In this task, you are given a paragraph, and your task is to construct a question from the given passage. Construct question in such a way that (i) it is well explained in the paragraph, (ii) the words may/may not be present in the paragraph, (iii) it should start with what/how/describe. Avoid creating a question that (i) is just relevant to one or two sentences, and (ii) not relevant to passage. 

[Q]: Electrical signals in the brain travel through nerves to muscles. Two types of proteins exist in filaments in the muscles. The filaments move when the brain instructs them to. The motion of the filaments cause the muscle to shorten and contract. Opposing pairs of muscles exist in order to provide the necessary range of motion. 
[A]: How do muscles work?


[Q]: Fuel produces heat. Water is boiled to make steam. Steam spins turbine. Generator is turned. Makes electricity. Electricity transfers to transformers. Produces the correct voltage. 
[A]: How does a nuclear-powered power station generate electricity?


[Q]: Oxygen-depleted blood enters the heart on the right atrium. The atrium contracts. Blood flows from your right atrium into your right ventricle through the open tricuspid valve. When the ventricle is full, the tricuspid valve shuts. The ventricle contracts. Blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs. The lungs oxygenate the blood. The oxygenated blood goes into the left atrium. The left atrium sends the blood throughout the body. 
[A]:
How does the heart work?