The
Human Heart
Your
heart is a muscular organ that pumps blood to your body. Your heart is at the
center of your circulatory system. This system consists of a network of blood
vessels, such as arteries, veins, and capillaries. These blood vessels carry blood
to and from all areas of your body.
An
electrical system controls your heart and uses electrical signals to contract
the heart's walls. When the walls contract, blood is pumped into your
circulatory system. Your heart is vital to your health and nearly everything
that goes on in your body. Without the heart's pumping action, blood can't move
throughout your body.
Your
blood carries the oxygen and nutrients that your organs need to work well.
Blood also carries carbon dioxide (a waste product) to your lungs so you can
breathe it out.
A
healthy heart supplies your body with the right amount of blood at the rate
needed to work well. If disease or injury weakens your heart, your body's
organs won't receive enough blood to work normally.
The
heart is one of the most important organs in the entire human body. It is
really nothing more than a pump, composed of muscle which pumps blood
throughout the body, beating approximately 72 times per minute of our lives.
The heart pumps the blood, which carries all the vital materials which help our
bodies function and removes the waste products that we do not need. For
example, the brain requires oxygen and glucose, which, if not received
continuously, will cause it to loose consciousness.
The
heart is essentially a muscle(a little larger than the fist). Like any other
muscle in the human body, it contracts and expands. Unlike skeletal muscles,
however, the heart works on the "All -or-Nothing Law". That is, each
time the heart contracts it does so with all its force. In skeletal muscles,
the principle of "gradation" is present. The pumping of the heart is
called the Cardiac Cycle, which occurs about 72 times per minute. This means
that each cycle lasts about eight-tenths of a second. During this cycle the entire
heart actually rests for about four-tenths of a second.
The
walls of the heart are made up of three layers, while the cavity is divided
into four parts. There are two upper chambers, called the right and left atria,
and two lower chambers, called the right and left ventricles. The Right Atrium,
as it is called, receives blood from the upper and lower body through the
superior vena cava and the inferior vena cava, respectively, and from the heart
muscle itself through the coronary sinus. The right atrium is the larger of the
two atria, having very thin walls. The right atrium opens into the right
ventricle through the right atrioventicular valve(tricuspid), which only allows
the blood to flow from the atria into the ventricle, but not in the reverse
direction. The right ventricle pumps the blood to the lungs to be reoxygenated.
The left atrium receives blood from the lungs via the four pulmonary veins. It
is smaller than the right atrium, but has thicker walls. The valve between the
left atrium and the left ventricle, the left atrioventicular valve(bicuspid),
is smaller than the tricuspid. It opens into the left ventricle and again is a
one way valve. The left ventricle pumps the blood throughout the body. It is
the Aorta, the largest artery in the body, which originates from the left
ventricle.
The
Heart works as a pump moving blood around in our bodies to nourish every cell.
Used blood, that is blood that has already been to the cells and has given up
its nutrients to them, is drawn from the body by the right half of the heart,
and then sent to the lungs to be reoxygenated. Blood that has been reoxygenated
by the lungs is drawn into the left side of the heart and then pumped into the
blood stream. It is the atria that draw the blood from the lungs and body, and
the ventricles that pump it to the lungs and body. The output of each ventricle
per beat is about 70 ml, or about 2 tablespoons. In a trained athlete this
amount is about double. With the average heart rate of 72 beats per minute the
heart will pump about 5 litres per ventricle, or about 10 litres total per
minute. This is called the cardiac output. In a trained athlete the total
cardiac output is about 20 litres. If we multiply the normal, non-athlete
output by the average age of 70 years, we see that the cardiac output of the
average human heart over a life time would be about 1 million litres, or about
250,000 gallons(US).
Causes
Most
heart attacks are caused by a blood clot that blocks one of the coronary
arteries. The coronary arteries bring blood and oxygen to the heart. If the
blood flow is blocked, the heart is starved of oxygen and heart cells die. A
plaque can build up in the walls of your coronary arteries. This plaque is made
up of cholesterol and other cells. A heart attack can occur as a result of plaque
buildup. The plaque can develop cracks or tears. Blood platelets stick to these
tears and form a blood clot. A heart attack can occur if this blood clot
completely blocks oxygen-rich blood from flowing to the heart. This is the most
common cause of heart attacks. The slow buildup of plaque may almost block one
of your coronary arteries. A heart attack may occur if not enough oxygen-rich
blood can flow through this blockage. This is more likely to happen when your
body is stressed (for example, by a serious illness). The cause of heart
attacks is not always known.
