Sunday, November 12, 2006

Biological control systems: (attempts in) Understanding the Nature's way

For anyone who has watched the evening twilight, dark clouds and the flock of wild geese fly across the sky, it is not difficult to figure out the relative motion among the birds and among the clouds...even from a moving vehicle. This may seem to be such a simple everyday experience that few really think twice about it, but this is considered one of the toughest problems in image processing. Posed in a more scientific terms, the problem is how can you distinguish the relative motion between two frames in a noisy environment? Any one who has fiddled with an SLR knows how difficult it is to get a perfect picture under varying environmental conditions. A slight tremor in hand can ruin a picture. However, our eyes do it without much concious effort in part due to the excellent in built control system that exactly regulates the amount of light entering the eye and focuses the image on retina. Other aspect of the built in control system is that it corrects for the movement of the head with an interface to the vestibular organ in the ear. Such fascinating control systems are part of every biological system governing almost every aspect of life...Respiration control, blood pressure and thermo regulation, circadian rhytms, chemical reaction in cells and many more. In this article we will discuss about the light regulation system in eye and a little bit about thermo regulation.
Let there be light:
As we think about the basic parts of our eyes (Fig. 1), we observe that they consist of cornea, lens, iris, ciliary muscle, and retina connected by optic nerve to brain. Functioning of eye depends on the amount of light entering the eye (Light intensity) and focusing of the image on retina. Two independent systems control these two aspects of vision.
Firstly, amount of light is regulated by the opening of pupil which is controlled by the two muscle groups in iris. Sphincter (controlled by cranial circuit which also controls the ciliary muscles which help in focusing) and dilator muscles (controlled by symphathetic nervous system of spinal cord: I wonder whether this is the reason why people look for dilated pupils when looking for vital signs in an unconcious person). Dilator muscles causes the pupil to open more whereas sphincter muscles cause the pupil to close as they contract. Acting together they control the opening of pupil in such a way that there is always an optimum light intensity falling over retina. This is a feedback control system where the pupil opening is the controlled variable( via the sphincter and dilatory muscles) while the system output is the light intensity on retina. The input is the light intensity of the environment and the control system aims to achieve a perfect pupil opening that optimizes the light intensity on retina under varying environmental conditions. By testing the pupil opening with narrow light beams (so that they do not have an effect on the light intensity regardless of pupil opening and thus disconnecting this feedback loop) it was found that the system is a very stable low gain system. Further, it is to be noted that this is not the only way eye responds to light intensity. There is another system on retina itself which adjust the signals to the optic fiber based on light intensity (reason why we can see the outlines a little better in a dark room after a few seconds of adaptation).

For more information about eye: http://www.arn.org/docs/glicksman/eyw_041001.htm

How about a little warmth as well: Maintianing optimum body temperature is vital for survival as most of the enzyme catalyzed reactions rates depend critically on it. Temperatures of cold blooded animals follows that of its surroundings (poikilothermy; one of the reasons such animals can be found mostly in tropical and temperate regions of the world) while that of warm blooded animals is tightly regulated (of course allowing for diurnal variations based on circadian rhytms) and is known as homeothermy. However, not everything is in pure black and white as is the rule in nature. During hibernation warm blooded animals such as hedgehog, bat and dormouse become coldblooded (to conserve their energy?) and this is referred to as heterothermy.
(More info on mammalian temperature regulation here: http://animals.about.com/cs/mammals/a/aa061601a.htm and Wikipedia entry:
http://en.wikipedia.org/wiki/Body_temperature )


It can be observed that for the thermoregulation system: the controlled variable is the heat producing/conserving mechanism while the output is body temperature. The input variable is the environment temperature and the temperature of the body. Now one can ask, where should be temperature be measured so that it best represents the body temperature? on the surface of the body? or closer to the internal organs? As anyone would point out, skin temperature is not the best place to estimate the body temperature, just as placing the thermometers on the outside of a building whose interior temperature has to adjusted is a bad idea. However, it is always a good idea to open/close the windows based on outside temperature while firing up the heater must be based on both outside and inside temperature. Something similar happens in our bodies too....the internal mechanism activates the heat producing/ conserving mechanism; while the case of conserving heat by closing windows regardless of inside temperature can be related to closure of sweat glands in cold weather regardless of internal temperature. This way the amount of energy expended to maintain the temperature can also be minimized. more often than not, such multiple optimization schemes are inbuilt in biological control systems.
Ref: Optimality principles in biology: Robert Rosen, Butterworths, London. 1967. [An Excellent book that deals with the issues we discussed in chapter 9]

In the next article, we hope to discuss how seemingly extremely complex branching pattern of blood circulation system can be derived from optimality arguments (again the above book has an excellent analysis).


