Download What Is the Electrical System in Your Heart?

Bryn Herdrich
Title: Caffeine, Sugar, and You!
Introduction:
Goals
* To observe the effect caffeine and sugar (the substances found in commercially sold energy
drinks) affect your heart rate.
* To compare the effect these substances have on the heart rate of a person who does not
normally drink large amounts of caffeine to the effects it has on a person who regularly drinks
large amounts of caffeine.
Relevance to Students:
* Many students regularly drink large amounts of commercially sold energy drinks to help them
stay up to study. We would like to see what kind of effect this caffeine is having on their bodies.
Variables:
* Independent: The amount of “energy drink” ingested measured in mL
* Dependant: Students’ heart rates measured in potential milivolts by electrocardiogram(EKG)
Materials:
-appx. 3 liters of any commercially sold energy drink (we are using Red Bull)
-exercise heart rate moniter
-electrocardiogram (EKG)
-saliene solution (to moisten heart rate moniter electrodes)
-lab pro adapter
-logger pro computer program
-computer
- 3 students
= 1 student who doesn’t drinks energy drinks…………………………………(Jessie)
= 1 student who drinks a moderate amount of energy drinks…………………(Phil)
= 1 student who drinks large amounts of energy drink regularly………………(Chris)
Method/Procedure
1. Hook up Lab Pro device to computer
2. Moisten heart rate moniter electrodes and ask student volunteer to put it on so that it fits
tightly across chest
3. Attach heart rate moniter sensor to lab pro device
4. Stick EKG electrode patches on insides of both of volunteer’s
elbows and on the inside of volunteer’s right wrist
5. plug electrocardiogram into LabPro device
6. connect micro alligator clips (circled in picture) to tabs on edges of
electrode patches, attatching the green clip to the right elbow, the
red clip to the left elbow, and the black clip to the right wrist
7. open logger pro softwar, and collect data for 5 minutes, asking
student volunteer to relax so you can establish a sitting heart rate
8. after 5 minutes, have student drink 250 mL, record data for 7
minutes
9. after seven minutes, have student drink another 250 mL
10. repeat steps 8 and 9 about 6 times
11. after 6th 250 mL drink, collect data for another 10 minutes
12. repeat steps on next volunteers
NOTE!!!!! Do not let amount of caffeine drunk by volunteers exceed 800 mg…any more
than this amount can be dangerous to a person’s health!!!!
Expectations:
***I expect that when we graph the results of our experiment, the graph of heart rate to amount of
energy drink drunk will not be linear. I think that for the first couple times the person drinks the
energy drink, it will not increase their heart rate very much, but then, by the third or fourth cup,
their heart rate will suddenly increase. I expect this will happen because for a certain amount of
time, I think the body will be able to deal with the caffeine and perhaps spread it out throughout
the bloodstream, but at a certain point the body will no longer be able to continue to keep up with
the amount of caffeine being put into the system, and so the heart rate will suddenly go up.
Results of Experiment Attempt #1:
*** We just attempted our experiment for the first time today, and we are had several problems
that made it so we couldn’t get accurate results. First, we had Jessie (our student volunteer) drink
only 100 mL of caffeine instead of 250mL. This was not enough caffeine to get any rapid effects.
Secondly, since we were limited on time, we had her drink the red bull every 3 minutes. This
caused two separate problems. First, as soon as Jessie raised her hand to drink the red bull, her
heart rate spiked, messing with our results. Secondly, three minutes wasn’t enough time for the
caffeine in the first cup of Red Bull to take effect, so by drinking the second so soon after the first
cup, both cups would start working at about the same time, again messing with the results. We
used these problems to alter our procedure to make it more specific, and hopefully we’ll be able to
do it next time.
Results of Completed Experiment : TBA
Appendix I:
Adenosine: A nucleoside that is a structural component of nucleic acids and the major molecular
component of ADP, AMP, and ATP.
When adenosine attaches to adenosine receptors in the brain, nerve cells activity is slowed,
making a person drowsy.
Adrenaline: A hormone secreted by the adrenal glands that helps the body meet physical or
emotional stress
Caffeine prevents adenosine from linking to adenosine receptors in the brain, and so nerve
cells are not slowed, and the body produces adrenaline to keep up with its energy needs.
Atrioventricular (A-T) Node: a small mass of tissue that is situated in the wall of the right
atrium adjacent to the septum between the atria, passes impulses received from the sinoatrial
node to the ventricles by way of the bundle of His, and in some pathological states replaces the
sinoatrial node as pacemaker of the heart.
The A-T Node acts as a bridge between the S-A node and the rest of the heart.
Caffeine: a drug that stimulates the central nervous system.
Caffeine, a stimulant, has many effects on the body including increased alertness and heart
rate.
cAMP: A cyclic nucleotide of adenosine that acts at the cellular level to regulate various metabolic
processes and mediate the effects of many hormones. cAMP is not destroyed when a person has
drunk a large amount of caffeine, and so the molecule continues to send messages to cells,
keeping them active, causeing the feeling of jitteriness that many people experience when
drinking caffeine.
Depolarization: a loss of polarity or polarization, Elimination or neutralization of polarity, as in
nerve cells.
Heart cells are depolarized when they are stimulated in some way, and positively charged
sodium ions are able to enter into the previously negatively charged cells.
Electrocardiogram: The curve traced by an electrocardiograph. Also called cardiogram
Electrocardiograph: An instrument used in the detection and diagnosis of heart abnormalities that
measures electrical potentials on the body surface and generates a record of the electrical currents
associated with heart muscle activity. Also called cardiograph.
By looking at an electrocardiogram, people are able to see how substances, such as caffeine,
affect the speed of the heart.
Electrode: A solid electric conductor through which an electric current enters or leaves an
electrolytic cell or other medium. A collector or emitter of electric charge or of electric-charge
carriers, as in a semiconducting device.
Electrodes attached to the skin are able to pick up on the electric fluctuations on the heart.
