A 16-year-old female patient has fainted after quickly changing her body position from horizontal to vertical one. Which process from the ones listed below has caused the loss of consciousness in the first place?

Answer options

1. Increasing arterial pressure
2. Decreasing venous return
3. Increasing venous return
4. Decreasing oncotic pressure of blood plasma
5. Increasing central venous pressure

Explanation

A sudden change of body position vertically decreases the venous blood return to the heart due to gravity. The body loses consciousness so that by the fall and consequent return to a horizontal position, blood return will be easier. Remember that’s why we get head rushes.