All cells maintain an ionic (and therefore electrical) potential difference across their membranes. In most cells, this potential difference is between -50 and -100 mV. That is, the inside of the cells is more negative than the outside by 50 to 100 mV. Although all cells in the body maintain this potential difference across their membranes, only certain cells (for example, neurons) are capable of generating action potentials.
a. How is this potential difference across the cell membrane generated?
b. What characteristics of membranes allow cells to concentrate or exclude ions?
c. What is it about neurons (nerve cells) that make their properties different from those of other cells? In other words, what enables nerve cells to produce action potentials?
d. How is an action potential started and propagated?
e. Is any direct or indirect energy input required to generate an action potential? If so, when and where is the energy used?
f. What happens in time and space (along the axon) once an action potential begins?
g. What factors ultimately limit the ability of the nervous system to respond (that is, to continue to generate impulses)?
Quick Reply
