The membrane potential in animal cells, but not in plants, depends largely on resting K+ channels. How do these channels contribute to the resting membrane potential? Why are these channels considered to be nongated channels? How do these channels achieve selectivity for K+ versus Na+, which is smaller than K+?

The membrane potential in animal cells, but not in plants, depends largely on resting K+ channels. How do these channels contribute to the resting membrane potential? Why are these channels considered to be nongated channels? How do these channels achieve selectivity for K+ versus Na+, which is smaller than K+?

Human Physiology: From Cells to Systems (MindTap Course List)

9th Edition

ISBN:9781285866932

Author:Lauralee Sherwood

Publisher:Lauralee Sherwood

Chapter4: Principles Of Neural And Hormonal Communication

Section4.3: Action Potentials

Problem 2CYU

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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 axons 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 152:561590. Cengage Learning 2017
Clostridium tetani toxin blocks the exocytosis of GABA. A. What anatomical part of a pre-synaptic neuron would be affected by this? B. How would a post-synaptic neuron’s likelihood of experiencing an action potential be affected by this toxin? C. Explain, using at least TWO of the following terms: threshold, depolarization, repolarization, hyperpolarization, summation, IPSP, EPSP, exocytosis
Compound X has been shown to block voltage-gated K+ channels with an IC50 of 0.1 mM. Which of the following is the most likely to occur in neurones following application of 0.03 mM X? Action potentials would be prolonged and the resting potential would be depolarised. Action potentials would be prolonged but the resting potential would remain the same. Neither resting potential nor action potentials would be affected because the concentration of X is less than the IC50 value. The resting membrane potential would depolarise but there would be no effect on action potentials.
Which of the following statements best describes the features of voltage-gated K+ channels? They consist of 4 subunits, are activated at the same time as voltage-gated Na+ channels, but do not inactivate. They consist of 4 subunits, are activated by depolarisation and close slowly during the refractory period. They have 24 membrane spanning alpha helices, 4 of which have positively charged amino acids which promote a conformational change in the channel following depolarisation. They consist of 4 subunits and are open at rest which causes the resting membrane potential to be close to the K+ equilibrium potential.
An analog of cGMP, 8-Br-cGMP, will permeate cellular membranes, is only slowly degraded by a rod cell’s PDE activity, and is as effective as cGMP in opening the gated channel in the cell’s outer segment. If you suspended rod cells in a buffer containing a relatively high [8-Br-cGMP], then illuminatedthe cells while measuring their membrane potential, what would you observe?
Separately, draw a table using arrows to depict the appropriate magnitude and direction of the forces and ion fluxes at different membrane potentials for a ligand-gated channel that is equally permeable to both ion X+ and ion Y+. The equilibrium potential for ion X+ is -60 mV, and the equilibrium potential for ion Y+ is -20 mV. Which item best represents the forces and fluxes for a membrane potential of -60 mV? Pick one of the four tables in the included image please for your answer.
What functions do Na1/K1-ATPase membrane pumps play in the membrane potential? Are these functions direct or indirect?
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Some cytoplasmic kinases, enzymes that phosphorylate substrates at the expense of ATP, bind to voltage-dependent anion channels. What might the advantage of this binding be?
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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