a. if dendrites were generally longer than axons
b. if the glia-to-neuron ratio were higher
*c. if selective permeability of the membrane did not exist
d. if it were an active transport system that required energy
78. The net effect of each cycle of the sodium-potassium pump is to ____.
*a. decrease the number of positively charged ions within the cell
b. increase the number of positively charged ions within the cell
c. decrease the number of positively charged ions outside the cell
d. increase the number of negatively charged ions within the cell
79. Dr. Delillo studies the resting potential of neurons. He has found that _______ is the main reason the neuron is able to maintain the resting potential.
a. the size difference between the axon and dendrites
*b. the sodium-potassium pump
c. the concentration gradient
d. the refractory period of the membrane
80. The concentration gradient refers to the ____.
a. fact that the concentration of ions is greater on the inside of a neuron
b. fact that the concentration of ions is greater on the outside of a neuron
*c. difference in distribution for various ions between the inside and outside of the membrane
d. negatively charged proteins inside the cell
81. Which event will increase the concentration gradient of sodium?
a. Decreasing permeability to potassium ions
*b. Increasing activity of the sodium potassium pump
c. Increasing membrane permeability to sodium ions
d. Increasing membrane permeability to chloride ions
82. The concentration gradient for potassium tends to ____.
a. draw potassium into the cell
b. push chloride out of the cell
c. push sodium out of the cell
*d. push potassium out of the cell
83. Professor Michaels is explaining to his students that, when the neuron is at rest, ______ is mostly responsible for the movement of potassium ions out of the cell.
a. potassium’s electrical gradient
*b. potassium’s concentration gradient
c. the sodium-potassium pump
d. sodium's electrical gradient
84. When a neuron is at rest, what is primarily responsible for moving potassium ions into the cell?
a. Concentration gradient
b. An electrical gradient
c. The sodium-potassium pump
*d. Both the sodium-potassium pump and electrical gradient
85. When a membrane is at rest, what attracts potassium ions to the inside of the cell?
*a. An electrical gradient
b. A concentration gradient
c. Both an electrical gradient and a concentration gradient
d. Neither an electrical gradient nor a concentration gradient
86. When a membrane is at rest, what attracts sodium ions to the inside of the cell?
a. An electrical gradient
b. A concentration gradient
*c. Both an electrical gradient and a concentration gradient
d. Neither an electrical gradient nor a concentration gradient
87. Professor Windell is lecturing about the resting potential of neurons. He will tell his class that the resting potential is advantageous because _____.
a. it minimizes the toxic effects of sodium
*b. the cell is ready to produce an action potential quickly following a stimulus
c. it prevents the cell from having to use any energy to keep itself prepared to fire an action potential.
d. this maintains equal levels of the ions both inside and outside of the neuron
88. Ordinarily, stimulation of a neuron takes place ____.
a. through hyperpolarization
*b. at the synapse
c. in the mitochondria
d. in the endoplasmic reticulum
89. What occurs when a stimulus shifts the potential inside a neuron from the resting potential to a more negative potential?
*a. Hyperpolarization
b. Depolarization
c. An action potential
d. A threshold
90. Dr. O’Reilly is trying to produce hyperpolarization in the neurons in her laboratory. What should she do?
a. Use a microelectrode to apply a positive charge
*b. Use a microelectrode to apply a negative charge
c. Add a drug that will increase the membrane’s permeability to sodium
d. Add a drug that will decrease the membrane’s permeability to potassium
91. In order to produce an action potential, the collective amount of depolarization must exceed the _____
*a. threshold of excitation
b. energy required to open the potassium channels