Ch 20

Question 1

cardiac output is equal to _____/ ______

Answer 1

Arterial pressure / total peripheral resistance

Question 2

What is the bainbridge reflex?

Answer 2

Stretching the sinus node in the right atrium (usually via increased venous return) increases heart rate by 10-15% by stimulating the vasomotor center of the brain and the SNS nerves and vagus

Question 3

What factors cause the heart to become hypereffective?

Answer 3

nervous stimulation or cardiac muscle hypertrophy

Question 4

What factors cause the heart to become hypoeffective?

Answer 4

-Increased hypertension
-Inhibited cardiac nervous excitation
-Arrhythmia
-Coronary artery blockage
-Valvular heart disease
-Congenital heart disease
-Myocarditis
-Cardiac hypoxia

Question 5

Which factors shift the cardiac output curve and therefore alter the external pressure on the heart?

Answer 5

-Cyclical changes of intrapleural pressure during respiration
-Breathing against negative pressure
-Positive pressure breathing
-Opening the thoracic cage
-Cardiac tamponade (assoc with pericardial fluid accumulation)

Question 6

What are the three principal factors that affect venous return to the heart from systemic circulation?

Answer 6

1. Right atrial pressure: exerts a backward force on the veins
2. Mean systemic filling pressure: forces systemic blood toward the heart
3. Resistance to blood flow: …b/w peripheral vessels and the right atrium

Question 7

How does mean systemic filling pressure influence venous return?

Answer 7

The greater the difference between the MSFP and right atrial pressure, the greater becomes venous return

Question 8

Where does most of the resistance to venous return occur?

Answer 8

In the veins (some in arterioles and arteries)

Question 9

How does the body compensate for increased blood volume? (hint: 3 ways)

Answer 9

1. Increased capillary pressure
2. Venous stress-relaxation, including the reservoirs such as the liver and spleen
3. Increased peripheral resistance to venous return

Question 10

In summary, how does sympathetic stimulation affect the heart and systemic circulation?

Answer 10

1. Makes the heart a stronger pump
2. In systemic circulation, it increases mean systemic filling pressure
3. Increases resistance to venous return