Category Archives: Physiology

Cephalopods don’t need a mirror test – they are mirrors themselves .

PZ probably already knows about this, but I found this discovery of super-reflective skin cells in squid, cuttlefish and octopus quite amazing!

Hanlon’s team discovered that the bottom layer of octopus skin, made up of cells called leucophores, is composed of a translucent, colourless, reflecting protein. “Protein reflectors are very odd in the animal kingdom,” says Hanlon, who is a zoologist. What’s even more odd is just how reflective these proteins are — they reflect all wavelengths of light that hit at any angle. “This is beautiful broadband reflection,” Hanlon told the Materials Research Society at their meeting in Boston last month. The result is a material that looks startlingly white in white light, and blue in the bluish light found beneath the waves. “These cells also match the intensity of the prevalent light,” says Hanlon’s research associate Lydia Mathger. All this helps the creatures to blend into their surroundings.

Hat-tip: Matt Dowling

Why do Elephants Have Large Ears?

It’s been almost three months since Arunn, in the comments to this post, promised to write a post about the thermoregulatory function of big, flappy elephant ears. Finally, he’s gotten to it, and now you can go and read his post. A perfect entry for the next edition of Panta Rei, which needs your entries ASAP.

Does Tryptophan from turkey meat make you sleepy?

Does Tryptophan from turkey meat make you sleepy?Well, it’s Thanksgiving tomorrow night so it’s time to republish this post from last year, just in time for the ageless debate: does eating turkey meat make you sleepy? Some people say Yes, some people say No, and the debate can escalate into a big fight. The truth is – we do not know.
But for this hypothesis to be true, several things need to happen. In this post I look at the evidence for each of the those several things. Unfortunately, nobody has put all the elements together yet, and certainly not in a human. I am wondering…is there a simple easily-controlled experiment that people can do on Thursday night, then report to one collecting place (e.g., a blog) where someone can do the statistics on the data and finally lay the debate to rest? Any ideas?
Also, I will add the comments that the post originally received and I hope for new comments from people with relevant expertise. Is Trp Hxlse really a rate-limiting enzyme? If so, why gavaging chickens and rats with Try increases plasma melatonin? Is it different in humans? You tell me!
(originally posted on November 25, 2005)

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Is Mothra making a comeback due to global warming?

Giant Insects Might Reign If Only There Was More Oxygen In The Air:

The delicate lady bug in your garden could be frighteningly large if only there was a greater concentration of oxygen in the air, a new study concludes. The study adds support to the theory that some insects were much larger during the late Paleozoic period because they had a much richer oxygen supply.

More on Antioxidants

I see that I was the only one answering this week’s Ask The ScienceBlogger question (so far). Perhaps these two new studies will inspire some of my SciBlings to add their own thoughts:
Everybody Dance: The Energy You Use Won’t Shorten Your Life:

The theory that animals die when they’ve expended their lifetime allotment of energy may be reaching the end of its own life, according to a study presented at The American Physiological Society conference, Comparative Physiology 2006. However, the longitudinal study leaves open a newer form of the theory — that antioxidants help prolong life by limiting the damage that oxidative stress can cause to cells.

Naked Mole-Rat Unfazed By Oxidative Stress:

The long-lived naked mole-rat shows much higher levels of oxidative stress and damage and less robust repair mechanisms than the short-lived mouse, findings that could change the oxidative stress theory of aging.

New study on evolution of vision

For easy-to-understand quick look at the evolution of vision I have to refer you to these two posts by PZ Myers, this post of mine, and these two posts by Carl Zimmer.
Now, armed with all that knowledge, you will curely appreciate the importance of this new study:
Compound Eyes, Evolutionary Ties:

