#24 Why do we cry while chopping onions? (English)

Why do we cry while chopping onions?

The tears you shed when chopping onions aren't emotional ones. That leaves two other categories of tears: basal and reflexive. Basal tears are the ones that hang around our eyes and eyelids to act as a lubricant so that leaves us with the final option: reflex tears. The lachrymal glands above the eyelids regulate the release of tears. In the case of reflex crying, an external irritant, such as dust or smoke, triggers nerve endings in the cornea to communicate with the brain stem. The brain registers the irritation in the eye then alerts the lachrymal gland to stimulate tear production to flush away the invader.  Since onions are part of the plant genus Allium they absorb sulfur in the earth, which helps form a class of volatile organic molecules called amino acid sulfoxides. These sulfoxides trigger tears when onions are chopped. As we chop up an onion, it releases lachrymatory-factor synthase enzymes. These catalysts cause the chemical chain reaction that ends with you tearing up. These enzymes react with the sulfoxides and convert them into sulfenic acid. Sulfenic acids are highly unstable and rearrange into a compound called syn-propanethial-S-oxide. When syn-propanethial-S-oxide enters the air around our faces and approaches our eyes, it evokes the reflexive tear response. Multiple nerve endings in the cornea register the sensation of the syn-propanethial-S-oxide as a substance that could harm our eyes, therefore the brain stem phones the lachrymal glands and the tears commence.

Friendly tip:

Chew gum while you chop onions! J

#23 Borborygmi (English)

Why do our stomachs growl?

Stomach growling can be explained by a closer look at how the digestive system functions. The digestive system is essentially a long tube that starts at the mouth and ends at the anus. This tube connects with the various organs and passages that play important roles in digestion. The digestive system moves food through peristalsis. This process can be defined as waves of muscle contractions that move and push the contents continually downward. In addition to moving your meal along its digestive path, these contractions also help churn food, liquid and different digestive juices together. Stomach growling is a result of this process. Most people believe that when your stomach growls it means you’re hungry, however this is not the case. It just so happens that growling can occur at any time but it just becomes quieter when there’s food in your stomach or small intestine. If this is so, then why are the muscle contractions that digest food happening if your stomach is empty? The reason has to do with hunger and appetite. About two hours after your stomach empties itself, it begins to produce hormones that stimulate local nerves to send a message to the brain. The brain replies by signaling for the digestive muscles to restart the process of peristalsis. First, the contractions sweep up any remaining food that was missed the first time around and then the vibrations of an empty stomach make you hungry. Muscle contractions will come and go about every hour, generally lasting 10 to 20 minutes, until you eat again. However if you are experiencing excessive grumbling it may be a sign of an upset stomach

 

Fun fact:

The technical name for the noises made by a grumbling stomach is borborygmi. The term comes from the Greek word borborugmos, an example of onomatopoeia. Borborygmi illustrates what stomach growling might sound like in word form.

#22 Why is the human brain wrinkled? (English)

Why is the human brain wrinkled?

Researchers found that the particular pattern of the ridges and crevices of the brain's convoluted surface (gyri and sulci) depends on two simple geometric parameters: the gray matter's growth rate and its thickness. Along with these physical constraints, genes also have a role in determining the brain's shape. Genes regulate how neurons increase rapidly and migrate to their destinations. All mammal species have similar layering in the cortex (brain’s outer layer,) but only large mammals have one that is folded. A folded brain surface has a greater surface area than a smooth one, which means a greater power for processing information. The white matter of the brain is made up primarily of axon tracts, the long, spindly appendages of some brain cells, whereas the gray matter is mostly neuron cell bodies and non-neuron brain cells called glial cells. 

Did you know that?

·        Lack of oxygen in the brain for 5-10 minutes leads to permanent brain damage

·        Your brain keeps developing until your late 40s

·        Your brain uses 20% of the total oxygen and blood in your body

·        When awake the human brain produces enough electricity to power a small light bulb

·        60% of your brain is fat

·        The smell of chocolate increases theta brain waves which triggers relaxation

·        When you learn something new the structure of your brain changes

 

 

This is a comparison with a typical brain and Einstein’s brain. The absence of the parietal operculum from Einstein’s brain may have allowed a part of his brain to grow wider than normal. Also, his lower parietal lobe (which is responsible for mathematical thought, visuospatial cognition, and imagery of movement) was 15% larger than average. Then, what is the parietal oerculum? The parietal operculum processes information from many of the senses like touch.



