Cardiac output and venous return Flashcards
What are the 3 definitions or caridac output?
- quantity of blood pumped into the aorta each minute by the heart
- quantity of blood that flows through the circulation
- sum of all the blood flows to all of the tissues of the body
How would you define cardiac index?
Cardiac output per square meter of body surface
What is the relationship between cardiac index and age?
Cardiac index peaks around 10 yrs and begins to decline as one ages
What is the relationship between cardiac output, cardic index, and oxygen consumption during exercise?
They all increase relative to the amount of work/exercise you are doing
Why would you uses the Fick principle of blood flow?
To calculate blood flow through an organ.
According to the Fick principle of blood flow, what equation would you use to calculate cardiac output?
Cardiac output = O2 Consumption / [O2] pul vein - [O2] pul art
- Measure oxygen consumption for the whole body
- measure pulmonary vein [O2] in systemic arterial blood
- measure pulmonry artery [O2} in systemic mixed venous blood
How are cardiac output, stroke volume, and heart rate related?
CO = SV x HR
What is the determining factor that controls how much blood the heart pumps out?
- Venous return
- it is the amount of blood returning to the heart that determines how much blood the heart pumps out
The cardiovascular system consists of two pumps and two circuits that are connected in ________?
Series
What are the 2 pumps of the cardiovascular system?
The left and right ventricles
Name the two the circuits of the cardiovascular system.
- Pulmonary circuit
- Systemic circuit
Because the 2 circuits of the cardiovascular system are in series what must be true about flow in the 2 circuits?
Flow must be equal in the 2 circuits
Because the 2 circuits of the cardiovascular system are in series, what is the relationship between cardiac output and flow of the 2 systems?
Cardiac output and rate of the 2 systems of the two circuits are equal
Because the 2 circuits of the cardiovascular system are connected in series, what relationship exists between the pressures of the 2 circuits?
All pressures are higher in the systemic circuit
Because the 2 circuits of the cardiovascular system are in series, the chemical composition os pulmonary venous blood is similar to that of _________ _________ blood?
Systemic arterial
Because the 2 circuits of the cardiovascular system are in series, the chemical composition of venous blood entering the right atrium is the same as the composition of _______ ________ blood?
Pulmonary arterial
Name 3 of the 4 factors that directly affect cardiac output.
- Basic level of body metabolism
- Whether the person is exercising
- Age
- Size of the body
What are the normal cardiac output values for healthy young men, women, and the resting adult?
- healthy young men- 5.6 L/min
- Women - 4.9 L/min
- Resting adult 5.0 L/min
Summarize the Frank-Starling law of the heart
The heart autoomatically pumps whatever amount of blood that flows into the right atrium.
Stretching of the heart causes the heart to pump ______?
Faster
Stretching of the right atrium initates nervous reflex called what?
The Bainbridge reflex (increases heart rate)
Under most normal non-stressull conditions, the cardiac ouput i controlled almost entirly by _________ factors that determine _______ ________?
Peripheral, venous return
What are the most imortant controllers of cardiac output?
Peripheral factors
How does Ohm’s law summarize the control of cardiac output?
Anytime the long-term level of total peripheral resitance changes (but no other functions of the circulation change), the cardiac output changes qantitatively in exactly the opposite direction
20-4
What two reflexes control heart rate?
- The bainbridge reflex
- The baroreceptor relex
How are the Bainbridge reflex and the barorecepto reflex different from each other?
- Bainbridge reflex (atrial stretch)—responds to changes in blood volume as detected by stretch receptors in the right atrium
- Baroreceptor reflex— responds to changes in arterial pressure
As total peripheral resistance increases cardiac output ________?
decreases
20-4
How are cardiac output, arterial pressure, and total peripheral resistance related?
Cardiac output = Arterial pressure / Total peripheral resistance
20-4
As arterial pressure increases cardiac output _________?
increases
List 2 of the 3 factors that cause a hyperefective heart
- Nervous stimulation
- Hypertrophy of the heart
- Exercise via the nervous system
Summarize why exercise via the nervous system causes a hypereffective heart?
- Intense increase in metabolism in active skeletal muscle causes the muscle arterioles to relax
- This allows more blood into these arterioles
- The brian sends motor signals to the muscle and to the ANS centers of the brain to excite circulatroy activty
- This causes large vein constrictiono
- This leads to increased heart rate, and increased contractility of the heart
Name 4 of the 7 factors that cause a hyporeffective heart
- increased arterial pressure (hypertension)
- inhibition of nervous excitation of the heart
- pathological factors causing abnormal heart rythm/rate
- coronary artery blockage
- valvular heart disease
- congenital heart disease
- cardiac hypoxia
20-5
List 3 of the 5 factors that cause decreased cardiac output.
- severe blood vessel blockage—->myocardial infarction
- severe valvular disease
- myocarditis
- cardiac tamponade
- cardiac metabolic arrangements
Beriberi causes a(n) _________ cardiac output as the result of _________ total peripheral resitance?
increased, reduced (chronically)
An arteriovenous (AV) fistula (shunt) causes _________ cardiac output as a result of _________ total peripheral resistance?
Increased, reduced (chronically)
Hyperthyroidism causes ________ cardiac output as a result from _________ total resistance?
Increased, reduced (chronically)
Anemia causes __________ cardiac output as a result of ________ total peripheral resistance?
increased, reduced (chronically)
Decreased skeletal muscle mass causes __________ cardiac output as a result from decreased ________ _________?
decreased, venous return
Decreased metabolic rate (hypothyroidism) causes decreased ________ ________ as a result from ________ venous return?
cardiac output, decreased
Name 3 of the 5 NON-CARDIAC factors that cause a decreased cardiac output
- Decreased blood volume
- acute venous dilation
- obstruction of large veins
- decreased tissue mass (especially muscle mass)
- decreased metabolic rate of tissues
The greater the difference betweeen the mean systemic filling pressure and the _______ _______ pressure, the greater the venous return
right atrial
What is the difference between the mean systemic filing pressure and the right atrial pressure?
Pressure gradient for venous return
About 2/3 of the resistance to venous return is determined by ________ ________?
venous resistance
About 1/3 of the resistance to venous return is determined by ________ and _______ _______ resistance?
arteriolar, small artery
What equation would you use to calculate venous return?
venous return = (systemic filling pressure - right atrial pressure) / Resistance to venous return
VR= (Psf-PRA) / RVR
Name 4 of the 6 chemicals that are responsible for stimulating large blood flow by dilating muscle arterioles during skeletal muscle activity
- reduction in O2
- adenosine
- potassium ions
- ATP
- Lactic acid
- Carbon dioxide