Biologists at the University of California, San Diego have discovered that the presence of a key protein in the compound eyes of the fruit fly (which glow at center due to a fluorescent protein) allows the formation of distinct light gathering units in each of its 800 unit eyes, an evolutionary change to an “open system” that enabled insects to make significant improvements in visual acuity and angular sensitivity. In contrast, beetles (shown surrounding the fruit fly), bees and many mosquito species have the light-gathering units fused together into a “closed system.”
In a paper published in this week’s early online edition of the journal Nature, the scientists report that one of three proteins needed to form these light gathering units is present in the visual system of fruit flies, house flies and other insects with open eye systems, but conspicuously absent in beetles, bees and other species with closed systems. The researchers showed that the loss of this protein, called “spacemaker,” can convert the eyes of fruitflies–which normally have open eye systems–into a closed one. In contrast, the introduction of spacemaker into eyes with a closed system transformed them into an open one.
Charles Darwin was so enamored by the intricate complexity of the eye that he wondered how it could have evolved. “These results help illustrate the beauty and power of evolution and show how ‘little steps’–like the presence of a single structural protein–can so spectacularly account for major changes in form and function,” said Charles Zuker, a professor of biology and neurosciences at UCSD and a Howard Hughes Medical Institute investigator, who headed the research team.

Viagra keeps you up at night

No, not (just) that part – your brain. A new study shows that a single dose of Viagra makes symptoms of sleep apnea worse. And sleep deprivation resulting from sleep apnea may be one of the reasons why you may need Viagra in the first place. What a vicious circle! What a conundrum! Sleepdoctor has the goods.

A Question

My sister in law is an artist and is writing a proposal for funding a project. She intends to use red clay to make some figurines. She has heard an old story that the composition of red clay is similar to the composition of the human body and is wondering how much off the mark is that statement. I am pretty sure that at the level of molecules/compounds the difference is huge, but I am not sure how big is the difference if one breaks down the chemical composition down to elements/atoms. I suspect that carbon and hydrogen may be close, but how about nitrogen, oxygen or, even more difficult for me to find out: copper, phosphorus, iron, sulphur, manganese, etc.? Do you know?

Are cryptochromes involved in magnetoreception in migratory birds?

Scientists discover molecule behind birds’ magnetic sense:

“Some birds, notably migratory species, are able to detect the Earth’s magnetic field and use it to navigate. New results from a team of Franco-German researchers suggest that light-sensitive molecules called cryptochromes could be the key to the birds’ magnetic sense.

They did not suggest it – they tested a 10-year old hypothesis.

Cryptochromes are photoreceptors which are sensitive to blue light, and they are involved in a number of processes linked to the circadian cycle, such as growth and development.

Caution: cryptochromes have different functions in different organisms. They are very closely related to photolyases, molecules involved in DNA repair. They are photopigments in plants, but have no circadian function in them. They are involved in circadian phototransduction in insects, but are not pigments and are not clock genes in them. They are core circadian genes in vertebrates, but are not pigments in them. So, we have to be careful when dealing with such a jack-of-all-trades.

Birds’ ability to detect magnetic fields is affected by light; this ‘sixth sense’ only works properly in the presence of blue or green light, while light of other wavelengths disrupts the magnetic sense.

Do you know how much I hate the phrase “sixth sense’?

The scientists realised that the cryptochromes could well be involved in the perception of the magnetic field, as they have all the physical and chemical properties needed, notably the absorption of blue and green light and the formation of ‘radical pairs’ – molecules which respond to magnetic fields. Crucially, the retina of birds’ eyes is rich in cryptochromes.
Unable to test their hypothesis on migratory birds, the researchers turned to a laboratory plant, Arabidopsis thaliana, with similar properties. It is known that the activation of their cryptochromes by blue light influences the behaviour of these plants; for example it inhibits the growth of the hypocotyle (stem).

This is creative, but poses a problem that I mentioned above – in different environments (i.e. inside the bodies of different organisms with different genomes), cryptochromes assume different functions.

To determine whether the magnetic field influences the function of the cryptochromes, researchers from France’s National Centre for Scientific Research (CNRS) and universities in Frankfurt and Marbourg grew the plants in the presence of blue and red light and magnetic fields of varying strengths. They found that increasing the magnetic field only increases the inhibition of the growth of the hypocotyle in the presence of blue light. When red light is used, the plant uses other photoreceptors called phytochromes, and the growth of the hypocotyle is not affected by changes in the magnetic field. Furthermore, mutant plants which have no cryptochromes are also insensitive to changes in the magnetic field.

