GOINDIS NATUROPATHY TRUST(INDIA)
Charity Registration No.845/4 dated 03.09.2003
THE NERVOUS SYSTEM
SANTOKH SINGH PARMAR
FOUNDER TRUSTEES:
Satyendra Singh Goindi, MSc, LLB, ND
Gurkirpal Kaur Goindi, BA, BEd, DPE, ND
Santokh Singh Parmar, B Arch, Dip TP, Dip LA, MRTPI, AITP, AIIA
Devinder Singh Saroya, PCS
Gurmukh Singh Girn, MSc, MCRP, AITP
2 THE NERVOUS System
What is Nervous System?
2.1 Your nervous system is made up of billions of special cells called neurons. The neurons have bundles of fibres called nerves. These nerves conduct messages rapidly throughout the body. Nerve impulses travel along nerve fibres at speeds of 1-90 meters per second. The pathways between neurons are called neural circuits. Your nervous system regulates and coordinates your body’s physical and mental activities in response to changes in the internal and external environment. The changes, called stimuli, initiate impulses in millions of sensory receptors spread throughout your body. The most familiar are the sense organs: the eyes, ears, nose, skin and tongue. In addition to these organs, there are other sensory receptors within the body and close to the surface of the skin. The receptors translate events in a person’s surroundings into nerve messages, which are known as impulses. The nervous system is broadly divided into three parts i.e. automatic nervous system, central nervous system and peripheral nervous system.
The Automatic Nervous System
2.2 This part, which is not under your control, regulates such automatic involuntary bodily processes as breathing and digestion. This part includes the lower brain and spinal chord.
The Central Nervous System
2.3 The brain and spinal chord make up the second part of the central nervous system. It acts as a switchboard that controls and coordinates the activities of the entire nervous system. The brain (about 1.4 kg) is the organ responsible for thought, memory, consciousness, creativity and emotion. It also receives sensory impulses, controls and coordinates muscular movements, and regulates vital body processes. The spinal chord is the pathway for sensory and motor nerve impulses traveling to and from the brain. It also processes some information without the aid of the brain, as demonstrated by reflexes such as the withdrawal reflex. Cerebrospinal fluid fills the open spaces in the brain and surrounds the spinal chord. This fluid acts as a shock absorber, protecting the brain and spinal chord from damage. It transports metabolic wastes out of the central nervous system. Nutrients, hormones, and other vital substances are transported throughout the central nervous system by the cerebrospinal fluid.
The Peripheral Nervous System
2.4 The 31 pairs of spinal nerves as well as all the other nerves and nerve cells outside of the central nervous system make up the third part of the nervous system. This system carries nerve impulses to and from the body’s sensory cells and the central nervous system. The central nervous system analyses the information it receives from the peripheral nervous system and responds to it. The motor neurons of the peripheral nervous system carry out the instructions received from the central nervous system. It acts as a switchboard that controls and coordinates the activities of the entire nervous system.
The Nervous Tissue
2.5 The tissue of the nervous system is composed of two basic types of cells, neurons and glia (glial cells). A neuron consists of a cell body; dendrites, branched structures that conduct impulses to the cell body; and an axon, a long fibre that transmits impulses away from the body. There are three types of neurons. Sensory neurons send signals from the sense organs to the spinal chord and the brain. Motor neurons send signals from the brain and the spinal chord to the body’s muscles. Association neurons link sensory neurons to motor neurons. Glial cells help support and nourish neurons and account for approximately one-half of the volume of the nervous tissue. There are four types of glial cells, each with a different function.
The Neurotransmitters
2.6 Neurons are separated from each other and from other body cells by a tiny gap called a synapse. When a nerve impulse reaches a synapse, the axon releases a chemical called a neurotransmitter. The neurotransmitter transfers the impulse across the synapse to the target cell. Then, the synapse is cleared so that another impulse can cross. Over 60 different chemicals have been identified either as neurotransmitters or as substances that modify the activity of neurotransmitters.
