PMS Heart Exam
1. What is the cardiac cycle?: Events from the beginning of one heartbeat to the next
- increasing HR decreases the duration of the cardiac cycle
2. Describe blood flow through the heart.: 1. Superior & Inferior Vena Cava
2. Right atrium
3. Tricuspid valve
4. Right ventricle
5. Pulmonary semilunar valve
6. Pulmonary trunk
7. Pulmonary arteries
8. Lungs
9. Pulmonary veins
10. Left atrium
11. Mitral/bicuspid valve
12. Left ventricle
13. Aortic semilunar valve
14. Aorta
15. Distributed into systemic circulation
3. What are the structures and functions of cardiac muscle?: 1. Intercalated discs - allow
1/9
,the heart to beat in a synchronized manner
2. Gap junctions - allow direct ion flow between cells, which assist intercalated discs in the spread of action potentials
within the cardiac muscle
3. Desmosomes - provide mechanical strength to cardiac muscle tissue
4. Which structure generates the normal rhythmical pulses of the heart?: SA node
5. What is the average action potential in ventricular muscle fiber?: 105 mV
6. What happens to intracellular potential during each beat?: Rises from about -85 mV
(resting membrane potential) to about +20 mV during each beat
7. Why does a plateau phase occur after depolarization?: - To give enough time for ventricle
to refill with blood after ventricular contraction
- abrupt repolarization occurs at the end of plateau
2/9
, 8. Which channels are involved in cardiac muscle action potentials?: Fast sodium
channels: same as those in skeletal muscle
L-type calcium channels (Slow calcium channels)
9. What happens to potassium ion permeability after the onset of the cardiac
action potential?: Decreases about fivefold immediately after onset of action potential
- this effect does not occur in skeletal muscle
- this occurs because if the permeability of K+ increased, the cell would become weaker as it enters the hyperpolarization
state and requires more energy to repolarize
10. Describe what triggers the 5 phases of the cardiac muscle action potential.-
: Phase 0 (Depolarization):
- Influx of Sodium ions (Na+)
Phase 1 (Initial Repolarization):
- Efflux of potassium ions (K+)
Phase 2 (Plateau):
3/9
1. What is the cardiac cycle?: Events from the beginning of one heartbeat to the next
- increasing HR decreases the duration of the cardiac cycle
2. Describe blood flow through the heart.: 1. Superior & Inferior Vena Cava
2. Right atrium
3. Tricuspid valve
4. Right ventricle
5. Pulmonary semilunar valve
6. Pulmonary trunk
7. Pulmonary arteries
8. Lungs
9. Pulmonary veins
10. Left atrium
11. Mitral/bicuspid valve
12. Left ventricle
13. Aortic semilunar valve
14. Aorta
15. Distributed into systemic circulation
3. What are the structures and functions of cardiac muscle?: 1. Intercalated discs - allow
1/9
,the heart to beat in a synchronized manner
2. Gap junctions - allow direct ion flow between cells, which assist intercalated discs in the spread of action potentials
within the cardiac muscle
3. Desmosomes - provide mechanical strength to cardiac muscle tissue
4. Which structure generates the normal rhythmical pulses of the heart?: SA node
5. What is the average action potential in ventricular muscle fiber?: 105 mV
6. What happens to intracellular potential during each beat?: Rises from about -85 mV
(resting membrane potential) to about +20 mV during each beat
7. Why does a plateau phase occur after depolarization?: - To give enough time for ventricle
to refill with blood after ventricular contraction
- abrupt repolarization occurs at the end of plateau
2/9
, 8. Which channels are involved in cardiac muscle action potentials?: Fast sodium
channels: same as those in skeletal muscle
L-type calcium channels (Slow calcium channels)
9. What happens to potassium ion permeability after the onset of the cardiac
action potential?: Decreases about fivefold immediately after onset of action potential
- this effect does not occur in skeletal muscle
- this occurs because if the permeability of K+ increased, the cell would become weaker as it enters the hyperpolarization
state and requires more energy to repolarize
10. Describe what triggers the 5 phases of the cardiac muscle action potential.-
: Phase 0 (Depolarization):
- Influx of Sodium ions (Na+)
Phase 1 (Initial Repolarization):
- Efflux of potassium ions (K+)
Phase 2 (Plateau):
3/9