This is a nice piece in the puzzle, but nothing conclusive yet, of course.

The study shows for the first time that in plants, the work of the cryptochromes is affected by magnetic fields and suggests that the mechanisms of magnetic field perception in plants, and by extension in migratory birds, use the same photosensitive molecules. The researchers also suggest that, as cryptochromes have been strongly conserved throughout evolution, all biological organisms could have the ability to detect magnetic fields, even if they do not use them.”

The phrase “and by extension” worries me for the reasons I noted above.
As for all organisms detecting magnetic fields – yes, decades of research show that most can, from bacteria to, perhaps, even humans. However, this does not mean that cryptochromes are the magnetosensory molecules in all of them, or even that the radical-pair model of magnetoreception applies to all organisms.
It is well established that many organisms do not require the presence of blue-green light in order to orient by he magnetic fields. It is also known that many organisms, from bacteria through salmon to pigeons, possess miniscule crystals of feromagnetite. In bacteria, those form a chain running through the posterior medial line of the cell. In salmon and pigeons, they are embedded inside cell membranes of the dendrites of the trigeminal nerve.
So, cryptochromes may be involved in some way in magnetic sense of some organisms. Extrapolating any broader (i.e., it is the only mechanism; cryptochromes are the main element of the mechanism; this mechanism works in all organisms) is unlikely to be correct. So, the press release is hypoing the work beyond what it really shows. It is good. Actually, it is really cool. But the press release soured me on it.
For an excellent (and quite current) review of the topic, see this review (pdf) and for a moer lay-audience oriented, also quite current article, see this article on The Science Creative Quarterly.

Friday Weird Sex Blogging – Cooling The Balls

What?….

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Why All Lard Is White

Why Piglets Shudder To Keep Warm:

Brown fat helps newborn mammals maintain their body temperature by burning fat, which converts into heat. The protein UCP1 (Uncoupling Protein 1) has a key role in this energy conversion, which takes place in the cell mitochondria.
No brown fat or UCP1 protein has been found in domesticated pigs, however. In their study, Berg and colleagues show that the UCP1 gene was shut down about 20 million years ago in an ancestor of the wild boar. They identified four different mutations, each of which would be sufficient to knock out the function of the protein.
This ancestor of pigs thereby lost the ability to use brown fat to maintain body temperature after birth. A reasonable explanation for this is that brown fat was not essential during a period in the evolution of pigs, in which they lived in a warm climate, says Leif Andersson, who directs the research team.
The ancestor of the domesticated pig, the wild boar, is the only pig that lives in cold climates. All other species inhabit tropical or subtropical climates. The wild boar has compensated for the loss of brown fat by a series of adaptations for survival in a cold climate. It is the only hoofed animal that builds a den when it is time to give birth see, and its young shudder to maintain their body temperature. In modern pig production, heat lamps are used to help the newborn piglets retain their body temperature.
The findings show that an important biological function can be lost if it is not vital to life during a period in the evolutionary history of a species; and that if the living conditions once again change, compensatory mechanisms can be developed. The findings we present are fully consistent with the theory of evolution. An important trait can be lost if it is not absolutely necessary to life during the development of a species, says Leif Andersson.

Should we rewrite the textbook chapters on voltage-gated potassium channels?

