My Science School

Only a few hundred years ago, the fastest way that a piece of news could travel was to be carried by a person on horseback. Messages sent overseas could only travel as fast as the fastest sailing ship and were at the mercy of the wind and weather. The development of steam locomotives and steamships made it possible for information to move around the world more quickly, but it still had to travel physically from one place to another, as a letter. The breakthrough came with the invention of the electric telegraph and messages in Morse code. The message was sent down a wire in bursts of electric current. Today, images of written documents, sound recordings or television pictures can be flashed around the globe in less than a second by means of satellites and radio communications.

It seems like advancements in technology and changes in communication always go hand in hand. When science was working to introduce new tools to let distant people contact each other, the landlines replaced telegraph and subsequently, cell phones replaced landlines. When the Internet arrived, it not only brought revolution in the sales industry but also opened new doors of personal communication. When science was looking for more convenient ways to send messages, e-mails replaced postal emails and social media replaced text messages. So it would not be wrong to say that technology has been shaping the communication industry for over a hundred years.

Previously, there were not much mediums of communication and today we are completely overwhelmed with the disparate mediums, thanks to the ever-changing technology! From Facebook to Instagram and skype to Whatsapp, we now have the limitless database of communication tools that have brought us closer to the entire world. All these communication mediums have also impacted our lives in different ways. For example, it’s true that Smartphones have brought us closer to our friends and relatives living in distant places, but at the same time, they have also made our society somewhat impersonal. Although they have helped increasing workplace engagement and productivity, they have also given rise to certain security and privacy issues.  While some of these issues are relatively minor, but some may have profound effects on the lives of users.

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Over millions of years, evolution is changing the way humans look. Over a shorter period, improved nutrition and medical discoveries have meant that people in some parts of the world today are generally bigger and stronger than their ancestors. But we are also losing some abilities that no longer seem useful. The smallest toe, for example, can no longer be moved independently by most people. As recently as Roman times, some people may have been able to “prick up their ears”, moving them slightly towards sounds as some animals can.

Humans are getting taller; they’re also fatter than ever and live longer than at any time in history. And all of these changes have occurred in the past 100 years, scientists say. So is evolution via natural selection at play here? Not in the sense of actual genetic changes, as one century is not enough time for such changes to occur, according to researchers.

Most of the transformations that occur within such a short time period “are simply the developmental responses of organisms to changed conditions,” such as differences in nutrition, food distribution, health care and hygiene practices, said Stephen Stearns, a professor of ecology and evolutionary biology at Yale University.

But the origin of these changes may be much deeper and more complex than that, said Stearns, pointing to a study finding that British soldiers have shot up in height in the past century. ”Evolution has shaped the developmental program that can respond flexibly to changes in the environment,” Stearns said. “So when you look at that change the British army recruits went through over about a 100-year period, that was shaped by the evolutionary past.”

And though it may seem that natural selection does not affect humans the way it did thousands of years ago, such evolutionary mechanisms still play a role in shaping humans as a species, Stearns said.

“A big take-home point of all current studies of human is that culture, particularly in the form of medicine, but also in the form of urbanization and technological support, clean air and clean water, is changing selection pressures on humans,” Stearns told Live Science.

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Veins are blood vessels that carry blood to the heart, while arteries carry it from the heart. The heart acts as a pump, pushing blood to every part of the body. Adults have between five and six litres (between nine and ten pints) of blood. As well as containing red cells to carry oxygen to the body’s organs, blood also plays an important part in fighting infection. White blood cells attack and digest harmful bacteria, while platelets in the blood form clots so that wounds can heal and no further infection can enter the body.

Arteries and veins both carry blood around the body, and they each have three main layers of tissue (a ring of endothelial tissue at the centre of the blood vessel surrounded by a layer of muscle and elastic fibres, which is surrounded by a layer of connective tissue). However, there are several differences between them:

1. Arteries carry blood from the heart to the rest of the body, whereas veins carry blood from the rest of the body back to the heart.


2. Almost all arteries carry oxygenated blood and almost all veins carry deoxygenated blood. The only exceptions are the pulmonary artery, which carries deoxygenated blood from the heart to the lungs, and the pulmonary vein, which carries oxygenated blood from the lungs to the heart.


3. Arteries have a thick elastic muscle layer, whereas the muscle layer for veins is much thinner. This is because the heart pumps blood into the arteries at high pressures, so the walls of the arteries must be able to cope with the changes in pressure during a heartbeat. Veins carry blood at much lower pressures so do not need such a thick wall.


4. Arteries have a much narrower lumen (the hole at the centre that the blood flows through) than veins. This helps keep higher blood pressures in the arteries, which is needed to keep blood flowing quickly to body tissues.


