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  • Brain Diagram

    What is the Human Brain Stem?

Ultimate Guide to Understanding The Delicate Human Brainstem
Human Brainstem Diagram

The human brainstem appears to be like a stalk emanating from your brain. It serves to connect your brain to your spinal cord through nerve tissue stemming up and down your spine and is part of your central nervous system (CNC). Spaces inside allow veins and arteries to supply blood flow to your brain. Your Arachnoid Mater (narrow, webbed layer of connective tissue with no nerves or blood vessels inside.) Beneath the Arachnoid Mater is your Cerebrospinal Fluid. (CSF.) CSF acts to cushion the CNC and also removes foreign bodies, and cleanses your spinal column.

The Peripheral Nervous System (PNS) is made up of spinal nerves branching from your spinal column and cranial nerves branching out from the brain. This is a complex system.

To understand the delicate brainstem, you must first know the basics of the brain. The human brain remains among the most complex of the bodily organ. The brain controls your hunger, thinking, ability to remember things, emotions, sense of touch, motor functions, skills, eyesight, breathing, body temperature, and every signal regulating the human body.

The Spine Sends The Signals

Combined, the brain and spinal column protruding from it compose the central nervous system. (CNS.).

Brain Composition?

The brain is made up of around 60% fat deposits and, on average, weighs 3 pounds for a typical adult male or female. Approximately 40% of your brain material is a composition of water, carbohydrates, salts, and proteins.

Contrary to popular opinion, the brain isn’t a muscle. Instead, it is a gelatinous bundle of blood vessels, nerves, neurons, and glial cells.

Understanding Gray Matter and White Matter?

Gray and white matter compose two distinct areas of the CNS. Gray matter describes the darker outer layer, and white means the lighter-colored layer underneath the gray matter.

T-12 Spinal Section

Just the Opposite Happens With the Spinal Cord

Strangely enough, with the spinal cord, the gray matter rests on the inner layer and the white point on the outside layer of nerve bundles.

If you look at the scientific brain and spinal cord cross-sections, you will see that:

  1. Gray matter contains mainly neuron somas (circular “central cell bodies”)
  2. White matter is composed primarily of axons (lengthy stems linking neurons in a chain) blanketed with a protective coating, myelin.

Reason for Differing Colors?

The reason for the colors is due to the differing composition of neurons. Because of this, tests will cause each section to have varying color shades.

What About The Brain’s Blood Supply?

The brain needs oxygen to function. The blood does this. But the blood needs to pump into the brain to keep it sparking.

Two types of blood vessels carry blood and oxygen to your brain:

  1. Vertebral arteries
  2. Carotid arteries.

Your external carotid arteries reach up your neck, and you can feel these pulsate if you check your pulse with your fingers.

Coma Patient Dummy Example

Your internal carotid arteries reach out and branch with your skull. These vessels operate to carry blood to the frontal lobe area.

    • Vertebral arteries run along the spinal cord into the skull and connect at the brainstem, forming the basilar artery. (supplies blood to the “base” areas of the brain.).

What is The Circle of Willis?

Doctors call this a loop of blood vessels close to the brain’s base, where significant arteries join to circulate blood through the brain, assisting communication of the brain’s arterial systems.

Cranial Nerves

The cranium or skull consists of 12 nerves, called cranial nerves:

      • Cranial nerve 1: An olfactory nerve controlling your sense of smell.
      • Cranial nerve 2: Optic nerve regulating eyesight. (located in the Occipital Lobe.)
      • Cranial nerve 3: Oculomotor nerve governing pupil dilation and other eye movements. (Leads from midbrain brainstem and gathers at the pons.).
      • Cranial nerve 4: Trochlear nerve governing eye muscles emanating from the rear midbrain-brainstem.
      • Cranial nerve 5: Trigeminal nerve remains the most complex and biggest cranial nerve system. It deals with sensory and motor functions stemming from the pons. It conducts senses emanating from the teeth, sinus cavities, cheeks, and mouth to your brain. (Responsible for helping you chew things.)
      • Cranial nerve 6: Abducens nerve innervates some of your eye muscles.
      • Cranial nerve 7: Facial nerves aiding in facial contortions and movement. (Overlaps senses of taste, glandular functions, etc.)
      • Cranial nerve 8: Vestibulocochlear nerve aids in balance and hearing.
      • Cranial nerve 9: Glossopharyngeal nerve also aids with taste. It also innervates ear and throat motion and others.
      • Cranial nerve 10: Vagus nerves govern sensation around your ears and digestive system and control heart, throat, and digestive system motor functions.
      • Cranial nerve 11: The accessory nerve helps specific head, neck, and shoulder muscles.
      • Cranial nerve 12: Hypoglossal nerve carries motor activity to your tongue.


The brainstem or middle brain brings together the cerebrum and attaches it to the spinal cord.

The first two nerves stem from the cerebrum, and the last ten cranial nerves arise at the brainstem, which contains three parts:

      1. Midbrain: Also called the mesencephalon, this structure is highly complex, with a range of varying neuron clusters called nuclei and colliculi, which help facilitate hearing and movement and calculating courses of action and responses to environmental changes. It also houses the substantia nigra. (Believed to be associated with Parkinson’s Disease, and replete with dopamine neurons and portions of the basal ganglia – aids with movement and coordination.
      2. Pons: The starting point of four of your cranial nerves. It helps with tear production, the ability to chew food, blink your eyes, and focus. It also helps with balance, facial expressions, and portions of the hearing. Titled the Latin word for “bridge,” the pons links the midbrain with the medulla.
      3. Medulla Oblongata: Your spinal cord leads from underneath the medulla through a passageway under the skull. Propped up by the vertebrae, it sends and receives neurological signals throughout your body.

