WHAT ARE THE FIVE SENSES OF HUMAN BODY?

The nervous system must receive and process information about the world outside in order to react, communicate, and keep the body healthy and safe. Much of this information comes through the sensory organs: the eyes, ears, nose, tongue, and skin. Specialized cells and tissues within these organs receive raw stimuli and translate them into signals the nervous system can use. Nerves relay the signals to the brain, which interprets them as sight (vision), sound (hearing), smell (olfaction), taste (gustation), and touch (tactile perception).

1. The Eyes Translate Light into Image Signals for the Brain to Process

The eyes sit in the orbits of the skull, protected by bone and fat. The white part of the eye is the sclera. It protects interior structures and surrounds a circular portal formed by the cornea, iris, and pupil. The cornea is transparent to allow light to enter the eye, and curved to direct it through the pupil behind it. The pupil is actually an opening in the colored disk of the iris. The iris dilates or constricts, adjusting how much light passes through the pupil and onto the lens. The curved lens then focuses the image onto the retina, the eye’s interior layer. The retina is a delicate membrane of nervous tissue containing photoreceptor cells. These cells, the rods and cones, translate light into nervous signals. The optic nerve carries the signals from the eye to the brain, which interprets them to form visual images.

2. The Ear Uses Bones and Fluid to Transform Sound Waves into Sound Signals

Music, laughter, car honks — all reach the ears as sound waves in the air. The outer ear funnels the waves down the ear canal (the external acoustic meatus) to the tympanic membrane (the “ear drum”). The sound waves beat against the tympanic membrane, creating mechanical vibrations in the membrane. The tympanic membrane transfers these vibrations to three small bones, known as auditory ossicles, found in the air-filled cavity of the middle ear. These bones – the malleus, incus, and stapes – carry the vibrations and knock against the opening to the inner ear. The inner ear consists of fluid-filled canals, including the spiral-shaped cochlea. As the ossicles pound away, specialized hair cells in the cochlea detect pressure waves in the fluid. They activate nervous receptors, sending signals through the cochlear nerve toward the brain, which interprets the signals as sounds.

3. Specialized Receptors in the Skin Send Touch Signals to the Brain

Skin consists of three major tissue layers: the outer epidermis, middle dermis, and inner hypodermis. Specialized receptor cells within these layers detect tactile sensations and relay signals through peripheral nerves toward the brain. The presence and location of the different types of receptors make certain body parts more sensitive. Merkel cells, for example, are found in the lower epidermis of lips, hands, and external genitalia. Meissner corpuscles are found in the upper dermis of hairless skin — fingertips, nipples, the soles of the feet. Both of these receptors detect touch, pressure, and vibration. Other touch receptors include Pacinian corpuscles, which also register pressure and vibration, and the free endings of specialized nerves that feel pain, itch, and tickle.

4. Olfaction: Chemicals in the Air Stimulate Signals the Brain Interprets as Smells

The sense of smell is called olfaction. It starts with specialized nerve receptors located on hairlike cilia in the epithelium at the top of the nasal cavity. When we sniff or inhale through the nose, some chemicals in the air bind to these receptors. That triggers a signal that travels up a nerve fiber, through the epithelium and the skull bone above, to the olfactory bulbs. The olfactory bulbs contain neuron cell bodies that transmit information along the cranial nerves, which are extensions of the olfactory bulbs. They send the signal down the olfactory nerves, toward the olfactory area of the cerebral cortex.

5. Home of the Taste Buds: The Tongue Is the Principal Organ of Gustation

What are all those small bumps on the top of the tongue? They’re called papillae. Many of them, including circumvallate papillae and fungiform papillae, contain taste buds. When we eat, chemicals from food enter the papillae and reach the taste buds. These chemicals (or tastants) stimulate specialized gustatory cells inside the taste buds, activating nervous receptors. The receptors send signals to fibers of the facial, glossopharyngeal, and vagus nerves. Those nerves carry the signals to the medulla oblongata, which relays them to the thalamus and cerebral cortex of the brain.

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REGULAR BLOOD DONATION ELIMINATES TOXIC ‘FOREVER CHEMICALS’ FROM BODY.

