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Who thinks about ‘Doctors in Distress’? Key Concepts Why do we have Different Blood Types?
Key Concepts
Why do we have Different Blood Types?
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If you’re in an accident and a panicked bystander asks you your type, here’s why you don’t respond with tall, dark-haired and charismatic. Much like your potential significant other, there’s a few options to choose from: A, B, AB and O. Why does this occur?
Red blood cells, like all cells (except white blood cells), have small globular proteins on their surface called antigens. These antigens act as markers to white blood cells, which have antibodies on their surface, to tell them that they are not pathogenic so that your white blood cells don’t attack them. This works because each antigen has its own complementary antibody. If a pathogen does enter the body, a white blood cell with the matching antigen binding site will come along and recognise it as a foreign threat and alert the white blood cells to destroy it. People have different antigens depending on their genetic makeup and these types can be categorized into the blood types mentioned above. An Austrian doctor, Karl Landsteiner, identified the most common blood antigens in 1901, which he called A and B. He also found that some people had neither antigen (type O), and in 1902 two of his students discovered that some people have both antigens (type AB).
Blood can also be classified using the Rhesus system, or Rh for short. Funnily enough, it was named after the rhesus monkey in which it was first discovered. In this system, if a person has RhD antigens on the surface of their red blood cells, they are Rh positive, if they don’t, they’re Rh negative. In Australia, around 83% of people are Rh positive. The two systems are usually combined in order to achieve maximum precision, giving us 8 possible blood types.
As a result, it is vital that blood transfusions occur between people of the same blood type. If not, the recipient’s antibodies will detect an impostor in the new blood’s different antigens and alert the white blood cells to attack in a process called haemolysis (when the red blood cells are destroyed). As the body wages an internal civil war, the patient may experience a dangerously high fever, blood in the urine, and kidney failure. Not fun. Luckily, nowadays, blood is meticulously screened before being administered to patients to avoid rejection; not only does it put the patient at risk, it’s a waste of a precious donation.
One difference between the Rhesus system and the ABO group system is that Rh negative people don’t usually possess antibodies against RhD (unless they have been previously exposed to it), whereas in the ABO group system if the antigen is absent from the red blood cell, the antibody against it is present in the plasma. Testing to see if you’re Rh positive or negative is routinely done during pregnancy, blood donation and before a blood transfusion. If a mother is Rh negative but her baby is Rh positive (which can happen if the father is Rh positive), the mother could produce antibodies that fight the baby’s red blood cells. This can happen if blood from the unborn baby enters the mother’s circulation. When there is a risk of this happening an injection called anti-D can be given to the
mother to help prevent these antibodies against Rh positive blood being produced.
As you can see, your blood is far more complicated than a simple red liquid and you should probably make sure you know your type. Blood type, that is.
Roxanna Fahid LVI
References:
https://www.sciencefocus.com/the-human-b ody/why-do-we-have-different-blood-types/
https://www.ncbi.nlm.nih.gov/books/NBK268 84/#:~:text=Each%20B%20cell%20produce s%20a,and%20antibody%2Dsecreting%20e ffector%20cell.
https://medlineplus.gov/ency/article/001303. htm#:~:text=A%20hemolytic%20transfusion %20reaction%20is,the%20process%20is%2 0called%20hemolysis.
https://www.mydr.com.au/tests-investigation s/blood-typing#:~:text=The%20rhesus%20( Rh)%20system,be%20Rhesus%20positive %20(Rh%2B).
The Neuroscience Behind PTSD
The brain is composed of 3 main parts the cerebrum, the cerebellum and the brainstem. The cerebrum is the largest part of the brain, consisting of the two main hemispheres. It is responsible for body functions such as movement, the 5 main senses (touching, seeing, hearing, tasting and smelling), speech and emotions. The cerebellum is the smaller bulb-shaped part of the brain located directly under the cerebrum. It is responsible for body coordination, general muscle movement and balance. The brainstem runs from the cerebrum, through to the cerebellum and connects them into the spinal cord. It performs automatic responses such as sneezing, regulating body temperature, regulating the sleep cycle and digestion.
