From: Martiny (email) (web)

Question: Why do you always have to go to the bathroom right when you walk in your door after school/work?

Answer:

The bladder is a storage resevoir for urine--a liquid containing waste products given off by the body and extracted from the bloodstream by the kidneys. The need to urinate, or expel the urine in the bladder, is first felt when 3.5-5 ounces of urine accumulate. As more urine accumulates, the feeling increases, becoming uncomfortable around 15 ounces.

People probably feel a need to urinate after arriving home because they haven't expelled the urine from their bladder for a number of hours, and that urine has built up.

Some people feel a need to urinate after arriving home even though their bladder is nearly empty. This may be Pavlonian conditioning -- a learned response to a certain set of stimuli. The conditioned reflex theory was developed by a Russian physiologist named Ivan Pavlov in the early 1900s. Using a dog as a research subject, Pavlov associated the sound of a bell with food. Every time the bell rung, the canine was fed. In time the dog would salivate at the sound of a bell, even if no food was in sight. This, Pavlov said, was a conditioned reflex.

As younger children in school, I think most of us were less likely to use the restroom. I know I prefer my home bathroom to a public restroom. Oftentimes, I'd just hold it until I got home. While I think most people get over this "fear of public restrooms," the need to urinate upon arriving home may be a conditioned reflex, left over from the time when you really did have to go pee when you got home.

Sources:

• "urination" Encyclopedia Britannica Online
  <http://www.eb.com:180/bol/topic?thes_id=396435>
  [Accessed April 23, 1999].
• "conditioning" Encyclopedia Britannica Online
  <http://www.eb.com:180/bol/topic?eu=25532&sctn=1>
  [Accessed April 23, 1999].

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