Download Regulation of Human Heart Rate

Scientific Method
Heart Rate Experiment
© 2006 Barbara J. Shaw Ph.D., Science A to Z
Permission is granted to make and distribute copies
of this lesson plan for educational use only.
Questions, Observations, and Information:
You are a vertebrate. Vertebrates have a backbone (as little as cartilage covering their brain and
running along the central nerve cord like lamprey or heavily armored with an internal skeleton
and skin bones, like turtles or armadillos). Vertebrate bodies have these organ systems:
 The Integumentary System is an organ system that protects the body from damage,
comprising the skin, hair, scales, feathers, nails, sweat glands and their products.
 The Muscular System is the system that allows an animal to move. There are three
types of muscles in vertebrates: skeletal (or striated), smooth (or involuntary) and cardiac
(muscles in your heart).
 The Skeletal System is a strong and often a rigid framework that supports the body of an
animal. Vertebrate skeletons are made from either cartilage (jawless fish and sharks, rays
and skates) or bone (all other vertebrates).
 The Nervous System is a network of specialized cells that communicate information
about an animals surroundings and itself; it processes this information and causes
reactions in other parts of the body. The nervous system is divided broadly into two
categories: the peripheral nervous system and the central nervous system. It includes
your brain, all your sensory organs (eyes, ears, etc.) and your nerve network.
 The Digestive System breaks down of chemicals in the body into a form that can be
absorbed by the blood stream. Your digestive system includes your mouth, esophagus,
stomach and associated organs for digestion (like the pancreas and bile duct, small and
the large intestines.
 The Urinary system (also called excretory system) produces, stores, and eliminates
urine. In mammals it includes two kidneys, two ureters, the bladder, and the urethra.
 The Respiratory System functions to allow gas exchange. The gases that are exchanged,
the anatomy or structure of the exchange system, and the precise physiological uses of
the exchanged gases vary depending on the organism. The organs of exchange are gills in
most aquatic vertebrate animals, and lungs and trachea in most terrestrial vertebrate
animals.
 The Circulatory System moves nutrients, gases, and wastes to and from cells, helps fight
diseases and helps stabilize body temperature and pH to maintain homeostasis. This
system includes heart, arteries, veins, and capillaries.
 The Lymphatic System in vertebrates is a network of conduits that carry a clear fluid
called lymph. The system also includes all the structures dedicated to the circulation and
production of lymphocytes, which includes the spleen, thymus, bone marrow and the
lymphoid tissue associated with the digestive system.
 The Reproductive System is for passing one’s genetic material (DNA) to the next
generation. Unlike most organ systems, the gonads (sex organs of either male or female
species) have significant differences. The reproductive system produces sperm in males,
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and eggs in females. Not all vertebrates are differentiated into discrete genders.
The Endocrine System is an information signal system much like the nervous system.
However, the nervous system uses nerves to conduct information, whereas the endocrine
system mainly uses blood vessels as information channels. Glands located in many
regions of the body release into the bloodstream specific chemical messengers called
hormones. Hormones regulate the many and varied functions of an organism, e.g., mood,
growth and development, tissue function, and metabolism, as well as sending messages
and acting on them. The major glands of the endocrine system are pineal, pituitary,
thyroid, thymus, adrenal, pancreas, and ovaries or testes.
Organ Systems:
top row, from left to right; Integumentary, Skeletal, Nervous, Endocrine, Circulatory
bottom row, from left to right; Muscular, Respiratory, Digestive, Urinary, and Reproductive.
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Today, we are going to focus on how your heart works – and why!
What does your heart do?
Your heart carries oxygenated blood to all the cells in your body. It also carries molecules
you get from eating for your metabolism.
How does the heart carry oxygen and molecules to the cells?
Your heart is a muscle that will beat around 42,075,904 times per year, give or take a couple
million. A reasonable estimate for the number of heartbeats in a lifetime is about three
billion! The only time your heart rests is between beats. A heartbeat is the heart contracting,
or making the chambers in the heart smaller to push the blood.
Your heart has 4 chambers called the
left and right atrium and the left and
right ventricle. If you listen closely, you
can hear it “lub DUB…lub DUB…lub
DUB.” Each lub is the atria (plural for
atrium) contracting. Blood with a high
concentration of carbon dioxide
returning to the heart from the body
enters the right atrium from the inferior
and superior vena cava. The “lub”
pushes the blood to the right ventricle
through the tricuspid valve. Each
“DUB” is the ventricles contracting.
The ventricles have heavy muscles to
push the blood to the body.
