Choking, chemoreceptors, and yawning

Some questions asked during the respiratory system discussion:

1. Why do some people choke themselves to get a high?

The choking game is a stupid and dangerous activity gaining popularity among teenagers and pre-teens. It involves asphyxiation (self-induced or caused by a friend), passing out, and feeling a kind of euphoria similar to a drug-induced high once oxygen rushes back to the brain. Click on the links for more information.

2. How do the sensors in the walls of the aorta and carotid// arteries work?

We said that the specialized cells in the walls of the aorta and carotid arteries are sensitive to blood pH, an indicator of CO2 levels. These cells are called chemoreceptors.

According to Duchen & Biscoe (1991), most evidence supports the theory that detection of pH levels is done by molecules called cytochromes in these cells. One type would be sensitive to high levels, one to low levels.

Depending on the level, these chemoreceptors send signals via nerves. Nerve signals are caused by K+ and Na+ ions being exchanged across the cell membrane. This movement causes an action potential that is like a pulse of electrical activity that travels the length of the nerve cells and ultimately ends up in the medulla oblongata.

We will discuss this more when we get to the nervous system. Meanwhile, you may feast your eyes on this flash animation.

// Why do we yawn?

Wong (2002), in his answer to a similar query in Scientific American, runs through what scientists now know about yawning–which is basically NOTHING conclusive. Although the “kulang sa oxygen” hypothesis is popular, there is no proof that this is true.

Click on the links and decide for yourself. πŸ™‚

PS. You kids ask the darndest questions! Don’t ever stop. πŸ˜€


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