Supply and Demand Flashcards
What are the ways in which an imbalance in tissues oxygen supply can lead to anaerobic metabolism?
Body prefers aerobic metabolism bc it is more efficient and does not produce lactic acid. If there is a descrepency bt supply and demand we get anaerobic metabolism.
* either a normal supply of oxygen and excessive demand or vise versa
HIT workouts are short and intense. What situation of supply/demand of oxygen does our body experience? And what metabolism is triggered?
normal supply and high demand
anaerobic metabolism- production of lactic acid
What are the 2 ways we metabolize for energy?
To get energy we need to metabolize - usually carbohydrates. We metabolize either aerobically or anaerobically to produce energy. There is a balance between the supply and demand for oxygen.
How would you write the Ohm’s law analogy for the cardiovascular system in terms of cardiac output, systemic vascular resistance (SVR) and driving pressure?
Delivery of O2 = Q (cardiac output) x O2 content of blood
mean arterial pressure (P1) and P2 is the venous pressure
delta P= P1 - P2 which is = Q (blood being pumped by heart) x SV
Ohm law: P= F x R
so [change in P = Q x SVR]!!
What is the relationship between oxygen content of blood, cardiac output (Q), and oxygen delivery?
The delivery O2 = O2 content of blood x volume of blood sent around to tissue
* by ohms law P= F x R
the flow here refers to the volume of blood/time sent to tissues called the cardiac output (Q)
What are the two things that contribute to resistance (SVR) in supply/demand?
- changes to the vascular tone
muscles around blood vessels that tighten/relax which change radius and by Poiselles law R is proportional to 1/r^4
so radius is powerful determinant of resistance - blockages or obstructions in vessels
both decrease radius which increases resistance
and changes increase in resistance will decrease flow
What is the relative importance in the body of changes in driving pressure versus changes in resistance in determining flow?
changes in resistance result from changes in radius due to blockage or muscle tone. Smaller radius - increased resistance.
Icreased resistance - determines flow (dec) when pressure remains the same
P = Q x SVR
What is the effect on blood flow of a partial blockage in a vessel supplying blood and oxygen to an organ?
picture artery (subepicardial outer side of heart) penetrating heart muscle or (subendocardial) when muscle contracts it squeezes the artery and blocks the flow, flow only occurs during relaxation
- subendocardial inner muscle layer of heart is particularly susceptible to problems of imbalance of supply/demand
The Fick principle equation:
oxygen consumption in heart:
delivery of O2 from heart to tissue is D02 = CaO2 (arterial content oxygen) x Q (cardiac output)
delivery of O2 from tissue back to heart is DO2 = CvO2 (content venous oxygen) x Q
so putting it together the oxygen consumption is going to be arterial - venous
aka
Q x CaO2 - Q x CvO2 = VO2
- -> Q(CaO2- CvO2) = VO2
- applies to the body as a whole
whats a safegurad the body uses to sustain aerobic metabolism? I.e. Fick Principle
the heart delivers O2 to tissues, if O2 delivery decreases
the body can actually extract more oxygen from each mL of blood in the arterial side as its going thru the tissue
then it returns less O2 in venous blood
* the ability to inc the difference bt CaO2 and CvO2 extracting more O2 allows body to stay aerobic if something happens to heart and Q goes down
- ability to sustain oxygen consumption even though cardiac output is falling critical for us to stay aerobic
what are the two primary factors that determine oxygen consumption?
- blood flow (or cardiac output)
- oxygen extraction
can the body increase oxygen extraction when cardiac output falls? yes - fick principle
which area of the heart is particulary at risk for low oxygen levels? what are the 2 factors why?
subendocardial/subendocardium
- the subendocardium is farthest from the blood supply; arterial blood must pass through penetrating vessels (vessels that go through the heart wall) that originate from epicardial coronary arteries. Because these vessels have some resistance, pressure decreases the farther downstream the blood moves. Therefore, the driving pressure for the subendocardial vessels is lower.
- the subendocardial vessels experience higher external compression forces (than vessels in other layers of the heart muscle) due to their proximity to the cavity of the left ventricle and the high pressure of the blood within that chamber. This compression narrows the vessels, thereby increasing resistance and decreasing flow
Imagine that cardiac output drops below a normal level due to a chronic illness such as heart failure. How does the body compensate to avoid entering an anaerobic state?
The tissues will extract more oxygen per liter of blood delivered, holding oxygen consumption constant
Patient with heart obstruction/ blockage (arterty lining radius reduced) video example
radius reduced -> increased resistance downstram of blockage (posielles principle)
Narrowing reduces the oxygen supply to the affected area of the heart muscle
by dialating the downstream vessels he is able to adjust supply of oxygen (this is why he is okay during rest and low activities)
stress causes hormones to affect heart muscles to constrict - pumps harder inc work of heart
he’s still able to increase supply to meet the demand
eating his meal - need to digest which increases blood demand -supply is still keeping up
smoking - causes vessels to constrict - more work on heart
going up the stairs - need blood flow to tissues his supply is at its max now and demand at max
he gets chest tightness and pain from his heart working anaerobically now (angina)
he sits down which lowers demand from heart
now supply and demand in balance he can walk home again
sign of coronary artery blockage
chest/abdominal pain or angina when exercising that stops when resting - has to do with supply/demand for oxygen
the heart compensates for a partial obstruction in a coronary vessel by dilating vessels downstream of the blockage. Oxygen extraction is nearly maximal even at rest for the left ventricular muscle under normal circumstances, so that adjusting flow is the crucial mechanism by which the heart tries to compensate for partial obstructions in coronary vessels. As we saw in the meal scenario elsewhere in this lesson, vasodilation can only compensate for a blockage up to a point in the face of increased demand; beyond that limit, angina ensues.
