what about goosebumps ?

porcupineThere’s one thing that porcupines will always do better than humans: having goosebumps. Ok, ok, we cannot¬†raise our quills when threatened, simply because we do not have quills. But when we have goosebumps, our body hairs behave exactly in the same way as porcupine quills do. Cutis anserina, a definitely less catchy way to call it, consists in the formation of bumps on the skin. The curious thing is that this phenomenon is involuntary ūüôā let’s try to understand how this happens.

goosebumpsA feeling of cold, a sudden strong emotion of¬†fear,¬†pleasure,¬†euphoria¬†and, yes, also¬†sexual arousal… Our body reacts to all these events in the simplest way possible: trying to protect itself. And we cannot control it, since it’s a reflex (click here to read about another reflex typical of human body). In a previous post we learnt an interesting thing about human body thermoregulation: homeostasic processes (that we saw also here) always try to keep our Body Temperature¬†(BT) of 37¬įC despite environment conditions. When outside it’s too cold, our energy losses get more important and our BT lowers too fast. We know that, for example, if we do some physical exercise (even a short run) we’ll warm up again quite fast. This is because the activation of muscles develops that energy needed to warm up the body and restore proper BT conditions. But when a sudden feeling of cold occurs, our skin receptors immediately send this information to the brain via the sympathetic nervous system. Our¬†brain cannot wait for us to take a decision and, as previously said,¬†automatically activates a protective action: shivering.
By doing this, our muscles produce really fast contractions that we cannot control (don’t forget we’re always dealing with a reflex!).

arrector pili muscles

The twitching movements of muscles produce heat, which helps to raise BT. The contraction of the arrector pili muscles, that are the tiny muscles at the base of each hair, pulls the hair erect. In that moment our body acts like that of a porcupine, even if the latter experiences this reflex when threatened (by appearing larger, the animal intimidates enemies).

In exactly the same way, if our¬†jaw muscles begin to shiver, we start chattering our teeth. The mechanism is always the same: BT lowering is detected and an automatic response is activated to raise it up again. In an extremely¬†stressful¬†situation, it is possible to have goosebumps also after experiencing the so-called fight or flight response, when (from this webpage) “the¬†sympathetic nervous system¬†floods the blood with¬†adrenaline¬†(epinephrine), a hormone that speeds up¬†heart rate,¬†metabolism, and body temperature in the presence of extreme stress”. But this is another story that we’ll see later. For tonight, don’t forget to feed your porcupine with a wonderful home-made soup (possibly warm)!

other sources: uno, due e tre

Wristify your body temperature!

Imagine you’re in the bus leading you home. Outside it’s snowing, the bus is stuck in traffic, you’re damn freezing. Well, soon you’ll just have to touch something on your wrist in order to feel warmer almost instantaneously.¬†This magic something is called Wristify and is one of the thousands awesome technological inventions made day by day at MIT. Press and official images can be found on the official webpage of the project. In this post we’ll see its basic working principle.


Technically, Wristify is a¬†thermoelectric bracelet based¬†on the principle that heating or cooling the skin on one part of the body can make the entire body feel warmer or colder.¬†Developed by four MIT engineering students¬†who adopted the motto “thermal comfort, reimagined“, this interesting device is supposed to help¬†cutting the amount of energy currently used to heat or cool entire buildings. Logically, if everyone could be able to autonomously tune their body temperature according to their preferences, there wouldn’t be need to continuously heat, for example, huge rooms for conferences or shopping malls areas. Ideally, in the long term, it would be reasonable to expect significant savings.

Currently at working prototype stage (15 models have been developed up to now), this portable mini-heater looks like a wristwatch. The key difference is the custom copper-alloy-based heat sink¬†on which Wristify’s working principle depends. Readings from embedded thermometers measure external and body temperature. With such information, an automated control system¬†automatically adjusts the intensity and duration of thermal pulses that are delivered to the wrist via the heat sink. Thanks to a lithium polymer battery, the current prototype can run for up to 8 hours. As previously said,¬†the team found that minute, rapid changes in temperature on one part of the human body can affect the whole body. They discovered that a change of 0.1¬į C per second is the minimum rate required to make the entire body feel several degrees warmer or colder (the current prototype is capable of a rate of change of up to 0.4¬į C per second).