The Brain Covering, or Meninges?

There are three layers of brain protection called meninges.

These barriers circle the brain and the spinal cord.

      1. Dura Mater: Thick, tough outer layer. Includes two layers:
        1. Periosteal layer: Lining the inner dome’s surface area inside your skull and along the meningeal layer underneath. Allows passage of veins and arteries to supply blood to the brain.
      2. Arachnoid mater: Weblike layer of connective tissue without nerves or blood vessels.
      3. The Pia mater is a thin membrane that follows the brain’s surface area. Loaded with veins and connected with arteries.

In addition to all this, there are glandular functions that control things. Injuries to any of these areas can affect the rest of the body. Damage due to swelling or similar injury could lead to severe blood issues, including stroke or hemorrhaging. Also, it could cause long-term problems. These include problems with motor control, breathing, or even speaking.

In other cases, such damage can cause severe shifts in personality or even memory loss. Furthermore, brain stem damage can lead to fainting, coma, and in some cases, paralysis. Some brain stem injury victims have been bedridden or in comas for the remainder of their lives. There are also long-term issues caused by such damage leading along the Arachnoid Mater that can lead to sudden death.

      • Trends in Treating Brain Stem Injuries

Modern science has made strides to treat such injuries. But brain stem injuries remain decades away from active treatment. Common causes of such an injury include car and motorcycle accidents. There can also be similar injuries due to high falls and work accidents.

These injuries can be especially severe and more likely for children.

  • Brain stem injuries can arise from contact sports such as football, recreational activities like skateboarding, and even horseback riding.

Brain Lobes And Functions

Each various lobe governs delineated functions.


The most prominent brain lobe sits in the front of the head. (Involved in personality traits, decision-making process, and bodily motor functions.).

Each hemisphere of your brain, or cerebrum, is made up of four distinct sections, or lobes:

      1. Frontal
      2. Parietal lobe: This is part of the middle brain; the parietal lobe helps people recognize things like space and depth perception. The parietal lobe also helps identify pain and body touch.
      3. Occipital lobe. The occipital lobe is the back part of the brain involved with vision and sight.
      4. Temporal lobe. Aids in short-term memorization, speech, musical rhythm, and some smell senses.

The ability to smell typical includes the frontal lobe, known as Broca’s area, which is associated with speech ability.

Deeper Structures Within the Brain Pituitary Gland

Sometimes called the “master gland,” the pituitary gland is a pea-sized structure found deep in the brain behind the bridge of the nose. The pituitary gland governs the function of other glands in the body, regulating the flow of hormones from the thyroid, adrenals, ovaries, and testicles.

It takes chemical signals from the hypothalamus into its stalk and blood flow.

      • Hypothalamus: Sets atop the pituitary gland. Emits chemical messages for function control. It also helps regulate body temperature and sleep patterns, control hunger, and thirst, and plays a role in memory and emotion.
      • Amygdala: Small, almond-shaped structure, an amygdala is located under each half (hemisphere) of the brain. Included in the limbic system, the amygdalae regulate emotion and memory. They are associated with the brain’s reward system, stress, and the “fight or flight” response when someone perceives a threat.
      • Hippocampus: shaped like a seahorse and rests beneath each temporal lobe. It consists of a more extensive area called the hippocampal formation. Aids in memory, ability to learn, navigate and perceive space. (It might have something to do with Alzheimer’s disease.)
      • Pineal Gland: Pineal Gland reacts to darkness and light, secreting melatonin – a chemical regulating circadian rhythms and sleep cycles.

All Brain Injuries Carry Risk

No matter what the cause, the effects on the brain are almost always severe. Most people suffering from brain stem injuries have extended therapy and hospital care periods. Such specialized care remains expensive, and care costs can bankrupt an entire family.

Such injuries can also lead to unexpected deaths and add a physical burden to the household. Those who suffer from these accidents can lose their jobs, and their family cannot make up for their income.

Speak To A Real, Serious Injury Lawyer Today!

Ehline Law’s offices up and down the state stand ready to hear from you. Our exceptional lawyers accept calls and emails 24/7 and are available for a free, no-pressure consultation to discuss your options.

Our helpful staff is happy to visit anywhere in California to discuss the case. We work on contingency, which means we don’t ask for a penny unless we recover for you. Contact our exceptional Los Angeles personal injury lawyers to learn more information at (213) 596-9642.

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Michael Ehline

Michael Ehline is an inactive U.S. Marine and world-famous legal historian. Michael helped draft the Cruise Ship Safety Act and has won some of U.S. history’s largest motorcycle accident settlements. Together with his legal team, Michael and the Ehline Law Firm collect damages on behalf of clients. We pride ourselves on being available to answer your most pressing and difficult questions 24/7. We are proud sponsors of the Paul Ehline Memorial Motorcycle Ride and a Service Disabled Veteran Operated Business. (SDVOB.) We are ready to fight.