 

 

 

 

 

 

 

 

 

Sujin and Aoife's Joint Project #2

#21 What happens when you swallow gum? (English)

What happens when you swallow gum ?

What is gum made of?

 Gum was originally made from the latex sap of the sapodilla tree. This sap was called chicle. There are other natural gum bases: sorva and jelutong. Sometimes beeswax or paraffin(used to make candles) is used as a gum base. After World War II, synthetic rubber to replace most natural rubber in chewing gum. The chewing gum contains sweeteners, flavouring, and softeners. Softeners are ingredients such as glycerin or vegetable oil. They blend other ingredients and help prevent the gum from becoming hard or stiff.

Latex Sap of the Sapodilla Tree

Sorva

 

 

 

 

 

 

What happens when you swallow gum?

Have you ever wondered what really happens when you swallow gum? Then you’ve probably heard that it stays in your stomach for SEVEN years! Right? Wrong.

Your digestive system treats the gum like any other food. Some parts of gum are broken down by the digestive juices in your stomach. Any nutrients your body can use are saved. The rest is pushed through your digestive system.  

However, there is one part of gum that cannot be digested, the gum base. Gum base consists of chemicals that scientists use to make the gum chewy. These chemicals resist digestion and instead the body moves it along the digestive process until it is eventually eliminated. It would usually take about two days to digest and eliminate any gum you have swallowed.

Even though swallowing gum is harmless, you should try not to as swallowing large amounts of gum on a regular basis could lead to digestive problems.

 

Sujin and Aoife's Joint Project #1

#20 Human Nutrition (English)

HUMAN NUTRITION

Nutrition is the taking in of nutrients which include organic substances and ions, containing raw materials or energy for growth and tissue repair, and then absorbing and assimilating them. A balanced diet should consist of all six nutrients including fiber. These nutrients should be in reasonable proportions. The total energy content of the food should be about the same as the total energy the person uses each day. Energy is measured in kilojoules.  

Humans need the following nutrients:
 

- Carbohydrates

-  Fats

-  Proteins

-  Vitamins

-  Minerals

-  Water

Why do humans need nutrients?

1.       Energy

2.       Building materials to build the cells in our body

3.       To provide us with chemicals used to help metabolic reactions

Carbohydrates

The carbohydrates with the smallest and simplest molecules are sugars. A sugar molecule contains three elements – carbon, hydrogen and oxygen. Glucose is an example of a simple sugar (monosaccharide) meaning it is made up of a single ring of carbon atoms. Complex sugars (disaccharides) are sugars with bigger molecules made up of two rings joined together. Sugar molecules can link together to form huge molecules made up of chains of hundreds of sugars. These big molecules are known as polysaccharides and include starch, glycogen and cellulose.

Carbohydrates provide us with energy. The carbohydrate molecules that we eat are taken into every cell in our bodies in the form of glucose. Inside these cells the energy in the glucose is released and changed into a form that our cells can use. This process is called respiration.

Proteins

Proteins are made up of many small molecules called amino acids. Amino acids contain five elements. These are carbon, hydrogen, oxygen, nitrogen and sometimes sulfur.

Proteins are needed to build new cells so they are important for growth and repair. They build new tissues, antibodies, enzymes, hormones and other compounds.

Fats

Fats are sometimes known as lipids. Fats that are liquid at room temperature are known as oils. A fat molecule is made up of two kinds of smaller molecules – glycerol and fatty acids. Like carbohydrates, fats contain carbon, hydrogen and oxygen.

Fat is needed for energy and for making cell membranes. Fat is especially useful for energy as it contains twice as much energy per gram as carbohydrates. The stored fat underneath your skin is useful as heat insulation.

Saturated fats are found in animal products and processed foods, such as meats, dairy products and chips. The chemical structure of a saturated fat is fully saturated with hydrogen atoms, and does not contain double bonds between carbon atoms. They are bad for your heart.

Unsaturated fats, on the other hand, are found foods such as nuts, avocados, and olives. They are liquid at room temperature and differ from saturated fats in that their chemical structure contains double bonds. Additionally, studies have shown that unsaturated fats are also heart-healthy fats.

 

Vitamins

Vitamins are organic substances that we need in only very small amounts to help some of the chemical reactions inside our cells take place. For example vitamin C and vitamin D. Vitamin C acts as an antioxidant, helping to protect cells from the damage caused by free radicals. Vitamin D is needed for health and to maintain strong bones. It does so by helping the body absorb calcium from food and supplements.