Post traumatic stress disorder is defined as an anxiety disorder caused by very stressful, frightening or distressing events. Like all psychological disorders, the trauma which causes PTSD, has significant effects on brain structures and their functions.
Where your body is experiencing trauma, the amygdala (located in the cerebrum) initiates an immediate, automatic response which alerts the body to be prepared to brace a threat. As a result, the hypothalamus (which detects this response) releases the stress hormone, cortisol, which keeps the body hypervigilant and alert. Eventually, when the prefrontal cortex (also in the cerebrum) has realised that the threat is no longer dangerous, it helps the body to calm down and return to its normal state. However, if someone experiences too much trauma over a period of time or a highly traumatic experience in a very short period of time, the amygdala can be overactivated and therefore too many stress hormones are being released and the prefrontal cortex cannot settle the body fast enough. This is why one of the main symptoms of PTSD is being constantly stressed, hypervigilant or excessively on edge. Moreover, the hippocampus (located in the cerebrum) is also significantly impacted by trauma. It is responsible for memory processes, and when it is overworked (from extreme trauma experiences) it can also essentially “malfunction” resulting in memory loss, memory flashbacks and repetitive memories of the event- all more common symptoms of PTSD.
On a molecular level, the molecule glutamate is a chemical messenger of brain signals between nerve cells and normally, it is responsible for sending nerve signals as well as playing a key role in memory. A study recently done by NCPTSD, a Yale psychologist and PET scanner Irina Esterlis showed that patients with PTSD had a significantly higher amount of glutamate (specifically mGluR5) being released in their brain than usual. As tested on animals, an increase in mGluR5 caused fear and stress-related behaviours, demonstrating another reason as to why people with PTSD share some of these behaviours. The PET scan image here shows the difference
between a normal patient and a patient with PTSD- specifically the difference in amount of mGluR5 present in their brains. It is interesting to note that similar amounts of glutamate has also been found in people suffering from Huntington’s disease: a genetic, neurological disease with similar symptoms such as memory lapses and increased aggressive/irritable behaviour.
References:
https://www.nhs.uk/conditions/post-tra umatic-stress-disorder-ptsd/ http://www.mayfieldclinic.com/pe-anatb rain.htm https://www.verywellmind.com/wh at-exactly-does-ptsd-do-to-the-brai n-2797210 https://news.yale.edu/2017/07/17/ new-ptsd-study-identifies-potential -path-treatment https://hopes.stanford.edu/about-gl utamate-toxicity/
Aya Kodmani LVI
The Truths to Obesity
Many of us think we are in control of what we eat, and this coupled with how we keep active dictates our shape and size. With the proliferation of exercise videos and meal plans for “all shapes and sizes” , a belief that obesity is a personal choice has been established. Millions of people, especially children, are bullied daily due to their weight and size . But what if they are not in control? What if our universal belief towards obesity is incorrect ?
Reaching for that serotonin sweet spot
As you may have noticed, we have the tendency to eat a lot when we feel emotional. There are times when we are sad or depressed and this can lead to emotional eating-- eating more than the required calories you would need in a day. In a fast paced life, people tend to feel isolated and that's when they find solace in food and primarily junk food. According to an American Medical Association study, researchers have found a connection between eating chocolate and being depressed. It is said that cocoa raises the level of serotonin, a neurotransmitter that produces feelings of happiness. But what is it that triggers the brain to reach out to high-fat foods despite knowing the fact that they may harm you in the long run? Many people turn to sugary and high-fat foods to comfort themselves. According to a study published in the Nature Neuroscience, eating such foods triggers the release of dopamine, another “feel-good” neurotransmitter in the brain. So, the more such foods you eat, the brain starts getting addicted to them, making you crave for more. It becomes a cycle and a trap for your brain.
Let the cavemen eat cake….
