The brain controls all your mental functions and physical functions using electrical or chemical signals, whether you’re aware of it or not. It is a powerful supercomputer that science is still learning about, and will literally astound you when you look more closely at its capabilities.
While scientists are making strides in understanding how different parts of the brain fire to control certain functions, there’s still a lot about our minds that are a mystery. The brain stem is the oldest and smallest region in the evolving human brain. It evolved hundreds of millions of years ago and is more like the entire brain of present-day reptiles. For this reason, it is often called the ‘reptilian brain’. Various clumps of cells in the brain stem determine the brain’s general level of alertness and regulate the vegetative processes of the body such as breathing and heartbeat.
It’s similar to the brain possessed by the hardy reptiles that preceded mammals, roughly 200 million years ago. It’s ‘preverbal’, but controls life functions such as autonomic brain, breathing, heart rate and the fight or flight mechanism. Lacking language, its impulses are instinctual and ritualistic. It’s concerned with fundamental needs such as survival, physical maintenance, hoarding, dominance, preening and mating. It is also found in lower life forms such as lizards, crocodiles and birds. It is at the base of your skull emerging from your spinal column.
The basic ruling emotions of love, hate, fear, lust, and contentment originate from this first stage of the brain. Over millions of years of evolution, layers of more sophisticated reasoning have been added upon this foundation. Our intellectual capacity for complex rational thought which has made us theoretically smarter than the rest of the animal kingdom.
The human brain has the same basic structure as other mammal brains. It weighs about 3.3 lbs. (1.5 kilograms) and contains about 86 billion nerve cells (neurons) — the “gray matter”. These neurons are connected by trillions of connections, or synapses.
A synapse is basically brain neurons (nerve cells) communicating with one another via electrical or chemical signals. Human-Memory.net has some staggering figures relating to this topic. The source notes the average human brain contains about 100 billion neurons that can be connected to up to 10,000 other neurons (other sources present varying numbers of neurons, but the numbers are still irrational).
When you do the math based, there are as many as 1,000 trillion synaptic connections, “equivalent by some estimates to a computer with a 1 trillion bit per second processor,” explains the site. For some context, modern home computers can perform at 4 GHz or higher, which is 4,000 million cycles per second. A trillion is a million times a million.
Anatomy of the human brain
The largest part of the human brain is the cerebrum, which is divided into two hemispheres. Underneath lies the brainstem, and behind that sits the cerebellum. The outermost layer of the cerebrum is the cerebral cortex, which consists of four lobes: the frontal lobe, the parietal lobe, the temporal lobe and the occipital lobe.
Like all vertebrate brains, the human brain develops from three sections known as the forebrain, midbrain and hindbrain. Each of these contains fluid-filled cavities called ventricles. The forebrain develops into the cerebrum and underlying structures; the midbrain becomes part of the brainstem; and the hindbrain gives rise to regions of the brainstem and the cerebellum.
The cerebral cortex is greatly enlarged in human brains, and is considered the seat of complex thought. Visual processing takes place in the occipital lobe, near the back of the skull. The temporal lobe processes sound and language, and includes the hippocampus and amygdala, which play roles in memory and emotion, respectively. The parietal lobe integrates input from different senses and is important for spatial orientation and navigation.
The brainstem connects to the spinal cord and consists of the medulla oblongata, pons and midbrain. The primary functions of the brainstem include: relaying information between the brain and the body; supplying some of the cranial nerves to the face and head; and performing critical functions in controlling the heart, breathing and consciousness.
Between the cerebrum and brainstem lie the thalamus and hypothalamus. The thalamus relays sensory and motor signals to the cortex and is involved in regulating consciousness, sleep and alertness. The hypothalamus connects the nervous system to the endocrine system — where hormones are produced — via the pituitary gland. The cerebellum lies beneath the cerebrum and has important functions in motor control. It plays a role in coordination and balance, and may also have some cognitive functions.
Left brain vs. right brain
The human brain is divided into two hemispheres, the left and right, connected by a bundle of nerve fibers called the corpus callosum. The hemispheres are strongly, though not entirely, symmetrical. The left-brain controls all the muscles on the right-hand side of the body; and the right brain controls the left side. One hemisphere may be slightly dominant, as with left- or right-handedness.
The popular notions about “left brain” and “right brain” qualities are generalizations that are not well supported by evidence. Still, there are some important differences between these areas. The left brain contains regions involved in speech and language (Broca’s area and Wernicke’s area), and is also associated with mathematical calculation and fact retrieval. The right brain plays a role in visual and auditory processing, spatial skills and artistic ability — though these functions involve both hemispheres. Everyone uses both halves all the time.
New Vessel System in the Human Brain
The human brain is a complicated organ that’s difficult to understand, so it’s only natural that we always have more to learn. But recently, researchers at the U.S. National Institute of Neurological Disorders and Stroke published images of a previously undocumented system of vessels that are part of the lymphatic system in the brain. That’s right, up until this very moment many weren’t even positive that these vessels, which transport fluids critical to metabolic and inflammatory processing, existed at all.
Up until the present, not only were these deep-purple vessels largely unheard of, most doctors have been taught that the skull contains no lymphatic vessels. This previous notion however existed in complete contradiction with how the rest of the body works. The lymphatic system both collects and drains fluids, removing waste, facilitating infection response and inflammation, and so much more. In-the-know about the necessity of the lymphatic system of the human brain, it feels like an absurdity in retrospect to think that somehow our brains would not work with the lymphatic system.
About this finding, Senior Investigator Daniel Reich stated that “The discovery of the central-nervous-system lymphatic system may call for a reassessment of basic assumptions in neuroimmunology.” In other words, while this is a major discovery, it could lead to other, greater discoveries in the exploration of our own biology.
In 2015, researchers discovered the “glymphatic system,” or fluids that were found in the brains of both humans and mice that could transport things like glucose and lipids. But at the time, they didn’t know how these fluids might connect and communicate with the rest of the body. This most recent discovery bridges that knowledge gap.
Because these vessels were so unknown, the initial reaction to this discovery varied, from, in Reich’s words, “No way, it’s not true,” to “Yeah, we’ve known that.”
But this discovery doesn’t just identify this system of vessels, it explores how it operates and just how complex and intricate it is. “The study shows that these vessels exist. We haven’t shown that they’re involved in any disease process,” Reich carefully worded, “but it’s reasonable to think that they might be.”
As we explore the far reaches of the Universe and stretch our knowledge far beyond our modest, planet-bound selves, it’s surprising to learn that we still have so much to learn about our own bodies. With this discovery, it is possible that there “is a connection between [the] two systems, glymphatic and lymphatic,” according to Reich. When a discovery this major is made, it creates a well of new questions about the human condition that no one ever suspected await our attention.
References: The Atlantic, ELifesciences.org