Why Do We Yawn Essay, Research Paper
Why Do We Yawn?
The definition of yawning is to open the mouth involuntarily with a prolonged, deep inhalation of air. Yawning is a normal response to fatigue and drowsiness, but excessive yawning can be caused by a vasovagal reaction and may indicate a heart problem. Normal yawning may be induced to cleanse the brain.
At the deepest part of the breath when the lungs have the greatest force, the lungs fill up the ribcage, then lift the ribs.The ribs lift the spine and the force is transferred from the top of the spine to a bone of the skull called the occipital bone. The occipital bone forms most of the seat for the brain, and it is pushed upward.
At the same moment the fully expanded lungs push away from the ribs and the bronchi are forced apart or away from each other.The bronchi are attached to the bronchi tubes causing them to pull down on the trachea.
The trachea pulls down on the thyroid. The thyroid is attached to the hyoid bone by the thyrohyoid membrane, which pulls evenly on the hyoid bone. The hyoid bone, which is being pulled downward, is attached to the skull by ligaments and muscle at two points called the styloid process of the temporal bones.
The two temporal bones are on each side of the occipital bone. The styloid processes are the two thorn-like protrusions where the muscles and ligaments attach from the hyoid bone to the temporal bones. While the temporal bones are being pulled downward on each side of the occipital bone, the occipital bone is being pushed up between them.
This action puts pressure on the brain.
The jaw, the tongue, and the hyoid bone together with many muscles work to pull down on the temporal bones during deep inspiration with the jaw opened wide. There are many muscles involved in this including the sternohyoid, the omohyoid, the sternothyroid, the thyrohyoid, the stylohyoid, the digastric, the mylohyoid, and the geniohyoid.
The occipital bone and the spine are like a piston pushing up between the temporal bones that are being pulled downward. The pressure that is put on the brain within the skull has the affect of accelerating the normal cerebrospinal fluid absorption process.
Cerebrospinal fluid is created by the choroid plexus found in the ventricles of the brain. Cerebrospinal fluid or CSF is a clear liquid that is believed to protect the brain from shock and to nourish the brain and remove brain waste products. CSF flows from the ventricles and surrounds the brain and spinal cord. CSF is known to be absorbed by the arachnoid villi / venous sinuses method. We produce about a pint of cerebrospinal fluid per day but we only have the capacity to hold about one fourth of that, so our cerebrospinal fluid is replaced several times per day during normal circulation.
The flow of the CSF has much to do with the intercranial pressure, which is different from the blood pressure of the body. When yawning puts pressure on the brain, the CSF is forced through its absorption pathways at an accelerated rate taking brain waste products with it.
Yawning cleans the brain.