Vert Phys Exam 2 BIO 3421 Practice Questions and Correct Answers

1. In the nervous system, the term membrane potential refers to the separation of charges across a biological membrane 2. Resting membrane potential is attributable primarily to the presence of ____________ channels in the plasma membrane voltage-gated 3. Calculate the equilibrium potential for potassium, the concentration of which is 4 mM extracellularly and 115 mM intracellularly R = 1.987 cal mol-1K-1, T = 310 K and F = 23,067 cal mol-1V-1 -90 mV 4. Given a pathway, potassium flows ____________ the cell, making Vm more ____________, ____________ the cell out of; negative, hyperpolarizing 5. Local passive current flow decreases with distance from the stimulus site because current leakage across the membrane attenuates current available for intracellular current flow 6. Increasing axonal diameter increases the length constant for that axon by decreasing longitudinal resistance 7. During the myosin cross-bridge cycle, the ____________ phase directly results in displacement of the thin filament relative to the thick filament power-stroke 8. The sarcomere lies within the boundaries of which of these structures Z lines 9. Threshold potential is -typically between -50 mV and -55 mV -the membrane potential at which a graded potential is converted to an action potential -typically 10 mV to 15 mV higher than resting potential 10. During the initial, depolarizing phase of the action potential, the voltage-gated Na+-channel is in which conformation closed but capable of opening 11. Once threshold potential has been achieved, the permeability of the membrane to Na+ is -greater than at rest -greater than to K+ -increased due to activation of voltage-gated Na+ channels 12. Norepinephrine is converted to epinephrine in the adrenal ____________ by the enzyme phenyethanolamine N-methyltransferase, whose synthesis is stimulated by the steroid ____________ , which is secreted from the adrenal ____________ cortex, cortisol, medulla