Please register and log-in to create and edit pages

User Tools

    Please register and log-in to create and edit pages

Site Tools


Main Menu

Main menu
Click categories to expand

Other categories


A-Z listingplugin-autotooltip__plain plugin-autotooltip_bigA-Z listing

This is an alphabetical index of all content pages.


Also see

Importance Ratingsplugin-autotooltip__plain plugin-autotooltip_bigImportance ratings

In a departure from the usual Wiki format, Wikenigma assigns 'Importance Ratings' to some pages.

The idea is to separate articles which are considered (by the editors) to cover exceptionally important unknown issues from those which (although also u…

Newsplugin-autotooltip__plain plugin-autotooltip_bigNews

[ newest at the top ]

• Mar. 2021 : Many thanks to the The British Library, which has now begun permanently archiving the contents of Wikenigma.

• Jan. 2021 : A milestone of 600 unknown articles has been reached.

• Oct. 2020 : A milestone of 500 unknown article…

Contactsplugin-autotooltip__plain plugin-autotooltip_bigContacts

Use this form to send a message to Wikenigma . . . [ * note: all fields must be completed ]

Legalplugin-autotooltip__plain plugin-autotooltip_bigLegal

Content in general

Please note that in common with other publicly editable wikis, this website is not responsible for content posted by the public. Nevertheless, the ongoing editing process should be able to remove unsuitable content in a reasonable time. If you…

Donate/Sponsorplugin-autotooltip__plain plugin-autotooltip_bigDonate to Wikenigma . . .

The best way to donate is by adding new original content !

That can either be by contributing to an existing article, or by creating a new page with an as-yet-unlisted 'Known Unknown'.

Any registered user can create content.

Registerplugin-autotooltip__plain plugin-autotooltip_bigRegistration

At present, only registered users can create and edit articles.

If you'd like to register as a contributor, please request a password.

When filling in the form, make sure you supply a valid e-mail address, as the login password will be sent to that addre…


Wikenigma supports:


Utilities
rss / xml feed
sitemap file
A-Z listing (archived)plugin-autotooltip__plain plugin-autotooltip_bigA-Z listing (archived)

This is an older, partial A-Z listing intended for search engines only.

Last updated : March 2021

For an up-to-date list see A-Z listing in the Main Menu

'Abracadabra' etymology

Acamprosate

Acrocyanosis

Acupuncture

Attention-Deficit / Hype…

Wikenigma - an Encyclopaedia of Unknowns Wikenigma - an Encyclopaedia of the Unknown Science

Sense of smell - Olfaction

It's known that humans have about 10 cm2 of olfactory epithelium, with roughly 5 million sensory neurons.

Smells are detected due to the activation of neurons by airbourne volatile chemicals and particles. Different chemicals affect different groups of neurons, which, after cerebral processing, lead to the impression of 'smell'.

The exact neurprocessing mechanism is still unclear.

Since any one receptor is responsive to various odorants, and there is a great deal of convergence at the level of the olfactory bulb, it may seem strange that human beings are able to distinguish so many different odors. It seems that a highly complex form of processing must be occurring; however, as it can be shown that, while many neurons in the olfactory bulb (and even the pyriform cortex and amygdala) are responsive to many different odors, half the neurons in the orbitofrontal cortex are responsive to only one odor, and the rest to only a few.
It has been shown through microelectrode studies that each individual odor gives a particular spatial map of excitation in the olfactory bulb. It is possible that the brain is able to distinguish specific odors through spatial encoding, but temporal coding must also be taken into account. Over time, the spatial maps change, even for one particular odor, and the brain must be able to process these details as well.
Source: Wikipedia

Also unclear is the number of odours which humans can differentiate. The current estimates are in the region of 1 Trillion, but the figures are currently under dispute. See : The number of olfactory stimuli that humans can discriminate is still unknown eLife. 2015; 4: e08127.


Also see : Tasteplugin-autotooltip__plain plugin-autotooltip_bigTaste

Current theory lists five main taste receptor categories : sweetness, bitterness, sourness, saltiness, and umami. Source: Wikipedia

The physical mechanisms for detection of each of these main flavour types have been extensively investigated, and the correspondi…


    Share this page :

X

Dear reader : Do you have any suggestions for the site's content?

Ideas for new topics, and suggested additions / corrections for old ones, are always welcome.

If you have skills or interests in a particular field, and have suggestions for Wikenigma, get in touch !


Or, if you'd like to become a regular contributor . . . request a login password. Registered users can edit the entire content of the site, and also create new pages.

( The 'Notes for contributors' section in the main menu has further information and guidelines etc.)

Show another (random) page

DOKUWIKI IMPLEMENTATION DESIGN BY UNIV.ORG.UK APRIL 2021