Correct me if I am wrong, but I think this is really ground-breaking:
Study Finds Brain Cell Regulator Is Volume Control, Not On/off Switch:

He and his colleagues studied an ion channel that controls neuronal activity called Kv2.1, a type of voltage-gated potassium channel that is found in every neuron of the nervous system.
“Our work showed that this channel can exist in millions of different functional states, giving the cell the ability to dial its activity up or down depending on the what’s going on in the external environment,” said Trimmer. This regulatory phenomenon is called ‘homeostatic plasticity’ and it refers, in this case, to the channel protein’s ability to change its function in order to maintain optimal electrical activity in the neuron in the face of large changes within the brain or the animal’s environment. “It’s an elegant feedback system,” he added.
——-snip——–
Using this technique, postdoctoral fellow Kang-Sik Park revealed 16 sites where the protein is modified by the cell by via addition of a phosphate group. Further study–in which each of the sites is removed to reveal its role in modulation– followed by careful biophysical analyses of channel function by postdoctoral fellow Durga Mohapatra, revealed that seven of these sites were involved in the regulation of neuronal activity. Since each site can be regulated independently on the four channel subunits, the neuron can generate a huge (>1018) number of possible forms of the channel.
Using this mechanism, Kv2.1 channels are quickly modified, even mimicking the activity of other potassium ion channels. “The beauty of doing it with a single protein is that it is already there and can change in a matter of minutes. It would take hours for the cell to produce an entirely different potassium channel,” Trimmer explained.
Based on these results, Trimmer and his colleagues hypothesize that parts of the Kv2.1 channel protein interact in ways that make it either easier or harder for it to change from closed to open. The protein, they believe, can exist in either loose states that require low amounts of energy, or voltage, to change from one state to another or a locked-down state that requires lots of energy (high voltage) to open or close. The number and position of phosphate molecules are what determine the amount of voltage required to open the channel.

It just makes intuitive sense. It appeals to my aesthetic sense as well. And it is a great example of the power of evolution.
Potassium-Channel-2-2004.JPG

So, elephants actually run (leave the ground with all four feet at the same time)

Have You Ever Seen An Elephant … Run?:

Dr John Hutchinson, a research leader at the UK’s Royal Veterinary College (RVC), has already shown that, contrary to previous studies and most popular opinion, elephants moving at speed appear to be running. Now with funding from the Biotechnology and Biological Sciences Research Council (BBSRC) his team is using Hollywood-style motion capture cameras combined with MRI and CT scans of elephants to build 3D computer models of elephant locomotion to show the forces and stresses at work on muscles, tendons and bones.
The research team has been working with elephants at UK wildlife and safari parks and will shortly travel to Africa and Thailand to study wild animals. Fifteen temporary markers are placed on the elephants’ joints and the animals then move past a motion capture camera, recording at 240 frames per second, at varying speeds. Back in the lab the researchers can then use the footage to reconstruct the rotations of the elephants’ joints on a computer, creating a 3D stick model of the animal.
The computer models are being used to establish how limb structure relates to elephant locomotion and to determine finally if elephants really can run – or in scientific terms, at some point do they have all their feet off the ground at the same time? Dr Hutchinson said: “We are particularly interested how elephants coordinate their limbs and working out which joints contribute most to the length and frequency of their steps. In examining whether elephants truly run or not we need to understand what limits their top speed. Is it the tendons and muscles having to withstand the impact of 7 tonnes of elephant or is it something else?”

Read the whole thing. I love this kind of stuff! I remember when, back in the late 1980s, I first saw a study (from Bulgaria, I believe) done like this – of a horse jumping over a fence. Way cool!
Next step – how do elephants fly! Certainly you’ve heard the old true-life anecdote:
Two elephants are sitting on a tree. A third elephant flies by. The first elephant turns to the second elephant and says: “Hmmm, I bet her nest is close by”
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Why hibernating animals occasionally wake up?

One of the several hypotheses floating around over the past several years to explain the phenomenon of repeated wake-up events in hibernating animals although such events are very energy-draining, is the notion that the immune system needs to be rewarmed in order to fend off any potential bacterial invasions that may have occured while the animal was hibernating:

