Review of Section 3 : Self-test
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1. What are four characteristics of myocardial tissue that allow it to integrate the heart’s electrical and mechanical activity?
2. What is the cardiac cycle? Name the three components of this cycle.
3. Define SYSTOLE and DIASTOLE.
4. What is the first mechanical event of the cardiac cycle?
5. Name 5 components of the cardiac conduction system.
6. What is the heart’s pacemaker? Where is it located?
7. What happens when the impulse reaches the terminal ends of the Purkinje fibers?
8. Pacemaker cells need no outside stimulus to generate electrical impulses. What system regulates the rate of cardiac contraction?
9. From what organ does this system originate?
10. In response to exercise or stress, what hormone is released by the sympathetic nerves?>
11. What neurotransmitter acts to decelerate the heart rate?
12 . Cardiac muscle cells interconnect to form a syncytium. What is the importance of this characteristic?
13. What happens after an excess of positive charges accumulates on the outside of the cell membrane?
14. Electrical activity in myocardial tissue depends on electrolyte imbalance and a difference in ___________ .
15. Name the two stages of the action potential.
1. Automaticity; Excitability; Conductivity; Contractility
2. A cardiac cycle is defined as a complete cardiac movement, including systole, intervening pause, and diastole.
3. Systole is the contraction phase, diastole is the filling phase of a cardiac chamber.
4. VENTRICULAR SYSTOLE is considered to be the first mechanical event of the cardiac cycle.
5. Sinoatrial node; Atrioventricular node; Atrioventricular bundle; Right and left bundle branches; Purkinje fibers.
6. The SA (sinoatrial node) is the heart’s pacemaker. It is located high in the wall of the right atrium near the entrance of the superior vena cava
7. The Purkinje fibers carry electrical impulses to the individual myocardial cells, resulting in simultaneous contraction of all parts of both ventricles.
8. The parasympathetic (vagus) and sympathetic systems innervate the heart, acting to increase or decrease overall cardiac function.
9. The medulla oblongata (brain stem).
10. Sympathetic stimulation increases the overall activity of the heart with release of norepinephrine.
11. Parasympathetic nerves travel from the brain to the heart in the vagus nerve. Stimulation of the vagus nerve releases the neurotransmitter acetylcholine, which indirectly slows the heart rate.
12. This characteristic allows excitation waves to pass quickly throughout the myocardium.
13. The cell depolarizes, creating electrical current.
14. Electrical potential.
15. Depolarization and Repolarization.