Our crave for calorific food is biological, developed through evolution. When we were cavemen we never knew when we would eat again and famine was a constant threat. Therefore even when we had eaten a full meal, fearing hunger, our brain signalled that we were still hungry and that we wanted to eat more. In modern times, this has evolved into the concept of ‘dessert tummy’ -- after a meal your body starts to crave food that is higher in calories as your body wants to store up in fat for the future. For example, grizzly bears after eating a full meal of fish, will have “dessert” by just eating the skin, as this has the highest fat and calories. The concept of ‘dessert tummy’ has been conserved through evolution and throughout the animal kingdom. This self preservation now has led to weight gain. But if everybody is preparing themselves for ‘famine’ then why isn’t everyone overweight? While self preservation and fear of starvation has developed an evolutionary tendency towards calorie hoarding, there has never been a historic abundance of food, and therefore we all have different responses to too much food.
My leptin’s broken….
Scientists discovered Leptin, a hormone that regulates your energy, including the number of calories you eat and expend, as well as how much fat you store in your body . The leptin system has evolved to keep humans from starving or overeating. Today, leptin is very effective at keeping us from starving. But there is something wrong with the mechanism that is supposed to prevent
us from overeating. In 1994 researchers found that the cause of obesity was in fact a mutation in this hormone.
Leptin is produced by your body’s fat cells. The more body fat cells, the more leptin is produced. Leptin is carried by the bloodstream into your brain, where it sends a signal to the hypothalamus — the part that controls when and how much you eat. The fat cells use leptin to tell your brain how much body fat they carry. High levels of leptin tell your brain that you have plenty of fat stored, while low levels tell your brain that fat stores are low and that you need to eat. When you eat, your body fat goes up, leading your leptin levels to go up. Thus, you eat less and burn more. Conversely, when you don’t eat, your body fat goes down, leading your leptin levels to drop. At that point, you eat more and burn less.
So how does it cause obesity?
People who are obese have a lot of body fat and therefore very high levels of leptin, which should in theory cause them to naturally limit their food intake. In other words, their brains should know that they have plenty of energy stored. However, scientists discovered that leptin signals in obese patients often do not work. While leptin may be present, the brain doesn’t see it .This condition is known as leptin resistance and it is now believed to be one of the main biological contributors to obesity.
To understand what was really going on, an experiment was done with obese children who had a mutation in their leptin hormone . This experiment included a variety of three year olds and a 3000 calorie breakfast. Most 3 year olds as you would expect, had one bite of toast whereas the children with the mutation were able to eat a lot more .This proved to scientists how this mutation can severely affect children today as not only was the quantity of food higher but they also had a preferred taste for fat. Interestingly, this same mutation causes food motivation in dogs as well. You probably know of Labradors, the familyfriendly dogs that are highly food motivated. Eighty percent of all Labradors have a similar leptin mutation which makes the dog very food motivated and consequently, why they are great guide dogs.
Although we can see there are biological and evolutionary factors which can lead to obesity, doctors would highlight the importance of personal responsibility for your own health . There are always ways to improve your condition, whether going on a brisk walk everyday, planning a low calorie diet or joining a weight loss group, small actions like these can significantly and rapidly increase your health and reduce the risk of obesity. Specialists would argue the most important step in preventing obesity is understanding your health situation and actively seeking help to improve .
We can see that there are genetic and biological reasons why people tend to be obese . The fast food, fast paced society we live in makes it even harder . People who find themselves here are already fighting a tough battle, and this is why it is important to realise and understand that obesity is not a personal choice. However this does not mean their situations cannot be improved. While genetics predispose a person to major challenges, learning about healthy diet, exercise and emotional support can help people regain control of their body and mind. Riya Nathan Year 11
Flower
“I chose to paint it because I like using nature as the inspiration for my artwork, mainly individual plants and animals, as I like the idea of being able to preserve living things in their most vibrant state; the flower in the painting will continue to look as it does in full bloom, while the real flower will wither. This emphasises the idea of the cycle of life, reminding us that all living organisms die, contrasting starkly with objects, which remain unchanged. ” Isabella Davidson LVI
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