Exam 3: Lecture 12 Flashcards
Define cardiac index
Cardiac output/square meter of body surface
*CI for normal human = 3L/min/m^2
Define cardiac output
1) Quantity of blood pumped into the aorta each minute
2) Quantity of blood that flows through circulation
3) Sum of all the blood flows to all tissues of the body
What are factors that control cardiac output?
Basic level of body metabolism
Whether person is exercising
Age
Size of body
What is the normal cardiac output value for young, healthy men?
5.6L/min
What is the normal cardiac output value for women?
4.9L/min
What is the normal cardiac output value for resting adults?
5.0L/min
What is the Frank-Starling law?
Heart will automatically pump whatever amount of blood flows into the right atrium
T/F: Peripheral factors are the most important controllers of cardiac output.
True, due to the Frank-Starling law
What is Ohm’s law?
Long-term changes in peripheral resistance levels cause cardiac output changes quantitatively in exactly the opposite direction
What is the Bainbridge reflex?
Controls HR along with baroreceptor reflex
a.k.a. Arterial Stretch Reflex
Responds to changes in blood volume as detected by stretch receptors in the right atrium
T/F: The Bainbridge reflex is only significant in humans immediately after birth.
True, because that is when a large volume of uteroplacental blood returns to the mother’s circulation and results in tachycardia
What is a hypereffective heart?
A heart functioning better than normal (athletic heart)
What are 3 factors that cause a hypereffective heart?
Nervous Stimulation
Hypertrophy of heart
Exercise via the nervous system
What is a hypoeffective heart?
A heart that is not functioning as well as it could
What are 7 conditions that lead to a hypoeffective heart?
1) Increased arterial pressure
2) Inhibition of nervous excitation of the heart
3) Coronary artery blockage
4) Congenital heart disease
5) Cardiac hypoxia
6) Valvular heart disease
7) Pathological factors
What are 4 conditions that cause increased cardiac output?
1) Beriberi
2) Atriovenous Fistula
3) Hyperthyroidism
4) Anemia
How does Beriberi increase cardiac output?
Caused by Vitamin B deficiency
Causes diminished ability of tissues to use some nutrients
Vessels vasodilate causing long-term venous return and cardiac output to rise
How does Atriovenous Fistula increase cardiac output?
Occurs when AV shunt placed between major artery and vein
Causes tremendous blood flow from artery into vein
Causes decreased peripheral resistance and increases venous return/cardiac output
How does Hyperthyroidism increase cardiac output?
Caused by increased metabolism of most tissues of body which increases vasodilator products
Causes total peripheral resistance to decrease and venous return/cardiac output to rise to 40-80% above normal
How does Anemia increase cardiac output?
Causes decreased viscosity of blood due to decreased [RBC] and deliver of O2 to tissues
Causes local vasodilation and cardiac output increases
What 2 conditions cause decreased cardiac output?
1) Decreased skeletal muscle mass
2) Decreased metabolic rate (hypothyroidism)
How does decreased skeletal muscle mass decrease cardiac output?
Causes decreased O2 consumption and blood flow needs to the muscles
Results in decreased skeletal muscle blood flow and cardiac output
How does decreased metabolic rate decrease cardiac output?
Means reduction of O2 consumption and nutrient needs to tissues
Therefore, blood flow decreases resulting in reduced cardiac output
When right atrial pressure is _____, venous return is _____.
+7 mmHg
0 mmHg
If right atrial pressure goes to -2 mmHg…
Venous return reaches a plateau due to collapse of veins entering chest
Mean systemic filling pressure - Right atrial pressure = ?
Pressure gradient for venous return
How much resistance of venous return is due to venous resistance?
~2/3
How much resistance to venous return is due to arteriolar/small arteries?
~1/3
Venous Return = ???
Pressure gradient for venous return / Resistance to venous return
What are the normal values for venous return, mean systemic filling pressure, & resistance to venous return?
VR = 5L SfP = 7 mmHg RVR = 1.4 mmHg/L/min
What are the local control factors that regulate blood flow to skeletal muscle?
Reduction in O2 Adenosine K+ ion ATP Lactic acid CO2
What are the nervous control factors that regulate blood flow to skeletal muscle?
Sympathetic vasoconstrictor nerves
Adrenal Medullae
What affect do sympathetic vasoconstrictor nerves have on nervous control?
Can decrease blood flow through resting muscles to as little as 1/2 or 1/3 normal
What affect do adrenal medullae have on nervous control?
Secrete norepinephrine/epinephrine
***Epinephrine also has a slight dilator effect
What 3 things happen during mass discharge of SNS?
1) HR increases
2) Most peripheral arteries are strongly contracted
3) Muscle walls of veins are contracted
T/F: All peripheral arteries are strongly contracted during a mass action SNS response.
False, all except…
Those in active muscles
Coronary arteries
Cerebral arteries
Increased arterial pressure caused by sympathetic stimulation causes…
Vasoconstriction of arterioles and small arteries in most tissues
Increased pumping activity of the heart
Increase in mean filling pressure caused mainly by venous contraction
Increase in cardiac output
What are the names of the 4 coronary arteries?
1) Right coronary artery
2) Left coronary artery
3) Left circumflex branch
4) Left anterior descending branch
Where is the right coronary artery located?
Extends from ascending aorta (between pulmonary trunk and vena cava) and runs along right, anterior atrium, then wraps around posteriorly
Where is the left coronary artery located?
Extends from ascending aorta (left of pulmonary trunk) and runs down left atrium, then splits into left circumflex & left anterior descending branches
Where is the left circumflex branch located?
Runs posteriorly along left atrial/ventricular border
Where is the left anterior descending branch located?
Runs anteriorly along septum dividing right/left ventricles and extends out to both ventricle
*Most critical branch
What is the phasic change of coronary blood during systole?
Coronary blood flow in the left ventricle falls to a low volume
What is the phasic change of coronary blood during diastole?
Cardiac muscle relaxes and no longer obstructs blood flow through the left ventricular capillaries
What is the primary controller of coronary blood flow?
Local muscle metabolism
What are the 4 causes of death after acute coronary occlusion?
1) Decreased cardiac output
2) Fibrillation of heart
3) Rupture of heart
4) Damming of blood in pulmonary blood vessels and death resulting from pulmonary edema
