Body mechanics refers to the way we move during every day activities.
Good body mechanics may be able to prevent or correct problems with
posture (the way you stand, sit, or lie.) Good body mechanics may also
protect our body, especially our back, from pain and injury. Using
good body mechanics is important for everyone.
In a way, our body could be referred to as a vehicle that we get to drive everyday. Our brain tells the muscle what to do and our muscle would then respond. Sensory organs like our eyes, ears and nose carries information obtained to our brain so that the brain can then decide what to do next. The fascinating thing is that our body is one of the best vehicles ever made. Let's take a look at some of the technology that makes our body so amazing.
Eyes
One way to understand how remarkable our eyes are is by comparing them to a digital camera. Let's say you possessed a digital camera that has five megapixels of resolution. This means that there are 5 million little light sensors inside the camera. In each of your eyes, contained 120 million rod cells. That’s 24 times more than the digital camera!
The rod cells give us black-and-white vision, and also the night vision. Our colour vision comes from about 6 to 7 million cones inside our eye. All the cones are packed together in a tiny area called the fovea. The rods are spread out over the back of the eyeball in a larger area called the retina.
The rods in our eye are much more sensitive to light than a digital camera is. A digital camera cannot “see” at night unless we use a flash. The human eye is so sensitive at night that we can see a single candle that is 10 miles away. How can the rods be that sensitive to light? They use a chemical called rhodopsin. This chemical is very sensitive to light. If you go out at night (or if you sit in a dark room), it takes about 30 minutes for the rhodopsin to build up in your rods. When a photon of light hits a molecule of rhodopsin, the molecule changes and sends a signal to your brain. Our brain can actually see single photons of light.
The funny thing about our night vision is that we cannot see anything that is straight in front of us. That’s where our fovea is, and our cones cannot see at night. Cones need a lot of light, just like a digital camera does. In order to see things directly in front of us at night, we have to look a little to the side. Or we have to shine a light at it.
Our fovea has three kinds of cones: red, green and blue. If we were to
look at 100 cones in your eye, 64 of them would be sensitive to red
light, 32 to green light and four to blue light. This means that people
“see” red more intensely. That may be why we paint our fire trucks and
stop signs red.
When we use a digital camera, it takes the whole picture of the scene
in one shot. Our eyes don’t work that way. Our fovea only sees a tiny
part of the scene. Without we realizing it, our brain flicks our eyes
all over the scene and creates a single image in our head from dozens
of little patches. These are called saccadic eye movements.
Bones
From the bones the bones in our feet to the bones in our skull, our body contained 206 different kind of bones altogether. These bones give our body its shape.
Bones are surprisingly strong. They get this strength from calcium (and a few other mineral like phosphorus) If you think about how hard and strong
cement is, you have an idea of how bone can be so strong. Cement, like
bone, contains a lot of calcium. But how is the calcium turned into
bone? There are cells called osteoblasts that do the work. When you eat
anything that contains calcium -- broccoli, yogurt, whatever -- the
calcium is absorbed from your small intestine into your blood.
Osteoblasts pull the calcium out of the blood and deposit it as new
bone.
Our bones are constantly rebuilding
themselves to stay strong. Cells called osteoclasts break down bone, and
then osteoblasts come and lay down new bone in its place. This happens
all through our life, making sure our bones are always fresh. This
process also explains why a broken bone can heal itself. Osteoblasts
cluster around the break and start multiplying. They will eventually
bridge the broken bone and then start filling it in with new calcium.
Meanwhile, osteoclasts will break down all the bone fragments nearby to
clean up the area.
Inside our larger bones is another
surprise – bone marrow. The marrow is able to generate new red and white
blood cells, as well as new osteoblasts and osteoclasts, and send them
out into the bloodstream. We have trillions of red blood cells in our
body right now and, as they wear out, the bone marrow creates new ones –
millions of them every second. A red blood cell lasts about four
months.
Muscles attach to bones so that the bones
can move. There are strong fibers at the end of muscles called tendons.
The tendons attach to bone and let the muscles pull on bones when they
contract. One interesting thing about muscles, tendons and bones is that
they can all get stronger. If we lift a lot of weights, our muscles
will get bigger and stronger. So will the tendons. So will the
attachment points where the tendons connect to the bones. And so will
the bones themselves. The whole system gets stronger, not just the
muscle. After we die, and when all that’s left of your body is the
bones, scientists will be able to see how strong we were by looking at our bones. If we exercise a lot, our bones will be stronger and the
places where the tendons connect will be stronger too. Or in other words, exercise is written into our bones!
