Impulse

...as I reach for the pack of large (about four inches in diameter, apiece) cookies, something happens in my forebrain, cascades through my nervous system to my muscles, resists the physical momentum of my arm, and stops my hand.  I grab a piece of fruit instead.

An impulse, in physics, is something that changes the momentum of an object (like my muscles acting on my arm and hand).

In signal processing, an impulse is an impossibly narrow peak.

In audio (and signal processing in general), we have a tool called a low-pass filter, which attenuates out high frequency information and leaves low frequency information alone.  In other words, it smooths out the wrinkley bits of a signal.

This is the schematic for the simplest version of a low pass filter, called an RC network, because it consists of a resistor and a capacitor.  A capacitor is is essentially two metal plates, separated by a bit of air - when you put it in a circuit, the plates have to "charge up" before current will jump across the air gap, so a capacitor has an impedance which is inversely proportional to the freqency (or angular momentum, or velocity) of the current.

Higher frequencies will tend to "drain" into the capacitor (indicated by "C"), instead of being applied across the load "VC."  The more "impulse-like" parts of the signal are drawn off from the smoother parts.

In psychology, an impulse is a sudden wish or urge.

A test for impulsivity (among other things) in children is the Marshmellow Test - in which a marshmellow is placed in front of the child, and they are told they can earn a second marshmellow if they can refrain from eating the first for fifteen minutes or so.  Here's my oldest daughter, Anika, taking the Marshmellow Test (ya, I'm mean)...

At fifteen minutes, it's a bit long and boring, but you can watch how Anika copes with this challenge, highlights at 1:30, 2:20, 3:40, 7:30, 8:00 & 13:00.

She looks away, she distracts herself, she whines and cries, she hides under the table, &etc.

In the same way a capacitor shunts off noisy impulses to smooth out a signal, Anika is shunting off the emotional energy involved in resisting that oh so tempting marshmellow into these behavioural outbursts.  Impuse control (in psychology) is like a high pass filter (in signal processing).

This is strictly a metaphor - I would be very surprised if it correlated with anything which actually went on in a human brain.