E2: CV-Maternal Adaptations

Question 1

Describe in general, the ECG wave complex.

When do these occur?

1. Atrial Depolarization
2. Atrial Repolarization
3. Ventricular Depolarization
4. Ventricular Repolarization

Answer 1

P-QRS-T wave complex;

1. Atrial Depolarization: PR interval
2. Atrial Repolarization: Hidden in QRS complex
3. Ventricular Depolarization: QRS complex
4. Ventricular Repolarization: T-wave

Question 2

Review*

Question 3

How do the following affect Stroke Volume (SV);

1. Increased Contractility
2. Increased Preload
3. Increased Afterload

Answer 3

1. Increased Contractility > Increased SV
2. Increased Preload > Increased SV
3. Increased Afterload > Decreased SV

Question 4

How does increased End-diastolic volume (Frank-starling Law) affect Cardiac Output?

Answer 4

Increased End-diastolic vol. stretches the heart, which increases the Preload.

Stretched cardiac fibers can contract more forcefully (Frank-Starling Law), which would then increase the Stroke volume.

An increased SV will increase Cardiac Output

(CO=SV*HR)

Question 5

How do positive Ionotropic agents (i.e. increased sympathetic stimulation) affect Cardiac output?

Answer 5

Positive Ionotropic Agents (i.e. increased sympathetic stimulation or EC calcium) cause increased Contractility

Increased Contractility is increased force of contraction on ALL physiological levels of stretch.

Increased contractility increases Stroke Volume, which then in turn increases Cardiac Output.

Question 6

How does decreased arterial Blood pressure (during diastole) affect Cardiac Output?

Answer 6

Decreased arterial Blood pressure during diastole results in Decreased Afterload

A Decrease in Afterload causes the semilunar valves to open sooner when blood pressure in the aorta & pulmonary artery is lower. This results in an Increased Stroke Volume and subsequent increase in Cardiac Output.

CO=SV*HR

Question 7

How does increased sympathetic & decreased parasympathetic stimulation affect Cardiac Output?

Answer 7

Increased sympathetic & decreased parasympathetic stimulation causes an increase in Heart Rate & subsequent increase in Cardiac Output.

*Sympathetic stimulation also increases Contractility and thus increasing Stroke Volume.

Question 8

How do Catecholamines or Thyroid hormones in the blood or moderate increases in Extracellular Calcium affect Cardiac Output?

Answer 8

Catecholamines or Thyroid hormones in the blood or moderate increases in Extracellular Calcium causes an increase in HR and subsequent increase in Cardiac Output.

Question 9

What “other factors” may increase Heart Rate?

Answer 9

• Age: Infants & Senior Citizens
• Sex: Females
• Physical Fitness: Low
• Body Temp: Elevated

Question 10

What Factors affect SV? What about HR?

Answer 10