Once picked up, they can be graphed to form an EKG (electrocardiogram)
Ion: An atom or a group of atoms that has acquired a net electric charge by gaining or losing one
or more electrons.
Positively charged sodium ions on the outside of heart cells cause the cells to become
polarized.
Heart: The chambered muscular organ in vertebrates that pumps blood received from the veins
into the arteries, thereby maintaining the flow of blood through the entire circulatory system.
Caffeine causes the heart to pump blood around the body more quickly.
Heart Rate: The number of heartbeats per unit of time, usually expressed as beats per minute.
Heart Rate Monitors are machines that use electricity to measure the number of beats per
minute a person is experiencing.
His-Purkinje system: This is the system of the heart including the atriums and ventricals.
Electrical signals start in the S-A node, goes through the A-T node into the His Purkinje
system.
Milivolts: 1/1000 of a volt, this is what electrical signals in the heart are measured in. The outside
of a heart is charged 90 mV more than the inside.
The charge inside a heart cell is about 90 milivolts less then the charge outside the heart.
Permeable: That can be permeated or penetrated, especially by liquids or gases. When a heart
cell is stimulated, it becomes more permeable, and so sodium ions are able to get through the
cell membrane, into the cell.
Polarized: To separate or accumulate positive and negative electric charges in two distinct regions.
Heart cells are polarized, as the total charge on the inside of them is far less than the charge
outside the membrane.
Potential Milivolts: The number of milivolts possibly able to be exchanged in depolarization.
In the case of heart molecules, they have 90 potential milivolts.
Phosphodiesterase: Any of a class of enzymes that catalyze the cleaving of phosphodiester
bonds, such as those between nucleotides in nucleic acids, to produce smaller nucleotide units or
mononucleotides but not inorganic phosphate.
Caffeine slows the production of Phosphodieterase in the body, and so the body is unable to
destroy molecules of cAMP.
Sinoatrial (S-A) Node: A small mass of specialized cardiac muscle fibers located in the posterior
wall of the right atrium of the heart that acts as a pacemaker of the cardiac conduction system by
generating at regular intervals the electric impulses of the heartbeat. Also called sinoauricular
node, sinus node.
It is the polarization and depolarization in the Sinoatrial Node that causes the rest of the
heart to contract.
Stimulant: An agent that arouses organic activity, strengthens the action of the heart, increases
vitality, and promotes a sense of well-being.
Caffeine is classified as a stimulant, along with other drugs such as cocaine.
Appendix II
Electrocardiographs: How They Work
1. Heart cells are polarized at rest.
An excess of positive sodium ions
on outside of the heart cell’s
membrane causes it to have a
positive charge relative to the
inside of the membrane. The inside
of the membrane is at a potential
of about 90 milivolts LESS than
the outside of the cell membrane.
This 90 mV difference is called
resting potential.
2.The typical cell membrane is
relatively impermeable to
sodium, however, when a
muscle is stimulated, it is made
more permeable to sodium.
Therefore, when heart muscles
are stimulated, sodium enters
them, causing a change in the
electrical field around the
cell(depolarization). This
change in negative to positive,
and then back to negative is a
voltage pulse called action
potential.
In muscle cells, this action potential causes a contraction.
Note: Other ions are involved in the depolarization and repolarization of the cardiac muscle
including potassium, calcium, chlorine, and charged protein molecules.
The sum (total) action potential of the heart can be recorded by electrodes placed on the surface of
the skin.
An electrocardiogram summarizes
all the action potentials of the heart.
It does not measure the mechanical
contractions of the heart directly,
like a heart rate monitor does.
Exercise Heart Rate Monitors:
This graph shows a person’s
average heart rate over a period of
time, which is very different from an
electrocardiogram, which shows
the polarization and depolarization
of a heart over time.
Heart rate monitors work much in the same way as electrocardiographs, but are slightly less exact.
A heart rate monitor measures the number of times a person’s heart depolarizes and polarizes, and
translates that as a single heart beat. The monitor then measures and records the average number of
times the heart beats per minute.
What Is the Electrical System in Your Heart?
The electrical system in your heart controls the speed of your heartbeat. The system includes a
network of electrical pathways, similar to the electrical wiring in your home. The pathways carry
electrical signals through your heart. The movement of the signals is what makes your heart beat.
When working properly, your heart's electrical system automatically responds to your body's
changing need for oxygen. It speeds up your heart rate as you climb stairs, for example, and slows
it down when you sleep. When your heart rate speeds up, it means your heart pumps faster and
your body gets more oxygen-rich blood.
Your heart's electrical system is also called the cardiac conduction system.
Parts of the Electrical System
Your heart's electrical system includes three important parts
1.
S-A node (sinoatrial node)
2.
A-V node (atrioventricular node)
3.
His-Purkinje system
1.The S-A Node: Your Heart's Natural Pacemaker
The S-A node is a bundle of specialized cells in your right
atrium. The S-A node cells are special because they create the
electricity that makes your heart beat. The S-A node normally
produces 60-100 electrical signals per minute — this is your
heart rate, or pulse.
The S-A node is called the "natural pacemaker" of your heart
because it controls your heart rate.
2.The A-V Node: Your Heart's Electrical Bridge
The A-V node is a bundle of specialized cells between your
heart's upper and lower chambers (between the atria and
ventricles). The A-V node cells are special because they allow
electricity to pass through them. Except in rare conditions, no
other cells between the atria and ventricles allow this. So, the AV node is the "electrical bridge" between the atria and ventricles.
Some types of slow heart rhythms (bradycardias) are caused by problems in the A-V node.
The His-Purkinje System
The His-Purkinje system is in your heart's ventricles. Electricity travels through the His-Purkinje
system to make your ventricles contract. The parts of the HisPurkinje system include:

