General Physics, 2nd Edition
2nd Edition
ISBN: 9780471522782
Author: Morton M. Sternheim
Publisher: WILEY
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Chapter 18, Problem 9RQ
To determine
If the radius of a myelinated axon is doubled. the velocity of the action potential changes by a factor of
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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…
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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- How many actin monomers within an actin filament would a myosin molecule need to ratchet in order to contract a cell by approximately 1 μm? How fast could a non-muscle cell make this contraction compared to a muscle cell if the relative rates of myosin walks on F-actin are 4.5 μm/sec and 0.04 μm/sec for myosin II and I respectively?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_forwarda) How does voltage change over distance from the stimulator on the artificial axon? AND why does this occur? (Think: where is the current going?) b) How and why are neurons affected by the addition of myelin (think membrane resistance, capacitance, and the length constant)?arrow_forward
- What 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| Va -Vc |arrow_forwardQuestion 7 50 40 40 Peak action potential Depolarization Repolarization 0.2/0.5 points Membrane potential (mV) 0 - Threshold of excitation -50 Initial stimulus -70 resting hyperpolarization resting return to resting -100 When are voltage gated Na+ channels closed (and inactivated)? The different ranges provided start at resting, go through an AP, and end at resting. (-70mV to -50mV) (-50mV to +40mV) (+40mV to -70mV) (-70mV to -80mV) (-80mV to -70mV)arrow_forward
- Find the radius of the unmyelinated axon (m) with space parameter A = 14 mm, (Resistance of a unit area of the membrane, Rm =0.2 Q.m², Resistivity of axoplasm, p, =2 Q.m). A. 0.00392 B. 0.01568 C. None D. 0.02352 E. 0.00784arrow_forwardWhen does an object have a store of GPE?arrow_forward(a) Suppose that a person has an average heart rate of 72.0 beats/min. How many beats does he or she have in 2.0 y? (b) In 2.00 y? (c) In 2.000 y?arrow_forward
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