69. Tetrodotoxin blocks voltage-gated sodium channels and ouabain blocks sodium-
ID: 73947 • Letter: 6
Question
69. Tetrodotoxin blocks voltage-gated sodium channels and ouabain blocks sodium-potassium pumps. If you added both tetrodotoxin and ouabain to a solution containing noural tissue, what responses would you expect? A) No effect; the substances counteract each other. B) immediate loss of resting potential C) immediate loss of action potential with gradual loss of resting potential D) slow decrease of resting potential and action potential amplitudes 70. The heart rate decreases in response to the arrival of A) gamma-aminobutyric acid (GABA) B) acetylcholine C) nitric oxide D) endorphin Neurotransmitters categorized as inhibitory are expected to A) hyperpolarize the membrane B) close potassium channels C) act independently of their receptor proteins D) open sodium channels 71. 72, A hyperpolarization of a membrane can be induced by A) increasing its membrane's permeability to Cat+ B) increasing its membrane's permeability to Na C) decreasing its membrane's permeability to Cl D) increasing its membrane's permeability to K+ 73. Differences between the sympathetic and parasympathetic divisions of the autonomic nervous system enable the two systems to affect behavior differently. Which of the following statements regarding the SYMPATHETIC system is true? A) most efferent neurons emerge from the brainstem and use acetlycholine as a neurotransmitter B) most efferent neurons emerge from the spinal cord and use norepinephrine as a neurotransmitter C) most efferent neurons emerge from the spinal cord and use acetlycholine as a neurotransmitter D) most efferent neurons emerge from the brainstem and use norepinephrine as a neurotransmitter 74. A toxin that binds specifically to voltage-gated sodium channels in axons and inhibits their activity would be expected to A) prevent the repolarization phase of the action potential B) prevent the depolarization phase of the action potential C) increase the release of neurotransmitter molecules D) prevent the hyperpolarization phase of the action potential 75. Which of the following statements about action potentials is correct? A) Action potentials are propagated down the length of the axon B) Movement of ions during the action potential occurs mostly through the sodium pump. C) Action potentials for a given neuron vary in duration. D) Action potentials for a given neuron vary in magnitude. 76. If you experimentally increase the concentration of Na+ outside a cell while maintaining other ion concentrations as they were, what would happen to the cell's RESTING membrane potential? A) The RESTING membrane potential would increase. B) The RESTING membrane potential would be unaffected C) The answer depends on the thermodynamic potential D) The RESTING membrane potential would decrease. Page 10 of 22Explanation / Answer
70). B). Acetyl choline
Acetyl choline decreases the heart rate through the muscarinic receptors and vagal nerve stimulation. it also decreases force of contraction and cardiac output.
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