His Bundle (the start of the system)

Right bundle branch

Left bundle branch

Purkinje fibers (the end of the system)
Caffeine:
more popularly known for its energy boosting effects as well as its ability to keep those who need
to stay awake up for longer periods of time.
How does caffeine “work”?
1. Every day, as you do activities, adenosine is produced in your body. As the day progesses,
adenosine levels build up in the brain.
2. Molecules of adenosine link up to adenosine receptors in the brain, slowing nerve cell activity,
making you sleepy
Caffeine molecue
Adenosine Molecule
sine
receptors mistake caffeine for adenosine and will bind to caffeine.
The binding of caffeine does not slow cell activity as much as the binding of adenosine, and a
person does not become as tired because all the nerve cells in the brain continue to be fully active.
At the same time, the caffeine blocks adenosine from binding to the receptors, keeping the person
from becoming tired
The body then perceives the active brain nerves as a signal of activity and will secrete adrenaline
to cope with it.
second messenger cAMP from a cell.
time and continues to excite the cell. As a result, excitory signals such as adrenaline have a
prolonged effect. This is why a person who has consumed caffeine feels more alert.
So how does this Affect the Heart?
When adrenaline is released into the system, it tells the S-A node to increase the heart rate. The
more caffeine you drink, the more adrenaline is released into you system, causing your heart rate
to also raise.