2.7 Neurotransmitters and Drugs – The use of psychoactive drugs alters the transmission of nerve impulses. For example, caffeine stimulates the nervous system by facilitating synaptic transmission. Cocaine, amphetamines, and some antidepressant drugs cause substances to remain in the synapse longer. The result is prolonged stimulation of the nervous system. Some psychoactive drugs are addictive. The body adjusts to the changes these drugs cause. If the drug is withdrawn, the body will be unable to function as it had previously. The addicted drug user will then experience withdrawal symptoms.
The Brain
2.8 The brain weighing about 1.4 kg contains about 1 trillion cells, and it consists of three basic parts: the cerebrum, the cerebellum and the brain stem. The cerebrum, which is the largest part of the brain, initiates all the body’s voluntary actions. The cerebellum controls balance of the muscle movement. The brain stem, which connects the cerebrum to the spinal chord, has nerve centres that regulate swallowing, the digestive process, circulation and respiration.
2.9 Cerebral Hemispheres – The cerebrum is made up of a right hemisphere and a left hemisphere, each divided into four lobes. Each hemisphere controls the actions of the opposite side of the body. In most people, the left hemisphere is dominant. In general, the left hemisphere is responsible for speech, writing, and reading. It also plays a major role in verbal, analytical, and computational skills. The right hemisphere is more involved with nonverbal functions, such as emotion, intuition, awareness and interpretation of space and connected by a structure called the corpus callosum, and there is constant communication between the two sides.
2.10 Blood-Brain Barrier – Some substances taken into the body can interfere with the proper functioning of the brain. Fortunately, a structure called the blood-brain barrier prevents most harmful substances from passing from the capillaries of the brain into the cerebrospinal fluid. The cells lining the brain’s blood vessels are tightly joined together and play the primary role in forming the blood-brain barrier. In addition, projections from one type of glial cell cover the outside of the brain’s blood vessels, making passage into the brain even more difficult. A special carrier system allows water, oxygen, carbon-dioxide, glucose and nutrients to pass through the blood-brain barrier.
Disorders of the Nervous System
2.11 Stroke – When the blood supply to the brain is cut off, a stroke occurs. Most strokes occur due to damage to the blood vessels, caused by high blood pressure. Nerve cells in the affected areas die, and the victim may lose the ability to carry out functions contolled by those areas of the brain such as speaking or moving a limb. A common disorder due to a stroke is the paralysis of one side of the body.
2.12 Tumours – Tumours are abnormal growths that can cause severe brain damage. The real cause of a brain tumour is not known. The extent of the damage depends on its size and location. The brain cells surrounding the tumour are destroyed by the tumour’s constant growth. As the tumour grows, it also creates pressure which may damage other areas of the brain, or interfere with other normal functions of the brain.
2.13 Epilepsy – This is a disease that causes a person to fall unconscious. It is often accompanied by violent uncontrolled movements of the body. Our brain cells produce some electrical energy which travels through our nervous system and activates the muscles. When the brain of a patient is not able to limit or control the production of electrical energy, epileptic seizures occur. Fatigue and emotional stress can enhance the occurrence of epileptic seizures.
2.14 Mental Illness – Any disease of the mind that affects a person’s thoughts, feelings or behaviour is a mental illness. These illnesses lead to unhappiness and socially unacceptable behaviour. Some mental illnesses may occur from a physical cause, such as a birth defect, a disease, or an injury to the brain. Certain conditions in the environment also affect a person’s mental state. The imbalance of certain brain chemicals may cause mental illnesses. Sometimes it is hereditary.
2.15 Encephalitis – This is an inflammation of the brain. In most cases encephalitis results from a virus infection. Bacteria, harmful chemical, and various tiny parasites can also cause the disease.
2.16 Meningitis – This is a disease that affects the membranes covering the brain and spinal chord. People of all ages can become victims of this disease, but it most frequently strikes infants and children. Meningitis results from infection by bacteria, viruses, fungi or other microbes. Physically weak or unhealthy people are more prone to this disease.