Heart
attacks may occur:
When you are resting or asleep
After a sudden increase in physical activityWhen
you are active outside in cold weather
After
sudden, severe emotional or physical stress, including an illness
Symptoms
The pain can be severe or mild. It can feel like:
A
tight band around the chest
Bad
indigestion
Something
heavy sitting on your chest
Squeezing
or heavy pressure
The
pain usually lasts longer than 20 minutes. Rest and a medicine called
nitroglycerin may not completely relieve the pain of a heart attack. Symptoms
may also go away and come back.
Other
symptoms of a heart attack include:
Anxiety
Cough
Fainting
Light-headedness,
dizziness
Nausea
or vomiting
Shortness
of breath
Sweating
Some people (the elderly, people with diabetes, and women) may have little or no chest pain. Or, they may have unusual symptoms (shortness of breath, fatigue, and weakness). A "silent heart attack" is a heart attack with no symptoms.
Citations:
http://www.webmd.com/heart-disease/guide/heart-disease-symptoms
http://www.medicalnewstoday.com/articles/151444.php
One thing that I can say that I truly understand is you have to go through a struggle in order to succeed. In March, we were assigned to read a book by a Haitian author named Edwidge Danticat. The book was called Create Dangerously. This book was a collection of essays about her life and Haitian issues. There was one essay in particular that really grasped my opinion. This essay was called “I Speak Out.” It was about another Haitian lady named Alérte Bélance that was mutilated by the Macout (the Haitian army), but surprisingly survived. People found her story so interesting that they flew her to the United States so she was able to share her story to other people. In my forum post responding to this I wrote “While reading “Speak Out” I was appalled by the actual reality of the things that were taking place in Haiti.” You can view my forum at this link.
In Mr. Block’s class we also did a very interesting project with garage band. We had to do a podcast interviewing someone about the boundaries they had crossed in their life. I interviewed my uncle who is a recovering addict. He has had a rough past with crack cocaine. He was on crack cocaine for about 22 years of his whole life and miraculously is clean today and has been clean for more that four years. During the podcast I expressed that this addiction has had negatively and positively affected his life. In the podcast I said, “Using crack cocaine was definitely his valley. Laughter family, and crossing the boundary of not using drugs was his peak.” You can view my podcast at this link.
Throughout the school year, I have learned that art can be interpreted in many ways; you just have to be creative enough to understand it. As the end of the school year was approaching, Mr. Block introduced us to a new unit in English class. He introduced us to the poetry unit. As soon as I heard poetry I started to have a sissy fit because I always thought that my mind was not physically able to think like a poet. My exact words in one of my English journal entries were, “I am not no Maya Angelou.” I was definitely not looking forward to the couple of weeks we were going to be in this unit. However, when I started to write my first poem “My Baby Love” I was surprised that I could be as creative as I appeared to be. When I wrote my introduction to my wiki space account, I wrote something that reflected my whole experience in the beginning. I said, “I stepped into this whole poetry unit blinded by the complexity I thought poetry had.” You can view my poetry page at this link.
I was assigned a book to read in about February called Passing by Nella Larsen. This book was about an African American woman named Clare Kendry who is passing for a white woman back in the 1960s. She is living a dangerous life because her husband who she has many ties to doesn’t know she is African American. By the end of the book, Clare ends up falling out of a window and there was a mystery to how she fell out. Mr. Block assigned us to create an artistic project about the book. My friend and I decided to work together on this project and decided to do an iMovie. In my forum post about the project described my entire process while doing the project. I said in my forum post, “We did two skits on our interpretation of how it would look on the news when Clare died.” This is the link to see my video
This year has definitely been a great one. I don’t regret anything I have done this school year because all of the mistakes I have made I have learned from them. I am so very grateful to have had a teacher like Mr. Block for History and English class. This school year would not have been the same without him. I hope the rest of my years in high school will be as self learning as this year was.
