The brain stem or medulla (lat. middle of something) is one of the parts of the brain that connects the cerebrum (i.e. the largest upper part of the brain) with the spinal cord (the long and thin, tube-like structure which serves as a communication path between the brain and the body).
Location and Function of the Brain Stem
This small (it’s only about three inches long!), but mighty part of the human brain is positioned at the back of the skull and the bottom of the brain. Technically speaking, it’s located under the skull (which protects it), above the spinal cord, and at the lower back of the brain.
The brain stem performs the most vital, automatic functions of the human body. Basically, it transfers all the messages and signals from the brain to other parts of the body – via the spinal cord, to be more precise.
Thus, it serves as a sort of ‘communication center’, conducted by the main motor and sensory nerves, the cranial nerves (the nerves that carry the signals to our eyes, nose, throat, ears, and the skin on the scalp) which pass through it.
This part of our brain controls the bodily functions that we are not normally aware of, by sending signals to the involuntary muscles (muscles whose activity is independent). Those are the muscles found around our heart, lungs, neck, legs, as well as the abdomen.
By performing this function, the brain medulla helps our body perform autonomic functions – breathing regulation, swallowing, heartbeat, eye movement, and blood pressure.
Anatomy and Function of the Parts of the Brain Stem
What parts does the brain stem consist of?
The brain stem consists of two parts: the hindbrain and the midbrain. The hindbrain also includes the pons, cerebellum, and medulla oblongata.
The Midbrain and the Hindbrain
The midbrain (or mesencephalon) is located below the cerebellum, right above the pons of the brain stem.
It’s composed of the following elements:
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- Tectum (lat. roof – forming the upper part of the midbrain)
- Tegmentum (lat. covering – forming the lower part of the midbrain)
- Cerebral aqueduct (a channel in the midbrain which is filled with cerebrospinal fluid)
- Cerebral peduncles (parts of the midbrain which link the brain stem to the cerebrum, thus helping the transport of nerve signals to the other parts of our nervous system)
- Nuclei (a network of cells in the brain which aid the transfer of signals from the parts of the brain to the parts of the body)
- Fasciculi (bundles of nerve fibers)
The hindbrain is located at the backmost part of the brain (in the skull) and functions as an extension of the spinal cord. This part of the brain stem consists of:
- Pons
- Cerebellum and
- Medulla oblongata.
The hindbrain conducts and controls the most vital functions of the automated systems of the human body that are of the highest importance for survival. Those are breathing, sleeping, the function of waking up from sleep, as well as all the motor activities.
Together, the hindbrain and the midbrain comprise the brain stem. While the midbrain is responsible for the transmission of sound and sight impulses, and the control of motor movements, the hindbrain regulates the involuntary functions, i.e. the autonomic motor activity of the body: breathing, the sleep cycles (the state of being asleep and the process of waking up), etc.
The Pons
The pons of the hindbrain is the ‘communication center’ between the two hemispheres of the brain. Actually, it’s the ‘bridge’ (lat. pons – bridge) through which the information from the brain passes to the other parts of the body.
This part of the brain stem is located above the medulla oblongata, and below the midbrain. It consists of nerves and nerve tracts, among which are the cranial nerves. Through these nerves, the brain conducts the most important signals, and both motor and sensory messages through all the systems of our body.
Also, by assisting the medulla oblongata, the pons connects the cerebrum to the spinal cord in order to create the ‘bridge’ which helps the signals from the parts of the brain reach and control the voluntary movements that happen when we move our arms and legs, or flex our muscles and the balance of our body.
In this way, the pons controls dizziness, dreaming, digestion, heartbeat, sneezing, hearing, and eye movement. Most importantly, the pons regulates two of the most vital processes in the human body – breathing and deep sleep.
Since sleep is highly important for the proper functioning of the brain and its good health, it’s good to know that the most refreshing sleep is achieved by the assistance of the pons.
Another function of the pons is to link the forebrain to the hindbrain by connecting the cerebrum to the cerebellum of the brain
The Cerebellum
The ‘little brain’, or the cerebellum, helps with the transfer of signals from the other parts of the brain to the motor neurons in order to control and coordinate the movements of our body, i.e. the motor movements, such as balance, movement coordination (walking, arm swaying, body posture, feet flexing, etc). It is positioned between the brain stem and the cerebrum.
Since it receives information from the sensory systems, the cerebellum also plays a significant role in cognition, i.e. learning, speaking, processing emotions, maintaining attention, etc.