'Forever chemicals' or PFAS are widely present in non-stick kitchenware, plastics, water-resistant materials, paints, carpets and clothes. On entering the body they accumulate in the bloodstream, and impact gut flora or lungs, causing asthma and other diseases.

As PFAS bind to serum proteins in the blood, regular blood or plasma donations result in a significant reduction in blood PFAS levels; plasma donations were more effective, corresponding to a 30 per cent decrease.

Although results suggest that this is a viable tool for removing PFAS from the bloodstream, what does it mean for recipients of the blood? Potential recipients are very likely to already have PFAS in their bloodstream, and there is no data to suggest that receiving blood contaminated with the compounds exposes them to additional risks.

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WHAT AND WHEN WAS THE FIRST HUMAN ORGAN TO BE TRANSPLANTED SUCCESSFULLY?

In 1954, the kidney was the first human organ to be transplanted successfully. Until the early 1980s, the potential of organ rejection limited the number of transplants performed.

 The first ever successful transplant of any organ was done at the Brigham & Women's Hospital in Boston, Ma. The surgery was done by Dr. Joseph Murray, who received the Nobel Prize in Medicine for his work. The reason for his success was due to Richard and Ronald Herrick of Maine. Richard Herrick was a in the Navy and became severely ill with acute renal failure. His brother Ronald donated his kidney to Richard, and Richard lived another 8 years before his death. Before this, transplant recipients didn't survive more than 30 days. The key to the successful transplant was the fact that Richard and Ronald were identical twin brothers and there was no need for anti-rejection medications, which was not known about at this point. This was the most pivotal moment in transplant surgery because now transplant teams knew that it could be successful and the role of rejection/anti-rejection medicine.

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WHAT IS AN ORGAN TRANSPLANTATION?

Organ transplantation is a medical procedure in which an organ is removed from one body and placed in the body of a recipient, to replace a damaged or missing organ. The donor and recipient may be at the same location, or organs may be transported from a donor site to another location. Organs and/or tissues that are transplanted within the same person's body are called autografts. Transplants that are recently performed between two subjects of the same species are called allografts. Allografts can either be from a living or cadaveric source.

Organs that have been successfully transplanted include the heart, kidneys, liver, lungs, pancreas, intestine, thymus and uterus. Tissues include bones, tendons (both referred to as musculoskeletal grafts), corneae, skin, heart valves, nerves and veins. Worldwide, the kidneys are the most commonly transplanted organs, followed by the liver and then the heart. Corneae and musculoskeletal grafts are the most commonly transplanted tissues; these outnumber organ transplants by more than tenfold.

Organ donors may be living, brain dead, or dead via circulatory death. Tissue may be recovered from donors who die of circulatory death, as well as of brain death – up to 24 hours past the cessation of heartbeat. Unlike organs, most tissues (with the exception of corneas) can be preserved and stored for up to five years, meaning they can be "banked". Transplantation raises a number of bioethical issues, including the definition of death, when and how consent should be given for an organ to be transplanted, and payment for organs for transplantation. Other ethical issues include transplantation tourism (medical tourism) and more broadly the socio-economic context in which organ procurement or transplantation may occur. A particular problem is organ trafficking.[5] There is also the ethical issue of not holding out false hope to patients.

Transplantation medicine is one of the most challenging and complex areas of modern medicine. Some of the key areas for medical management are the problems of transplant rejection, during which the body has an immune response to the transplanted organ, possibly leading to transplant failure and the need to immediately remove the organ from the recipient. When possible, transplant rejection can be reduced through serotyping to determine the most appropriate donor-recipient match and through the use of immunosuppressant drugs.

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WHAT ELEMENT IN HEMOGLOBIN MAKES BLOOD RED?

Human blood is red because of the protein hemoglobin, which contains a red-colored compound called heme that’s crucial for carrying oxygen through your bloodstream. Heme contains an iron atom which binds to oxygen; it’s this molecule that transports oxygen from your lungs to other parts of the body.

Chemicals appear particular colors to our eyes based on the wavelengths of light they reflect. Hemoglobin bound to oxygen absorbs blue-green light, which means that it reflects red-orange light into our eyes, appearing red. That’s why blood turns bright cherry red when oxygen binds to its iron. Without oxygen connected, blood is a darker red color.