Minerals

This means that minerals are needed for the body to work properly, for growth and development, and overall, for maintaining normal health. For example iron and calcium. Iron is needed for making hemoglobin. Hemoglobin carries oxygen around our bodies. Calcium is required for making teeth and bones as well as to help blood clot.

 

 

 

 

 

Water

 

Water acts as a solvent meaning I allows many different substances to dissolve in it. It transports substances around the body and is also a reactant in many metabolic reactions. Water keeps body temperature normal, lubricates and cushions your joints, protects your spinal cord and other sensitive tissues and gets rid of wastes.

 

Fiber

Fiber is needed in our diet as well however it is not considered as a nutrient. Fiber normalizes bowel movements, helps maintain bowel health, lowers cholesterol levels and helps control blood sugar levels. Insufficient amounts of fiber can lead to constipation. A good example of food high in fiber are lentils.

 

Food tests

 

 

 

 

 

Deficiency diseases

Name	Lack of	Symptoms
Scurvy	Vitamin C	Bad gums (teeth can fall out), fatigue, pain in joints
Rickets	Vitamin D and calcium	Delayed growth, muscle weakness, pain in spine, pelvis and legs
Anemia	Iron	Fatigue, headaches, shortness of breath

 

#19 Drugs (English)

Drugs

What are drugs?

We can define a drug as a substance taken into the bod that modifies or effects chemical reactions in the body. When most people hear the word ‘drug’ they automatically think of substances like cocaine or heroin. Yes, those are drugs however there are four different types of drugs; stimulants, depressants, painkillers and hallucinogens.

What are stimulants?

Stimulants are substances that increase brain activity. This includes nicotine, caffeine and ecstasy. Some short term effects are exhaustion, apathy and the depression that follows the original high. It is this immediate and lasting exhaustion that leads the user to want the drug again. This can lead to addiction. Stimulants also have long term effects. Repeated high doses of some stimulants over a short period of time can lead to feelings of hostility or paranoia.

What are depressants?

Depressants do the opposite of stimulants by slowing down brain activity. The most common example of a depressant is alcohol. Short term effects include slow pulse and breathing, lowered blood pressure, poor concentration, confusion, fatigue, disorientation, slurred speech, fever and addiction. Higher doses can cause impairment of memory, irritability, paranoia, and suicidal thoughts. However, some people experience the opposite of the intended effect, such as agitation or aggression. Depressants have many long term effects too. Tolerance to many depressants can develop rapidly, with larger doses needed to achieve the same effect. The user, trying to reach the same high, may raise the dose to a level that results in coma or death by overdose. As a dependency on the drug increases, cravings, anxiety or panic are common if the user is unable to get more. When the user tries to get off the drug withdrawal symptoms include insomnia, weakness and nausea.

What are painkillers?

Painkillers block nerve impulses and in addition to this can also produce a high. The most powerful painkillers are called opioids. The most commonly abused opioid painkillers include oxycodone, hydrocodone, meperidine, hydromorphone and propoxyphene. Oxycodone is as powerful as heroin and affects the nervous system the same way. Hydrocodone is used in combination with other chemicals and is available in prescription pain medications as tablets, capsules and syrups. Meperidine (Demerol) and hydromorphone (Dilaudid) come in tablets and propoxyphene (Darvon) in capsules, but all three have been known to be crushed and injected, snorted or smoked.

What are hallucinogens?

Hallucinogens alter what we hear and see such as cannabis or LSD. Almost all hallucinogens contain nitrogen and are classified as alkaloids. Many hallucinogens have chemical structures similar to those of natural neurotransmitters. While the exact mechanisms by which hallucinogens exert their effects remain unclear, research suggests that these drugs work, at least partially, by temporarily interfering with neurotransmitter action or by binding to their receptor sites.

 

Drug classification

Some drugs are legal while others are illegal, or must only be prescribed by a doctor. Some prescription drugs are mistreated and taken for recreational use, rather than for medical reasons. They become illegal under these circumstances. Illegal drugs are classified from Class A to Class C. Class A drugs are the most dangerous, with the most serious penalties for possession or dealing. Class B drugs are the second most dangerous and class C are the least dangerous, with the lightest penalties, but this does not mean they are safe to use. 