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Mokie-Koke

When I saw this article in SEED Maagazine, I had only one thought – Mokie-Koke!
Readers of science fiction know what I am talking about. I was reminded of “The Merchant’s War“, the 1984 sequel to the 1952 brilliant dystopia “The Space Merchants“, the book that beat “1984” and “Brave New World” in its accuracy of prediction. The initial novel – one of the all-time-greats of the genre, was written by Frederick Pohl and Cyril Kornbluth. The sequel, 32 years later, was written by Pohl alone.
It’s been at least 15 years since I last read The Merchants’ War, but if I remember correctly, each megacorporation (one of the very few ruling the world of the future) manufactures its own brands of a coke-like drink, a candy bar and cigarettes. These three products are designed to be addictive in themselves, but also, to induce cravings for each other. So, drinking Mokie-Koke makes you want to light up a cigarette (made by the same company), which in turn makes you want the candy bar, eating which makes you crave a Moki-Koke. Thus, workers/citizens of the future world are forever loyal to the Corporation-State.
The SEED article highlights some recent science showing that such connections between different commercial products are a reality – although not by corporate design. Alcohol and nicotine are in cahoots with each other – when you have a drink, you are more likely to want to smoke (and it feels better) and vice versa. I have certainly noticed this in myself and others. However, I have also noticed (since I am not a big alcohol consumer, but a big caffeine consumer), that Coke and cigarettes tend to induce cravings for each other (as does coffee – this is anecdotal, but a well known anecdote). Chocolate (any brand) makes me want to drink Coke which makes me want to light one up.
This should not be that surprising, as the brain tends to deal with all of its addictions in pretty much the same place using pretty much the same neurochemicals. So, being addicted to gambling, pornography or Internet will also make you drink and smoke? Perhaps….

Teaching Biology Lab – Week 2

Teaching Biology Lab - Week 2This is by far the most popular of the four installments in this series because it contains the nifty puzzle exercise. Click on the spider-web-clock icon to see the comments on the original post.
Just like last week, I have scheduled this post to appear at the time when I am actually teaching this very lab again. If there are any notable difference, I’ll let you know in the afternoon.

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Hot Peppers – Why Are They Hot?

Blogging on Peer-Reviewed Research

Some plants do not want to get eaten. They may grow in places difficult to approach, they may look unappetizing, or they may evolve vile smells. Some have a fuzzy, hairy or sticky surface, others evolve thorns. Animals need to eat those plants to survive and plants need not be eaten by animals to survive, so a co-evolutionary arms-race leads to ever more bizzare adaptations by plants to deter the animals and ever more ingenious adaptations by animals to get around the deterrents.
One of the most efficient ways for a plant to deter a herbivore is to divert one of its existing biochemical pathways to synthetise a novel chemical – something that will give the plant bad taste, induce vomiting or even pain or may be toxic enough to kill the animal.
But there are other kinds of co-evolution between plants and herbivores. Some plants need to have a part eaten – usually the seed – so they can propagate themselves. So, they evolved fruits. The seeds are enveloped in meaty, juicy, tasty packages of pure energy. Those fruits often evolve a sweet smell that can be detected from a distance. And the fruits are often advertised with bright colors – red, orange, yellow, green or purple: “Here I am! Here I am! Please eat me!”
hot_pepper_fresno.jpg
So, the hot peppers are a real evolutionary conundrum. On one hand, they are boldly colored and sweet-smelling fruits – obvious sign of advertising to herbivores. On the other hand, once bitten into, they are far too hot and spicy to be a pleasant experience to the animal. So, what gives?
Back in 1960s, Dan Johnson had an interesting proposal he dubbed “directed deterrence” which suggested that some plants may make choices as to exactly which herbivores to attract and which to deter. Hot peppers are prime candidates for such a phenomenon. What is hot in peppers is capsaicin, a chemical that elicits a sensation of pain when it bind the vanilloid receptors in the nerve endings (usually inside the mouth) of the trigeminal nerve. As it happens, all mammals have capsaicin receptors, but it was found, relatively recently, that birds do not.
To test that hypothesis, Josh Tewksbury used two variants of hot peppers – one very hot (Capsicum annuum) and the other with a mutation that made it not hot at all (Capsicum chacoense) – and offered both as meals to rodents (packrats and cactus mice) and to birds (curve-billed thrashers).
All species ate the sweet kind about equally. When Josh offered them identically prepared meals made out of the hot stuff, the two rodents refused to eat it while the birds happily munched on it.
hot%20peppers%20graph.JPG
The study appeared in 2001 in Nature (pdf) and I saw Josh give a talk about it at that time as he was joining our department to postdoc with Dr.Nick Haddad. While my lab-buddy Chris and I gave him a lot of grief in the Q&A session on his lenient criteria of what constitutes a “hungry animal” (he needed them to be hungry for the feeding tests), still the main conclusions of the study are OK.
More importantly, it really happens in nature. Mammals avoid hot peppers out in Arizona where Josh studied them (and made videos of their behavior), but the birds gorged on peppers. When he analyzed the droppings of rodents and birds fed peppers, he saw that seeds that passed through avian intestinal tracts were fully fertile, while seeds eaten by mammals were chewed, crushed, broken or semi-digested and not fertile at all.
Additionally, the thrashers tend to spend a lot of time on fruiting shrubs of different kinds. While there, they poop. The hot pepper seeds in the droppings germinate right there and this is an ideal shady spot for them to grow.
What a great example of (co)evolutionary adaptations. Next time on this blog, the second Big Question: Why do we like to eat hot peppers?
Related: Hot Peppers

