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What causes brain freeze?

Since, according to the British Medical Journal (BMJ), it is the most common cause of headache, odds are most of you have experienced “brain freeze,” or sphenopalatino ganglioneuralgia, as the science-types call it.

Brain freeze occurs when very cold beverages or foods are pressed up against the top of the mouth for an extended period of time, and the result is similar to why people have a flushed face on a cold day.

The cold food causes the blood vessels in the top of the mouth to rapidly contract. When the cold food leaves the area, blood rushes back into the top of the mouth, resulting in rapid expansion. This rapid expansion is sensed by the trigeminal nerve, which signals the brain to “feel pain.”
So why is brain freeze most commonly felt in the forehead if the signal is coming from the top of the mouth? It has to do with a phenomenon called “referred pain,” where a nerve, which is responsible for sending information from a part of the body (in this case, the face) is artificially stimulated on its way to the brain. Referred pain is also common in heart attack victims, where pain can be felt in the neck, shoulders and back, instead of the chest.

According to BMJ, “brain freeze” is currently thought to be related to migraine headaches, since the symptoms of both are described as being similar, and brain freeze has been known to trigger migraines in sufferers. But it is important to note that while the worst ice cream headache lasts for a few minutes, migraines can last significantly longer.

According to an article appearing in the February 2008 issue of Scientific American Mind, it is impossible to get brain freeze on a cold day, presumably because the rapid dilation of the blood vessels would be slowed by the cool ambient temperatures.

What is the difference between a virus and a prion?

Viruses, like the human immunodeficiency virus (HIV), and prions, like the one responsible for mad cow disease, have a few things in common. However, like all things, it is their differences which set them apart.

Both viruses and prions are very small, and need to be described in terms of nanometers, or millionths of a milimetre. To put that into perspective, a virus or prion can be many hundred times smaller than a bacterial cell, which is already pretty small. Neither is considered “alive,” as they cannot reproduce without the chemical machinery of their hosts, and both are agents of disease, but this is where their similarities end.

Viruses, unlike prions, have a genome, or a set of genetic instructions in the form of DNA or RNA, which they use to replicate their structural pieces and enzymes.

Prions, on the other hand, do not have a genome, and are mostly made entirely out of improperly folded protein. When ribosomes — the enzymes that translate your genome into protein — build a new protein, they do it in a linear fashion, similar to how cars are added to the back of a train. As the ribosome is adding new amino acids to the growing protein, chaperones start folding the front of the “train” into 3-D shapes. A prion is created when one of these “3-D shapes” is made, or folded, incorrectly. However that is not the complete story.

What makes a prion so dangerous is its ability to “encourage” other proteins around them to also fold incorrectly, creating more and more prions at the cost of healthy tissue.

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