PPT 4 - chap 16-17 Flashcards
(23 cards)
The volume of flow in any vessel relates to which two factors?
Directly to the pressure gradient between the two ends of the vessels
Inversely to the resistance encountered to fluid flow
Three factors that determine resistance…
Blood thickness or viscosity
Length of the conducting tube
Blood vessel radius
What is poiseuille’s law?
Expresses the general relationship among pressure differential, resistance, and flow
Poiseuille’s law equation
Q= pressure gradient X vessel radius
divided by
vessel length X fluid viscosity
Which of the 4 factors of poiseuille’s law contributes most to blood flow?
radius because:
Physiologically, constriction and dilation of the smaller arterial blood vessels provide the crucial mechanism to regulate regional blood flow
What happens to local arterioles during exercise?
Local arterioles of active muscles dilate while vessels to tissues that can temporarily compromise their blood supply, constrict.
What 2 factors contribute to reduced blood flow to non-active tissues?
Increased sympathetic nervous system outflow
Local chemicals that directly stimulate vasoconstriction or enhance the effects of other vasoconstrictors
What are the 3 benefits of opening dormant capillaries in exercise?
1) Increases total muscle blood flow
2) Delivers a large blood volume with only a minimal increase in blood flow velocity
3) Increases the effective surface for gas and nutrient exchange between the blood and muscle fibers
(FYI, normally at rest 1 out of 30-40 capillaries are open).
What does nitric oxide serve to do?
an important signal molecule that dilates blood vessels and decreases vascular resistance
How does coronary artery disease affect the endothelium?
makes the endothelium produce LESS NITRIC OXIDE
Cardiac output (Q) expresses the amount of blood pumped by the heart during a ____-minute period
1
Cardiac output equation
Heart rate X stroke volume
What are the 3 methods to asses CO?
Direct Fick
Indicator dilution
CO2 rebreathing
What does the direct fick method measure?
- Measuring oxygen consumption involves open-circuit spirometry methods
- Measuring a-vO2 difference involves a sample of arterial blood and from an anatomic “mixing chamber”, then sampling arterial and mixed-venous blood simultaneously
What does the dilution-concentration curve of the indicator dilution method signify?
reflects the average concentration of indicator material in blood leaving the heart
what does the CO2 rebreathing method measure?
mixed-venous and arterial CO2 levels.
measures CO2 production
Average CO for males and females is?
5L male
4L female
Why do endurance trained athletes have large stroke volume and low HR?
Increased vagal tone and decreased sympathetic drive, both of which slow the heart
Increased blood volume, myocardial contractility, and compliance of the left ventricle, all of which augment the heart’s stroke volume
When does CO levels plateau during exercise?
when blood flow meets exercise metabolic requirements
How do endurance trained athletes achieve large maximal CO?
through large stroke volume
Three mechanisms that increase heart’s stroke volume during exercise
Enhanced cardiac filling in diastole followed by a more forceful systolic contraction
Normal ventricular filling with a subsequent forceful ejection and emptying during systole
Training adaptations that expand blood volume and reduce resistance to blood flow in peripheral tissues
What is Frank-Starling Law?
that the force of
contraction of the cardiac muscle remains proportional
to its initial resting length
Does sheering stress or vessel stretch from increased blood flow provoke synthesis and release of nitric acid?
yes
