Question

During sleep, a man's blood pressure:

• A. Increases
• B. Decreases
• C. Remains constant
• D. Fluctuates

Hint:

Sleep has alternating stages, and blood pressure tracks the shift between them instead of moving in only one direction.

Answer 1

The Correct Option is D

Step 1: Recall how blood pressure is controlled.
Blood pressure is not a fixed number. It is set moment to moment by the autonomic nervous system, which balances the sympathetic branch (raises heart rate and pressure) against the parasympathetic branch (lowers them). Across a full day and night this balance keeps shifting, so blood pressure is a moving value, not a constant one.

Step 2: Understand the normal night time dip.
During the early and deep stages of sleep, called non REM sleep, the parasympathetic system takes over. Heart rate slows, blood vessels relax a little, and blood pressure drops by roughly 10 to 20 percent below the daytime average. Doctors call this normal drop the nocturnal dip. This is where the idea of blood pressure simply decreasing during sleep comes from.

Step 3: Understand what happens in REM sleep.
Sleep is not one flat state. It cycles between non REM and REM stages through the night. In REM sleep, which is the dreaming stage, the sympathetic system becomes active again in short bursts. Heart rate and blood pressure can rise back up toward waking levels, sometimes with brief spikes, before falling again as the next non REM phase begins.

Step 4: Put the whole night together and rule out the other options.
Because the body keeps cycling between non REM dips and REM rises every 90 minutes or so, blood pressure over a full night traces a rising and falling pattern rather than one single direction. Option (A), that it only increases, is wrong because the dominant nightly trend is a fall, not a rise. Option (C), that it stays constant, is wrong because pressure clearly moves with each sleep stage. Option (B), that it decreases, captures only the non REM dip and misses the REM rises, so it describes part of the night, not the whole night. Taking the entire sleep cycle into account, the pressure goes up and down repeatedly, which is best described as fluctuating.

Final Answer:
Over a complete night, blood pressure moves up during REM bursts and down during non REM stages, so it fluctuates through sleep.