Brainstem: Structure, Parts & Functions

The brainstem is an important part of the brain that connects the cerebrum and diencephalon with the spinal cord. It is the stalklike portion of your brain that forms a complex organ of the human body.

• The brainstem controls various cognitive & physiological functions.
• It is 2.6 per cent of the total weight of the brain.
• The distal part of the brain consists of the Midbrain, Hindbrain, Pons, & Medulla.
• It is part of the central nervous system.
• The brain is also known as the central processing organ or control centre of the body.
• It is comprised of more than 100 billion nerves that impart in trillions of associations called neural connections.
• Some of the essential functions performed by the brainstem are breathing, sleeping, regulating heart rate, etc.

Key Terms: Brainstem, Brain, Spinal cord, Midbrain, Hindbrain, Pons, Medulla, Tegmentum, Tectum, Frontal, Temporal Lobes, Cerebellum, Forebrain, Bones, Cranial Bones, Cortex, Respiration

Brainstem Structure

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The human brain lies inside a small bony pocket known as a skull. Our skull is part of the axial skeleton and can be classified into two groups in which the first group consists of the facial bones, and the second group consists of cranial bones. 

• The brainstem is a soft and delicate structure that looks like a walnut.
• The stem consists of a wrinkled surface.
• It is situated at the bottom of your brain, at the back of your skull. 
• Facial bones are 14 in number and are usually meant to support facial tissues.
• On the other hand, cranial bones are 8 in number, and they form the protective covering for the brain. 
• All of these bones are formed by the intramembrane ossification and joined by sutures. 

There are several ways in which brain and brainstem can be classified. One such way is dividing the brain into three divisions, i.e., Forebrain, Midbrain & Hindbrain. 

• The forebrain is the brain's largest division, constituting 2/3rd of the entire brain. 
• It has a cerebrum, which is further divided into lobes such as frontal, parietal, temporal & occipital lobes. 
• The cortex is the surface of the cerebrum, which has grey and white folding appearances on it.
• It is referred to as grey and white matter. 

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Parts of Brainstem

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Some important parts of brainstem are as follows:

Midbrain 

The midbrain is also known as the mesencephalon. It is a comparatively smaller central part of the brain that bridges the other two parts of the forebrain and the hindbrain. 

• The primary function of the midbrain is to look for motor functions of audio-visual systems. 

Let us now discuss some of the important components of the midbrain:

Tectum

The tectum is the dorsal segment of the midbrain and consists of four swelled bulges collectively known as corpora quadrigemina. The lobes positioned on the upper side and the lower side are known as superior & inferior colliculi, respectively. 

• The superior colliculi are involved in visual processing or visual reflexes.
• It helps coordinate and control head and eye movements to establish a fixed focus. 
• On the other hand, inferior colliculi are involved in auditory reflexes.
• It involves coordinating the head and eye movement so that the ear can detect the sound from its surroundings.

Tegmentum

Tegmentum consists of fibrous tracts, which are involved in movements of sleep, arousal, attention, etc.

Substantia Nigra

Substantia nigra portion of the brain controls voluntary movements and moods. It produces the neurotransmitter dopamine.

Hindbrain 

Hindbrain is also known as Rhombencephalon. It is the posterior part of the brain, and it includes the parts of the pons, cerebellum, and medulla oblongata.

The detailed functions of each part of the hindbrain are as follows:

Pons

Pons is a horseshoe mass of nerve fibres comprised of a pneumatic centre. It helps regulate the respiratory cycle. Pons also serves as a neural connection between the cerebral cortex and cerebellum. 

• Some other functions of the pons are regulating sleep-wake cycles and sensations of taste and hearing.

Medulla Oblongata

The Medulla Oblongata is the small posterior essential part of the brain that connects the brain to the spinal cord. It has several centres in it which help in digestion, breathing, and cardiovascular activities.

• One of the centres is the rhythmic respiratory centre, which delays the inspiration phase to match the body's demand.

Cerebellum

The cerebellum is the second largest part of the brain and accounts for nearly 10% of the brain mass and more than 50% of the total neurons formed by the brain. 

• The primary function of the cerebellum is to maintain the balance of the body.
• It helps in various activities like swimming, running, and walking.

Brainstem 

Functions of Brainstem

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Some important functions of the brainstem are as follows:

• It helps in sensing pain and accessing body temperature.
• The stem helps in breathing, digestion and maintaining your heart rate. 

The brainstem plays an important role in conduction, which involves relaying information from the body to the cerebrum and cerebellum and vice versa.

• It helps in controlling the cardiovascular and respiratory systems.
• Other functions include alertness, awareness, and consciousness.
• It supplies cranial nerves to the face, head, and viscera. 
• The brainstem also helps in controlling blood pressure.

Disorders that affect the Brainstem

The disorders that affect the brainstem are as follows:

• Brain Tumors
• Blood Clots
• Heart Attack
• Stroke
• Encephalitis
• Sudden Cardiac Attack
• Traumatic Brain Injury

Things to Remember

• The brainstem is the posterior, stalk-like portion of the brain that contains nuclei of all the cranial nerves.
• It helps control breathing and blood pressure and regulates the heartbeat. 
• The midbrain, pons and medulla oblongata are three parts of the brain.
• The pneumatic centre is present in the pons, and the rhythmic respiration centre is present in the medulla oblongata.
• The brainstem helps regulate the central nervous system.

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