Dr. Brainy creates a nerve cell that is only permeable to Caesium ions (Cs+1) at rest.She measures that the concentration of Caesium is 400mM outside the cell and only 50mM inside the cell. She calculates the Equilibrium potential for Cs+1 (Ecs) to be +35 mV.If the cell is only permeable to Cs, the resting membrane potential will be:+58 mV0 mV+35 mV-58 mV

Nernst Equation: Dr. Brainy likely used the Nernst equation to calculate the Equilibrium potential…

Answered: Dr. Brainy creates a nerve cell that is…

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

Section4.1: Introduction To Neural Communication

Problem 2CYU

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Conformational changes in channel proteins brought about by voltage changes are responsible for opening and closing Na+ and K+ gates during the generation of an action potential. (True or false?)
The action potential is split into 4 parts (A-D). For each part, 1. Describe what stimulated the channel responsible for this part, 2. what is the likely ion that is moving and 3. explain which direction the ion had to move to create the measured membrane potential. +40 B D membrane potential (mV) -40 -60 A { 2 time (ms)
a) Explain in detail what is occurring at stage A in the graph. (Be specific in terms of what's happening to the ion channels in your explanation if necessary!) b) What does this graph represent as a whole? Explain the main idea it portrays. +40| -70- A 1 2 4 Time/ms Potential Difference/mV B
Based upon the changes in permeability seen in the trace below and your knowledge of ion distributions across a cell, predict how ion movements would change during an action potential. Drag and drop each phrase into the appropriate box on the action potential trace. Drag the appropriate labels to their respective targets. Note: not all labels will be used. ►View Available Hint(s) Sodium (Na+) ions move to the axon Sodium (Na) ions move out of the axon Less potassium (K) ions move out of the axon Potassium (K) ions move out of the axon Potassium (K¹) ions move into the axon Sodium (Na) ions stop moving in Membrane potential (mv) +30 +10 0 -10- -30 -50 -70 -90 A PNa 0 PNa 5 6 1 PK Threshold PK 2 Reset Help
Describe the contribution of each of the following to the establishment and maintenance of membrane potential: Part A Na+K+ Pump Passive movement of K+ across the membrane Passive movement of Na+ across the membrane Part B Resting membrane potential is approximately -70mV. Explain what resting membrane potential is and what -70mV refers to.
Draw details of the repolarization phase of an action potential from the following descriptions of the sequences of AfterHyperPolarization (AHP) and AfterDePolarization (ADP) sequences. Make the distinct phases clear and noticeable (5 % each) A complex AHP consisting of a first component AHP, an ADP, and a second component AHP before repolarization to resting membrane potential a first fast AHP component, followed by a slower AHP, followed by a fast ADP, and a second late AHP component before repolarization to rest
The change of membrane potential from -70mV to -90 mV is hyperpolarization. T/F
In an experiment, the extracellular [Na+] surrounding a nerve cell was reduced from 145 to 45 mM. Which of the following is the most likely effect of this on action potentials? No action potentials would occur because the concentration of extracellular Na+ is too low. The membrane potential would become more negative so the threshold for action potential generation could not be reached. The nerve cell would still produce an action potential but its amplitude would be reduced and the depolarisation phase would be slower. The nerve cell would still produce an action potential but its amplitude would be reduced and the depolarization phase would be more rapid.
At the peak of the action potential, Vm is approximately -65 mV. Assuming normal intracellular and extracellular K+ concentrations (refer to the table), (1) calculate the driving force (in mV) that acts on K+ ions and (2) use the information obtained in part 1 to determine the direction in which K+ ions will flow (i.e., into the cell or out of cell)
Consider the following three diagrams of a nerve cell membrane. They show resting potential, depolarization, and hyperpolarization. Figure out which one is which, then draw them in the order they occur in a cell that undergoes an action potential outside + Na* inside K* Na* Nat K Nat K Na potential: -80 mV outside + Na K* Na* inside Na+ K Nat Na* K+ potential: +30 mV outside Na Na Na Na* K+ inside K* Na* Kt potential: -70 mV
Place the following events in chronological order from 1-8: Nat enters the cell, and depolarization occurs to approximately +30 mV. The voltage across the cell membrane is -70 mV, the resting membrane potential. Upon reaching the peak of the action potential, the VG Nat channels are inactivated by the closing of their inactivation gate and the activation gate of each VG K channel opens. VG K channels close by the closing of their activation gate, and the resting membrane potential is gradually restored. An excitatory post-synaptic potential depolarizes the membrane to threshold and the activation gate of VG Nat channels open. Upon returning to the resting membrane potential, VG Na channels are reset by opening of the inactivation gate and the closing of the activation gate. VG K+ channels are slow to close, resulting in an excess of K* efflux and hyperpolarization. Depolarization occurs as K+ flows out of the cell.
In the figure to the left, name the 4 phases of the action potential (Note: you have to write in where phase 4 occurs). Describe what happens in each phase with a focus on Na+ and K+ flow through channels and the membrane potential. Discuss the importance of threshold. How does this relate to the concept of APs being all or none?

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