26 comments:

Prashanth said...

I'm interesting in knowing how these control mechanisms relate to the biological pathways. But I guess that would be going too deep into the subject...

Prashanth said...

Grrrr.... didn't see the typo until today and I just *have* to correct it...


interested*
NOT
"interesting"

atma_tripta said...

No problem. I didnt notice it when I was replying earlier either. Anyway, coming to the answer yes it has been investigated and I will try to post something on that soon.

Anonymous said...

[url=http://community.bsu.edu/members/buy+online+Viagra.aspx]Viagra without perscription[/url]

[url=http://eterporno.ru/prostitutki-g-hmelnickiy.php]проститутки г хмельницкий[/url]
[url=http://eterporno.ru/pamyatnik-prostitutke-praga.php]памятник проститутке прага[/url]

[url=http://pc.eterporno.ru/poznakomlus-s-semeynoy-paroy.php]познакомлюсь с семейной парой[/url]
[url=http://pc.eterporno.ru/putany-g-permi.php]путаны г перми[/url]

[url=http://pv.eterporno.ru/trans-intim-dosug.php]транс интим досуг[/url]
[url=http://pv.eterporno.ru/znakomstva-g-usinsk.php]знакомства г усинск[/url]

[url=http://px.eterporno.ru/dvorovaya-shluha.php]дворовая шлюха[/url]
[url=http://px.eterporno.ru/g-marks-znakomstva.php]г маркс знакомства[/url]

[url=http://pz.eterporno.ru/mama-doch-prostitutki.php]мама дочь проститутки[/url]
[url=http://pz.eterporno.ru/gde-poznakomitsya-s-geem.php]где познакомиться с геем[/url]

Anonymous said...

Интересно написано....но многое остается непонятнымb

Anonymous said...

I want not concur on it. I assume nice post. Specially the title attracted me to be familiar with the unscathed story.

Anonymous said...

Amiable brief and this post helped me alot in my college assignement. Say thank you you for your information.

Firesales Costa Rica said...

Thank you for sharing information. It is quite useful for us also. I always love to read such type of things.

costa rica vacations said...

This blog is very interesting, i liked because show many good new ideas.

Green Parks said...

Hello.. Firstly I would like to send greetings to all readers. After this, I recognize the content so interesting about this article. For me personally I liked all the information. I would like to know of cases like this more often. In my personal experience I might mention a book called Green Parks Costa Rica in this book that I mentioned have very interesting topics, and also you have much to do with the main theme of this article.

Anonymous said...

[color=green][size=24]секс знакомства vkontakte[/size][/color]
мамба ру секс знакомства секс знакомства в ливнах объявления секс знакомства ставрополь секс знакомства в ейске
секс знакомства для геев map24 секс знакомства в петропавловске камчатском
секс знакомства в туле бесплатные секс знакомства в орле полностью бесплатный сайт секс знакомств знакомства сумы секс
секс знакомства в днепропетровской области map19 сайт секс знакомств без регестрации
кемеровские секс знакомства
секс знакомства омск без регистрации
зарегистрироваться на сайте секс знакомств
секс видео знакомства без регистрации
Девушки
секс знакомства кишинев
секс знакомства в киселевске
Интим
вэб секс знакомства
секс знакомства одинцово
секс знакомства на 1 ночь
бесплатные секс знакомства в контакте

Anonymous said...

Audi 90, 2005 Bristol Fighter 88400 1996 Chevrolet Suburban 6.2л, 2003 Daewoo Rezzo $41600 2008 Ирак angola-hotels2009.info Август Vector W8 Twin Turbo, 1993 г.в. Minelli Artemis Apts Side Stone Palace Novotel Lombok Coggiola T Rex, 2002 Casa Bonita Mazda Xedos 6, $52800, 1991 Иран Villa Vumark Caterham Super Seven 4.2л, $29100, 2008 г.в. Kiris Sun 5* Август 21 Комментарии на: BELVEDERE MEDULIN 3* Geely Beauty Leopard 7.4л, $27800, 2006 monako-resort.info Nissan Stanza 7.8л, $87700, 1999 г.в. слово

Web desing in miami said...

