Can a single line of Gcode have variable extrusion rate? Fairly long winded, but hopefully makes sense;

I understand that G-code is executed line-by-line, and in the main printing phase each instruction is effectively go to location XY (assuming staying within the layer) at a set speed with a set extrusion amount (not rate, as far as I can tell).  

Imagine you were printing a single road width, say 10&nbsp;mm long. If the single instruction says to move that 10&nbsp;mm at a set speed and extrude 10mm of material (which is, I guess, not 10mm of filament), with infinite acceleration and deceleration of the nozzle and extruder gears, then a linear amount of material would be extruded per unit length along the 10&nbsp;mm. However, given that there is some acceleration and deceleration, that extrusion must be non-linear. 

My questions are as follows;
- Is it possible to counteract this within a single line of Gcode by having a variable extrusion rate? 
- Can the machine do so regardless of the instructions given to it? 
- Is this effect embraced somehow? 
- Does the need to accelerate both the nozzle position and filament effectively cancel out? 
-Would/could you aim instead to split a single straight line of filament into multiple lines of G-code, some extruding (say in the middle), and some not (say at each end)?
My understanding is that the printer firmware will define the maximum acceleration and speeds for each axis (X, Y, Z, and E). When executing a line of g-code that involves more than one axis, the acceleration for each will be limited such that they all begin and end, including acceleration together.

During the start and end of a line, when the print nozzle is moving more slowly, the extruder will also move slowly. In the middle of the line, the extruder will move faster. The amount of material extruded per distance will be constant over the length of the line.

Another way to look at it - suppose you could accelerate quickly on X with a high top speed, but slowly on Y. A move only in the X direction could happen quickly. A move only in the Y direction would be slower. If you want to move at a 45-degree angle,  you will need to slow down X so that it doesn't get ahead of Y.

If you did want to intentionally vary the amount of extrusion per distance during a line, you would need to break it into multiple segments with individual lines of g-code.