Genetic Disorders
2.17 Our genes (the hereditary materials in cells) carry instructions for the development of the brain. These instructions are extremely complex and so errors occasionally occur. Errors in the instructional material can lead to serious defects, like mental retardness in the structure and functioning of the brain.
Concussion
2.18 When the head receives a violent blow – such as from a fall – the brain is jarred. The force of the blow hitting the skull interferes with normal brain function and is called a concussion. If the force is mild, loss of consciousness may occur but will usually last only a few seconds. However, if the force is intense, loss of consciousness may be prolonged and damage may be extensive. It is common for a person to experience confusion or even amnesia following a concussion. Although the damage may not be obvious from the outside, concussions can be very dangerous.
The Spinal Cord
2.19 The spinal cord is a cable of nerve tissue that extends from the base of the brain to just below the level of the ribs. In adults, it is about the thickness of the little finger. The spinal cord is surrounded by the spinal column (backbone), which protects it. Thirty-one pairs of spinal nerves connect the spinal chord with the rest of the body. The spinal nerves are composed of millions of both sensory neurons and motor neurons. These neurons transfer millions of messages or impulses between the body and the brain.
2.20 Spinal Cord Injuries – Spinal cord injuries are relatively common. About 45 percent of all spinal cord injuries are incurred in motor-vehicle accidents. Injuries to the spinal cord can alter or prevent communication between the brain and the body. If the injury is serious enough, paralysis can occur. In general, the higher up on the spinal cord the injury is, the more severe the damage will be. Damage to the spinal cord in the neck can result in paralysis from the neck down, while injuries lower on the spinal chord may produce paralysis only in the legs.
Reflexes
2.21 Reflexes are involuntary responses to stimuli and are not controlled by the brain. Reflex movements take only a split second to occur. For example, when a person touches a hot stove, a nerve impulse travels through a sensory neuron in the person’s hand to the spinal chord. There, it is transferred first to an association neuron and then to a motor neuron traveling quickly back to the hand. In a split second, the withdrawal reflex pulls the hand away from the stove. If this message had to go through the brain, the response time would be longer increasing the possibility of injury.
Sensory Receptors and Sense Organs
2.22 Your senses are the window through which you view the world around you. They allow you to interpret changes in your internal and external environment. One day you may feel well; the next day you may have a headache. Your senses are what provide this information to the brain, which in turn, interprets it. Not everyone interprets information in the same way chord
2.23 Internal Sensory Receptors – Sense receptors located deep within the body enable a person to feel internal pain, hunger, thirst, tiredness, and nausea. Other receptors located in skeletal muscles, tendons, and the connective tissue surrounding joints are sensitive to changes in stretch and tension. They continuously relay information about body position, equilibrium, and movement to the central nervous system, and together they make up what is called the kinesthetic sense. Many internal sensations are not recognised at a conscious level. For example, some sensors monitor blood pressure; the information they send to the brain is not processed by the cerebrum, so an individual is not aware of this sensation.
2.24 Sensation and the Skin – Touch is the sensation produced by pressure on the surface of the body and is sometimes called the tactile sense. Pressure receptors are located all over the skin. On sensitive parts of the body, such as the tongue, lips and finger pads, their concentration is very high. Touch messages are transmitted by bundles of sensory nerve fibres that come through the subcutaneous layer to the dermis, or inner layer of skin. The bundle of fibres, some of which reach into the epidermis, or outer layer of the skin. These nerve endings in the epidermis are sensitive to pressure. Other sensory nerve fibres end in specialised receptors in the dermis, which sense temperature or pain.
Smell and Taste
2.25 Your sense of taste and your sense of smell are both stimulated by chemicals. Their main purposes are to help you detect harmful substances and to stimulate your appetite and digestion. Even though taste and smell messages travel separately to different regions of the brain, they create a combined feeling of either pleasure or displeasure when you are eating. For example, think of how the aroma of a delicious meal can make your mouth water.
