Human physiology is a complex process that requires checks and balances to operate at peak capacity. The body as a whole must adjust to environmental inputs to maintain balance and to avoid potentially harmful situations.
The master control of the body is the brain. Our environment offers many challenges for any living organism and the ability to adjust in an instant is just one of the many amazing features the brain offers.
The brain controls a variety of involuntary processes like maintaining a constant heartbeat, with the option to change rate in response to resting or being active. The brain can provide precise instructions to the many voluntary processes of the body, such as movement, by coordinating learned efficiency with stimulation of the skeletal muscle.
The brain also has an amazing capacity to process and store information, which it can use for survival or to create beautiful thought and art. The full scope of the brain’s functions provides a complex picture that is still being explored today.
8 Fun Brain Facts
- The brain weighs approximately 3 pounds and is the largest when compared to body size in vertebrates. [1]
- Most the brain (85 percent) is made up of the cerebrum, which is the primary processing portion for environmental inputs. [1]
- There are approximately 86 billion neurons (nerve cells) in the brain. [1]
- The brain is made up of about 75 percent water. [2]
- Anywhere from 20 to 50 percent of your blood supply is pumped through your brain every heartbeat, depending on brain activity. [2]
- The brain can process up to 70,000 thoughts a day. [2]
- There are 150,000 miles of blood vessels in the brain, enough to circle the earth at the equator just over six times. [3]
- It has been estimated that 50 percent of the human genome (our individual genetics) is dedicated to the brain. [3]
Brain Anatomy
The brain is in the skull, which creates a boney protective casing that prevents direct trauma to the tissue. The brain is also surrounded by three layers of tissue called the meninges. The outermost layer is called the dura mater (“tough mother”) and made of a durable leathery tissue which contacts the skull.
The middle layer is called the arachnoid mater (“spider-like mother”) because it has a fibrous web-like texture, and the innermost layer is called the pia mater (“tender mother”). The brain and spinal cord make direct contact with the pia mater, which contains many blood vessels which supply the brain with oxygen and nutrients. [4]
The brain is separated into three primary regions which contain various sub-regions. The forebrain contains the cerebrum, thalamus, hypothalamus, and pineal gland. The midbrain is located within the brainstem, and the hindbrain is made up of the rest of the brain stem and the cerebellum. [4]
There are two primary cell types found in the brain, called neurons and neuroglia.
Neurons
The most abundant cell type found in the brain and are arranged into two classes: grey matter and white matter. Information is processed in the grey matter, while the white matter passes information between the various grey matter regions for synchronization. [4]
Neuroglia
These provide support to the neurons. There are four types of neuroglia: astrocytes, oligodendrocytes, microglia, and ependymal cells. [4]
The brain connects to the rest of the body through the spinal cord, which runs down the length of the spine. Nerve groupings connect the brain to all body systems and can start from the brain itself (cranial nerves) or the spinal cord (spinal nerves).
Brain Function
The brain performs many functions, both voluntary and involuntary. It processes any input from the environment and provides a response so that the body can maintain balance.
The neurons perform the primary function of the brain, which is to process the input and dictate the output. The cerebrum, which is made of primarily neurons, is the processing center, and is separated into functional regions which include the cerebral cortex, the basal nuclei, and the limbic system. [4]
Neurons use two methods to pass information to each other. Within the cell, the message is sent electrically; between cells, the message is sent chemically. The chemicals that jump from one neuron to another are called neurotransmitters.
There are a variety of neurotransmitters that signal a variety of functions. Some of the more common varieties include serotonin, dopamine, and norepinephrine (noradrenaline). Neurotransmitters can stimulate movement, sleep, relaxation, increased metabolism, and other important functions. [5]
The neurons of the cerebral cortex fall into the grey matter category. This region of the cerebrum is primarily used to formulate complex thought and to provide analysis of sensory inputs such as vision and auditory (sound) stimuli.
Below the cerebral cortex is a region of white matter that connects the brain. Since the brain is split into two hemispheres, a special region of white matter called the corpus callosum connects both halves.
Buried deep with the white matter regions of the brain are two specialized patches of grey matter called the basal nuclei and limbic system. The basal nuclei play a significant role in fine movement and the limbic system is involved with memory and emotions. [4]
The brainstem is a part of both the midbrain and the hindbrain regions. The midbrain region has a role in both voluntary movement and involuntary movement such as reflex reactions. The hindbrain portion of the brainstem includes both the medulla oblongata and the pons.
The medulla oblongata is mostly white matter but contains a few pockets of grey matter that control heart and lung functions. The pons connects the primary portion of the brain to the cerebellum which forms that final part of the hindbrain.
The cerebellum is the final portion of the movement center within the brain and is made of mostly grey matter. Information from the body is processed by the cerebellum to maintain balance and posture. Other functions of the cerebellum include speech and writing. [4]
The neuroglia cells are less prevalent in the brain when compared to neurons, but their functions are still vital to brain health. Astrocytes help create part of the blood/brain barrier, a filter system which prevents harmful materials from entering the brain.
