2 - Cardiac Flashcards
(103 cards)
Why does cardiac output decrease with age?
Indicative of decreased basal metabolic rate and decreased muscle mass
When the right atrium is stretched, it triggers which reflex?
Bainbridge
According to Ohm’s Law, what is the calculation for Cardiac Output?
Arterial Pressure/Total Peripheral Resistance
How does BerBeri effect cardiac output?
Massively increased
Interferes with cells’ ability to use nutrients, creating enormous vasodilation to try to get more nutrients to the cells
Decreased peripheral resistance –> increased CO
Would an AV shunt/fistula cause increased or decreased cardiac ouput?
Increased
More venous return
How does hyperthyroidims effect cardiac output?
Increases 40-80% above normal
Increased metabolic rate
How does anemia influence cardiac output?
Increases
Decreased O2 carrying capacity, triggers vasodilation in the periphery
What are 5 peripheral factors that lower cardiac ouput?
Decreased Blood volume
Acute venous dilation
Large Vein obstruction
Decreased tissue mass (skeletal esp)
Decreased metabolic rate
What is the mean systemic filling pressure?
The pressure at which all systemic flow in the periphery ceases, and both atrial and venous pressures reach equilibrium
Venous return increases as RA pressure decreases, but if RA pressure are less than 0, venous return plateaus even if the RA becomes more and more negative. Why?
Because the veins collapse
Negative pressure in the RA sucks the walls of the large veins entering the thorax together
What is the mean circulatory filling pressure?
Pressure that would be measured in the entire circulatory system if cardiac pumping stopped completely
A big increase in blood volume (bolus) only increases cardiac output for a couple of minutes. What three compensatory effects cause this?
- Increased cardiac output increase capillary pressure, creating diffusion out of the capillary
- stress-relaxation in veins causes them to distend in response to the increased volume
- Autoregulation increases peripheral vascular resistance, which decreases venous return
How does a Fick equation determine cardiac output?
Measures the rate of oxygen diffusion by comparing a mixed venous O2 levels with arterial levels
During exercise, why do capillaries dilate?
- Internal:
decreased o2 and presence of vasodilators (K, ATP, lactic acid, CO2, adenosine)
- External:
sympathetic stimulation
During exercise, while the capillaries are dilating, the major vessels are _________
contracting
increases flow
Most of the venous flow from the L ventricle returns to the heart via _______
Most of the venous return from the R ventricle returns via __________
coronary sinus
anterior cardiac veins
How does the heart get extra nutrients during exercise?
Partially through increased coronary flow, but that alone isn’t sufficient. The heart has to be more efficient and utilize energy optimally to make up the difference and provide the needed cardiac output.
Coronary arteries perfuse the heart during _______
Diastole
At a normal resting state, what is the % VO2 of cardiac muscle?
70%!
Constrictor receptors are called ________
Dilator receptors are called _________
Alpha Receptors
Beta Receptors
The epicardial coronary vessels have mostly ______ adrenergic receptors.
The intramuscular arteries have most ______ adrenergic receptors.
Alpha
Beta
What is the major driver of vasodilation and vasoconstriction in the coronary arteries?
Metabolic control
Very little sympathetic control
In all tissues, more than 95% of the energy liberated ffrom foods is used to ________
form ATP in the mitochondria
What is the role of adenosine in capillaries?
When ATP is broken down and not resynthesized, adenosine is floating freely in the cell. If it escapes into the vasculature, that’s a sign to the body that the tissue needs more oxygen/nutrient delivery, and the capillary dilates