Alcohol

As you now know alcohol is a depressant as it slows down the activity of the brain. In some countries drinking alcoholic drinks is common while in others it is forbidden. Alcohol is quickly absorbed through the walls of the stomach and is then quickly transported all over the body in the blood. When it reaches the brain it slows down reflex reactions by reducing the rate at which neurons can conduct nerve impulses and pass them from one neuron to another. This is why drinking and driving is highly forbidden since drivers are unable to respond quickly. A very high proportion of injuries and deaths come from car accidents where the driver has been drinking.

Smoking

The image shows the comparison of healthy lungs to lungs of those who smoke. Cigarette smoke is made of nicotine, tar, particulates and carbon monoxide. The nicotine is what makes smoking addictive. It affects the brain and makes people feel more relaxed. As well as this it affects the circulatory system by increasing the rate at which the heart beats and increasing blood pressure. People who smoke are more likely to suffer from heart disease than non-smokers. Tar in cigarette smoke can cause cancer. The chemicals in tar affect the cells that line the passage ways leading to the lungs, and also the cells in the lungs themselves. This may cause the cells to lose the ability to control their division which results in uncontrollable division forming a lump called a tumor which can cause cancer. Tar and carbon monoxide also affect the cilia and goblet cells that line the trachea and the bronchi. The carbon monoxide causes the cilia to stop working and in a heavy smoker the cilia may completely disappear. The smoke makes the goblet cells work harder producing more and more mucus and as there are no cilia to sweep it up the mucus trickles down into the lungs where it collects, making the person cough. The constant coughing can damage the delicate walls of the alveoli which eventually break down preventing oxygen from easily diffusing from the alveoli to the blood. Particulates cause irritation since they aren’t stopped by the malfunctioning cilia leading to more damage of the alveolar walls.  

#18 Enzymes in the Human Body 人体中的酶 (Chinese)

食物中的营养物质怎样才能进入人体细胞中呢？水、无机盐、维生素等小分子物质能直接通过细胞膜被细胞吸收，而淀粉、脂肪和蛋白质等大分子有机物，必须先分解成小分子的有机物，才能被细胞吸收，人体中的消化酶的作用便是将大分子有机物分解为可以被人体吸收的小分子有机物。

1、淀粉酶

 --> 口腔

唾液淀粉酶将食物中的淀粉分解为麦芽糖，但麦芽糖还并不能被细胞吸收。

•   淀粉是由碳，氢和氧组成的有机物，并不能被细胞直接吸收。

•    唾液腺分泌的唾液中含有大量的唾液淀粉酶。通过牙齿的咀嚼和舌的搅拌，食物中的淀粉与唾液充分混匀，也就在这个期间，唾液淀粉酶将食物中一部分淀粉分解为麦芽糖。

--> 小肠

小肠中的淀粉酶将被初次分解过的淀粉（麦芽糖）分解为可以被细胞吸收的葡萄糖。

•   在小肠中的胰腺和肠腺分泌的大量的消化液，其中就含有淀粉酶。

•   在小肠的上半部分十二指肠中，淀粉被最终分解为葡萄糖。

2.  胃蛋白酶

胃蛋白酶将大分子有机物蛋白质分解为小一些的多肽分子。

--> 胃

•   蛋白酶的最适温度均为55℃,最适pH均为8.0。

•   胃通过蠕动搅和食物，使胃蛋白酶有充分的机会分解蛋白质。

•   蛋白质是由20多种不同的氨基酸组成的。蛋白质被初次分解为多肽后，虽然小了很多，但还是不能被人体细胞吸收。

3.  胰蛋白酶

胰蛋白酶将被胃蛋白酶初次分解过的多肽分子分解为可以被人体吸收的氨基酸。

--> 小肠

•   小肠中的胰腺和肠腺分泌的大量的消化液，其中就含有胰蛋白酶。

•   胰液中含有碱性的碳酸氢钠，在进入小肠后，碳酸氢钠将酸性的胃液中化，因为胰蛋白酶在酸性液体中会变形并停止工作。

•   蛋白质在这里被分解为小分子氨基酸，并被小肠吸收。

4.  脂肪酶

脂肪酶将大分子脂肪分解为甘油和脂肪酸。

--> 小肠

•   小肠中的胰腺和肠腺分泌的大量的消化液，其中就含有脂肪酶。

•   甘油和脂肪酸可以被人体吸收并被用做身体能量的来源。