m, and cell-wall dielectric constant ? = 2.3. A diagram shows a collection of positive and negative charges in and around an axon. The diagram is divided into three sections, one on top of the other. The top section is labeled "External fluid". A row of positive charges labeled "Positive charge layer" lies along the bottom side of this section. Above the row of positive charges, there is an even mixture of…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 %D resting state, the outer surface of the axon wall is charged positively with Kt 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 = KƐ A/d and Q = CAV to investigate the charge as follows. Use typical values for a cylindrical axon of cell -8 wall thickness d = 1.5 x 10 m, axon radius r = 2.0 x 10- um, and cell-wall dielectric constant K = 2.9. External fluid + Positive charge layer Axon wall membrane d Negative charge layer Internal fluid Axon radius = r (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.) 1.035E-9 Your response differs from the correct answer by more than 10%.…arrow_forwardThe 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_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 = 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_forwardAn unmyelinated segment of the axon has a radius of r-2 um and a length of L=5 cm. what is its membrane capacitance (Farad) ?. (The capacitance per unit area, C = 0.01 F/m?). A. 0.00000000628 B. 0.00000002512 C. 0.00000001884 D. 0.00000001256 E. Nonearrow_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_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 = 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_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 = 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 × 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_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_forwardA myelinated axon conducts nerve impulses at a speed of 40 m/s. What is the signal speed if the thickness of the myelin sheath is halved but no other changes are made to the axon?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 = 1.1 ✕ 10−8 m, axon radius r = 2.0 ✕ 101 ?m, and cell-wall dielectric constant ? = 2.7. A diagram shows a collection of positive and negative charges in and around an axon. The diagram is divided into three sections, one on top of the other. The top section is labeled "External fluid". A row of positive charges labeled "Positive charge layer" lies along the bottom side of this section. Above the row of positive charges, there is an even mixture of…arrow_forward
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