Category: science

Why does your voice change as you get older?

Naturally developing voices are capable of incredible variety. And as we age, our bodies undergo two major changes which explore that range. So how exactly does our voice box work, and what causes these shifts in speech?

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The specific sound of a speaking voice is the result of many anatomical variables, but it’s mostly determined by the age and health of our vocal cords and the size of our larynxes. The larynx is a complex system of muscle and cartilage that supports and moves the vocal cords, or, as they’re more accurately known, the vocal folds. Strung between the thyroid and arytenoid cartilages, these two muscles form an elastic curtain that opens and shuts across the trachea, the tube that carries air through the throat. The folds are apart when we’re breathing, but when we speak, they slam shut. Our lungs push air against the closed folds, blowing them open and vibrating the tissue to produce sound. By pushing air faster or slower, we change the frequency and amplitude of these vibrations, which respectively translate to the pitch and volume of our voices. Rapid and small vibrations create high-pitched, quiet tones, while slow, large vibrations produce deep, bellowing rumbles. 

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This process is the same from your first words to your last, but as you age, your larynx ages too. During puberty, the first major shift starts, as your voice begins to deepen. This happens when your larynx grows in size, elongating the vocal folds and opening up more room for them to vibrate. These longer folds have slower, larger vibrations, which result in a lower baseline pitch. This growth is especially dramatic in many males, whose high testosterone levels lead first to voice cracks, and then to deeper, more booming voices, and laryngeal protrusions called Adam’s apples. Another vocal development during puberty occurs when the homogenous tissue covering the folds specializes into three distinct functional layers: a central muscle, a layer of stiff collagen wrapped in stretchy elastin fibers, and an outer layer of mucus membrane. These layers add nuance and depth to the voice, giving it a distinct timbre that sets it apart from its pre-pubescent tones. 

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After puberty, most people’s voices remain more or less the same for about 50 years. But we all use our voices differently, and eventually we experience the symptoms associated with aging larynxes, known as presbyphonia. First, the collagen in our folds stiffens and the surrounding elastin fibers atrophy and decay. This decreased flexibility increases the pitch of older voices.

Ultimately, these anatomical changes are just a few of the factors that can affect your voice. But when kept in good condition, your voice box is a finely tuned instrument, capable of operatic arias, moody monologues, and stirring speeches.

From the TED-Ed Lesson Why does your voice change as you get older? – Shaylin A. Schundler

Animation by @rewfoe

teded: Despite what many may think, handedness…

teded:

Despite what many may think, handedness is not a choice. It can be predicted even before birth based on the fetus’ position in the womb. So, if handedness is inborn, does that mean it’s genetic? 

Well, yes and no. Identical twins, who have the same genes, can have different dominant hands. In fact, this happens as often as it does with any other sibling pair.

From the TED-Ed Lesson Why are some people left-handed? – Daniel M. Abrams

Animation by TED-Ed

Happy Left Hander’s Day!

Proud to be a lefty? Grab yourself a Left Hand, Best Hand t-shirt, designed by TED-Ed! 

Poison dart frogs have evolved a resistance to…

Poison dart frogs have evolved a resistance to their own toxins. These tiny animals defend themselves using hundreds of bitter-tasting compounds called alkaloids that they accumulate from consuming small arthropods like mites and ants. One of their most potent alkaloids is the chemical epibatidine, which binds to the same receptors in the brain as nicotine but is at least ten times stronger. 

An amount barely heavier than a grain of sugar would kill you. So what prevents poison frogs from poisoning themselves? Think of the molecular target of a neurotoxic alkaloid as a lock, and the alkaloid itself as the key. When the toxic key slides into the lock, it sets off a cascade of chemical and electrical signals that can cause paralysis, unconsciousness, and eventually death. But if you change the shape of the lock, the key can’t fit. For poison dart frogs and many other animals with neurotoxic defenses, a few genetic changes alter the structure of the alkaloid-binding site just enough to keep the neurotoxin from exerting its adverse effects.

