College Physics: A Strategic Approach (3rd Edition)
3rd Edition
ISBN: 9780321879721
Author: Randall D. Knight (Professor Emeritus), Brian Jones, Stuart Field
Publisher: PEARSON
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Textbook Question
Chapter 23, Problem 29CQ
Adding a myelin sheath to an axon results in faster signal propagation. It also means that less energy is required for a signal to propagate down the axon. Explain why this is so.
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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…
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…
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 = 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…
Chapter 23 Solutions
College Physics: A Strategic Approach (3rd Edition)
Ch. 23 - The tip of a flashlight bulb is touching the top...Ch. 23 - A flashlight bulb is connected to a battery and is...Ch. 23 - Current Iin flows into three resistors connected...Ch. 23 - The circuit in Figure Q23.4 has two resistors,...Ch. 23 - The circuit in Figure Q23.5 has a battery and two...Ch. 23 - In the circuit shown in Figure Q23.6, bulbs A and...Ch. 23 - Figure Q23.7 shows two circuits. The two batteries...Ch. 23 - Figure Q23.8 shows two circuits. The two batteries...Ch. 23 - a. In Figure Q23.9, what fraction of current I...Ch. 23 - Two of the three resistors in Figure Q23.10 are...
Ch. 23 - Two of the three resistors in Figure Q23.11 are...Ch. 23 - Rank in order, from largest to smallest, the...Ch. 23 - The three bulbs in Figure Q23.13 are identical....Ch. 23 - The four bulbs in Figure Q23.14 are identical....Ch. 23 - Figure Q23.15 shows five identical bulbs connected...Ch. 23 - a. The three bulbs in Figure Q23.16 are identical....Ch. 23 - Initially, bulbs A and B in Figure Q23.17 are both...Ch. 23 - a. Consider the points a and b in Figure Q23.18....Ch. 23 - When the switch in Figure Q23.19 is closed, a....Ch. 23 - A voltmeter is (incorrectly) inserted into a...Ch. 23 - An ammeter is (incorrectly) inserted into a...Ch. 23 - Rank in order, from largest to smallest, the...Ch. 23 - Figure Q23.23 shows a circuit consisting of a...Ch. 23 - Figure Q23.24 shows the volt age as a function of...Ch. 23 - A charged capacitor could be connected to two...Ch. 23 - A flashing light is controlled by the charging and...Ch. 23 - A device to make an electrical measurement of skin...Ch. 23 - Consider the model of nerve conduction in...Ch. 23 - Adding a myelin sheath to an axon results in...Ch. 23 - What is the current in the circuit of Figure...Ch. 23 - Which resistor in Figure Q23.30 dissipates the...Ch. 23 - Normally, household lightbulbs are connected in...Ch. 23 - A metal wire of resistance R is cut into two...Ch. 23 - What is the value of resistor R in Figure Q23.34?...Ch. 23 - Two capacitors are connected in series. They are...Ch. 23 - If a cells membrane thickness doubles but the cell...Ch. 23 - If a cells diameter is reduced by 50% without...Ch. 23 - Draw a circuit diagram tor the circuit of Figure...Ch. 23 - Draw a circuit diagram for the circuit of Figure...Ch. 23 - Draw a circuit diagram for the circuit of Figure...Ch. 23 - In Figure P23.4, what is the current in the wire...Ch. 23 - The lightbulb in the circuit diagram of Figure...Ch. 23 - a. What are the magnitude and direction of the...Ch. 23 - a. What are the magnitude and direction of the...Ch. 23 - a. What is the potential difference across each...Ch. 23 - The current in a circuit with only one battery is...Ch. 23 - What is the equivalent resistance of each group of...Ch. 23 - What is the equivalent resistance of each group of...Ch. 23 - Prob. 12PCh. 23 - Prob. 13PCh. 23 - You have a collection of 1.0 k resistors. How can...Ch. 23 - You have a collection of six 1.0 k resistors. What...Ch. 23 - You have six 1.0 k resistors. How can you connect...Ch. 23 - What is the equivalent resistance between points a...Ch. 23 - What is the equivalent resistance between points a...Ch. 23 - The currents in two resistors in a circuit are...Ch. 23 - Two batteries supply current to the circuit in...Ch. 23 - Part of a circuit is shown in Figure P23.21. a....Ch. 23 - What is the value of resistor R in Figure P23.22?...Ch. 