Download Heart beat activity - Liberty Union High School District

3013Heartbeat activity
Name:___________________________________
What causes a Heart beat?
The atria and ventricles work together, alternately contracting and
relaxing to pump blood through your heart. The electrical system
of your heart is the power source that makes this possible.
Your heartbeat is triggered by electrical impulses that travel
down a special pathway through your heart:
1. SA node (sinoatrial node) – known as the heart’s natural pacemaker
The impulse starts in a small bundle of specialized cells located in
the right atrium, called the SA node. The electrical activity spreads
through the walls of the atria and causes them to contract. This
forces blood into the ventricles. The SA node sets the rate and
rhythm of your heartbeat. Normal heart rhythm is often called
normal sinus rhythm because the SA (sinus) node fires regularly.
2. AV node (atrioventricular node)
The AV node is a cluster of cells in the center of the heart between
the atria and ventricles, and acts like a gate that slows the electrical
signal before it enters the ventricles. This delay gives the atria
time to contract before the ventricles do.
3. His-Purkinje Network
This pathway of fibers sends the impulse to the muscular walls of the ventricles and causes them to contract. This
forces blood out of the heart to the lungs and body.
4. The SA node fires another impulse and the cycle begins again.
At rest, a normal heart beats around 50 to 99 times a minute. Exercise, emotions, fever and some medications can cause
your heart to beat faster, sometimes to well over 100 beats per minute.
How fast the heart beats depends on the body's need for oxygen-rich blood! The more oxygen the body demands,
the faster the heart beats to oxygenate the blood.
Take your pulse
. Place your index and middle finger of your hand on the inner wrist of the other arm, just below the base of the
thumb.
You should feel a tapping or pulsing against your fingers.
Count the number of taps you feel in 10 seconds.
Multiply that number by 6 to find out your heart-rate for one minute:
Pulse in 10 seconds x 6 = ____ beats per minute (your heart-rate)
When feeling your pulse, you can also tell if your heart rhythm is regular or not.
My resting heart rate =
Now plan an experiment to increase your heart beat. Do at least two variations of the experiment and chart your
heartbeat.
Hypothesis?_________________________________________________________________________________
____________________________________________________________________________________________
Independent variable?_____________________
Dependent variable?__________________________
Create a chart of your data with appropriate headings and graph results on next page. Write a conclusion and
include the hearts role in maintaining homeostasis.