On September 10th, 1945, in Fruita, Colorado the pivotal importance of specific regions of the brain and origins of critical systemic functions were all revealed… by a chicken… named Mike… being decapitated. The headless chicken, however, did not die but instead lived for another 18 months where it eventually died from, no not hypovolemia or brain death but instead of choking on a corn kernel. Mike was able to balance on a perch, clumsily walk, perform grooming behaviors, and crow all without his head. However, without a beak, oropharynx or larynx his crow was more like a gurgling noise. After Mike’s owners saw that he continued to live post-decapitation they were able to sustain him by feeding with a syringe ejecting food into his esophageal opening. Mike gained worldwide attention and began touring the country. On display, it is estimated that he averaged around $4,500 a month in 1945 which translates to approximately $48,300 per month in current time.
How is this possible? Well, when Mike’s head was cut off it was done above the jugular veins and left the brain stem intact. Clots closed of primary blood vessels and prevented Mike from bleeding out.In the absence of higher brain function, central motor generators are able to carry out basic homeostatic functions. This is a living example of how important the brain stem really is for systemic function and allowed Mike to remain relatively healthy. The fact that the brainstem was retained was critically important for his survival. The brainstem consists of the midbrain, pons, and medulla oblongata. The medulla oblongata specifically supports autonomic control of heart rate, breathing, blood pressure, and systemic reflexes.
Respiration is either increased or decreased based on levels of acidity in the blood detected by chemoreceptors in the carotid arteries or aorta. A change in pH in the blood would be afferently communicated back to the medulla oblongata where is would efferently send a signal through the phrenic nerve which increases the contraction rate of the intercostal and diaphragm muscles. This inter increases oxygen levels in the blood while decreasing CO2.
The cardiovascular centre is also located in the medulla oblongata and increases or decreases the stroke volume or amount of blood pumped by the heart based on physiological cues. Again chemoreceptors in the aorta and carotid arteries detected changes in pH and communicate them to the medulla. Changes in blood pressure are also detected by baroreceptors in the aortic and carotid sinuses. The medulla responds to increased pH levels by sending signals to the sinoatrial node through the sympathetic nerve tract in order to increase the strength and repetition of heart contractions. The medulla uses the ever popular vagus nerve to slow the heart and decrease contractility when needed.
Reflexes like coughing, vomiting, sneezing, and swallowing are also carried out by the medulla. Apparently crowing and grooming also might be controlled by the medulla in chickens. Swallowing is a pharyngeal reflex that helped Mikes heads stub with consuming food.
After better understanding how Mike was able to live post-decapitation it leaves the question of whether a human could survey under the same circumstances. I performed a preliminary investigation in the hopes of finding nothing and fearful of uncovering a morbid and disturbing headless monstrosity. However, instead I found that there is a rare developmental condition called hydranencephaly where the cerebral hemispheres are not developed. The condition can vary in its severity but one child was born with only a brain stem and was able to live for 12 years. There are many other examples of individuals living throughout the world in absence of very large brain structures that were either never developed or removed sometime in their life.
If you wish to know more about Mike the famous headless chicken then you are welcome to view his history channel documentary or visit his webpage (Links are posted below). You can also participate in the headless chicken 5k marathon or hopefully see me at the 20th annual headless chicken festival celebrated in Fruita, Colorado June 1st and 2nd.
References
Crew, B. (2014, September 26). Meet Miracle Mike, the Colorado Chicken who lived for 18 months without his head. Retrieved from https://blogs.scientificamerican.com/running-ponies/meet-miracle-mike-the-chicken-who-lived-for-18-months-without-his-head/
Herkewitz, W. (2017, November 14). How Much of the Brain Do We Really Need? Retrieved from http://www.popularmechanics.com/science/health/a13017/how-much-of-the-brain-can-a-person-do-without-17223085/
Hydranencephaly Information Page. (n.d.). Retrieved from https://www.ninds.nih.gov/Disorders/All-Disorders/Hydranencephaly-Information-Page
The chicken that lived for 18 months without a head. (2015, September 10). Retrieved from http://www.bbc.com/news/magazine-34198390
G. (2008, September 12). Mike the headless chicken. Retrieved from https://www.youtube.com/watch?v=LqDjRCHyjTY
Hello Steve,
ReplyDeleteThank you for this informative and humorous blog post. Your post made me curious about the criteria that must be met to declare a person brain dead. I found a medical report about a patient that showed isolated medulla oblongata function after a severe traumatic brain injury that left him otherwise brain dead. The criteria include testing for signs of a respiratory drive after maximal stimulation of the respiratory centers while using hypercarbia aponeic oxygenation techniques. Basically, this means that someone can be declared brain dead after someone is found to have an irreversible loss of all functions of the brain, including the brainstem. The three essential findings in brain death are coma, absence of brainstem reflexes, and apnoea. Finally, a patient determined to be brain dead is legally and clinically dead.
References:
Wijdicks EFM, Atkinson JLD, Okazaki H. (2001). Isolated medulla oblongata function after severe traumatic brain injury. Journal of Neurology, Neurosurgery & Psychiatry.70:127-129.