The current flowing through individual ion channels has a different reversal potential than the macroscopic ionic current has. exhibits the same time course across all individual sodium channels. has a different voltage dependence than the macroscopic ionic current has. reflects the passage of thousands of ions per millisecond. was visualized with the advent of the voltage clamp in 1956.

The current flowing through individual ion channels has a different reversal potential than the macroscopic ionic current has. exhibits the same time course across all individual sodium channels. has a different voltage dependence than the macroscopic ionic current has. reflects the passage of thousands of ions per millisecond. was visualized with the advent of the voltage clamp in 1956.

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

Section: Chapter Questions

Problem 1RE: Conformational changes in channel proteins brought about by voltage changes are responsible for...

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Draw the current that you would expect to flow during a voltage clamp experiment on a typical neuron. Voltages and time course are shown. Briefly explain why the currents are inward or outward. Be sure to provide scale bars. You should definitely label the Y axis so that the peak current value is obvious. Draw the Na+ current you would expect if there were physiological ionic gradients. Draw the K+ current you would expect if there are physiological ionic gradients. Draw the K+ current you would expect if the bath solution and the intracellular solution are both 125 mM.
The traces below show the action potential waveforms in an external meidum of different concentrations of * 40 100% 50% 33% 40 1 2 time (msec) calcium chloride potassium O sodium
The membrane potential for an excitable cell membrane is -70 mV, for sodium ions the Nernst equilibrium potential is +50 mV, the conductivity of the single sodium channel is 10 pS. What is the electrochemical potential difference that is the driving force for sodium ions to migrate? How much current flows through an open sodium channel under these conditions?
There is no inward current at a membrane potential of +65mV because: The membrane potential is near or at the equilibrium potential for Na+ The membrane potential is near or at the equilibrium potential for neither Na+ or K+ The membrane potential is near or at the equilibrium potential for both Na+ and K+ The membrane potential is near or at the equilibrium potential for K+
The resting potential of most cells is most dependent concentration gradient of: on the transmembrane Chloride Sodium Potassium Calcium
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.
Patch clamping is a technique to record the electrical potential or to measure currents generated by ions moving across the cell membrane. The figure shows the patch clamp records of a neurone before (control) and after treatment with tetrodotoxin (TTX) from pufferfish. TTX most like binds to and blocks Control inward current 50 pA 5 ms TTX voltage-gated sodium channels voltage-gated chloride channels sodium potassium pumps nicotinic acetylcholine receptors alpha adrenergic receptors muscarinic acetylcholine receptors beta adrenergic receptors
Which of the following statements about voltage gated channels is true? Voltage-gated sodium channels open at a higher (more positive) membrane potential than do potassium-gated channels Voltage-gated sodium channels open at a lower (more negative) membrane potential than do potassium-gated channels Sodium- and postassium-gated channels open at about the same membrane potential, but they have different effects because there are different numbers of the two kinds of channels in neuron cell membranes
A membrane potential (Vm) labeled axis on the graph In the graph draw the phases of the action potential Include the channels involved and when they open and close matching them to the Vm Indicate the periods in which the action potential can or cannot occur
The voltage produced by a single nerve or muscle cell is quite small, but there are many species of fish that use multiple action potentials in series to produce significant voltages. The electric organs in these fish are composed of specialized disk-shaped cells called electrocytes. The cell at rest has the usual potential difference between the inside and the outside, but the net potential difference across the cell is zero. An electrocyte is connected to nerve fibers that initially trigger a depolarization in one side of the cell but not the other. For the very short time of this depolarization, there is a net potential difference across the cell, as shown. Stacks of these cells connected in series can produce a large total voltage. Each stack can produce a small current; for more total current, more stacks are needed, connected in parallel. In an electric eel, each electrocyte can develop a voltage of 150 mV for a short time. For a total voltage of 450 V, how many electrocytes must…
When Tetrodotoxin is administered in bathing medium of a nerve fibre during voltage clamp experiments the membrane current may show which one of the following changes? Absence of inward membrane current Higher amplitude of inward membrane current Absence of outward membrane current O Higher amplitude of outward membrane current
The resting potential is dependent upon the electrochemical gradient for potassium ions because: The permeability of the resting membrane to potassium is higher than for other ions Of the activity of the sodium/potassium ATPase pump Cells contain largely potassium The permeability to sodium ions is very small except during action potentials