Carbon monoxide, a potentially deadly gas, can also bind to heme, with a bond around 200 times stronger than that of oxygen. With carbon monoxide in place, oxygen can’t bind to hemoglobin, which can lead to death. Because the carbon monoxide doesn’t let go of the heme, your blood stays cherry red, sometimes making a victim of carbon monoxide poisoning appear rosy-cheeked even in death.

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WHAT ARE THE FUNCTIONS, DESEASE AND TREATMENTS OF THE LIVER?

The liver is a large, meaty organ that sits on the right side of the belly. Weighing about 3 pounds, the liver is reddish-brown in color and feels rubbery to the touch. Normally you can't feel the liver, because it's protected by the rib cage.

The liver has two large sections, called the right and the left lobes. The gallbladder sits under the liver, along with parts of the pancreas and intestines. The liver and these organs work together to digest, absorb, and process food.

The liver's main job is to filter the blood coming from the digestive tract, before passing it to the rest of the body. The liver also detoxifies chemicals and metabolizes drugs. As it does so, the liver secretes bile that ends up back in the intestines. The liver also makes proteins important for blood clotting and other functions.

Types of liver disease include:

Hepatitis: Inflammation of the liver, usually caused by viruses like hepatitis A, B, and C. Hepatitis can have non-infectious causes too, including heavy drinking, drugs, allergic reactions, or obesity.
Cirrhosis: Long-term damage to the liver from any cause can lead to permanent scarring, called cirrhosis. The liver then becomes unable to function well.
Liver cancer: The most common type of liver cancer, hepatocellular carcinoma, almost always occurs after cirrhosis is present.
Liver failure: Liver failure has many causes including infection, genetic diseases, and excessive alcohol.
Ascites: As cirrhosis results, the liver leaks fluid (ascites) into the belly, which becomes distended and heavy.
Gallstones: If a gallstone becomes stuck in the bile duct draining the liver, hepatitis and bile duct infection (cholangitis) can result.
Hemochromatosis: Hemochromatosis allows iron to deposit in the liver, damaging it. The iron also deposits throughout the body, causing multiple other health problems.
Primary sclerosing cholangitis: A rare disease with unknown causes, primary sclerosing cholangitis causes inflammation and scarring in the bile ducts in the liver.
Primary biliary cirrhosis: In this rare disorder, an unclear process slowly destroys the bile ducts in the liver. Permanent liver scarring (cirrhosis) eventually develops.

Liver Treatments

Hepatitis A treatment: Hepatitis A usually goes away with time.
Hepatitis B treatment: Chronic hepatitis B often requires treatment with antiviral medication.
Hepatitis C treatment: Treatment for hepatitis C depends on several factors.
Liver transplant: A liver transplant is needed when the liver no longer functions adequately, whatever the cause.
Liver cancer treatment: While liver cancer is usually difficult to cure, treatment consists of chemotherapy and radiation. In some cases, surgical resection or liver transplantation is performed.
Paracentesis: When severe ascites -- swelling in the belly from liver failure -- causes discomfort, a needle can be inserted through the skin to drain fluid from the abdomen.
ERCP (Endocscopic retrograde cholangiopancreatography): Using a long, flexible tube with a camera and tools on the end, doctors can diagnose and even treat some liver problems.

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How does the stomach work?

The stomach is a muscular hollow organ. It takes in food from the esophagus (gullet or food pipe), mixes it, breaks it down, and then passes it on to the small intestine in small portions.

The entire digestive system is made up of one muscular tube extending from the mouth to the anus. The stomach is an enlarged pouch-like section of this digestive tube. It is located on the left side of the upper abdomen and shaped somewhat like an oversized comma, with its bulge pointing out to the left. The stomach’s shape and size vary from person to person, depending on things like people’s sex and build, but also on how much they eat.

At the point where the esophagus leads into the stomach, the digestive tube is usually kept shut by muscles of the esophagus and diaphragm. When you swallow, these muscles relax and the lower end of the esophagus opens, allowing food to enter the stomach. If this mechanism does not work properly, acidic gastric juice might get into the esophagus, leading to heartburn or an inflammation.

