Answer:
I, II, III
Explanation:
A threshold stimulus is a stimulus that is capable to produce a response in excitable tissues such as neurons and muscle fibers. At threshold potential, the outward movement of K+ and inward movement of Na+ become equal to each other. When the potential exceeds the threshold potential, more and more Na+ enter the cell to depolarize it and to allow the opening of Na+ channels. Therefore, to fire an action potential, the threshold must be exceeded.
Conduction of action potential is all or none phenomenon which means that either it occurs or it does not occur. As an impulse is passed by each successive part of an exon, it enters the refractory period during which there is no conduction of nerve impulse. It ensures the one-way conduction of impulse from the cell body to the axon terminal only.
Answer:
Cells from the cheek are a type of epithelial cell, similar to skin. ... They can be seen faintly even at 40x (scanning power), but the most dramatic images are at 400x where the nucleus is clearly visible as a dark spot in the center of the cell.
Explanation:
Answer:
The moon isn't visible on the left side. There is a shadow on the left side on the sphere. The light or sun is casting down reflecting light of the right side of each surface.
Explanation:
This property allows fish living in lakes and ponds to survive the winter. The ice that freezes on the surface insulates the water below so it stays warmer! In general, it is extremely unusual for the solid phase of a substance to be less dense than its liquid phase, but lucky for aquatic life it is!