I can't believe in this blog essence, I think you always are innovating and doing a excellent job here. I have been completely agreed with you in this special topic

Miami computer rentals said...

I like your blog, is very interesting what you wrotte before so I can only say that you have a lot of knowledge and you have a lot of things that I want to know and learn, thanks for share all your good things...

logo design said...

I think it is very cruel that some people do not care about the environment1 The billboard is nice but it could be placed wherever else least on a tree.

glass dining table said...

hi there i stumbled upon your site searching around the web. I wanted to say I like the look of things around here. Keep it up will save for sure.

Anonymous said...

секс знакомства + в грозном проститутки московская область интим услуги белебей знакомства с толстыми девушками ижевск секс знакомства discussion интим досуг в г курске знакомства лисбиянок беломорские шлюхи секс Камышлов снегурочка шлюха ливны знакомства секс секс знакомства петропавловск казахстан женщины любящие анал и куннилингус бесплатные секс знакомства липецк forum

сексзнакомства бельгия

research writtin services said...

Cool server. A lot of useful information, even too much. I wish him continued prosperity.

pay per head said...

Wow, nice post,there are many person searching about that now they will find enough resources by your post

site said...

Really useful material, lots of thanks for your post.

Anonymous said...

Once you found the most impressive template, you’re sure to create highly competitive brochures for your business. server games. Never forget to make an extensive online research. pocket pc vpn client cisco

Anonymous said...

In this method of printing, a thick metal plate is used to stamp your personalization. The dentist may rejoice at the end of the procedure, but it is not because of the pain they will have inflicted on you, but rather on the success of the procedure: as there are simply too many things that could have gone wrong. freepops . ssl. There’s a lot more to experience. Early personal computer games often needed a keyboard for game play, or more commonly, required the user to buy a separate joystick with at least one button., gold toe and socks. Hire open source developer for open source development that provides efficient expert service providers for multiple service benefits and business solutions. ssh client for unix

Anonymous said...

For kids it’s really important to provide play areas where they can enjoy the best with their toys and books., chicago private detective. When a person wears aligners one's teeth can look larger. That said, color rendition is still pleasing and realistic. idolforums media network neurox photography zone. These charges have made it very hard for businesses to operate smoothly. network local printer

Anonymous said...

Its like you read my mind! You appear to grasp
a lot about this, like you wrote the book in
it or something. I believe that you simply could do with a few p.
c. to pressure the message home a little bit, but instead of that, this is excellent blog.
A great read. I will certainly be back.

my page: hemorrhoid treatments

Anonymous said...

http://krawindaibull.tk/ind/anketa24997.htm Проститутки M. Красные ворота - Индивидуалка Саша, Район ЦАО, +7 (985) 349-52-42
http://bhakfocadeath1975.tk/ind/anketa86189.htm Проститутки M. Аэропорт - Индивидуалка Жасмин, Район Аэропорт, +7 (968) 684-69-72
http://deticomta1974.tk/ind/anketa85026.htm Проститутки M. Университет - Индивидуалка Beverly, Район ЗАО,Раменки, +7 (968) 540-29-61
http://jockinsrinti.tk/ind/anketa79375.htm Проститутки Индивидуалка sofia, +7 (968) 836-18-83
http://rambdacountcus.tk/ind/anketa81154.htm Проститутки M. Медведково - Индивидуалка Альбина, Район СВАО, +7 (968) 822-77-59

проститутки ростова порно

Anonymous said...

I rarely leave comments, but i did some searching and wound up here
"Biological control systems: (attempts in) Understanding the Nature's way".
And I do have 2 questions for you if it's allright. Is it just me or does it give the impression like a few of the responses appear like they are written by brain dead folks? :-P And, if you are posting on other social sites, I'd
like to follow everything fresh you have to post.

Would you make a list of the complete urls of all your community sites like your linkedin profile,
Facebook page or twitter feed?

My webpage metabolic rate calculator