The upper-left part of the stomach near the opening curves upward towards the diaphragm. This part is called fundus. It is usually filled with air that enters the stomach when you swallow. In the largest part of the stomach, called the body, food is churned and broken into smaller pieces, mixed with acidic gastric juice and enzymes, and pre-digested. At the exit of the stomach, the body of the stomach narrows to form the pyloric canal, where the partially digested food is passed on to the small intestine in portions.

The stomach wall is made up of several layers of mucous membrane, connective tissue with blood vessels and nerves, and muscle fibers. The muscle layer alone has three different sub-layers. The muscles move the contents of the stomach around so vigorously that solid parts of the food are crushed and ground, and mixed into a smooth food pulp.

The inner mucous membrane (lining) has large folds that are visible to the naked eye. These folds run toward the exit of the stomach, providing “pathways” along which liquids can quickly flow through the stomach. If you look at the mucous membrane under a microscope, you can see lots of tiny glands. There are three different types of glands. These glands make digestive enzymes, hydrochloric acid, mucus and bicarbonate.

Gastric juice is made up of digestive enzymes, hydrochloric acid and other substances that are important for absorbing nutrients – about 3 to 4 liters of gastric juice are produced per day. The hydrochloric acid in the gastric juice breaks down the food and the digestive enzymes split up the proteins. The acidic gastric juice also kills bacteria. The mucus covers the stomach wall with a protective coating. Together with the bicarbonate, this ensures that the stomach wall itself is not damaged by the hydrochloric acid.

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Which is the smallest muscle in human body?

Did you know the smallest muscle in the body is located in the ear? Called the stapedius, it is said to be less than 2 mm long. It supports the smallest bone in the body, called the stapes, which is part of the middle ear and helps conduct vibrations to the inner ear. Its purpose is to stabilise the smallest bone in the body.

The stapedius dampens the vibrations of the stapes by pulling on the neck of that bone. As one of the muscles involved in the acoustic reflex it prevents excess movement of the stapes, helping to control the amplitude of sound waves from the general external environment to the inner ear.

If there is damage to the nerve to stapedius, wider oscillations of the stapes will occur resulting in hyperacusis—sounds being perceived as extremely loud, more so than they actually are to a person without damage to this nerve.

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What is a stroke?

 Stroke is a medical condition in which blood supply is severely reduced to parts of the brain resulting in cell death. A stroke occurs when a blood vessel in the brain ruptures and bleeds, or when there’s a blockage in the blood supply to the brain. The rupture or blockage prevents blood and oxygen from reaching the brain’s tissues. Without oxygen, brain cells and tissue become damaged and begin to die within minutes. According to the Centers for Disease Control and Prevention (CDC)Trusted Source, stroke is a leading cause of death in the United States. Every year, more than 795,000 U.S. people have a stroke. There are three primary types of strokes:

Transient ischemic attack (TIA) involves a blood clot that typically reverses on its own.
Ischemic stroke involves a blockage caused by either a clot or plaque in the artery. The symptoms and complications of ischemic stroke can last longer than those of a TIA, or may become permanent.
Hemorrhagic stroke is caused by either a burst or leaking blood vessel that seeps into the brain.

Stroke symptoms can include: ,paralysis numbness or weakness in the arm, face, and leg, especially on one side of the body, trouble speaking or understanding others, slurred speech,confusion, disorientation, or lack of responsiveness, sudden behavioral changes, especially increased agitation, vision problems, such as trouble seeing in one or both eyes with vision blackened or blurred, or double vision, trouble walking, loss of balance or coordination, dizziness, severe, sudden headache with an unknown cause,  seizures, nausea or vomiting

Proper medical evaluation and prompt treatment are vital to recovering from a stroke. According to the American Heart Association and American Stroke Association, “Time lost is brain lost.”

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Brain triggers, cues and planned movement

When we are confronted with a red signal, we wait till it turns green before we make any movement - be it crossing the road on foot or riding a vehicle. In any sprinting race, the starters-both elite athletes in the international stage and youngsters in school-level races - wait for a signal before bursting from the starting line to race to the finish.

Our brain has planned our precise movements but waits for the execution until a specific cue. Scientists from the Max Planck Florida Institute for Neuroscience, HHMI's Janelia Research Campus, the Allen Institute for Brain Science, and others have discovered the brain network that responds to a cue by turning plans into action.