Heart and Blood
We already know that, as it’s beating
inside our chest, our heart pumps blood sending it all over your body.
But why is that? Our heart has two sides. Each side acts like two
different pumps. The first pump sends blood to the lungs. In the lungs,
two things happen. Your red blood cells attach to oxygen in the lungs.
They also release carbon dioxide molecules that they have carried from
your body’s cells. This is why we breathe in air that contains a lot of
oxygen, but breathe out air that contains a lot of carbon dioxide.
Next, our blood goes back to the heart,
and the second pump shoots it out to your body. Along the way, many
different things happen. Probably the most important thing is that the
red blood cells release their oxygen to your body’s cells and then they
pick up carbon dioxide released by the cells. Miles and miles of tiny
blood vessels called capillaries take the blood close to every cell in
your body.
The blood passes near the small intestines,
and if we have eaten recently, the blood picks up all sorts of food
molecules. Fat molecules, sugar molecules, protein molecules, vitamin
molecules, mineral molecules and water molecules leak through the wall
of the small intestine into the blood. The blood then carries these
molecules all over our body to every cell that needs them.
What if we haven’t eaten recently? Along
the way, our blood flows through our liver, and the liver does two
things. It helps convert toxins out of the blood. Our liver also stores
and releases glucose. Our liver is like a big sugar storage tank. For
example, when we wake up after sleeping for 10 hours and our muscles
need glucose to get moving, they get it from the liver. Our blood also
goes through our kidneys. Our kidneys take out excess water, along
with ammonia and many toxins and send it all to our bladder in urine.
Our blood passes many organs that either
create or use hormones. Hormones are chemicals that let different parts
of your body send signals to other parts. Adrenaline is one hormone that
you may have heard of. You have two glands called the adrenal glands
that sit on top of your kidneys. They can squirt adrenaline into the
blood. The adrenaline tells your heart to beat faster, your pupils to
constrict, your blood vessels to stop sending blood to the stomach and
the skin, and your liver to make more glucose available in the blood.
As you can see, every molecule that moves
in your body uses the transportation system called blood. And your heart
keeps the blood moving. Without blood, the cells in your body would not
have any oxygen. They would not have any glucose. There would be too
much carbon dioxide, and there would be toxins everywhere. Blood is
really important.
Muscles
Everything that we do with the outside world involves muscles. When we
walk, we use muscles. When we lift something,we use muscles. Even
when we talk or smile, we use muscles. We have hundreds of muscles in our body. There are big ones in our arms and tiny ones in our face.
Let’s look at our smile. When we smile, what is happening? A couple of
different muscles are working together to make our lips break into a
beautiful smile. One muscle group is the zygomaticus major, and the
other is the Levator anguli oris. These muscles contract, and they pull
up the corners of your mouth into a smile. How do these muscles
contract? That is the amazing part. Muscles are like chemical motors
that turn sugar into motion. If we understand how muscles work, we
understand a lot about how your body works.
A muscle fiber contains many myofibrils, which are cylinders of muscle
proteins. These proteins allow a muscle cell to contract. Myofibrils
contain two types of filaments -- thick filaments made of a protein
called myosin and thin filaments made of a protein called actin. Each
thick filament of myosin is surrounded by six thin filaments of actin.
It is these filaments that do the actual work of a muscle. To make the
muscle fiber contract, the myosin filament reaches out, grabs the actin
filaments and pulls on them like six pieces of rope. As this happens,
the myosin filament changes shape to pull the actin filaments along.
What makes the myosin filaments change shape? Calcium causes the change
in one direction. Something called ATP handles the other direction.
Where does the ATP come from? Our cells make it using sugar and oxygen.
Inside our cells, our body uses ATP to release energy. In the
process, it converts the ATP to ADP and phosphate. Then our cells use
glucose and oxygen to put ADP and phosphate back together to form ATP
again. This cycle is where all the energy in your muscles comes from.
What tells a muscle to start contracting? A signal comes from our brain
through a nerve fiber to a muscle. The nerve signal causes your muscle
cells to release calcium. The calcium causes myosin fibers to start
binding to actin fibers to move them. When our brain stops sending the
message through the nerve, the muscle cell soaks up all the calcium and
stores it for next time.
This process is an amazing little chemical engine that keeps our body
moving every day. Without it, we could not do anything. It all happens
because of a series of molecules working in a chain reaction inside our
muscle cells.
