Question

After sitting for many hours during a trans‑Pacific flight, a passenger jumps up quickly as soon as the "fasten seat belt" light is turned off, and immediately falls to the floor, unconscious! Within seconds of being in the horizontal position, however, consciousness is restored. Select the option that completes the explanation of what happened.

Upon standing, there is a time lag before the person’s heart responds to the:
O increased downward force of the top of her head on her blood. Lying horizontally removes the downward force.
O increased pressure difference between her feet and her head. Lying horizontally reduces the pressure difference.
O reduced fluid density in her brain, which causes a lack of oxygen. Lying horizontally restores the proper fluid density.
O rush of blood and other fluids up into her head. Lying horizontally equalizes her fluid levels once again.

Answer 1

increased pressure difference between her feet and her head. Lying horizontally reduces the pressure difference.

Explanation:

The autonomic nervous system controls heart function to adapt to the effect of body positional changes. In some circumstances it takes a few seconds. So even if the passenger would have been held upright she would have recovered consciousness. The horizontal position sped up things