The other part of the blood/brain barrier are the microglia, which are specialized immune cells like white blood cells. The microglia attack and destroy any potential pathogens that may sneak past the blood/brain barrier.
Oligodendrocytes create a material called myelin which is a “fat-like” wrapping that helps generate faster nerve impulses, and ependymal cells filter blood plasma to produce cerebral spinal fluid, which both nourishes and supports the brain by providing shock absorption. [4]
The final functional regions of the brain are; the thalamus, which sends input to the correct region of the brain for processing; the hypothalamus, which regulates hunger, thirst, body temperature, and hormone release by stimulation of the pituitary gland; and finally the pineal gland, which is involved in the sleep cycle. [4]
Brain Disease
Brain disease can be expressed in a variety of ways. There are brain diseases that can become acute medical emergencies, such as stroke and aneurysm. Other varieties affect behavior, which can ultimately lead to poor health. [6]
Brain disease can be classified into categories based on the type of effects each have on health. Diseases such as dementia, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease) are considered degenerative diseases, which involve loss of functioning neurons.
Brain disorders generally linked to chemical imbalances can lead to severe behavioral issues that affect health negatively. Attention deficit-hyperactivity disorder (ADHD), autism, anxiety, depression, and obsessive-compulsive disorder (OCD) are just a few examples that can have lasting effects on overall health.
There are also diseases such as brain tumors and stroke, which originate from poor overall health practices that begin to affect the brain over time.
Some of the brain diseases listed earlier are apparent in childhood; however, many are associated with the aging process. It has been estimated that the brain decreases in size by about 5 percent each decade after the age of forty, which is thought to contribute to the issue. [7]
Reductions in neurotransmitters such as dopamine have also been linked to the age-related decline in brain health. Parkinson’s disease is the second most common degenerative brain disease in the US and affects over 1 million individuals. The progression of Parkinson’s is linked to loss of dopamine production in the midbrain, which affects movement. [8]
Loss of memory can be benign in some cases and catastrophic in others. Dementia-related diseases which most commonly fall under the category of Alzheimer’s disease can be very severe, especially in aging populations.
The progression of Alzheimer’s begins with the formation of tangled plaques made of deformed proteins. The proteins cause the death of neurons, leading to the memory loss associated with the disease. [9]
Stroke occurs when blood vessels supplying the brain with oxygen are blocked by clot formation due to accumulation of cholesterol. This process is very similar to coronary artery disease—only instead of causing death to heart cells, brain cells die.
Stroke is the fifth-leading cause of death in the US, and in some instances can cause severe brain hemorrhaging (bleeding). [10]
There are also a variety of brain cancers, ranging in severity and outcome. The most common form is also the deadliest. Astrocytoma has several grades, with glioblastoma (GBM) being the worst. The 5-year survival rate is estimated to be 4 percent for GBM. [11]
Brain Health
Brain health can be influenced by multiple factors which include genetics, diet, exercise, and age. Brain disorders such as autism and ADHD are with you from birth, though diet and exercise can play a major role in the progression.
A strong link has been made between gut health and autism. It has been shown that children who suffer from autism have increased permeability in the gut, which can lead to environmental toxin accumulation. [12]
Impaired carbohydrate metabolism has been suggested as well for autism. The link has been mostly anecdotal; however, animal studies have shown fewer symptoms when fed a low-carbohydrate diet. Other dietary factors such as low-casein (milk protein) diets have been shown to be beneficial as well. [13] [12]
Nutrition can greatly improve behavior in ADHD individuals as well; so can regular physical activity. It has been reported that intrusive thoughts are reduced as well as compulsive behavior, which are both hallmarks of ADHD. [14] [15]
Exercise is also positively associated with reductions in anxiety and depression. Anxiety and depression are often linked to reduction in the production of the neurotransmitter serotonin. Exercise has been linked to increased production and release of serotonin. [16] [17]
Foods containing the amino acid tryptophan coupled with exercise have been linked to greater serotonin availability as well. Foods high in protein such as turkey and eggs are suggested to provide sufficient precursors for serotonin production. [18]
The degenerative diseases that affect the brain are associated with poor health habits during childhood and early adulthood. Like the progression of heart disease, a diet high in processed foods can have a lasting effect on blood lipid (fat) levels.
Avoiding processed foods and choosing diets high in whole foods, like fresh fruits and vegetables, can prevent the formation of clots which can lead to stroke.
One final interesting point is the use of brain exercises to maintain cognitive function. The practice is called neuroplasticity and there has been some controversy about its practice. However, studies have shown that not only do brain exercises improve function, but also may increase grey matter over time. [19]
Healthy diet, regular physical activity, and cognitive stimulation can maintain the health of the brain late into adulthood.