If the cerebellum suffers an injury, we won’t be able to control and coordinate our movements, nor maintain balance. This can lead to several medical conditions and disorders:
- Ataxia (inability to maintain balance, as well as involuntary movements of extremities and eyes)
- Vertigo (dizziness)
- Tremor (involuntary trembling of some parts of the body, ex. trembling hands)
- Dystonia (involuntary contraction of muscles)
- Dyslexia (difficulty in reading, speaking, or spelling words)
- Anxiety (feeling of unease, uncertainty, panic)
- Schizophrenia (inability to understand the reality which results in inappropriate feelings and reactions.)
Medulla Oblongata
Located at the lowest part of the brain stem and in front of the cerebellum, the long stem-like continuation of the spinal cord is called medulla oblongata (or simply – medulla). The medulla is a center of the heart, lung, and digestive functions of our body (i.e. vasomotor respiration, and digestion control).
Correspondingly, the medulla oblongata controls and regulates the autonomic activities of these organs, such as breathing, heartbeat, vomiting, coughing, digestion, the sleep cycles (falling asleep and waking up), sneezing, swallowing, and blood pressure.
However, the main function of the medulla oblongata is to control the muscles that aid our breathing by sending them signals from the corresponding brain region, i.e to the ventral respiratory group of neurons (responsible for the rhythm of our breathing). In this way, breathing becomes an automatic action of the lungs produced by a group of neurons in the hindbrain.
If the medulla oblongata suffers an injury, that can lead to several medical conditions and disorders:
- Paralysis
- Loss of the sense of touch
- Vertigo
- Difficulty with swallowing
- Difficulty vomiting
- Loss of sense of pain
- Loss of coordination
- Facial numbness
To Sum Up
The brain stem is one of the tiniest, but also one of the mightiest parts of the human brain. Located at the back of the skull and the bottom of the brain, it controls and conducts the performance of several of the most vital functions of the human body.
It serves as a sort of ‘communication center’, from where it transfers all messages and signals from all parts of the brain to all parts of the body via cranial nerves. In this way, the brain stem controls the automatic bodily functions, such as breathing, swallowing, heart rate, sleep cycles, consciousness, etc.
This super-powerful part of the brain is made by the midbrain and the hindbrain. Furthermore, the hindbrain consists of pons, cerebellum, and medulla oblongata, while the midbrain consists of the tectum, tegmentum, cerebral aqueduct, cerebral peduncles, nuclei, and fasciculi.
If any of the constructing parts of the brain stem suffer an injury, the result is a medical condition that can impair bodily functions to a large extent.
Fun Facts
Did you know?
- Even though it’s small and tiny, the brain stem is actually a very powerful part of our brain. It’s so powerful, that it regulates one of the most vital processes of our body – breathing. But the list of its ‘super-powers’ does not end here. It also includes swallowing, eye-movement, chewing – all of the automatic body processes, in fact.
- The brain stem is the main ‘communicator’ of the brain – all of the brain parts send their information through this part of the brain in order to reach, control, and regulate the parts of our body. In this manner, the brain stem serves as a kind of ‘bridge’ between the head and the body.
- Logically, we cannot survive without the brain stem, since it regulates the most vital and life-sustaining functions of the body.
- Do you know that feeling of having ‘butterflies’ in your stomach upon the sight of your crush, or the feeling before an exam, or knowing that you did something wrong? Well, the brain stem is responsible for that. This part of our brain regulates our heartbeat automatically, too.
- The brain stem is made of a complex net of neurons that help us wake up from sleep.
- In continuation, when a person’s brain stem becomes damaged, that person falls into a condition of prolonged sleepiness, or unconsciousness, called coma.
- Also, if no signals pass from the central nervous system through the brain stem, the person could lose all its ability for physical movement, i.e. could become paralyzed.
- Luckily, the brain stem of the human body is well protected in the skull, which makes those types of injuries or conditions rare. However, in order to protect the brain and the brain stem from mechanical injuries, always wear a helmet or a head-protector when riding a bicycle, skateboard, or driving a scooter.
- Our brain, the brain stem included, grows and develops by exercising, just like any other muscle in the human body. We’re not talking only about physical exercises, but of brain training as well. This includes all cognitive processes – learning languages, logical tasks, arts, memorizing patterns, dance choreographies, etc.
- Even though the brain stem is only 3 inches (or 8 centimeters) in size, it’s vital for our survival.