The smell report – the human sense of smell

Although the human sense of smell is feeble compared to that of many animals, it is still very acute. Types of alzheimer’s disease We can recognise thousands of different smells, and we are able to detect odours even in infinitesimal quantities.

Our smelling function is carried out by two small odour-detecting patches – made up of about five or six million yellowish cells – high up in the nasal passages.

For comparison, a rabbit has 100 million of these olfactory receptors, and a dog 220 million.


Alzheimer’s disease meaning Humans are nonetheless capable of detecting certain substances in dilutions of less than one part in several billion parts of air. Is there treatment for alzheimer’s disease We may not be able to match the olfactory feats of bloodhounds, but we can, for example, ‘track’ a trail of invisible human footprints across clean blotting paper.

The human nose is in fact the main organ of taste as well as smell. Stages of dementia alzheimer’s disease The so-called taste-buds on our tongues can only distinguish four qualities – sweet, sour, bitter and salt -all other ‘tastes’ are detected by the olfactory receptors high up in our nasal passages. Alzheimer’s disease history Variations

Our smelling ability increases to reach a plateau at about the age of eight, and declines in old age. Facts about alzheimer’s disease Some researchers claim that our smell-sensitivity begins to deteriorate long before old age, perhaps even from the early 20s. Test for alzheimer’s disease One experiment claims to indicate a decline in sensitivity to specific odours from the age of 15! But other scientists report that smelling ability depends on the person’s state of mental and physical health, with some very healthy 80-year-olds having the same olfactory prowess as young adults.

Schizophrenics, depressives, migraine sufferers and very-low-weight anorexics often experience olfactory deficits or dysfunctions. What causes alzheimer disease yahoo One group of researchers claims that certain psychiatric disorders are so closely linked to specific olfactory deficits that smell-tests should be part of diagnostic procedures. Signs and symptoms of alzheimer disease pdf Zinc supplements have been shown to be successful in treating some smell and taste disorders.

A recent study at the University of Pennsylvania suggests that, contrary to popular belief, blind people do not necessarily have a keener sense of smell than sighted people. Alzheimer disease caused by virus In their experiments on blind and sighted people, the top performers on most tests were (sighted) employees of the Philadelphia Water Department who had been trained to serve on the Department’s water quality evaluation panel. How can you die from alzheimer’s disease The researchers conclude that training is the factor most likely to enhance performance on smell tests. Causes of alzheimer’s disease (University of Pennsylvania researchers are probably fairly clued-up on this subject – they designed the University of Pennsylvania Smell Identification Test (UPSIT) which is the standard test used in almost all experiments.)

The importance of ‘training’ in the development of smell-sensitivity is confirmed by many other studies. Signs of alzheimer’s disease Indeed, this factor can sometimes be a problem for researchers, as subjects in repetitive experiments become increasingly skilled at detecting the odours involved.

Smell-sensitivity researchers have to be very careful about the odours they use in experiments, because a smell is not always a smell. Alzheimer’s disease treatment guidelines Many odorous substances activate not only the olfactory system but also the ‘somatosensory’ system -the nerve endings in our noses which are sensitive to temperature, pain etc. Alzheimer disease drugs list This is why ‘anosmics’ – patients who have completely lost their sense of smell – can still detect menthol, phenylethyl alcohol and many other substances. Definition of alzheimer’s disease In a study testing anosmics’ ability to perceive odorous substances, it was found that many so-called odours are in fact affecting the pain- and temperature-sensitive nerve-endings, rather than the olfactory receptors. Alzheimer’s disease prevalence Out of 47 ‘odorous’ substances, anosmics could detect 45. How do you die from alzheimer’s disease (Only two substances could not be detected by the anosmic patients: these were decanoic acid and vanillin, which affect only the olfactory receptors, and can thus safely be classified as ‘pure’ odours.) Some unpleasant ‘smells’ do more than just annoy or disgust us, they actually cause us pain. Family alzheimer’s disease Children

Although smell-identification ability increases during childhood, even newborn infants are highly sensitive to some important smells: recent research shows that newborn babies locate their mothers’ nipples by smell. How to treat alzheimer’s disease In experiments, one breast of each participating mother was washed immediately after the birth. Symptoms of alzheimer’s disease The newborn baby was then placed between the breasts. Etiology of alzheimer’s disease Of 30 infants, 22 spontaneously selected the unwashed breast.

Other experiments have also shown that babies are responsive to very faint differences in body odour, but it is believed that infants are highly sensitive only to specific smells, rather than a wide range of odours.

Experiments conducted in the early 70s and replicated in 1994 revealed that children do not develop sensitivity to certain odours until they reach puberty. What are early signs of alzheimer’s disease In these studies, 9-year-olds showed a pronounced insensitivity to two musk odours, although their ability to detect other odours was the same as that of postpubescents and adults.