Why Is Cornea Clear?

Scientists Discover Why Cornea Is Transparent And Free Of Blood Vessels, Allowing Vision:

The key, say the researchers, is the unexpected presence of large amounts of the protein VEGFR-3 (vascular endothelial growth factor receptor-3) on the top epithelial layer of normal healthy corneas.
According to their findings, VEGFR-3 halts angiogenesis (blood vessel growth) by acting as a “sink” to bind or neutralize the growth factors sent by the body to stimulate the growth of blood vessels.

Nice, except that “Why” is an evolutionary question: they should have used “How” throughout the press release.

Friday Weird Sex Blogging – Corkscrewing

You really think I am going to put this above the fold? No way – you have to click:

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Why fish in the Arctic seas do not freeze?

Here is a wonderful new study that demonstrates that the antifreeze substances in notothenioid fish are not produced by the liver as was believed for decades and taught in Comparative Physiology courses. Instead, it is produced in two places: most of it in the exocrine pancreas, and somewhat less in a portion of the stomach at the entry of the esophagus:

…..AFGPs are secreted into the intestinal lumen where they protect the intestinal fluid from being frozen by ice crystals that come in with seawater and food. Internal fluids in notothenioids are about one-half as salty as seawater. While seawater reaches its freezing point at -1.91 degrees Celsius, fish fluids freeze at about -1 degree Celsius. These species dwell in water that rarely rises above the freezing point and is regularly filled with ice crystals.
From the intestine, the AFGPs are, apparently, absorbed into the blood. This hypothesis is based on the near-identical composition and abundance of AFGPs found in the fish serum.

They also looked at other groups of Arctic fish, in some of which liver does produce antifreeze susbtances. In those species, the antifreeze was now also found to be secreted by the stomach and pancreas as well.

Daily Rhythms in Cnidaria

Blogging on Peer-Reviewed Research

The origin and early evolution of circadian clocks are far from clear. It is now widely believed that the clocks in cyanobacteria and the clocks in Eukarya evolved independently from each other. It is also possible that some Archaea possess clock – at least they have clock genes, thought to have arived there by lateral transfer from cyanobacteria.[continued under the fold]

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Viagra – The Future, part 2

From L.A.Times (you’ll have to click – I am purposefully citing out of context for humorous purposes):

Military researchers are considering a study to see whether Viagra could help soldiers function better at high altitudes.

High altitudes? How high? Who/what needs to get that high?

None of the cyclists reported an erection during the trials, she said.

Self-reporting, self-schmeporting! What do you think they were thinking about while “cycling”?

“If we send a group of guys into the mountains of Afghanistan, they need to be able to deal with the altitude,” Fulco said.

Eh, as if our boys over there were not rambunctious enough, and sex-deprived by definition. Why do you think they used to but bromine in soldiers’ tea?