23 - What are the resistances R and the emf of the...Ch. 23 - The ammeter in Figure P23.24 reads 3.0 A. Find I1,...Ch. 23 - Find the current through and the potential...Ch. 23 - Find the current through and the potential...Ch. 23 - For the circuit shown in Figure P23.27, find the...Ch. 23 - Consider the potential differences between pairs...Ch. 23 - For the circuit shown in Figure P23.29, find the...Ch. 23 - A photoresistor, whose resistance decreases with...Ch. 23 - The two unknown resistors in Figure P23.31 have...Ch. 23 - A 6.0 F capacitor, a 10 F capacitor, and a 16 F...Ch. 23 - A 6.0 F capacitor, a 10 F capacitor, and a 16 F...Ch. 23 - You need a capacitance of 50 F, but you dont...Ch. 23 - You need a capacitance of 50 F, but you dont...Ch. 23 - What is the equivalent capacitance of the three...Ch. 23 - What is the equivalent capacitance of the three...Ch. 23 - For the circuit of Figure P23.38, a. What is the...Ch. 23 - For the circuit of Figure P23.39. a. What is the...Ch. 23 - What is the time constant for the discharge of the...Ch. 23 - What is the time constant for the discharge of the...Ch. 23 - After how many time constants has the voltage...Ch. 23 - A 10F capacitor initially charged to 20C is...Ch. 23 - A capacitor charging circuit consists of a...Ch. 23 - The switch in Figure P23.45 has been in position a...Ch. 23 - A 9.0-nm-thick cell membrane undergoes an action...Ch. 23 - A cell membrane has a resistance and a capacitance...Ch. 23 - Changing the thickness of the myelin sheath...Ch. 23 - A particular myelinated axon has nodes spaced 0.80...Ch. 23 - To measure signal propagation in a nerve in the...Ch. 23 - A myelinated axon conducts nerve impulses at a...Ch. 23 - How much power is dissipated by each resistor in...Ch. 23 - Two 75 W (120 V) lightbulbs are wired in series,...Ch. 23 - The corroded contacts in a lightbulb socket have...Ch. 23 - A real battery is not just an emf. We can If model...Ch. 23 - For the real battery shown in Figure P23.55,...Ch. 23 - Batteries are recharged by connecting them to a...Ch. 23 - When two resistors are connected in parallel...Ch. 23 - The 10 resistor in Figure P23.59 is dissipating 40...Ch. 23 - At this instant the current in the circuit of...Ch. 23 - What is the equivalent resistance between points a...Ch. 23 - What is the current through the battery in Figure...Ch. 23 - What is the ratio P parallel/P series of the total...Ch. 23 - You have a device that needs a voltage reference...Ch. 23 - There is a current of 0.25 A in the circuit of...Ch. 23 - A circuit youre building needs an ammeter that...Ch. 23 - A circuit youre building needs a voltmeter that...Ch. 23 - For the circuit shown in Figure P23.68, find the...Ch. 23 - You have three 12 F capacitors. Draw diagrams...Ch. 23 - Initially, the switch in Figure P23.70 is in...Ch. 23 - The capacitor in an RC circuit with a time...Ch. 23 - The capacitor in Figure P23.72 is initially...Ch. 23 - What value resistor will discharge a 1.0 F...Ch. 23 - The charging circuit for the flash system of a...Ch. 23 - A capacitor is discharged through a 100 resistor....Ch. 23 - A 50 /F capacitor that had been charged to 30 V is...Ch. 23 - The switch in Figure P23.77 has been closed for a...Ch. 23 - Intermittent windshield wipers use a variable...Ch. 23 - In Example 23.14 we estimated the capacitance of...Ch. 23 - The giant axon of a squid is 0.5 mm in diameter,...Ch. 23 - A cell has a 7.0-nm-thick membrane with a total...Ch. 23 - The Defibrillator A defibrillator is designed to...Ch. 23 - The Defibrillator A defibrillator is designed to...Ch. 23 - The Defibrillator A defibrillator is designed to...Ch. 23 - A defibrillator is designed to pass a large...Ch. 23 - The voltage produced by a single nerve or muscle...Ch. 23 - The voltage produced by a single nerve or muscle...Ch. 23 - The voltage produced by a single nerve or muscle...Ch. 23 - The voltage produced by a single nerve or muscle...
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- 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_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 = 1.6 ✕ 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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