Understanding the Human Brain and Nervous System

The human brain is one of the most complex and amazing structures in nature. The most powerful natural computer we know of, the brain not only enables the motor control we use to move around, but it also permits us to calculate numbers and employ critical thinking. When combined with the spinal cord, the brain helps make up the central nervous system. While most animals have a central nervous system, the human version is uniquely complex. We sometimes divide up the brain by logical functions and talk about a cognitive brain (all of the higher-order functions) and an emotional brain (instinctive, involuntary functions). Normally, our cognitive brain runs the show and controls our actions. When the emotional brain overwhelms cognition, we may experience states such as fear or anxiety.

The Brain

The human brain consists of three distinct parts: the cerebrum, the cerebellum, and the brain stem. Each part bears responsibility for a portion of the human experience. The cerebrum is the largest part of the brain and handles what we think of as higher-order thinking. That means that the cerebrum processes the data gained from our senses, handles communication (including language), and is responsible for our ability to learn and retain information. The cerebellum is directly responsible for motor control. It functions as a kind of interface between the cerebrum's decision to make a movement and the actual muscle systems that move us. Finally, the brain stem connects the cerebrum to the spinal cord. While it is the smallest part of the brain, the stem actually bears responsibility for some of the brain's most crucial functions. The heart rate and respiratory rate are directly influenced by signals from the brain stem, and it also relays critical information from a variety of body systems. Everything from fine motor function to our senses of pain, vibration, and temperature rely on the brain stem.

The Spinal Cord

The human brain's impressive computing power is useless without a way to communicate with the rest of the body. The spinal cord functions as the brain's information superhighway, conveying electrical impulses at high speeds. Stretching from the brain down through most of the spine, this column of fibers sends signals from the brain to the body's other nerve centers. The brain and spinal cord are supported in accomplishing this feat by a protective material called cerebrospinal fluid. Cerebrospinal fluid insulates the brain from infection and physical trauma, such as impact or vibration. Similar in makeup to blood plasma, it also provides natural buoyancy and aids in maintaining proper chemical balance. Not all cells in the central nervous system are signal-carrying neurons. The brain and spinal cord also rely on glia, non-neuron cells that keep the system healthy. Glial cells supply nutrients and oxygen, and they form an insulating material called myelin.

Fun Brain Facts

  • Brain signals travel at different speeds. Impulses that help us react quickly to danger are prioritized over more mundane signals. For instance, when telling your legs to run, the message travels at about 250 miles per hour. That allows our bodies to adjust quickly when running. Our sense of touch, however, might send out signals at less than 30 miles per hour.
  • The average adult human body is made up of about 50-65% water, but that percentage is even higher in the brain. The human brain consists of about 75% water, meaning that dehydration can have a significant negative effect on brain function.
  • The blood vessels in the brain are thought to stretch almost 100,000 miles if you laid them end to end.
  • It's thought that cerebrospinal fluid also acts as a waste disposal system for the brain. During sleep, the fluid flows over the brain, sweeping away unwanted proteins and other waste material.


Anxiety: A condition of apprehension or distress

Brain Stem: The smallest part of the brain, responsible for involuntary control of crucial functions

Cerebrum: The largest part of the brain, where most higher forms of thinking are centered

Cerebellum: Responsible primarily for motor control but also involved in learning and retention of knowledge

Glia: Non-neuron cells in the brain that do not carry electrical impulses but are instead crucial for chemical balance and neuron support

Myelin: A fatty support tissue that surrounds and protects nerve fibers

Neuron: A cell that transmits data in the nervous system

Motor neuron: A specialized neuron having to do with muscular movement

Sensory neuron: A specialized neuron that conveys information from senses to the nervous system.

Spinal cord: The primary means of conducting electrical signals from the brain to other body systems