In a laboratory situation, a nerve can be stimulated by applying voltage from a stimulator. If a stimulus was applied in the middle of a nerve roughly halfway between the cell bodies and the axon terminals, would resulting action potentials travel only from the stimulus point to the axon terminal? Why or why not? How is this similar to or different from the basic characteristics of an action
potential discussed in this chapter? What does this tell you about the nature of the axon?
What will be an ideal response?
Action potentials would travel in both directions from the stimulus point, simultaneously toward the cell bodies and toward the axon terminals. This is because the axon segments on each side of the stimulus point are
presumably not refractory when the stimulus is delivered, thus there is nothing to prevent the action potentials from traveling in both directions. In normal transmission, the action potential begins where the axon starts, and travels only away from that point, not toward, because the membrane becomes refractory for a period of time after the action potential occurs. Thus, the axon is quite capable of transmitting action potentials in either direction, even though normally it is prevented from doing so.
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Which of the following processes is most important to continuation of the human
species? A) Movement B) Respiration C) Reproduction D) Responsiveness
Match the organelle (1-4 ) with the correct description (5-8). 1 ) mitochondrion 5 ) synthesizing molecules 2 ) centriole 6 ) liquid in cell 3 ) endoplasmic reticulum 7 ) provides cell with energy 4 ) cytosol 8 ) aids the formation of the spindle apparatus
A) 1 and 7, 2 and 6, 3 and 8, 4 and 5 B) 1 and 8, 2 and 5, 3 and 6, 4 and 7 C) 1 and 7, 2 and 8, 3 and 5, 4 and 6 D) 1 and 5, 2 and 6, 3 and 7, 4 and 8 E) 1 and 6, 2 and 8, 3 and 5, 4 and 7
Which of the following time periods is termed electromechanical delay?
A. the time required for conduction of the nerve impulse to the neuromuscular junction B. the time required for the nerve impulse to cross the neuromuscular junction C. the time required for the muscle to initiate the development of tension after receipt of the nerve impulse D. the time required for a muscle to reach peak tension after the development of tension is initiated
The respiratory pump assists blood movement within the veins of the trunk, because as a person inspires,
A. intra-abdominal and intrathoracic pressure both increase. B. intra-abdominal pressure decreases and intrathoracic pressure increases. C. intra-abdominal and intrathoracic pressure both decrease. D. intra-abdominal pressure increases and intrathoracic pressure decreases.