Translated!

My post about sleep has been translated by Davide ‘Folletto’ Casali into Italian, and posted on his blog. You can see the translated post here. If you can read Italian (and even you do not – just for fun, and to reward his hard work), go and look around his blog.

Sixth Sense? Give Me A Break!

ClockWeb%20logo2.JPG
This was my December 29, 2004 post written in reaction to media reports on the “sixth sense” in animals, avoiding the tsunami by climbing to high ground:

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ClockTutorial #1 – What Is Chronobiology

ClockWeb%20logo2.JPG This is the first in a series of posts from Circadiana designed as ClockTutorials, covering the basics of the field of Chronobiology. It was first written on January 12, 2005:

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Melatonin in Human Milk

Blogging on Peer-Reviewed Research

Melatonin is secreted in human mother’s milk with a daily rhythm – high at night, undetectable during the day (see the figure under the fold):

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BIO101 – Lecture 7 – Physiology: Coordinated Response

Last week we looked at the organ systems involved in regulation and control of body functions: the nervous, sensory, endocrine and circadian systems. This week, we will cover the organ systems that are regulated and controlled. Again, we will use the zebra-and-lion example to emphasize the way all organ systems work in concert to maintain the optimal internal conditions of the body:

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BIO101 – Lecture 6 – Physiology: Regulation and Control

It is impossible to cover all organ systems in detail over the course of just two lectures. Thus, we will stick only to the basics. Still, I want to emphasize how much organ systems work together, in concert, to maintain the homeostasis (and rheostasis) of the body. I’d also like to emphasize how fuzzy are the boundaries between organ systems – many organs are, both anatomically and functionally, simultaneously parts of two or more organ systems. So, I will use an example you are familiar with from our study of animal behavior – stress response – to illustrate the unity of the well-coordinated response of all organ systems when faced with a challenge. We will use our old zebra-and-lion example as a roadmap in our exploration of (human, and generally mammalian) physiology:

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Teaching Update

This Monday night I taught lecture #7 of the 8-week Intro Biology course (adult education at a community college). First, I gave them their Exam #2 (on Diversity, see my lecture notes on those topics here, here and here). The flat distribution of the first exam has now turned bimodal: some students are making big improvements and I will probably end with a nice cluster of As and Bs, while other students are falling and may end up with a few Ds and Fs, with nobody left in-between.
Then, I continued with the physiology topics. The week before, I covered nervous, sensory, endocrine and circadian systems. This week, I covered the muscular, circulatory, respiratory, excretory and reproductive systems. How does one teach all of those systems in such short time? By sticking to the basics of the basics, of course, skipping a lot of stuff that textbook deems important. I am late at writing and posting here my lecture notes for those two lectures, but once I do, you’ll see the strategy I took, putting emphasis on how all those systems are intertwined and work together in solving challenges posed by the environment.
Next week is the final exam on anatomy and physiology. The students will then give oral presentations on an organ system each. Unlike me, they will keep the systems separate from each other, and focus entirely on the human body. One student will do the immune system which I did not have time to cover at all. This will be an opposrtunity for me to add teh information that I could not sqeeze into my formal lecture before.
Last week, they also gave short presentations on diseases. I have to say that I learned a lot about Shingles, Grave’s disease, Herpes Simplex, Osteoporosis, etc. They did a great job, all of them. Finally, they will do the evaluations and the class will be over. Later this summer I will teach the lab only, then in Fall it’s back to both the lecture and the lab again.
Technorati Tag: teaching-carnival

Obligatory Reading of the Day

Amanda reviews the lies about sex and contraception that are peddled by the Catholic church in their pre-marital classes:
Pandagon goes undercover the lazy way on a Catholic anti-contraception seminar
and
Pandagon goes undercover the lazy way on a Catholic anti-contraception seminar, Pt. II

BIO101 – Lecture 5: Introduction to Anatomy and Physiology

After three lectures on the basics, a long lecture on diversity, and a hard first exam, it is time to turn our attention to anatomy and physiology for the rest of the course:

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