If an axon is wrapped with glial cells, nerve impulses are propagated down this axon
a. as the action potential travels steadily down the membrane of the axon.
b. along the membranes of the surface regions of the glial cells.
c. more slowly than they would be on or via an unwrapped axon, allowing for greater control over transmission.
d. from one interruption in the myelin sheath to the next.
e. in two directions from the middle of an axon.
D; The function of one type of glial cell is to form the myelin sheath around a nerve. This speeds the transmission of the impulse down the axon because the action potential jumps from axon membrane at one gap in the sheath to the next gap instead of running down the entire length of the axon membrane (choice a). The glial cells themselves do not conduct impulses (choice b). The whole point of the myelination is to speed impulses (choice c). The direction is unchanged (choice e).
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Proteins derived from infecting viruses are taken up and digested in the cytoplasm in a structure called the
A) phagosome. B) liposome. C) proteasome. D) nucleosome.
Answer the following statements true (T) or false (F)
1. Modern humans show a type I survivorship curve. 2. K-selected populations tend to reproduce quickly. 3. Exponential growth is rare because resources are usually limiting. 4. r-selected species tend to have type III survivorship curves. 5. Drought and floods are considered to be density-dependent factors potentially affecting population size.
Why would it be better to transplant a plant with a ball of soil surrounding its roots?
a. The root hairs will remain intact. b. The nutrients will not escape from the roots. c. The plant is used to that particular soil. d. The weight of the soil helps the plant.
Certain organisms break down glucose in the absence of oxygen. This process is called ________
Fill in the blank(s) with correct word