Nerves do not give off a flow of nerve energy. Nerves are gland cells. They produce and release a hormone that causes the inhibition or the contraction of muscle cells and the inhibition or enhancement of secretion by a gland cell that includes another nerve cell. That is all they do, no more, no less. They do not actually conduct electricity or any other form of energy.
When a nerve cell undergoes its function of secreting a hormone, changes occur in its outer cell membrane that allow electrically-charged ions to move in and out of the cell in a step-wise fashion along the full extent of the nerve. This is what really occurs when a nerve is described as "conducting an impulse" or "firing." A spinal nerve at the intervertebral opening is actually a thin tube of connective tissue containing the extensions of millions of nerve cells. These extensions are the axons that are also described as "fibers." This latter term is misleading because it connotes a certain firmness such as fine wires would have. Nothing could be more incorrect. The axons are delicate, flimsy structures. Since they are merely elongated or drawn out parts of cells they need nourishment along with the cells that make up their sheaths. Therefore, delicate blood vessels are contained in what is called a nerve at the visible level. If compression of a nerve does not directly kill the axons, the axons may die because the compression cuts off the flow of blood in the vessels of the nerve. Compression of a nerve cell anywhere along its extent can cause it to secrete its hormone. If it is a sensory nerve cell, it can cause the brain to experience pain. If it is a motor nerve cell, the hormone can cause a muscle cell to contract.
If the motor nerve cells to a skeletal (voluntary) muscle die, the muscle will be paralyzed and also die. This is because the motor nerve cells continuously supply skeletal muscle cells with substances needed for their survival, above and beyond the hormone the nerve cells secrete to make the muscle contract. This is not the case with the motor nerve cells to glands, heart muscle, or smooth (involuntary) muscle. Complete severance of the motor nerves from the spinal nerves to the heart, glands (salivary, thyroid, liver, pancreas, etc.), and smooth muscle of the lungs, esophagus, stomach, gall bladder, intestines, etc., has only transient effects. The gland cells and smooth and cardiac muscle cells not only survive, but function normally. They surely do not become diseased.
