Biol152(Exam(#1(Spring(2017((1(Biol152 Introductory Biology Exam #1 Key Houlihan Spring 2017 There is one best answer for each question. 1) When two excitatory postsynaptic potentials (EPSPs) occur at two adjacent synapses, the EPSPs add together producing _____. A) temporal summation B) spatial summation C) tetanus D) the refractory state E) an action potential with an abnormally high peak of depolarization 2) A stimulus causes potassium channels to open. The resulting potassium flow across the membrane causes the membrane potential __. A) to hyperpolarize. B) to depolarize. C) to not change. 3) What would happen to the shape of the action potential if the activation gate of the potassium voltage-gated ion channel opened at a faster rate? Assume everything else remain the same. A) The peak of the action potential would be lower (less positive). B) The peak of the action potential would be higher. (more positive) C) The action potential would remain depolarized for a longer period of time. D) The action potential would remain depolarized for a shorter period of time. E) Both a and d are correct. 4) The operation of the sodium-potassium "pump" moves _____. A) sodium and potassium ions into the cell B) sodium and potassium ions out of the cell C) sodium ions into the cell and potassium ions out of the cell D) sodium ions out of the cell and potassium ions into the cell E) sodium and potassium ions into the mitochondria 5) What would happen to the resting potential if a cycle of the sodium potassium pump moved twice as many potassium ions than usual? Assume everything else is the same. A) The resting potential would become more positive. B) The resting potential would become more negative. C) The resting potential would stay the same.Biol152(Exam(#1(Spring(2017((2(6) ATP directly powers the movement of _____. A) K+ out of cells B) Na+ out of cells C) Na+ into cells D) Ca++ into cells E) Cl- into cells 7) The "threshold" potential of a membrane is the _____. A) point of separation from a living to a dead neuron B) lowest frequency of action potentials a neuron can produce C) minimum hyperpolarization needed to prevent the occurrence of action potentials D) minimum depolarization needed to operate the voltage-gated sodium and voltage-gated potassium channels E) peak amount of depolarization seen in an action potential Refer to the following graph of an action potential to answer questions 8 to 11. 8) The maximum amount of potassium has moved across the membrane at label _____. A) A B) B C) C D) D E) E 9) The membrane's permeability to sodium ions is at its maximum at label _____. A) A B) B C) C D) D E) EBiol152(Exam(#1(Spring(2017((3( 10) The neuronal membrane is at maximum depolarization at label _____. A) A B) B C) C D) D E) E 11) The cell is not hyperpolarized; however, repolarization is in progress, as the sodium channels are closing or closed, and many potassium channels have opened at label _____. A) A B) B C) C D) D E) E 12) If you experimentally increase the concentration of K+ outside a cell while maintaining other ion concentrations as they were, what would happen to the cell's membrane potential? A) The membrane potential would become more negative. B) The membrane potential would become less negative. C) The membrane potential would remain the same. 13) If the activity of the sodium-potassium pump were completely stopped, what would happen to the neuron's membrane potential? A) immediate loss of resting potential B) immediate loss of action potentials C) slow decrease of resting potential D) no effect 14) A toxin that binds specifically to voltage-gated sodium channels in axons would be expected to _____. A) prevent the hyperpolarization phase of the action potential B) prevent the depolarization phase of the action potential C) prevent graded potentials D) increase the release of neurotransmitter molecules E) have most of its effects on the dendritic region of a neuron 15) The "undershoot" phase of after-hyperpolarization is due to _____. A) slow opening of voltage-gated sodium channels B) sustained opening of voltage-gated potassium channels C) rapid opening of voltage-gated calcium channels D) slow restorative actions of the sodium-potassium ATPase E) ions that move away from their open ion channelsBiol152(Exam(#1(Spring(2017((4(16) ) Immediately after an action potential passes along an axon, it is not possible to generate a second action potential. Thus, we state that the membrane is briefly _____. A) hyperexcitable B) refractory C) fully depolarized D) above threshold E) at the equilibrium potential 17) Tetrodotoxin blocks voltage-gated sodium channels and ouabain blocks sodium-potassium pumps. If you added both tetrodotoxin and ouabain to a solution containing neural tissue, what responses would you expect? A) immediate loss of resting potential B) immediate loss of action potential with gradual loss of resting potential C) slow decrease of resting potential and action potential amplitudes D) No effect; the substances counteract each other. 18) Chum salmon (Oncorhynchus keta) are born in freshwater environments and then migrate to the sea. Near the end of their lives, they return to the freshwater stream where they were born to spawn. In freshwater, water constantly diffuses into the body and ions are lost from the body. In salt water, body water diffuses out of the body and excess ions are gained from the water. A salmon's gills have special cells to pump salt in or out of the body to maintain homeostasis. In response to the salmon's moves between freshwater and salt water, some cells in the gills are produced and others are destroyed. The ability to make changes in the cells of the gills during the lifetime of an individual salmon are an example of which of the following? A) evolution B) trade-off C) acclimatization D) adaptation 19) You observe two female fish of the same species breeding. One female lays 100 eggs and the other female lays 1000 eggs. Which one of the following is MOST likely given the limits of fitness trade-offs? A) The female laying 100 eggs breeds more often than the female laying 1000 eggs. B) The female laying 100 eggs lives shorter than the female laying 1000 eggs. C) The eggs from the female laying 1000 eggs have larger yolks than the yolks of the eggs from the female laying 100 eggs. D) The female laying 1000 eggs is smaller than the female laying 100 eggs.Biol152(Exam(#1(Spring(2017((5(20) ) If you were to