Brain is like an orchestra

One of the authors of the paper, published in the scientific journal Cell in March, suggests that the brain is like an orchestra. Just like how an orchestra needs a conductor to ensure a perfect symphony, the brain too has areas that act as a conductor and ensure that plans are converted into action at exactly the right time. By simultaneously recording the activity of hundreds of neurons when a mouse performed a cue-triggered movement task, the team was able to identify the neural circuits that serve as the conductor. The task involved the mice licking to the right if whiskers were touched or to the left if whiskers were not touched. The mice not only had to get it correct, but also had to delay their movement until a go cue was played in order to receive a reward.

The scientists were able to correlate complex neuronal activity to various stages of the tasks. They next identified a circuit of neurons in which brain activity occurred after the go cue, leading to the execution. By using optogenetics to activate or inactivate this circuit of neurons in the brain while performing additional tasks, the researchers were able to confirm their discovery.

Can it improve mobility?

 Apart from serving as fundamental advances in our understanding of how our brain functions, this discovery could also have important clinical implications. People who have had an accident or experiencing motor disorders sometimes have difficulty in self-initiated movement. Environmental cues, both visual and auditory, could well trigger movements that can improve the person's mobility dramatically. 

This phenomenon wherein different mechanisms are employed for self-initiated and cue-triggered movements is known as paradoxical kinesia. Understanding how our brain functions during cue-triggered movements may help us in treatments.

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Cluster Headache Awareness Day (March 21)

The 21st of March is the “Cluster Headache Awareness Day”, a prominent event to promote CH on scientific and public levels. The spring equinox represents the perfect choice for a disease with such a great circadian and circannual  rhythmicity. Indeed, a vast majority of CH subjects experienced a CH reactivation during the seasonal shift in spring and autumn; in some cases, the circannual timing becomes so scheduled that patients do not plan activities and slowly slide toward social withdrawal just for the fear of a novel cluster period. The 21st of March is well remembered by CH patients, because starting from this date when the daylight increases there are positive effects for patients with night attacks.

With a prevalence of 0.12%, Cluster Headache (CH) is the most frequent trigeminal autonomic cephalalgia. CH is characterised by a typical clinical picture, namely a strictly unilateral, very severe, headache lasting 15 to 180 minutes associated with prominent cranial autonomic features, which are lateralized and ipsilateral to the headache.

In its episodic subtype (85% of CH subjects), CH attacks are present only in limited period of the years, lasting weeks to months (the so-called cluster periods), alternating with remission phases of at least 3 months of duration. By contrast, in the chronic CH subtype the remissions are shorter or not present at all, and the burden on the individual becomes not imaginable.

During the day, CH subjects may experience several attacks during day, often distributed during the night and with a typical circadian rhythm.

People suffering from CH consistently report severe limitations in activities of daily living and social-activity participation. Nonetheless, their working activity and career may be hindered.

CH has historically been considered as “rare”. If it is true that its prevalence falls far below migraine, it is also true that CH does not represent a rare disease. All in all, the direct and indirect (work absenteeism, sick leave, and so on) costs make CH a burden not only for the individual but for the society globally.

Therapeutic options are still limited, with most of the preventive medications being non-CH specific and borrowed from other medical conditions. Subcutaneous sumatriptan and high-flow oxygen represent the first-line choices for the acute management of CH pain. A novel anti-CGRP monoclonal antibody, which proved effective in migraine, has been approved for the preventive treatment of episodic CH, but not for the most severe chronic CH subtype. Long-term observation is needed to confirm the real-life impact of these novel drugs, hoping for a novel and specific alternative to treat CH.

Finally, CH is still little known outside the headache centres leading to diagnostic delay, low quality of counselling to the patients and sub-optimal therapeutic management.

Credit : International Headache Society 

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Which is the smallest bone in human body?

The stapes is the smallest bone in the human body. The malleus is sometimes compared to a hammer, because it strikes the anvil-shaped incus. The vibrations then travel through the stapes.

The stapes can be compared to a tuning fork, as it has a horseshoe-like shape. The word means “stirrup” in Latin.

The two branches of the stapes, known as the inferior and superior crus, convey sound vibrations to the bone’s flat base.

