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Name: __________________________________ Human A&P Membrane Potentials & Nerve Impulses Answer all of the following questions. You will find all of the answers contained within Chapter 8 (pgs. 203 to 205) and in your lecture notes. 1. What is the difference in charge between the interior and exterior of most cells? What do we call this differential? 2. What two factors contribute to this polarity? 3. Which ions are involved? What are their relative concentration inside/outside of the cell? 4. What is the function of the sodium-potassium ion pump? How does this relate to the relative permeability of the membrane regarding these two ions? 5. Please study figures 8.7 and 8.8 thoroughly. 6. Check () all descriptions that apply to a resting neuron: _____ Its inside is negative relative to its outside. _____ Its outside is negative relative to its inside. _____ The cytoplasm contains more sodium and less potassium than does the extracellular fluid. _____ The cytoplasm contains more potassium and less sodium than does the extracellular fluid. _____ A charge separation exists at the membrane. _____ The electrochemical gradient for the movement of sodium across the membrane is greater than that for potassium. _____ The electrochemical gradient for the movement of potassium across the membrane is greater than that for sodium. _____ The membrane is more permeable to sodium than potassium. _____ The membrane is more permeable to potassium than sodium. 7. Using the choices below, select the terms defined in the following statements. Write the LETTER of the correct answer in the blank provided. A. Absolute refractory G. Polarized period H. Relative refractory B. Action potential period. C. Depolarization I. Repolarization D. Frequency of impulses. J. Sodium-potassium pump E. Graded potential K. Subthreshold F. Hyperpolarization L. Threshold _____ Corresponds to the period of repolarization of the neuron. _____ Process by which the resting potential is decreased as sodium ions move into the axon. _____ State of an unstimulated neuron’s membrane. _____ Period (event) during which potassium ions move out of the axon. _____ Also called the nerve impulse. _____ Period when a neuron cannot be restimulated because its sodium gates are open. _____ Mechanism by which ATP is used to move sodium ions out of the cell and potassium ions into the cell; completely restores and maintains the resting conditions of the neuron. _____ Point at which an axon “fires.” _____ Term for a weak stimulus. _____ Self-propagated depolarization. _____ Codes for intensity of the stimulus. _____ Membrane potential at which the outward current carried by K+ is exactly equal to the inward current carried by Na+. _____ A voltage change that reduces the ability of a neuron to conduct an impulse; the membrane potential becomes more negative. _____ A local change in membrane potential in which current flow is quickly dissipated, that is decremental. _____ An all-or-none event. _____ A voltage change that brings a neuron closer to its threshold for firing; the membrane potential becomes less negative and moves toward zero. _____ Results from the opening of voltage-regulated ionic gates. _____ Results from the opening of chemically regulated gates or energetic stimuli. _____ Characterized by a rapid polarity reversal. 8. Circle the term that does not belong in each of the following groupings: (Note: Cl- = chloride ion; K+ = potassium ion; Na+ = sodium ion) a. Inside resting cell High Na+ b. High Clresting cell c. out Protein anions Na+/K+ Pump ATP required Low Na+ High K+ Low Cl- Cytoplasm 3 Na+ out / 2 K+ in d. Nerve impulse Graded potential Short-lived signal e. Depolarization Inside Hyperpolarization -70 mV to -50 mV f. Can generate AP processes Cell bodies of 3 Na+ in / 2 K+ Short-distance membrane Axons less signal negative Peripheral 9. Graph the following set of data. Then, label the following: absolute refractory period, action potential (AP), depolarization, graded potential, hyperpolarization, relative refractory period, repolarization, resting membrane potential (RMP). **If you have the capability, you may plot these data points on your TI Graphing Calculator or Computer (excel) and then print the graph. Voltage (mV) Time (ms) -70 -70 -65 -70 -70 -60 -70 -70 -50 +30 -65 -75 -78 -71 -70 -70 2.0 0.5 0.7 1.0 1.5 1.7 2.0 2.5 3.0 3.5 4.0 4.2 4.5 5.0 5.5 6.0 ** Remember to label axes and give your graph a title!! Your graph should be approximately one page in size to accommodate all data points and labels.