2.26 Smell – Olfactory (smell) receptors are located in a dime-sized area in the roof of the nasal passages. They are able to sense minute amounts of chemicals in the air. These receptors are actually specialised neurons whose dendrites are modified into hair-like projections called cilia. Their axons transmit nerve impulses through an opening in the skull directly to the olfactory bulb in the forebrain. When a person has a stopped-up nose, little air passes over the olfactory receptor cells, resulting in a diminished sense of smell. Compared to some other mammals, humans have a poor sense of smell. For example, humans have anywhere from 5 million to 20 million olfactory receptors, while dogs have 40 million or more.
2.27 Taste – The tongue is covered with small, rough bumps called papillae. Each papilla is covered with taste buds, clusters of taste sensors. Taste receptors sense chemicals – classified as sweet, sour, salty, or bitter – in foods and beverages. When chewed-up food mixed with saliva washes across the papillae, the chemicals in the food stimulate the taste receptors. The receptors transmit nerve impulses to the brain through the gustatory nerve, and the brain interprets the taste. Babies have about 10,000 taste buds, but this number decreases as a person gets older. There are other reasons why the ability to taste can diminish. For example, there is good evidence that long-term cigarette smoking damages taste receptors, adding to the loss that normally comes with age.
The Vision
2.28 Human beings have excellent eyesight. In fact, only birds can see better than humans can, although squids and octopuses can see just as well. Your vision is a response to light falling on the retina of the eye. Light rays enter your eye through the pupil and are focused onto the retina, which is actually an extension of your brain. Nerve fibres of the retina join to form the optic nerve, which transmits nerve impulses to the occipital lobe of your brain. Your brain then interprets these impulses as an image, and you “see” it.
2.29 Eye – The outer surface of the eye is covered by the cornea, a transparent membrane that protects the eye but allows light to enter. Behind the cornea is the iris, a thin, coloured, circular membrane. In the centre of the iris is an opening called the pupil. Muscles in the iris control the amount of light that is let in by altering the diameter of the pupil. The pupil dilates, or enlarges, to let more light in and contracts to let in less light. Behind the pupil is the lens, a thick, curved structure that focuses the light rays so that they will fall on the retina, the thin lining on the back of the eye. The image on the retina is inverted.
30. Receptor Cells – There are approximately 1 billion receptor cells in the retina. Rods are cells that are extremely sensitive to light; however, they cannot detect colour, and they produce poorly defined images. Cones are cells that detect colour and produce sharp images. At the centre of the retina is a concentration of about 3 million cone cells. People usually move their eyes so that the light rays from an object they want to see fall on this area. There are no cones or rods at the point where the optic nerve enters the retina. Light that falls on this area does not stimulate any sight receptors, resulting in a “blind spot” in the field of vision.
Eye Disorders
2.31 Image Forming – When the eyes view an image, each eye sees the image from a slightly different angle. About one-third of the visual fields overlap, but the other two-thirds differ. This overlap produces binocular vision, which enables people to perceive depth. Also, the optic nerves do not connect to only one hemisphere. About one-half of each optic nerve crosses over into the opposite side of the brain; because of this, each hemisphere receives visual information from both eyes. The brain combines all the information it receives to produce one image.
2.32 Where do tears come from and what is their purpose? – Tears are produced by a gland found above and to the outside of each eyeball. Each gland produces a watery secretion that mixes with a slightly oily secretion from accessory glands. The tear glands have between 10 and 12 ducts, and every time the eyes blink, tears are spread across the surface of the eye. Tears protect the eyes by lubricating them and washing away debris. Also, they contain an enzyme that helps prevent eye infection. Tears drain into two ducts in the inner corners of the eye. These ducts drain into the back of the nose.
2.33 Nearsight, Farsight and Astigmatism – Some people are nearsighted or farsighted; others have astigmatism. Why is this? For an image to appear clear, the lens must focus light rays directly onto the retina. The lens does this by using tiny muscles and ligaments to adjust its thickness. If the shape of the eyeball is too elongated or too short, the lens will be unable to change sufficiently to focus the image properly. In nearsighted people, the focal point is in front of the retina, resulting in poor distance vision. In farsighted people, the focal point is behind the retina, resulting in poor close vision. Astigmatism is caused by an irregularly shaped cornea. This causes the light rays to be focused erratically and to mostly miss the retina. Corrective lenses adjust the light ray’s focal point so that it is on the retina.