The right ventricle pushes the blood to the lungs through the pulmonary artery, where the
carbon dioxide leaves, and oxygen enters the red blood cells. The blood then returns to the
left atrium through the pulmonary vein. The lub pushes the blood from the left atrium to the
left ventricle, through the mitral valve. The left ventricle is the largest chamber, and has the
greatest concentration of muscle. It must push the blood to the brain and the rest of the body,
which is much harder than pushing the blood to the lungs. The “DUB” pushes blood to the
body through the aorta, the largest artery in the body. Arteries carry blood away from the
heart. As they get smaller, they are called arterioles. The arterioles lead to capillaries. The
capillaries are so small that only one red blood cell can pass through at a time. This is where
the cells get oxygen and give carbon dioxide to the red blood cell. The blood enters small
venuoles from the capillaries, then to larger veins, and back to the superior and inferior vena
cava.
What do your lungs do?
Your lungs are part of the respiratory organ system, which include your trachea,
lungs, diaphragm (a thin muscle and membrane associated with breathing), and
muscles. The lungs are the primary organs of gas exchange. Carbon dioxide is
blown-off while oxygen is up-taken.
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Why do we need oxygen?
Our cells are constantly making and breaking chemical bonds so that you
function. This is called your metabolism. During this metabolic activity, oxygen
is needed to help your cells make little power packets called ATP (adenosine triphosphate is a molecule for energy made in mitochondria). They are similar to
rechargeable batteries, in that they store energy, and eventually they run out and
need to be “recharged.” Instead of plugging them into a wall to recharge them,
they use sugar (from the food you eat) and oxygen to get that energy.
Why do we need to get rid of carbon dioxide?
While “recharging” your ATP
molecules, the sugar and oxygen form
carbon dioxide as waste. If too much
carbon dioxide builds up in your body, it
can harm you. Your body needs to get
rid of it by carrying the carbon dioxide
in your blood back to your lungs.
How do the lungs work?
When you breathe in (inhale), a muscular membrane called the diaphragm pulls down,
away from your lungs. This causes low pressure in your lungs, and air rushes in. When
you breathe out (exhale), the diaphragm pulls
up, causing high pressure in the lungs, and
air rushes out. As you inhale, oxygen in the
air enters your lungs, and some of it is
“grabbed” by the red blood cell in capillaries.
Trachea
Before the red blood cell can grab the
Bronchus
oxygen, it has to let go of the carbon dioxide
Bronchioles
it is holding. As the carbon dioxide leaves
the blood, it enters your lungs, and the
concentration of carbon dioxide increases in
the lungs, which then leaves your lungs when
you exhale. The air enters your nose, goes
into the trachea, into the bronchus, into the
bronchioles, into the alveolus (small pockets
where the capillaries from the circulatory
system can exchange gas).
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What happens to your heartbeat when you exercise?
What happens to your heartbeat after you stop exercising?
Hypotheses:
Write your prediction down on your paper to each of the three questions above. Finish this
sentence:
 My heart rate will _______________________________________.when I exercise.
 My heart rate will ____________________________ over the 16 minutes after I finish
exercising.
Experimental Design:
You will be measuring heart rate by counting the number of pulses in the artery in the wrist in a
15 second interval. Your instructor will show you how to find your pulse. You can find it by
using your index and middle finger on your wrist, just below your thumb pad, or you can find it
on the side of your neck, between the esophagus and tendons.
Wrist Pulse: Place the tips of the
first two fingers of one hand on the
palm side of your wrist, over toward
the thumb side of your wrist. Don’t
press too hard, or you won’t feel the
pulse of blood that each heartbeat
sends through the artery. Don't use
your thumb to feel the pulse in the
wrist, because your thumb has a
pulse of its own.
Neck Pulse: Place your index and middle fingers directly under
your ear, and then slide your fingers down until they are directly
under your jawbone, pressing lightly.
To measure heart rate, count the number of pulses in 30 seconds.
In our experiment, we will take your resting heart rate and record the number of beats for 30
seconds. Use the data sheet to record your data. After everyone has recorded his/her resting
heart rate, you will exercise (running in place or jumping jacks) for 1 minute. Immediately after
exercising, you will take your heart rate for 30 seconds and record the number of beats. Every
two minutes, take your heart rate and record that number. You will continue to record your heart
rate every 2 minutes for 16 minutes after exercising. Your instructor will time the 2 minutes, but
you need to watch the clock to record your heart rate for 30 seconds. Between taking your heart
rate, remain calm and seated.
