Category Archives: Physiology

Simplifies the physiology of animals by using object oriented models i.e. wash basins and drinking milkshakes!

Ins & Outs of Fluid balance in Desert Animals (Part 1)

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Maintaining their hydration is a major problem for desert animals. Large mammals e.g. Gemsbok & small mammals e.g. rodents use different strategies to cope with arid conditions. We will discuss the special behavioral or physiological adaptations that have evolved in … Continue reading

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Uncoupled heating: Warthogs lack brown fat & live in burrows.

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One obvious reason why warthogs live in burrows is to escape from their predators. But another important reason is for temperature control and in particular to keep warm in the cold months (1). Temperature in animals is regulated by changes in … Continue reading

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Brain Blood Flow in Owls: why they can turn their heads 270 degrees

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This blog will discuss why the owl twists his head and how it is able to do it without cutting of his brain blood supply. It was triggered by the fascinating new research by Fabian de Kok-Mercado, Michael Habib, Tim Phelps, Lydia … Continue reading

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Hyenas: the “how” of female masculinization (Part 4)

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Ambiguous genitalia at birth can be produce by genetic and/or hormonal causes. Genetic causes e.g. true hermaphrodites with gonads containing both female & male genes are very rare. More frequently ambiguous genitalia are caused by mutations in genes controlling sex hormone metabolism of … Continue reading

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Hyenas: the “how” of female masculinization (Part 3)

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In part 3 we will discuss normal mammalian testosterone metabolism using a simple input/output model. We will first look at its basic biochemistry & its influence on external genital development in the fetus. Finally in part 4, using this basic … Continue reading

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Hyenas: the why of female masculinization (Part 2)

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The disadvantages for the female hyena of having a masculinized urogenital tract when giving birth are clear (see part 1) but are there advantages for the hyena’s society of a having a masculinized and very dominant female? The “why” question … Continue reading

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Hyenas: maternal masculinization makes birth no laughing matter (part 1)

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Birth of their baby is usually fast & uncomplicated in higher primates such as gorillas, chimpanzees, & orangutans. However in man a natural birth is usually prolonged & painful. The evolution of these processes has been discussed in my previous blogs on  … Continue reading

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The key to understanding the neurotoxicity of snake bites: why is the mongoose immune to cobra venom (Part 3)

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In the final post on the snake venom topic we will discuss how the mongoose has been able to overcome the neurotoxic effects of cobra venom. We have learnt how ACh fits into the shape of the specific shape of … Continue reading

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The key to understanding the neurotoxicity of snake & spider bites (Part 2)

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In this blog we will discuss how different neurotoxins (snake & spider) can interfere with nerve impulse conduction & muscle contractions. We will do this using the wash basin model  to see how toxins change the effective ACh concentrations at … Continue reading

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The key to understanding the neurotoxicity of snake & spider bites (Part 1)

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I want to briefly discuss the biochemistry underlying the toxic effects of venoms trying to explain basic concepts with my beloved wash-basin analogy & also the lock & key theory. Snake & spider venom contain various toxic substances. These via … Continue reading

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Birth in Australopithecus, apes, & man: a passage over time (part 3)

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We have in the previous two parts of this 3 part series on the passage of babies through the birth canal briefly discussed the process as well as the differences  in labor between humans & the giant apes. The title … Continue reading

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Birth in Australopithecus, apes, & man: a passage over time (part 2)

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Walking into trouble: birth in higher primates. Birth of their baby is usually fast & uncomplicated in higher primates such as gorillas, chimpanzees, & orangutans. However in man the birth is usually prolonged and obstructed labor a common problem, with … Continue reading

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Birth in Australopithecus, apes, & man: a passage over time (part 1)

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I would like to discuss the differences between the birth of a baby in humans & the great apes e.g. gorillas, chimpanzees, & orangutans. In this part 1 we will first look the normal birth process. In part 2, I … Continue reading

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Not too hot and not too cold: mammals (endotherms) in the Kalahari. (Part 6)

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The Kalahari Desert can get extremely hot in summer & very cold in winter. Large & small mammals in the desert maintain their optimal temperature despite these large changes in ambient temperature. As we have previously discussed in the reptiles behavioral mechanisms … Continue reading

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Not too hot and not too cold: reptiles (ectotherms) in the Kalahari.(Part 5)

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The Kalahari desert can get extremely hot in summer & very cold in winter. Snakes & lizards in the desert have to maintain their optimal temperature despite these large changes in ambient temperature. Behavioral mechanisms play an essential role & when … Continue reading

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Not too hot and not too cold: Thermal stress & how organisms adapt? (part 4)

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Seasonal migrations in terrestrial & aquatic animals & daily choice by mammals of the right time of day for hunting illustrate how changes in temperature influence animal behavior. Temperature greatly affects all organisms & imposes limits on where they can survive … Continue reading

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Not too hot and not too cold: Jargon in heat regulation; Its Greek to me! (Part 3)

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Warm blooded and cool blooded are easily understood terms. Unfortunately in describing heat regulation of different animal species they are not always correct. There are lots of variations in how mammals, birds, reptiles, & fishes regulate their temperatures and thus … Continue reading

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Not too hot and not too cold: temperature regulation in premature babies. (Part 2)

The ins & outs of keeping a  premature  baby warm We will discuss the difficult problem of heat regulation in the preterm human baby because the principles illustrated will help us understand heat regulation in small & large animals in hot & cold environments. Before … Continue reading

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Not too hot & not too cold: temperature regulation in animals (part 1)

The geographical distribution of animals reflects the temperature gradients they can survive in The optimal temperature range can differ markedly in various species and the animals have developed various biochemical, physiological and behavioral  adaptations to maintain their optimal temperature as the … Continue reading

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Introduction to using the Milkshake flow model

As explained earlier I try to simplify difficult concepts by using everyday analogies. These simple objects e.g. milkshakes are repeatedly used. This does obviously sometimes result in “poetic scientific licence”. For example the milk shake, will not only be used to … Continue reading

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The visual cycle (part 2)

The ability to see in the dark depends on an adequate concentration of retinal. The ins and outs of photosenstive cis retinal and its recycling  from trans-retinal are illustrated here. Photo-receptors e.g. the eye, have the ability to convert light’s energy in … Continue reading

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Vitamin A Metabolism: An adequate concentration of vitamin A in its storage depot, the liver depends on the balance between the input and the output. In this example, using the  “wash basin model” to analyse a biological process, note that the concentration of the metabolite … Continue reading

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