G-LOC is caused by cerebral hypoperfusion due to reduced venous return. Which option matches this mechanism?

• A. Cerebral hypoperfusion from reduced venous return
• B. Hyperperfusion of the brain
• C. Increased intracranial pressure
• D. Cardiac arrhythmia

Answer: (A)

G-LOC happens when gravity during high-G loads causes blood to pool in the lower body, reducing venous return to the heart. This lowers cardiac output and brain blood flow (cerebral perfusion). When cerebral perfusion drops below what the brain needs, consciousness can be lost. The statement that describes cerebral hypoperfusion from reduced venous return captures this sequence precisely.

The other possibilities point to different mechanisms: hyperperfusion would mean too much blood flow to the brain, which isn’t what happens in G-LOC; increased intracranial pressure can cause symptoms but isn’t the primary cause of loss of consciousness from high-G exposure; cardiac arrhythmia would cause LOC through rhythm disturbance rather than the venous return issue created by G forces.