From the TED-Ed Lesson Why don’t poisonous animals poison themselves? – Rebecca D. Tarvin

Animation by Giulia Martinelli

Why don’t poisonous animals poison themselves?

In fact, how do any toxic animals survive their own secretions? The answer is that they use one of two basic strategies: securely storing these compounds or evolving resistance to them. Snakes employ both strategies – they store their flesh-eating, blood-clotting compounds in specialized compartments that only have one exit: through the fangs and into their prey or predator and they have built-in biochemical resistance. Rattlesnakes and other types of vipers manufacture special proteins that bind and inactivate venom components in the blood.

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Poisonous and venomous animals aren’t the only ones that can develop this resistance: their predators and prey can, too. The garter snake, which dines on neurotoxic salamanders, has evolved resistance to salamander toxins through some of the same genetic changes as the salamanders themselves.

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That means that only the most toxic salamanders can avoid being eaten— and only the most resistant snakes will survive the meal. The result is that the genes providing the highest resistance and toxicity will be passed on in greatest quantities to the next generations.

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As toxicity ramps up, resistance does too, in an evolutionary arms race that plays out over millions of years. This pattern appears over and over again. Grasshopper mice resist painful venom from scorpion prey through genetic changes in their nervous systems. Horned lizards readily consume harvester ants, resisting their envenomed sting with specialized blood plasma. And sea slugs eat jellyfish nematocysts, prevent their activation with compounds in their mucus, and repurpose them for their own defenses.

From the TED-Ed Lesson Why don’t poisonous animals poison themselves? – Rebecca D. Tarvin

Animation by Giulia Martinelli

Hallucinatory experiences are much more closel…

Hallucinatory experiences are much more closely tied to ordinary perception than we once thought.

We know from fMRI studies that hallucinations activate the same brain areas as sight, areas that are not activated by imagination. Many other hallucinations, including smells, sights, and sounds, also involve the same brain areas as real sensory experiences. Because of this, the cerebral cortex is thought to play a part in hallucinations. This thin layer of grey matter covers the entire cerebrum, with different areas processing information from each of our senses. But even in people with completely unimpaired senses, the brain constructs the world we perceive from incomplete information. 

For example, our eyes have blind spots where the optic nerve blocks part of the retina. When the visual cortex processes light into coherent images, it fills in these blind spots with information from the surrounding area. Occasionally, we might notice a glitch, but most of the time we’re none the wiser. When the visual cortex is deprived of input from the eyes, even temporarily, the brain still tries to create a coherent picture, but the limits of its abilities become a lot more obvious. 

By studying hallucinations, we stand to learn a great deal about how our brains construct the world we see, hear, smell, and touch. As we learn more, we’ll likely come to appreciate just how subjective and individual each person’s island universe of perception really is.

For more on the science and research of hallucinations, check out the TED-Ed Lesson What causes hallucinations? – Elizabeth Cox

Animation by Nerdo

An elderly woman named Rosalie was sitting in …

An elderly woman named Rosalie was sitting in her nursing home when her room suddenly burst to life with twirling fabrics.

Through the elaborate drapings, she could make out animals, children and costumed characters. Rosalie was alarmed, not by the intrusion, but because she knew this entourage was an extremely detailed hallucination. Her cognitive function was excellent, and she had not taken any medications that might cause hallucinations. Strangest of all, had a real-life crowd of circus performers burst into her room, she wouldn’t have been able to see them: she was completely blind.

Rosalie had developed a condition known as Charles Bonnet Syndrome, in which patients with either impaired vision or total blindness suddenly hallucinate whole scenes in vivid color. These hallucinations appear suddenly, and can last for mere minutes or recur for years. We still don’t fully understand what causes them to come and go, or why certain patients develop them when others don’t.

For more on the science and research of hallucinations, check out the TED-Ed Lesson What causes hallucinations? – Elizabeth Cox

Animation by Nerdo

teded: Did you know that dogs smell in stereo?…

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Did you know that dogs smell in stereo? The ability to smell separately – with each nostril – helps them determine from what direction smells come. This is just one of the many ways that dogs’ wonderfully developed noses make them so scent-savvy.

