The brain is a main organ of the body. The brain controls memory, vision, hearing and body movement. The brain has three main regions called the hindbrain, midbrain and forebrain. Vital body functions are controlled by the hindbrain, whereas nonvital functions are controlled by the forebrain. A "brain dead" patient has damage to a nonvital region of the brain.
Hindbrain
The hindbrain is positioned atop the spinal cord and in back of the midbrain. Key structures include the cerebellum, brain stem and upper region of the spinal cord, according to the National Institutes of Health. The brain stem is composed of sensory and motor innervation called cranial nerves. The hindbrain is responsible for human life's most basic functions, such as heart rate and breathing.
Midbrain
The midbrain or mesencephalon is positioned between between the hindbrain and forebrain. The main structures include the tectum and cerebral peduncle. The tectum contains superior and inferior colliculi. The superior colliculus processes visual information and the inferior colliculus processes auditory information. The cerebral peduncle region includes the pretectum, crus cerebri and midbrain tegmentum. The pretectum contains a grouping of neurons that controls the diameter of the eye's pupil. The crus cerebri is the back part of the cerebral peduncle and possesses motor tracts. The midbrain tegmentum extends to the cerebral aqueduct from the substantia nigra.
Forebrain
The forebrain or prosencephalon is the forward-most part of the brain, located in front of the midbrain. The main part of the forebrain is the cerebrum, which is also the largest unit of the entire brain. Other structures include the thalamus and hypothalamus. In addition, the limbic system is apart of the forebrain, and includes the amygdala and hippocampus.
The cerebrum contains two hemispheres, left and right. When people speak of "left brain" or "right brain," they refer to the left or right cerebral hemispheres. The hemispheres are connected by a mass of white matter called the corpus callosum. This region allows communication between the two sides of the brain. The grey matter, or cerebral cortex, is a convoluted structure that stores memories and controls higher cognitive functions.
Neuron Signals
"Action potential" describes events responsible for communication along neurons, the main cellular units of the brain. These cells of the brain do not physically connect, but contain a small space called a synapse. In this synapse, the transmitting neuron sends a signal through the space to the receiving neuron. The receiving neuron may then become the transmitting neuron, sending a signal to another neuron. Neurons, like a chain, align to send signals from one area to another. Without neural signals, we would have no memories, have no sensation and be unable to function.
Relationship to Body
The brain has a distinct relationship to the body. This organ, along with the spinal cord, comprises the central nervous system. The central nervous system communicates with the peripheral nervous system. The peripheral nervous system contains several nerves that receive information from the entire body. Body temperature, body movement and reacting to touching a hot mug are all functions that require peripheral nervous system communication with the central nervous system.