Data Analysis:
When you have completed collecting the data (your heart rate for 30 seconds every two minutes
for a total of 16 minutes), you will multiply each of those rates by two. Why do you multiply by
2? You want to look at heart rate PER MINUTE, (30 seconds x 2 = 60 seconds, or 1 minute).
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After you have multiplied each datum by 2 to get the rate per minute, you will develop a graph to
picture what happened to your heart rate.
Graph: The line at the bottom of the graph is the minutes. The first line is labeled “B” for before
exercise, then “0” for just after you exercised. Then the graph is labeled 2, 4, 6, 8, 10, 12, 14,
and 16 for each 2-minute time interval. The line running up and down on the left side of the
paper is labeled from 30 to 250, and this is for your heart rate.
Use your first datum (singular for data), heart rate before exercise. It will go in the first column
(“B”), and find the number closest to your initial heart rate between 0 and 250 (it will probably
be in the around 60-90 beats per minute). Put a dot there with your pencil. Go to the “0”
column, and record your heart rate right after exercising. This will probably be the highest
number of beats per minute. It will probably be around 130-170 beats per minute. At the “2”
column, record the number of beats 2 minutes after exercising. Continue until you have placed
each datum on your graph.
Connect the dots. What is the shape of the line that connects the dots? Is it straight, curved,
goes up and down? What does it look like?
Conclusions and Communication:
Look at your neighbor’s graph. Is it similar or different from your graph? Compare with several
people’s graphs. Do any of the graphs look different, or are they all basically the same? Discuss
with your neighbor. Can you explain the graphs? What happened at the beginning before you
exercised? Was your heart rate fastest or slowest? How about just after exercise? What
happened each 2 minutes?
Scientific Method:
You have just conducted the scientific method. These are basic steps we follow in science.
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Questions
o We find questions when we read or make observations about our natural world.
They can be questions about anything in our natural world that can be tested.
o Once we have a question that interests us, we read everything we can about the
subject. Scientists who work in the same area as our interest may have some
interesting results, which would change our ideas about our question.
Hypothesis
o A hypothesis is simply our best guess what we think will happen when we
conduct an experiment. The most interesting results are when our prediction is
wrong!
Experiment Design
o After we have as much information about our question as we can discover and
made a prediction what we think will happen, we figure out how we can answer
our question. We have to think about all the different aspects, and try to make it
as simple as possible, only testing one variable at a time.
Analyze Data
o After we have collected all our data, we analyze it. Sometimes we need to
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perform mathematical equations before we can use our data. Data is almost
always numbers, or it can be converted to numbers. After our data is “cleaned”
(meaning that we have made the necessary calculations – in our experiment, we
multiplied each datum by two, to get your heart rate per minute), we make graphs
so that we can picture those numbers. The graphs tell us our answer.
Conclusion
o The conclusion is the answer we find in our graph to our question.
Communication
o In our class, you discussed your results with your neighbor, and talked about what
your graph meant. In science, we write papers that are published in magazines
called journals.
More and more questions
o While conducting the scientific method, scientists discover all kinds of questions
that are not part of their experiment. This becomes future science, and paves the
way to new discoveries!
Picture Citation:
Organ Systems
http://www.geocities.com/dennishhong/webquest_files/image003.jpg
ATP
http://scienceaid.co.uk/biology/physiology/images/atp.jpg
Mitochondria
http://www.cartage.org.lb/en/themes/sciences/zoology/AnimalPhysiology/Anatomy/AnimalCellStructure/Mitoc
hondria/mitochondria.jpg
How the lungs work
http://www.nhlbi.nih.gov/health/dci/Diseases/Copd/Copd_HowLungsWork.html
Diagram of the heart
http://www.abbottdiagnostics.com/Your_Health/Heart_Disease/images/heart_failure_1.gif
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Hypothesis (prediction)
Questions:
What happens to your heartbeat when you exercise?
What happens to your heartbeat after you stop exercising?
Hypotheses (plural of hypothesis):
Write your prediction down on your paper to each of the three questions above. Finish this
sentence:
 My heart rate will _________________________________________________________
when I exercise.
 My heart rate will _________________________________________________________
_______________________________________________________________________
over the 16 minutes after I finish exercising.
Data Table
Interval
Beats per 30 seconds
Times 2
Beats per minute
Before exercise
0 minutes
2 minutes
4 minutes
6 minutes
8 minutes
10 minutes
12 minutes
14 minutes
16 minutes
8
250
240
230
220
210
200
190
Heart Rate per minute
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
B
0
2
4
6
8
10
12
14
16
Before, Exercise, and Minutes After Exercise
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