5. Veins have valves and arteries do not. In arteries, blood flows in the right direction because of the heart pumping it forwards at high pressures. The lower blood pressure in veins means that valves are needed to stop blood flowing backwards (for example, in veins in the legs, blood needs to flow upwards against the pull of gravity).

Food is the fuel that our bodies need for movement. But we also need some fuel simply to maintain all the parts of our bodies. Individual cells are being renewed all the time. And even if we do not move the outside of our bodies at all, there are many parts inside that are constantly in motion. How much food we need depends on our size, age, gender and level of activity.

Nutrition is how food affects the health of the body. Food is essential—it provides vital nutrients for survival, and helps the body function and stay healthy. Food is comprised of macronutrients including protein, carbohydrate and fat that not only offer calories to fuel the body and give it energy but play specific roles in maintaining health. Food also supplies micronutrients (vitamins and minerals) and phytochemicals that don't provide calories but serve a variety of critical functions to ensure the body operates optimally.

Protein: Found in beef, pork, chicken, game and wild meats, fish and seafood, eggs, soybeans and other legumes included in traditional Central America cuisine, protein provides the body with amino acids. Amino acids are the building blocks of proteins which are needed for growth, development, and repair and maintenance of body tissues. Protein provides structure to muscle and bone, repairs tissues when damaged and helps immune cells fight inflammation and infection.

Carbohydrates: The main role of a carbohydrate is to provide energy and fuel the body the same way gasoline fuels a car. Foods such as corn, chayote, beans, plantains, rice, tortilla, potatoes and other root vegetables such as yucca, bread and fruit deliver sugars or starches that provide carbohydrates for energy.

Energy allows the body to do daily activities as simple as walking and talking and as complex as running and moving heavy objects. Fuel is needed for growth, which makes sufficient fuel especially important for growing children and pregnant women. Even at rest, the body needs calories to perform vital functions such as maintaining body temperature, keeping the heart beating and digesting food.

Fat: Dietary fat, which is found in oils, coconut, nuts, milk, cheese, meat, poultry and fish, provides structure to cells and cushions membranes to help prevent damage. Oils and fats are also essential for absorbing fat-soluble vitamins including vitamin A, a nutrient important for healthy eyes and lungs.

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There are more than 600 muscles in the human body. Over 100 of these are in our faces, which is why we can have so many different expressions. Although we can perform a great variety of movements, each muscle can only do one thing: contract. That is why muscles often work in pairs, so that one muscle can move a part of the body in one direction, while its partner can move it back again. Perhaps the most important muscle in the human body is the heart, which is contracting and relaxing all the time to pump blood around the body.

There are about 700 named skeletal muscles in the human body, including roughly 400 that no one cares about except specialists. There is just one important cardiac muscle. And there are literally countless smooth muscles (which do the work of the autonomic nervous system, mostly squeezing and squishing stuff in tubes).

It’s surprisingly hard to tell. You wouldn’t think the total number would be ambiguous, but it’s difficult to know what to include and exclude, and anatomists don’t always agree. Some muscle tissue really can’t be separated into countable muscles. And, believe it or not, the science of anatomy is still advancing. No, entirely new muscles aren’t being discovered — but novel variations in individual muscle anatomy are found more or less constantly, and supernumerary muscles — extra muscles — are not unusual. Many muscles, like the four-part quadriceps, are normally split into different parts that may or may not traditionally count as separate muscles — but then some people’s muscles are more divided than others. It makes a firm count just about impossible.

There are only about 200 to 300 muscles that anyone, even a massage therapist, might actually be interested in knowing about. When most people ask how many muscles are in the human body, they mean the serious bone-movers — Pecs, delts, lats, traps, glutes, biceps & triceps, hams & quads & let’s not forget the cloits & dloits!muscles that do real work, muscles like pecs, delts, lats, traps, glutes, biceps and triceps, hams and quads, and let’s not forget the cloits and dloits! There are maybe another hundred muscles if you include the fiddly little muscles of the hands and feet, and the major face muscles.

But that’s including about 600 muscles that, mostly, no one cares about except specialists. I am aware of a few that have clinical importance to a massage therapist, but I’m mostly just barely aware of their existence — like the smaller facial muscles, like the mess of little muscles around and under the tongue and around the voice box, like the muscles around the eyeball, or the crazy trampoline of muscles on the pelvic floor.

Our bodies are very complicated. It is impossible to think about all the processes that are going on inside them at the same time, so doctors often consider the body as being made up of several different systems, each one with different organs and mechanisms working together to perform particular functions.

