This wikipedia article covers most of the aspects of how analog television works: http://en.wikipedia.org/wiki/Analog_television
I will give a brief summary, though.
The picture is formed with a series of horizontal scan lines. Sometimes you will see TVs or cameras advertized with a certain number of 'lines' of resolution - this is why. You don't get pixels until you're talking about a digital signal. The lines are transmitted serially one at a time. In the days of CRT televisions, the lines would be sent to the electron guns in the TV as they arrived and the electron gun would draw the line on the screen. Nowadays, the TV just digitizes the signal and dumps it in a buffer.
Audio and video are transmitted as two separate signals. In the case of cable TV and broadcast TV, both signals are modulated onto carrier waves, with different carrier waves for each channel and a known offset between the video and audio carriers. Then the TV can tune into a channel just by picking the correct video and audio carrier frequencies and demodulating the signals.
the RF signals of each frequency are translated into voltage waves that are then superimposed onto one, thereby creating one electrical signal that is sent through the cable.
On the one hand, I think you've got it. On the other, I'm not sure you understand what's going on well enough to get it for the right reasons.
If we want to broadcast an rf signal through space, we have to emit that signal from an antenna. To get the signal from our generating equipment to the antenna we use a transmission line, typically a coaxial cable. The voltage signal on the transmission line excites the antenna, which generates EM waves that travel to the receiving antenna.
At the receiving antenna, the EM waves are delivered to another transmission line (again, typically coax) to get them to the receiving equipment.
Sending signals over coax is just like that, but without the antennas. The generating equipment is just connected to the receiving equipment by the cable. The same voltage signals in the cable that would have excited the antenna, travelled through space, been collected by the other antenna, etc, are just delivered straight to the coax that feeds the receiving equipment.
My point is there's no fundamental difference between the signals in a coax cable and "rf signals". Both are just voltages (or electric fields) varying with time.
And there's no need to "translate" rf signals into voltages. The RF signals already are (or started out as) voltages before they were broadcast as EM waves.
In fact you can also look at the signal in the coaxial cable as an EM wave, but it just happens to be travelling in a dielectric sandwiched between two conductors instead of travelling in free space.
Best Answer
For RF signals, the shield carries the signal just as much as the center conductor, and if it is broken anywhere, the cable performance will seriously degrade.
The shield does limit noise, by containing the desired "signal" EM field between the center conductor and the inside of the shield, acting essentially as a Faraday cage, keeping your signal inside, and other signals (noise) outside. The shield is able to completely (ideally) contain the EM field carrying the signal precisely because it carries equal and opposite currents to those in the center conductor at every point along the cable. Were this not the case, there would have to be an external field. Thus, the shield is also the return current path.
The geometry of the shield relative to the center conductor also defines the characteristic impedance of the cable. If there are any discontinuities in the shield, the signal will be distorted by reflections. In the case of the shield being entirely disconnected at one end, the distortions are likely quite horrible, and the power transfer from line driver to receiver will likely be quite poor, as most of the power will be reflected back at the line driver.