Brain Freezes, Knuckle Cracking and Ear Wiggles: Strange Biology
Strange and Interesting Behavior
The human body is complex and awe-inspiring. It also exhibits some strange behaviors that make some of us scratch our head and wonder what the heck is going on.
One of these weird activities is the creation of a "brain freeze", a sudden, sharp headache that some people experience as they eat very cold food, such as ice cream. Others are the knuckle cracking and ear wiggling that some folks perform either for their own enjoyment or to impress people who lack the ability.
I experience brain freezes myself and admire the knuckle cracks and ear wiggles of others. Strange as it may seem to people who consider these to be interesting but unimportant phenomena, they may be valuable. Learning more about strange activities in the body may help scientists understand related behaviors that are more serious in nature.
Cold Food and Drinks and Brain Freezes
A brain freeze occurs when a person eats or drinks something very cold very quickly. Common triggers are ice cream and ice-cold beverages. The disorder is sometimes known as an ice cream headache.
The technical name for a brain freeze is sphenopalatine ganglioneuralgia, which somehow lacks the impact of the common name. The sharp, stabbing headache develops almost immediately after taking a cold substance into the mouth. The pain lasts from as little as ten seconds to as long as five minutes.
Many people experience brain freezes, but they occur more commonly in migraine sufferers than in people who don't experience migraines. Discovering the cause or causes of brain freezes may enable researchers to discover new treatments for headache disorders.
Relieving or Avoiding the Pain
My brain freezes don't last long, so I just endure the headaches until they disappear. People who experience a brain freeze headache for a longer time might want to try one of the suggested treatments. I have no experience with these, but some sufferers say they work. Eating warm food to heat up the palate or placing the tongue against the palate reportedly work for some people. Eating cold food slowly and in very small mouthfuls may prevent a brain freeze in susceptible people who simply can't resist an icy treat.
The Circle of Willis
The circle of Willis is named after Thomas Willis, an English physician who lived from 1621 to 1675. He is officially recognized as the first person to notice the circle of arteries on the undersurface of the brain.
The Anterior Cerebral Arteries
There are two main theories to explain the production of a brain freeze. Either one may be correct, or alternatively they may both be correct. The most recent theory involves changes in blood flow in a brain artery, which in turn affects nerves and causes pain.
The artery that is believed to be affected by the cold temperature is the anterior cerebral artery. This artery begins on the undersurface of the brain as a branch from another artery and then enters the brain to supply it with blood.
Although the term "anterior cerebral artery" is often used in the singular, there are actually two of these arteries, as shown in the diagram below. One originates on each side of the brain. The two arteries enter the brain together through the fissure, or groove, that separates the right side of the brain from the left side.
What Causes a Brain Freeze?
The Anterior Cerebral Artery and Brain Freezes
When cold food or drink reaches the palate on the roof of the mouth, the sudden decrease in temperature is thought to affect blood flow in the anterior cerebral artery. The artery rapidly dilates, or expands, presumably enabling more warm blood to enter the brain to protect it from the cold. The dilated artery likely puts pressure on nerves present on the surface of the brain, causing pain. (The brain itself doesn't feel pain.)
The flow of extra blood into the relatively closed structure of the brain could raise blood pressure. The dilation of the anterior cerebral artery is quickly followed by its constriction, which presumably protects the brain from continued high blood pressure and eliminates the pain.
One group of researchers has found some interesting evidence suggesting that the above theory may be correct. The scientists have shown that the dilation of the anterior cerebral artery in human volunteers coincides with the pain of a brain freeze headache. The constriction of the artery that follows the dilation corresponds with the disappearance of the headache. More research is needed to prove that the arterial changes are the cause of the brain freeze headache instead of the result, however.
Branches of the Trigeminal Nerve
Brain Freezes and the Trigeminal Nerve
An older theory for the cause of a brain freeze says that the trigeminal nerve is responsible for the pain. The trigeminal nerve is one of the cranial nerves transferring information to and from the brain. The nerve has branches that extend into the face, as shown by the yellow lines in the diagram on the above. Like the anterior cerebral arteries, the cranial nerves are paired, so there is a trigeminal nerve on each side of the body.
