The prospect of dying frightens some: "And so it stays just on the edge of vision/A small, unfocused blur, a standing chill/That slows each impulse down to indecision," Philip Larkin wrote in his desperately bleak poem Aubade.
As you follow these back toward the highway, using your hands, sliding occasionally, sitting deliberately beneath the spray to cool off or taking your boots off to chill your feet in the water, you get the uncanny sensation that you're a water molecule yourself, propelled by gravity, surging, dropping, leaping, carried by a sure, almost effortless impulse down, down, down toward the valley below.
Open image in new window Figure 3 Impulse down.
To send an electrical impulse down the length of a nerve fiber, neurons depend on ion channels embedded in their membranes that open and close in response to changes in the voltage difference between the inside and outside of the cell.
Responses are induced by nerve impulses traveling down the descending tracts that stimulate motor neurons or that initiate glandular secretion.
He finds himself torn, however, by dueling impulses handed down from his father's generation to his own.
Sending neural impulses quickly down a long nerve fiber requires insulation with myelin, which is formed by a cell called an oligodendrocyte that wraps itself around a neuron.
Improving behavioral self-regulation (i.e., inhibiting impulses, calming down when upset) may also be important for preventing childhood obesity.
Now as the input frequency x of t increases, this impulse moves up in frequency, but this impulse moves down in frequency.
