Biology: The Dynamic Science (MindTap Course List)
4th Edition
ISBN: 9781305389892
Author: Peter J. Russell, Paul E. Hertz, Beverly McMillan
Publisher: Cengage Learning
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Chapter 39, Problem 1ITD
You learned in this chapter that Na+/K+ active transport pumps in the plasma membrane of the axons are responsible for creating the imbalance between Na+ and K+ inside and outside of the neuron that produces the resting membrane potential. In early research studying the role of ions and the involvement of active transport of ions in neural signaling, investigators used the giant axon of a squid as a model. The diameter of a giant axon is far greater than that of a mammalian axon, which enabled researchers to isolate it easily and use it in in vitro experiments. In one early experiment, researchers investigated the active transport of Na+ out of the axon in response to the presence of cyanide. Experimentally they hooked up a section of axon to a syringe, immersed the axon in artificial seawater, introduced radioactive 22Na (as 22NaCl) into the axon, and then quantified the transport of 22Na out through the axon’s plasma membrane. The rate of 22Na transport out of the axon was determined by measuring the radioactivity released into the fluid sur- rounding the axon over a period of time. The Figure shows the results of the experiment.
What is the effect of cyanide on Na1 transport out of the squid axon? How do the data show the effect?
Source: P. C. Caldwell et al. 1960. The effects of injecting “energy-rich” phosphate compounds on the active transport of ions in the giant axons of Loligo. The Journal of Physiology 152:561–590.
© Cengage Learning 2017
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Students have asked these similar questions
The giant squid axon has a diameter = 1mm and 1 = 13mm. Compared to a mammalian neuron with a diameter = 1 um and ^ = 0.2mm, which of the following is correct?
graded potentials can generate action potentials in the mammalian axon but not in the squid axon.
graded potential of similar magnitude would result in action potentials with larger amplitude in the mammalian axon
graded potentials of similar magnitude would result in action potentials with larger amplitude in the squid axon
graded potentials of similar magnitude would travel furthest from their point of origin in the mammalian axon
graded potentials of similar magnitude would travel furthest from their point of origin in the squid axon
Three currents are produced by a 56 mV depolarization leading to an action
potential in a squid axon membrane during a voltage clamp experiment as
shown. What is the mechanism underlying the capacitive current?
56 mV Depolarization
Capacitative
current
Late current
Early current
Time (ms)
Opening of Na* channels
Current due to the Na/K*
pump
O Neutralization of the charge on the membrane
Opening of K channels
Membrane
Membeane
current imA/cm potential (mV)
Consider a typical mammalian neuron with all of the appropriate membrane
channels. If you know that neuron is at rest, at a temperature of 37°C and you
know the intracellular and extracellular concentration of the potassium,
which of the following statements is most likely to be true?
a. The equilibrium potential of potassium would be negative if the
concentration of potassium is higher on the inside.
b. The equilibrium potential of potassium would be positive if the
concentration of potassium is higher on the inside
c. The equilibrium potential of potassium cannot be calculated because
the Nernst equation requires that you know the concentration of all
ions
d. The equilibrium potential of potassium be zero if the concentration of
potassium is higher on the outside
e. None of the above
Chapter 39 Solutions
Biology: The Dynamic Science (MindTap Course List)
Ch. 39.1 - Prob. 1SBCh. 39.1 - Prob. 2SBCh. 39.1 - Prob. 3SBCh. 39.2 - Prob. 1SBCh. 39.2 - Prob. 2SBCh. 39.3 - Prob. 1SBCh. 39.3 - Prob. 2SBCh. 39.4 - Prob. 1SBCh. 39 - Prob. 1TYKCh. 39 - Prob. 2TYK
Ch. 39 - An example of a synapse could be the site where:...Ch. 39 - Prob. 4TYKCh. 39 - The major role of the Na+/K+ pump is to: a. cause...Ch. 39 - In the propagation of a nerve impulse: a. the...Ch. 39 - Which of the following does not contribute to...Ch. 39 - Which of the following statements best describes...Ch. 39 - Prob. 9TYKCh. 39 - Prob. 10TYKCh. 39 - Prob. 11TYKCh. 39 - Prob. 12TYKCh. 39 - Prob. 13TYKCh. 39 - Prob. 14TYKCh. 39 - Prob. 15TYKCh. 39 - Prob. 16TYKCh. 39 - You learned in this chapter that Na+/K+ active...Ch. 39 - Prob. 2ITDCh. 39 - Prob. 3ITD
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