Why Does Having a Fever Make You Feel Cold?

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iStock


During fever, why do we feel cold when our body temperature rises?Nicole Van Groningen:

Anyone who has ever had the flu knows that fever isn’t uncomfortable because you feel hot—it’s uncomfortable because you feel freezing cold. You get goosebumps, you’re shivering, you’re piling on the covers.

Fever, also known as pyrexia, is defined as an elevation in body temperature above the normal range due to an increase in the body’s natural set point. Most people associate fever with infections, but fever can also frequently occur with autoimmune diseases, cancer, drug reactions, and even blood clots. Fever is not a direct result of these conditions, but rather a consequence of triggering the body’s inflammatory pathways. One key member of this inflammatory cascade is a group of molecules called pyrogens, which directly interact with the hypothalamus in the brain to produce fever.

The hypothalamus serves as the body’s thermostat. When triggered by pyrogens, the hypothalamus tells the body to generate heat by inducing shivering, goosebumps, and constriction of blood vessels near the surface of the skin. It even causes a subjective feeling of cold, which encourages behavioral responses to raise the body temperature, like reaching for the covers.

All of these things are adaptive when your body temperature falls below its usual set-point (about 98.6 degrees Fahrenheit), which typically occurs in cold weather. But they become abnormal in the setting of fever, when your hypothalamus signals to the body to raise its temperature well above the normal range.

If pyrogens suddenly disappear from the bloodstream, as is the case with intermittent fevers, the hypothalamus all of a sudden senses that things are way too hot, and tells the body to kick in its usual cooling-off mechanisms. That’s why people sweat profusely when their fever “breaks.”

This post originally appeared on Quora. Click here to view.

Why Are Sloths So Slow?

Sloths have little problem holding still for nature photographers.
Sloths have little problem holding still for nature photographers.
Geoview/iStock via Getty Images

When it comes to physical activity, few animals have as maligned a reputation as the sloth. The six sloth species, which call Brazil and Panama home, move with no urgency, having seemingly adapted to an existence that allows for a life lived in slow motion. But what makes sloths so sedate? And what horrible, poop-related price must they pay in order to maintain life in the slow lane?

According to HowStuffWorks, the sloth’s limited movements are primarily the result of their diet. Residing mainly in the canopy vines of Central and South American forests, sloths dine out on leaves, fruits, and buds. With virtually no fat or protein, sloths conserve energy by taking a leisurely approach to life. On average, a sloth will climb or travel roughly 125 feet per day. On land, it takes them roughly one minute to move just one foot.

A sloth’s digestive system matches their locomotion. After munching leaves using their lips—they have no incisors—it can take up to a month for their meals to be fully digested. And a sloth's metabolic rate is 40 to 45 percent slower than most mammals' to help compensate for their low caloric intake. With so little fuel to burn, a sloth makes the most of it.

Deliberate movement shouldn’t be confused for weakness, however. Sloths can hang from branches for hours, showing off some impressive stamina. And because they spend most of their time high up in trees, they have no need for rapid movement to evade predators.

There is, however, one major downside to the sloth's leisurely lifestyle. Owing to their meager diet, they typically only have to poop once per week. Like going in a public bathroom, this can be a stressful event, as it means going to the ground and risking detection by predators—which puts their lives on the line. Worse, that slow bowel motility means they’re trying to push out nearly one-third of their body weight in feces at a time. It's something to consider the next time you feel envious of their chill lifestyle.

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Are Any of the Scientific Instruments Left on the Moon By the Apollo Astronauts Still Functional?

Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Heritage Space/Heritage Images/Getty Images

C Stuart Hardwick:

The retroreflectors left as part of the Apollo Lunar Ranging Experiment are still fully functional, though their reflective efficiency has diminished over the years.

This deterioration is actually now delivering valuable data. The deterioration has multiple causes including micrometeorite impacts and dust deposition on the reflector surface, and chemical degradation of the mirror surface on the underside—among other things.

As technology has advanced, ground station sensitivity has been repeatedly upgraded faster than the reflectors have deteriorated. As a result, measurements have gotten better, not worse, and measurements of the degradation itself have, among other things, lent support to the idea that static electric charge gives the moon an ephemeral periodic near-surface pseudo-atmosphere of electrically levitating dust.

No other Apollo experiments on the moon remain functional. All the missions except the first included experiment packages powered by radiothermoelectric generators (RTGs), which operated until they were ordered to shut down on September 30, 1977. This was done to save money, but also because by then the RTGs could no longer power the transmitters or any instruments, and the control room used to maintain contact was needed for other purposes.

Because of fears that some problem might force Apollo 11 to abort back to orbit soon after landing, Apollo 11 deployed a simplified experiment package including a solar-powered seismometer which failed after 21 days.

This post originally appeared on Quora. Click here to view.

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