You tend to pull your hand back in a swift motion when you touch some hot object -- by far one of the simplest examples of spinal reflex.
When heat sensation is felt at the site -- the hand in this case -- a signal is sent to the spinal cord via sensory pathway. In response, the spinal cord sends a return signal via motor pathway, and prompts you to move your hand away from the hot object.
It might seem a long-drawn-out process with signal traveling from hand to spinal cord and back, but it takes no more than a fraction of a second.
In human anatomy, the nervous system is basically a network of specialized cells, which coordinate the actions of an individual by sending signals from one part of the body to another. This transfer of signals takes place in form of electrochemical waves, or by means of chemical release.
The nervous system is divided into two parts -- the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), made up of sensory neurons and the nerves that connect them to each other.
Central Nervous System
Central nervous system is made up of two vital organs - the brain and spinal cord.
The brain weighs approximately 3 lbs and measures around 6.5 inches, while the spinal cord measures around 18-19 inches.
When we talk about the functions of central nervous system, we basically refer to the functions of brain and spinal cord working as a unit to coordinate the activities between different parts of the body. Working in collaboration with the peripheral nervous system, the central nervous system plays a fundamental role in controlling our behavior.
Central Nervous System Functions
The central nervous system is basically the processing unit of our nervous system, where all the information from the peripheral nervous system is collected and processed. Together, the brain and spinal cord control various physiological and psychological functions of our body, including movement, sensation, thinking, memory, and speech.
The human brain is divided into three parts: the forebrain, midbrain, and the hindbrain (cerebellum, pons, and medulla oblongata.)
Basically, our brain is divided into three parts: the forebrain (prosencephalon), midbrain (mesencephalon), and the hindbrain (rhombencephalon). It is connected to the spinal cord at the brainstem, i.e., the medulla oblongata to be precise.
The spinal cord, and the central nervous system neurons located within it, are primarily assigned the task of transmitting messages back and forth between the brain and peripheral nerves. At times though, the spinal cord can initiate some actions on its own -- without involving the brain.
The forebrain is the frontal portion of the human brain, and also happens to be its largest part. Most of it is made up of cerebrum, which works in coordination with the cerebellum to control all the voluntary actions of our body.
The cerebrum is covered by a sheet of neural tissue known as the cerebral cortex; often referred to as the gray matter. It accounts for almost two-thirds of the total brain mass, and handles most of the information processing attributed to the brain.
Cerebral cortex is divided into cerebral hemispheres by a longitudinal fissure. The two hemispheres, often referred to as the right brain and left brain, are connected by a bundle of neural fibers known as corpus callosum. Each of these hemispheres are designated certain functions.
Right brain functions include visual and spatial skills, memory storage in auditory and visual modalities, imagery, etc. Left brain functions, on the other hand, include sequential analysis, memory storage in particular order, logical interpretations, and so on.
Lobes of Cerebral Cortex
The cerebral cortex is divided into several regions called 'lobes', each of which is assigned specific tasks.
The frontal lobe deals with planning and execution of our actions, and assesses their consequences. Similarly, the parietal lobe helps us with perception of stimuli and spatial information processing, occipital lobe deals with visual processing, and temporal lobe is associated with memories, language, speech, visual recognition, auditory processing, etc.
There exist several other components of the brain which are responsible for our behavior and perceptions. The hypothalamus, for instance, links our nervous system to endocrine system, which controls the metabolic activity of our body. It also controls our body temperature, emotions, and even thirst and hunger.
Then there are other parts, like the hippocampus, which consolidates long-term and short-term memory, and thalamus, which receives and processes sensory information and movement-related information.
Of the three major parts of the brain, the midbrain, which happens to be the smallest, is entitled the task of relaying auditory and visual information. And lastly, there is the hindbrain, made up of cerebellum, pons, and medulla oblongata, which is in charge of some of the most important functions of our body, including respiration and heartbeat.
The cerebellum or little brain controls the coordination of our movement. Pons and medulla oblongata are the parts of the brainstem, which connect the brain to spinal cord to complete the central nervous system.
The spinal cord, and the central nervous system neurons located within, are primarily assigned the task of transmitting messages back and forth between the brain and peripheral nerves. At the same time, it is also equipped with neural circuits that help it control certain reflexes and central pattern generators (CPGs).
Even though the brain and spinal cord usually work together to control various functions of the body, reflex movements can occur through spinal cord pathways, without the brain getting involved. In case of spinal reflex, the spinal cord acts as the central area -- bypassing the brain -- where the information is processed and necessary steps are initiated.
Any damage caused to head or spine can lead to adverse effects on the individual's body, and hamper various nervous system functions. Even though the brain is protected by skull, and the spinal cord by spinal column or vertebrae, they are still vulnerable to injuries.
In fact, the spinal cord can be damaged or punctured by the vertebrae itself. Injury to the central nervous system can even result in partial or complete paralysis. The central nervous system has an important role to play in various functions of our body, and even the slightest damage caused to it can affect us to a great extent.