From the TED-Ed Lesson How do dogs “see” with their noses? – Alexandra Horowitz 

Animation by Provincia Studio

Fun Fact Friday!

Fun Fact Friday!

Did you know that only one in four folks smell something funky in their pee after eating asparagus? Are you part of that unlucky 25%?

From the TED-Ed lesson How do we smell – Rose Eveleth?

Animation by Igor Coric

The Genius of Marie Curie

teded:

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Growing up in Warsaw in Russian-occupied Poland, the young Marie Curie, originally named Maria Sklodowska, was a brilliant student, but she faced some challenging barriers. As a woman, she was barred from pursuing higher education, so in an act of defiance, Marie enrolled in the Floating University, a secret institution that provided clandestine education to Polish youth. By saving money and working as a governess and tutor, she eventually was able to move to Paris to study at the reputed Sorbonne. here, Marie earned both a physics and mathematics degree surviving largely on bread and tea, and sometimes fainting from near starvation. 

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In 1896, Henri Becquerel discovered that uranium spontaneously emitted a mysterious X-ray-like radiation that could interact with photographic film. Curie soon found that the element thorium emitted similar radiation. Most importantly, the strength of the radiation depended solely on the element’s quantity, and was not affected by physical or chemical changes. This led her to conclude that radiation was coming from something fundamental within the atoms of each element. The idea was radical and helped to disprove the long-standing model of atoms as indivisible objects. Next, by focusing on a super radioactive ore called pitchblende, the Curies realized that uranium alone couldn’t be creating all the radiation. So, were there other radioactive elements that might be responsible?

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In 1898, they reported two new elements, polonium, named for Marie’s native Poland, and radium, the Latin word for ray. They also coined the term radioactivity along the way. By 1902, the Curies had extracted a tenth of a gram of pure radium chloride salt from several tons of pitchblende, an incredible feat at the time. Later that year, Pierre Curie and Henri Becquerel were nominated for the Nobel Prize in physics, but Marie was overlooked. Pierre took a stand in support of his wife’s well-earned recognition. And so both of the Curies and Becquerel shared the 1903 Nobel Prize, making Marie Curie the first female Nobel Laureate.

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In 1911, she won yet another Nobel, this time in chemistry for her earlier discovery of radium and polonium, and her extraction and analysis of pure radium and its compounds. This made her the first, and to this date, only person to win Nobel Prizes in two different sciences. Professor Curie put her discoveries to work, changing the landscape of medical research and treatments. She opened mobile radiology units during World War I, and investigated radiation’s effects on tumors.

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However, these benefits to humanity may have come at a high personal cost. Curie died in 1934 of a bone marrow disease, which many today think was caused by her radiation exposure. Marie Curie’s revolutionary research laid the groundwork for our understanding of physics and chemistry, blazing trails in oncology, technology, medicine, and nuclear physics, to name a few. For good or ill, her discoveries in radiation launched a new era, unearthing some of science’s greatest secrets.

From the TED-Ed Lesson The genius of Marie Curie – Shohini Ghose

Animation by Anna Nowakowska

In 1898, Marie and Pierre Curie discovered rad…

In 1898, Marie and Pierre Curie discovered radium. Claimed to have restorative properties, radium was added to toothpaste, medicine, water, and food. A glowing, luminous green, it was also used in beauty products and jewelry. It wasn’t until the mid-20th century we realized that radium’s harmful effects as a radioactive element outweighed its visual benefits.

Unfortunately, radium isn’t the only pigment that historically seemed harmless or useful but turned out to be deadly. That lamentable distinction includes a trio of colors and pigments that we’ve long used to decorate ourselves and the things we make: white, green, and orange.

To learn about these other ‘deadly colors’, watch the TED-Ed Lesson History’s deadliest colors – J. V. Maranto

Animation by Juan M. Urbina