Brain & Nervous System
Now that computers are so prevalent in our society, the brain can best be thought of as a central computer which controls all of a person's bodily functions. The nervous system is the network that sends messages back and forth from the brain to all the various parts of the body. This is accomplished via the spinal cord, which runs down through the back and contains small, threadlike nerves which branch out to every body part and organ.
When a message comes into the brain from anywhere in the body, the brain quickly tells the body just how it should react. For instance, if a person accidentally touches a hot object, the nerves in the skin shoot a message signaling pain back to the brain. The brain sends a message back to the hand to move away. This neurological relay race takes place instantaneously.
The brain is also very compact, weighing in at just 3 pounds. The many folds and grooves of the brain provide it with the surface area required for storing all of the body's information. The spinal cord, however, is a long bundle of nerve tissues stretching about 18 inches. It is about 3/4 inch thick and extends from the lower part of the brain all the way down through the spine. The various nerves which branch out to the entire body are called the peripheral nervous system.
The brain and the spinal cord are both protected by bone. The brain gets its protection from the bones of the skull, and the spinal cord is protected by a set of ring-shaped bones which are known as vertebrae. Both are cushioned by layers of membranes called meninges as well as a fluid called cerebrospinal fluid. This fluid aids in protecting the nerve tissues, keeping it healthy, and in removing waste products.
The human brain performs an amazing number of tasks, including:
- Controlling body temperature, blood pressure, heart rate and breathing.
- Handling physical movements when standing, sitting, walking and talking.
- Accepting an incredible amount of information from the various senses (seeing, smelling, tasting, touching and hearing).
- Allowing an individual to think, reason, dream and experience emotions.
All of these functions are controlled, regulated and coordinated by this one organ which is only about the size of a small head of lettuce.
The brain, in combination with the spinal cord and peripheral nerves, makes up a complex but integrated control system called the central nervous system. This system regulates the unconscious and conscious acts of everyday life.
The brain is made up of approximately 100 billion nerve cells which are called neurons. Neurons gather and transmit electrochemical signals, not unlike the gates and wires in a computer.
Although neurons have the same characteristics and makeup as other cells in the body, the electrochemical aspect allows them to transmit signals over long distances (up to a few meters) and to send messages to each other.
Regardless of the animal, brains have the following parts:
- Brain stem - Consisting of the medulla (an enlarged portion of the upper spinal cord), the pons and the midbrain (lower animals have only a medulla). The brain stem controls the reflexes and automatic functions such as the heart rate and blood pressure, limb movements and visceral functions such as digestion and urination.
- Cerebellum - This part of the brain integrates information from the vestibular system that indicates movement and position and utilizes this data to perform limb movements.
- Hypothalamus and pituitary gland - These are responsible for visceral functions such as body temperature and behavioral acts such as drinking, eating, aggression, pleasure and sexual responses.
- Cerebrum, or cerebral cortex - This area of the brain consists of the cortex, large fiber tracts and some deeper structures (the basal ganglia, amygdala and hippocampus). It integrates information from all of the sensory organs, initiates motor functions, controls emotions and holds memory and thought processes.
The peripheral nervous system can be divided into three parts based on the specific functions taking place: the somatic nervous system, the autonomic nervous system and the enteric nervous system. The somatic nervous system receives external stimuli and coordinates the movements of the body, while the autonomic nervous system is responsible for those functions that are not under conscious control.
The autonomic nervous system can be again classified into sympathetic, parasympathetic and enteric divisions. The sympathetic nervous system responds to stress or anxiety, while the parasympathetic nervous system takes control when a person is relaxing or sleeping. The enteric nervous system, on the other hand, manages the tasks involved in digestion.
The nervous system is a complex network which controls and coordinates virtually all of the body's activities by transmitting signals from the brain to all the different regions of the body. This happens with the help of neurons, which conduct the impulses between the central and peripheral nervous systems.
The sensory neurons generate and transmit the stimuli received from the body's sensory organs (such as the eyes, nose, or skin) to the brain and the spinal cord. The brain then processes those stimuli and sends them back to the other areas of the body, telling these areas how to react because of particular stimulus.
The motor neurons are responsible for receiving signals from the brain and spinal cord and transmitting them to the other organs of the body. The neurons use electromechanical signals in the transmission of signals from one neuron to another.
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Brain & Nervous System Disorders
Carpal Tunnel Syndrome
Carpal Tunnel Syndrome (CTS) is characterized by pain in the wrist and hand, especially when the thumb is bent toward the palm. Sensations include a burning, tingling, or aching that may spread to the forearm and shoulder. Pain may be persistent or intermittent, and is frequently experienced at night. When the condition is severe, the muscles of the hand stop functioning, and may waste away from lack of use.
Dizziness is defined as to impairment in stability and spatial perception and is usually divided into four types. Vertigo is the perception that environment or body around is spinning. Presyncope is another form of dizziness that gives off a feeling of light-headedness. Disequilibrium is a sense of imbalance. There is another category of dizziness which is often vague or described as floating; many times there are other conditions accompanying it such as nausea, headache, or abdominal pain. Dizziness is usually harmless and short-lasting, but there are times where it can be persist. Dizziness affects as many as 40 % of people over the age of 40 and is more common with age.
Each year a seemingly infinite number of people are plagued by headaches. While sometimes the degree of severity is trivial, at other times headaches can lead to excruciating agony. An estimated 15 percent of the population has a headache at least once a week. The number of Americans affected by migraines is estimated at 23 million. Since hormones have a role in the onset of migraines, more migraine sufferers are women. Evidence is shown migraines occur by a sudden dilation of blood vessels around the brain. Several conditions can cause migraines.
Multiple sclerosis is an autoimmune disease in which the myelin sheath, a fatty protective coating around nerve cells, is destroyed by the body's own defence system. The disease presents a wide variety of symptoms, which range in severity and can come and go. MS symptoms include weakness of an arm or leg, unexplained tingling or funny sensations in various places in the body, double vision, loss of vision, problems with speech or walking, increased urinary frequency, incontinence, and memory impairment.
Parkinson’s disease is a progressive, debilitating central nervous system disorder that results in damage to the brain cells. Men are 50 percent more likely to get Parkinson’s than women. Though the disease is usually associated with the people over 60, young people may become affected as well due to such things as carbon monoxide, encephalitis, heavy metal poisoning, or drug use. Parkinson’s occurs when the area of the brain called the substantia nigra, which is responsible for producing dopamine, deteriorates or dies. Adequate levels of dopamine are responsible for making neuronal movement fluid and smooth. When there’s an inadequate level of dopamine, abnormal movements occur, including rigidity, tremors, shuffling, slow gait, and loss of balance.
Because of the similarity between heart attacks and strokes, the two are some¬times confused. Both involve a cut off of blood supply: In a heart attack, the supply to the heart—and consequently to all the other organs—is cut off, while with a stroke, blood supply to the brain is cut off, as a result of a clot or a hemorrhage. Once this happens, oxygen becomes depleted and brain tissue dies. This can ultimately result in paralysis, blindness, speech difficulties, loss of function in an arm or leg, and other serious disabilities. There may also be cognitive impairment, i.e., the person cannot think or remember as well as before.
Sciatica is described as a radiating pain that runs from the lower back or buttock down one leg. There may also be a feeling of weakness or numbness. The symptoms may be due to damage or pressure to the sciatic nerve, a large nerve that runs down the back of each leg and controls the muscles while also providing sensation. The symptoms usually occur suddenly and may take a few weeks until symptoms go away.