From there, the vibrations enter the inner ear, where they are processed into neural data to be transmitted to the brain via the cochlear and the auditory nerve.

If the stapes becomes damaged, such as from severe head trauma, a person may lose some or all of their ability to hear. Because the ossicles are a chain of bones, this also holds true for the incus and malleus.

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What is ear barotrauma?

Ear barotrauma, also known as airplane ear, is that clogged-up, sometimes painful feeling you get in your ears when the air pressure changes quickly.

It's the biggest health problem for people who fly. And it can be especially painful for babies and young kids because their ears aren't fully developed.

Ear barotrauma also can happen when you ride in an elevator or drive in the mountains. It can happen in the water, too. Scuba divers call it "ear squeeze." As a diver goes deeper underwater, the pressure in the middle ear (the part behind the eardrum) is "squeezed" by the increasing pressure of the water from outside.

The middle ear is an air-filled space formed by bone and the eardrum. It is connected to the back of the nose by a tunnel called the eustachian tube. Outside air passing through the eustachian tube keeps the pressure in the middle ear equal to that of the outside world. If the eustachian tube malfunctions and there’s a pressure difference across the eardrum, pain or ear squeeze happens.

Airplane ear occurs when the air pressure in the middle ear and the air pressure in the environment don't match, preventing your eardrum (tympanic membrane) from vibrating normally. A narrow passage called the eustachian tube, which is connected to the middle ear, regulates air pressure.

When an airplane climbs or descends, the air pressure changes rapidly. The eustachian tube often can't react fast enough, which causes the symptoms of airplane ear. Swallowing or yawning opens the eustachian tube and allows the middle ear to get more air, equalizing the air pressure.

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Which is the lowest frequency of sound that the human ears can pick up?

The human hearing range depends on both the pitch of the sound – whether it is high or low – and the loudness of the sound. Pitch is measured in Hertz (Hz) and loudness is measured in decibels (dB).

For a person with normal hearing, when it comes to pitch the human hearing range starts low at about 20 Hz. That’s about the same as the lowest pedal on a pipe organ. On the other side of the human hearing range, the highest possible frequency heard without discomfort is 20,000Hz. While 20 to 20,000Hz forms the absolute borders of the human hearing range, our hearing is most sensitive in the 2000 - 5000 Hz frequency range.

As far as loudness is concerned, humans can typically hear starting at 0 dB. Sounds that are more than 85dB can be dangerous for your hearing in the case of prolonged exposure.

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What is the role of Eustachian tube and vestibular complex in ear?

The eustachian tube is a small tube that connects the middle ear to the airway in the back of the nose (nasopharynx). This tube allows outside air to enter the middle ear (behind the eardrum). The eustachian tube, which opens when a person swallows, helps maintain equal air pressure on both sides of the eardrum and prevents fluid from accumulating in the middle ear. If air pressure is not equal, the eardrum may bulge or retract, which can be uncomfortable and distort hearing. Swallowing or voluntary "popping" of the ears can relieve pressure on the eardrum caused by sudden changes in air pressure, as often occurs when flying in an airplane. The eustachian tube's connection with the middle ear explains why upper respiratory infections (such as the common cold), which inflame and block the eustachian tube, can lead to middle ear infections or changes in middle ear pressure, resulting in pain.

The vestibular system consists of

  • Two fluid-filled sacs called the saccule and the utricle
  • Three fluid-filled tubes called the semicircular canals

These sacs and tubes gather information about the position and movement of the head. The brain uses this information to help maintain balance.

The saccule and utricle contain cells that sense movement of the head in a straight line, that is, back and forth or up and down.

The semicircular canals are three fluid-filled tubes at right angles to one another that sense rotation of the head. Rotation of the head causes the fluid in the canals to move. Depending on the direction the head moves, the fluid movement will be greater in one of the canals than in the others. The canals contain hair cells that respond to this movement of fluid. The hair cells initiate nerve impulses that tell the brain which way the head is moving so that appropriate action can be taken to maintain balance.

If the semicircular canals malfunction, which can occur in an upper respiratory infection or other temporary or permanent disorder, the person's sense of balance may be lost or a false sensation of moving or spinning (vertigo) may develop.

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