I wrote a lesson about heat and heart attacks. I learned different symptoms and causes of heart attacks and how it works. Below is the lesson.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 activity
When
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