According to the trigeminal nerve theory for brain freezes, the initial stimulus for the headache is the cold food or drink touching the palate. The low temperature triggers nerves in the area to stimulate blood vessels to dilate. The dilation enables the vessels to provide lots of warm blood to the palate to increase its temperature. Unfortunately, the dilated blood vessels also stimulate pain receptors, which send a message to the brain through a nearby branch of the trigeminal nerve.
The trigeminal nerve has branches that travel to other parts of the face besides the mouth. It's thought that the brain mistakenly "believes" that the pain stimulus is coming from a branch serving the forehead and therefore creates the sensation of a headache in this area. The phenomenon in which pain created by a stimulus in one part of the body appears to come from another part of the body is known as referred pain.
Some other examples of referred pain in the body include pain in the left arm accompanying a heart attack and pain in the right shoulder accompanying a gall bladder attack.
A Brain Freeze Poll
Do you experience brain freezes when you eat or drink something cold?
Demonstration of a Knuckle Crack
Some people crack their knuckles to impress others, but for other people stretching the fingers to produce a popping sound can be a pleasurable or even a relaxing experience. Listeners may think that the popping sound is funny and even enviable, but some listeners wince as they hear the sound and think about what the person is doing to their joints.
Knuckle crackers have various techniques to make the cracking sound in their finger joints. Some pull the tip of each finger until they hear a pop. Others stretch all their fingers backwards at the same time.
Cause of a Knuckle Crack or Pop
A joint is a region where the end of one bone lies close to the start of another one. The bones are held together by fibrous ligaments, which are omitted in the above diagram. In a synovial joint, such as the ones that occur in the knuckles, the space between the bones is filled with a liquid known as synovial fluid. This fluid acts as a lubricant during joint movement.
When a joint is stretched, the space between the bones increases and the pressure in the synovial fluid decreases. The reduced pressure causes tiny bubbles of gas to develop in the fluid. These bubbles fuse to form larger ones. As new fluid is released into the space from the joint lining, the bubbles burst, producing the popping sound.
There is a common belief that frequent knuckle cracking will cause arthritis, but researchers say that this isn't true. They say that the activity won't damage the inside of the joint and is mostly harmless. However, there is a slight chance that frequent knuckle cracking may damage the ligaments that hold the bones together or the tendons that attach muscles to the joint.
A Knuckle Cracking Poll
Do you crack your knuckles deliberately?
Demonstration of Ear Wiggling
Ear Wiggling in Humans
In other mammals, such as cats and dogs, ear wiggling is used to point the ears in the direction of a sound and enhance hearing. Each ear is capable of moving in a different direction from the other one.
Only about 10% to 20% of humans can wiggle their ears, and even then the movement isn't as impressive as that of other mammals. The fact that some of us can wiggle our ears and some of us can't is due to genetic differences.
Ear wiggling is said to be a vestigial feature—one that was beneficial for our ancestors but is no longer necessary for us. Vision is a more important sense than hearing for humans. Being able to wiggle the ears does have one advantage, however. It has great entertainment value.
A Young Kitten Wiggles Its Ears
How Do Our Ears Move?
The ear is made of several sections and is mostly located inside a bone of the skull. The external ear flap that we can see is called the pinna or the auricle. The three auricular muscles around the pinna are responsible for ear wiggling. The functions of these muscles are as follows.
- Anterior auricular muscle (in front of the pinna) - moves the pinna forward and upward
- Superior auricular muscle (above the pinna) - moves the pinna upwards
- Posterior auricular muscle (behind the pinna) - moves the pinna backwards
We all have these muscles in our body as well as nerves connected to the muscles. Only some of use can voluntarily make the muscles work, however.
An Ear Wiggling Poll
Can you wiggle your ears?
The Value of Understanding Weird Human Biology
Understanding how brain freezes occur may help us to understand migraines and other headache disorders better. Understanding how knuckles crack may improve our understanding of the activity inside joints. At the moment, understanding ear wiggling doesn't seem to have any practical importance. This may not always be the case, however. Maybe in the future someone studying the genetic differences between wigglers and non-wigglers will learn something new about the way in which genes or muscles operate. All knowledge about the human body is valuable.
© 2014 Linda Crampton