Medulla oblongata
The medulla oblongata, often referred to simply as the medulla, is a critical structure located at the base of the brainstem, connecting the brain to the spinal cord. This bulb-like region plays a vital role in regulating involuntary functions essential for survival, including heart rate, breathing, blood pressure, and digestive processes. The medulla facilitates communication between the body and the brain through eight cranial nerves and is organized into distinct parts such as the pyramids and olivary bodies, which are involved in motor control and balance, respectively.
In addition to managing life-sustaining processes, the medulla is involved in various automatic body responses, such as swallowing and coughing. Due to its essential functions, any significant damage to the medulla can have severe consequences, potentially leading to respiratory failure or cardiac arrest. Conditions like brain injury, tumors, or strokes that impact the medulla can be life-threatening, underscoring its critical role in maintaining bodily functions. Overall, the medulla oblongata is indispensable for both involuntary activities and the coordination of responses to physical demands, highlighting its importance in human physiology.
Medulla oblongata
The medulla oblongata, also known simply as the medulla, is part of the brain stem found in humans and other animals. Located in the hindbrain, or lower portion of the brain stem, the medulla regulates involuntary functions such as those performed by the circulatory and respiratory systems. The life-sustaining nature of these functions means that damage to the medulla oblongata is often fatal.
Anatomy
The medulla oblongata resembles a bulb at the topmost portion of the spinal cord and is the lowest portion of the brain stem. The brain stem is the portion of the brain that connects the main brain structure and the spinal cord. The medulla controls key bodily functions and transfers neural messages between the body and the brain. Eight cranial nerves—nerves five through twelve, inclusive—are associated with the medulla in whole or in part.
There are several parts to the medulla known as pyramids, decussation of pyramids, and olivary bodies, or olives. Nerves that control some motor functions of the body go through the pyramids; damage to this area by the rapid overextension of the neck is a cause of the condition commonly referred to as whiplash. The decussation of pyramids refers to pairs of nerve bundles that cross over (decussate) to ensure that both halves of the brain have motor function. The decussation defines the end of the medulla and the beginning of the spinal cord. The olives are situated near the top and on each side of the medulla. Made of nerve cells, the olives convey information about the muscles and joints to the brain and may have a role in the ability to maintain equilibrium, or balance.
Function
A number of crucial involuntary body functions—those which occur without any conscious thought and require no coordination from a person—are controlled by the medulla oblongata. These include the pumping of the heart, including the strength and speed of its contractions, as well as the rhythm of breathing. The medulla is responsible for regulating and coordinating these functions to meet the body's needs, speeding them up during exercise, for instance, as well as allowing them to return to normal after exertion. All of this happens without any thought and is therefore considered an automatic or involuntary function of the body.
The medulla can also work in coordination with other parts of the brain when it comes to these functions. For instance, the medulla accepts input from other parts of the body via the nerves in deciding to increase circulation and respiration in response to exercise. The medulla and the pons, another portion of the brain stem, also work together when a person wants to deliberately control breathing, such as when meditating, playing a trumpet, or blowing out a candle.
Regulating blood pressure is another instance where the medulla coordinates input from other areas of the body and adjusts body systems to compensate as needed. For instance, a life or death situation will cause the release of more adrenalin into the bloodstream by the adrenal gland; this tells the medulla to increase respiration and circulation to prepare for fleeing the situation.
The functions of the digestive system are also controlled by the medulla. The presence of food in the mouth alerts the medulla oblongata to signal the digestive system to make saliva and the gastric secretions that are necessary for the body to digest the food.
In addition to these life-sustaining functions, the medulla oblongata also controls a number of other automatic responses of the body, including swallowing, coughing, sneezing, hiccupping, and vomiting.
Diseases and Disorders
The life-sustaining nature of the functions provided by the medulla oblongata means that injuries or illnesses that affect this portion of the brain can have dire consequences. A person who sustains a brain injury or suffers from a tumor or stroke can survive if the medulla is not affected. However, damage to the medulla can cause the heart to stop or prevent the respiratory system from functioning, resulting in the need for life support systems or causing death. The condition known as brain death is the result of irreparable damage to the medulla oblongata.
Less severe injuries can affect the nerves that run through the medulla oblongata. This can cause partial or total paralysis, or result in numbness that limits the effectiveness of the body's ability to control such functions as swallowing or breathing.
A number of drugs as well as extreme heat or cold can also affect the medulla oblongata. When its function is depressed, or severely limited, by the presence of an opiate, for example, or by an extreme drop in body temperature caused by hypothermia, the medulla may be unable to effectively control circulation and respiration, and the body may cease to function.
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