Literally, internal organs or intestines. Usually it refers to "toughness" or strength of character. For example, the phrase "he's got guts" means he is bold and strong. "Gutless" would mean wimp.
Ach decreases the heart rate and the force of the contraction. This is done through signaling molecules, and how they have a different effect on the heart vs salivary glands is that they have different receptors but sometimes they have the same receptor just the internal machinery is different.
The strong nuclear force acts only on neutrons and protons in the nucleus of an atom. The opposite would be a weak nuclear force.
There are four "fundamental forces": the strong force, the weak force, the electromagnetic forces, and gravity. Others might be discovered in the future, but until then, anything else is not a fundamental force.
The stars so they say.
a force that some believe controls events
An admiral controls a task force or fleet of ships.
the suns heat
EMF force or voltage