The team recently took out the first prize in MIT’s annual Making And Designing Materials Engineering Competition MADMEC (USD 10,000). They plan to use the money to continue development of the device, aiming to develop more advanced algorithms and improve the automation of the thermal pulses.


sources: this, that and another one 

we risk freezing down

Seriously, it’s too hot outside. All of a sudden I’ve turned the heating off in my small apartment, started watering plants daily and begun the countdown for the first bath of 2013!


Inspired by such a summerish weather, I thought it could be interesting to read something about Hypothermia and its causes. Hope this post will help cooling down a bit – but not too much, it wouldn’t be nice to freeze down completely ūüôā

The first notion to know is that of Body Temperature (BT), the temperature that a living being autonomously keeps more or less constant through biologic processes such as¬†homeostasis¬†or¬†thermoregulation. BT is about 37 ¬įC for a human being, 38.5 ¬įC for a pig, 39 ¬įC for cats and cows, between 34 ¬įC and 40 ¬įC for camels and dromedaries, 42 ¬įC for birds (whoa!) and so on… There is a sort of threshold, different for each single species, for the minimum¬†temperature required to allow normal¬†metabolism¬†and body functions. Now, cows hypothermia is for sure an awesome topic and could raise kind of interesting discussion, but we’ll focus on the human being. For a normal healthy man, the threshold value is 35.0 ¬įC. If our core temperature¬†(i.e. “the temperature of an organism at which it is meant to operate”) drops below such 35 ¬įC, we start feeling bad since our body does not like working in suboptimal conditions.

body heat lossWiki says that “Hypothermia usually occurs from exposure to low temperatures, and is frequently complicated by¬†alcohol. Any condition that decreases heat production, increases heat loss, or impairs thermoregulation, however, may contribute”.

That’s the point! We lose our body heat in many ways, as shown in this nice image. Or better, we continouosly¬†exchange our body heat with every single thing that surrounds us in daily life. In a sense, we are nothing more that walking heaters. Our internal mechanisms, normally, are enough to keep a constant BT. But in the case of, for example, prolonged exposure to cold, our body might become unable to replenish the heat that is being lost. As a consequence, a drop in core temperature occurs. This change causes a host of characteristic symptoms (according to the hypothermia degree), such as:

  • shivering,
  • mental confusion (difficulty in speaking, sluggish thinking, and¬†amnesia),
  • muscle mis-coordination,
  • cyanosis (exposed extremities become blue),
  • decreased heart rate, respiratory rate and¬†blood pressure.

If you ever plan to swim or dive in cold water, to explore snowy landscapes, to drink alcohol and smoke outside at night (alcohol and tobacco -> vasodilatation -> sensation of warmth while, instead, heating loss is rapidly increasing), to chase russians in their homeland in 1812 and so on… well, you’d better take your time and think about all the risks you’re going to take.

A subject found in hypothermic conditions needs to be rewarmed. Rewarming can be achieved in three main ways:

  1. warm uppassive external rewarming: the subject is moved to a warm environment and provided with properly insulated dry clothing. Then, their own heat generating ability will be enough to restore proper BT conditions.
  2. active external rewarming: external warming devices, such as warmed forced air or hot water bottles placed in both armpits and groin, are employed to help the subject warming up faster.
  3. active internal rewarming: it involves the use of intravenous warmed fluids, irrigation of body cavities with warmed fluids or inhalation of warm humidified air.

In case of severe hypothermia, extracorporeal rewarming such as via a heart lung machine may reveal to be the fastest (and only) solution.

Watch out also for really hot environments! Hyperthermia, the opposite of hypothermia, can lead to heat exhaustion and heat stroke.

sources: one, two and google images