NAME & section #:
PRELAB EXERCISE
HEART FUNCTION IN THE FROG
(Martini 682-686, 687-692, 697-714)
TO BE COMPLETED BEFORE THE LAB
Bring your dissecting kit to the lab!!!!!
1. Define systole and diastole.
2. What is the sequence of contraction of the atria and ventricles in the human heart? For example, does the
right atrium contract first, followed by the right ventricle, then the left atria and last of all the left ventricle?
If not, what is the correct sequence?
3. Complete the following table:
SKELETAL MUSCLES
ALL-OR-NONE LAW
MEANS OF STIMULATION
LENGTH OF THE
ABSOLUTE REFRACTORY
PERIOD
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CARDIAC MUSCLE
4. What is the absolute refractory period during muscle contraction? What is the advantage for cardiac
muscle to have a long absolute refractory period?
5. The ability of the cardiac muscle to depolarize and contract is intrinsic: it is a property of the heart
muscle itself and does not depend on extrinsic nerve impulses. In fact, if all nerve connections to the heart
are cut, the heart continues to beat rhythmically.
On a separate page, answer the following questions (or make drawings):
Describe where the action potentials are generated in the heart (where are the autorhythmic cells in the
heart? which ones predominate and set the intrinsic heart rate?).
Describe the pathway that the depolarization wave follows when it spreads from the sinoatrial (SA) node
throughout the heart and initiates contraction of the cardiac muscle.
As you describe this pathway, relate the sequence of electrical events to the actual atrial and ventricular
systole and diastole.
6. Describe the neural control of heart rate. What are the nerves involved? What are their
neurotransmitters? What are their effects on heart rate?
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