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 0- E -70- A 1 2 3 4 Time/ms Potential Difference/mV

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

Graded potentials in neurons:   Question 5 options:   a. Graded potentials that result from an influx of chloride ions are always hyperpolarizing.   b. Graded potentials can undergo both spatial and temporal summation.   c. The initiation of a graded potential can only occur after the cell membrane depolarizes to threshold (about -55 mV).   d. Both a) and b) are correct and c) is incorrect   e. Statements a), b) and c) are all correct

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)