Organ Systems

Different organs can work together to perform a common function, like how the parts of your digestive system break down food. We refer to an integrated unit as an organ system. Groups of organ systems work together to make complete, functional organisms like us! There are 11 major organ systems in the human body, which include the circulatory, respiratory, digestive, excretory, nervous and endocrine systems. The immune, integumentary, skeletal, muscle and reproductive systems are also part of the human body.

The Circulatory & Respiratory Systems

The circulatory system is responsible for transporting blood throughout the body. It consists of the heart and blood vessels known as veins, arteries and capillaries. Think of blood vessels as the highways of the body, bringing important cargo to and from the cells. In the circulatory system, blood is pumped from the heart to the lungs, so they'll get oxygen, and then pumped to the body's cells. Here is a diagram of the human circulatory system, including the heart and major arteries, which are in red, and veins, which are in blue.

In order for blood to provide oxygen to the body, the body must have a way of obtaining that oxygen. The respiratory system allows air to enter the lungs and for oxygen to diffuse into the blood en route to the body's tissues. The entrance to the respiratory system can be found in the nose and the mouth, where air enters the body and then travels through the larynx and pharynx in the throat to the trachea or windpipe. From the trachea, right and left branches, known as bronchi, carry oxygen to the alveoli, where oxygen moves into the blood, while carbon dioxide moves into the lungs to be exhaled.

Digestive & Excretory Systems

The digestive system is responsible for bringing food into the body and breaking it down to useable components. It starts at the mouth, where we ingest our food and use our saliva, teeth and tongue to bite and mash it. The food then travels through the esophagus into the stomach, where strong acids break it down even further. During the last two stages of digestion, nutrients and water are absorbed through the small intestine and the large intestine, respectively. Any remaining waste products are stored in the rectum and eliminated through the anus.

The urinary or excretory system is where liquid waste is eliminated as urine. The excretory system starts with the kidneys, important organs for cleaning the blood and balancing water in the body. In the excretory system, the liquid part of the blood, or plasma, enters through the kidneys, where important nutrients, like sugar and some salt, are reabsorbed into the body. Compounds we don't need, like urea or excess water, are sent to the bladder in the form of urine. Urine leaves the body through the urinary tract and exits the body at the urethra.

Nervous, Endocrine & Immune Systems

Without a master control system that tells our bodies what to do, none of the organ systems we've talked about so far would work. The organs in the human nervous system are made up of cells, called neurons that use chemicals and electricity to send messages. This system has two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The central nervous system consists of the brain and the spinal cord, which serve as the main control centers for the body and process all incoming and outgoing messages. The peripheral nervous system includes all the nerves in your body that bring messages to the central nervous system and from the CNS to the muscles.

Whereas the nervous system mainly uses electrical signals to communicate between cells, the endocrine system relies upon chemicals, called hormones, to send long distance messages through the body. The main organs found in the human endocrine system are located in the brain and include the hypothalamus, thalamus and pituitary gland. They talk to other endocrine organs, like the adrenal glands, testes and ovaries to assist with other organ systems.

There is much that we do not yet know about how the brain works, but we do know that the brain communicates with the rest of the body through a thick cord of nerves running down the middle of the spine and branching off to reach the limbs and internal organs. The nerves are pathways for messages to the brain, to inform it about what is happening elsewhere in the body, and from the brain to tell the rest of the body how to act. These messages, and the processes happening within the brain, are made up of tiny electrical impulses. By far the largest part of the brain is the cerebrum, which is divided into two halves, called hemispheres. The rest of the brain is made up of the cerebellum, the pons and the medulla, which join together at the top of the spinal cord.

With 80-100 billion nerve cells, known as neurons, the human brain is capable of some astonishing feats. Each neuron is connected to more than 1,000 other neurons, making the total number of connections in the brain around 60 trillion! Neurons are organized into patterns and networks within the brain and communicate with each other at incredible speeds.

The largest part of the human brain is the cerebrum, which is divided into two hemispheres, according to the Mayfield Clinic. Underneath lies the brainstem, and behind that sits the cerebellum. The outermost layer of the cerebrum is the cerebral cortex, which consists of four lobes: the frontal, parietal, temporal and occipital.

Like all vertebrate brains, the human brain develops from three sections known as the forebrain, midbrain and hindbrain. Each of these contains fluid-filled cavities called ventricles. The forebrain develops into the cerebrum and underlying structures; the midbrain becomes part of the brainstem; and the hindbrain gives rise to regions of the brainstem and the cerebellum.

The cerebral cortex is greatly enlarged in human brains and is considered the seat of complex thought. Visual processing takes place in the occipital lobe, near the back of the skull. The temporal lobe processes sound and language, and includes the hippocampus and amygdala, which play roles in memory and emotion, respectively. The parietal lobe integrates input from different senses and is important for spatial orientation and navigation.

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