2.34 Colour blindness – A condition that is almost always genetic in origin, is the inability to distinguish colours. It is caused by an abnormality of one or more of the three types of light-sensitive pigments in the cone cells. The inability to distinguish red light from green light is the most common type of colour blindness. About 10 percent of all males have some degree of colour blindness while less than 1 percent of females are affected. Total colour blindness is extremely rare.
2.35 Cataracts – When a person has cataracts, the lens of the eye is no longer transparent. Light cannot pass through the lens easily, so vision is diminished. Although ageing is the most common cause of cataracts, they can also result from a reaction to a drug, from radiation including solar exposure, and from disease. In the past, people with cataracts became blind; however, today the condition can be corrected surgically. The faulty lens is removed and replaced with an artificial one. Glasses or contact lenses are then prescribed to adjust the vision.
2.36 Cornea Scar – Some diseases cause scarring of the cornea. When this occurs, blindness may result because light cannot pass through the damaged cornea. This condition can be corrected by a corneal transplant. The central portion of the scarred cornea is removed and replaced with a cornea from an organ donor.
Hearing and Equilibrium
2.37 When you think of your ears, you may only consider your external ear, the part that sticks out on each side of your head. But you also have a middle ear and an inner ear, the portions responsible for sensing sound.
2.38 Hearing – The external ear funnels sounds through the ear canal to the eardrum. On the other side of the eardrum is an air-filled cavity called the middle ear. This part of the ear opens to the back of the throat through a tube called the eustacian tube. As sound waves apply pressure to the eardrum, the eardrum vibrates. Three bones located in the middle ear – the hammer, the anvil, and the stirrup – transfer this vibration to a fluid-filled chamber, the cochlea. Inside are tiny hair cells that serve as sound receptors. They respond to the vibrations and send impulses to the brain, which interprets the vibrations as sound.
2.39 Equilibrium – The two other portions of the inner ear, the semicircular canals and the vestibule, are involved with the sense of equilibrium. The semicircular canals detect movement of the head. The vestibule contains sensory cells that respond to changes in head position with respect to gravity. It is the inner ear that contains the sense cells, which enable you to hear, and that produces your sense of equilibrium, or balance and stability in space.
2.40 Hearing loss – Certain conditions, diseases, and types of trauma can result in hearing loss. For example, a build up of wax in the ear or an ear infection can create a barrier to sound waves entering the ear, preventing vibration of the ear drum and the inner-ear bones. Repeated inner-ear infections can result in scarring of the eardrum and damage to the bones of the inner ear. If this occurred, sound waves would not be conducted as well and hearing would be diminished. This type of hearing loss is referred to as conductive deafness.
2.41 Repeated exposure to excessively loud sounds will destroy the tiny hair cells in the cochlea, resulting in hearing loss. Once destroyed, these hair cells can never be replaced. Rock concerts and exposure to other loud noises, such as power saws cause this type of hearing loss. Wearing ear plugs protects the ears from this type of damage. There is now evidence that prolonged exposure to even moderately loud sounds, such as head phones, has a cumulative effect and can cause hearing loss classified as nerve deafness.
2.42 Where does earwax come from? – Sebaceous glands and ceruminous glands, specialised sweat glands, located in the ear canal produce this wax-like secretion. Earwax, called cerumen, protects the ear from infection and traps debris or small insects that enter the ear. It also helps prevent the ear drum from drying out. Usually the wax moves outward, moving anything it trapped along with it.
Santokh Singh Parmar
Naturo-Food Therapist & Lifestyle Consultant
Mobile: +91(0) 9815922330
Websites: www.naturofoodtherapy.org & www.foodtherapy.org
Note: The above information and advice and indicative remedies are not a substitute for the advice, your doctor or naturo-food therapist may give you based on his/her knowledge of yourself.