Q41. Some sensory neurons in our bodies generate action potentials in response to pressure or movement, allowing us to feel things through our sense of touch. Based on what you learned, how does such a neuron indicate stimulus strength/intensity?
By altering the speed of action potential propagation: Stronger stimuli cause action potentials to travel faster down the axon.By altering the peak membrane potential (Vm) during the action potential: Stronger stimuli produce taller action potentials.By altering the rate of action potential generation: Stronger stimuli produce more frequent action potentials.By altering the amount of neurotransmitter released by the neuron: Stronger stimuli make each action potential release more neurotransmitter.

Q42. What information does the pain receptor relay to the brain about stimuli BELOW threshold?
The duration of the stimulation.The location of the stimulation.The membrane potential at the site of stimulation.None of the above.

Q43. Which statement below describes how Vm changes over time during the action potential?
At the start of the action potential, Vm quickly becomes more positive, and then it becomes more negative.At the start of the action potential, Vm quickly becomes more negative, and then it becomes more positive.Vm becomes more and more positive with each action potential.Vm usually doesn't change during the action potential.

Q44. Which statement below is TRUE about neurotransmitters?
The entry of neurotransmitter through K+ channels into neurons triggers the rising phase of the action potential.Neurotransmitters are released from muscle cells to activate motor neurons in the presence of botulinum toxin.Neurotransmitters are released from a neuron when the action potential reaches the end of its axon.All of the above.
Q45. Why do neurons generate an action potential, instead of simply relying on the opening of ion channels near the stimulus site to transmit information?
Because without the action potential, changes in Vm at the stimulus site might not reach the axon terminal.Because without the action potential, the neuron would not depolarize.Because action potentials help the body keep ion concentrations at appropriate levels.Because without the action potential, the neuron would not return to resting potential.

Q46. If calcium ions, each of which has a charge of +2 (Ca2+), moved INTO a neuron, and no other ions were moving, what would be true?

The area outside the neuron would be become more positively charged.The concentration of Ca2+ inside the cell would decrease.The neuron would become more negative.The neuron would become more positive.'

Q47. Why does Na+ enter the cell during the action potential?
Because the Na+ channels are open and only let Na+ move from outside to inside.Because the action potential pulls positive ions into the cell while Na+ and K+ channels are open.Because Na+ channels are open and allow Na+ ions to move down the length of the axon to produce neurotransmitter at the axon terminal.Because Na+ channels are open and there is a higher concentration of Na+ outside of the neuron than inside.

Q48. Which statement below is TRUE about the voltage-gated Na+ channels during the action potential?
The voltage-gated Na+ channels are open the entire time that the neuron is depolarized (when Vm is above resting potential).The voltage-gated Na+ channels open after the voltage-gated K+ channels.The voltage-gated Na+ channels open to restore Vm to the resting potential after the action potential peak.The voltage-gated Na+ channels are open when Vm is rapidly increasing during the action potential.

Q49. What is the role of myelin in neurons?
To change the direction that Na+ and K+ move through ion channels during the action potential.To increase the speed that action potentials travel down the neuron.To prevent the neuron from generating action potentials.To cause multiple sclerosis when present and intact, as it blocks action potential movement and must be removed by the immune system.

Q50. Marathon runners can lose a great deal of Na+ (through sweat). Some runners compensate by drinking large quantities of water (far more than they lost). In extreme cases, this causes mental confusion and loss of muscle coordination. What is happening to the neurons of such a runner?
The person has run out of neurotransmitter by firing too many action potentials.Na+ loss and dilution results in increased K+ entry into neurons through Na+ channels.Na+ loss and dilution has lowered the Na+ concentration outside of neurons so that less Na+ flows into neurons through open Na+ channels.Neutral oxygen molecules (O2) are entering through oxygen channels and depolarize the neuron.