Lecture 1-Exam 3 (cardiac) Flashcards
What does blood flow depend on?
on the pressure difference between arteries and veins and on how much resistance to flow is offered by the vascular system.
What vessels are the most significant point of control of the flow to capillary beds? Why?
Arterioles are most significant point of control of flow to capillary beds
* On proximal side of capillary beds and best positioned to regulate flow into the capillaries
* Outnumber any other type of artery, providing the most numerous control points
* More muscular in proportion to their diameter. Highly capable of changing radius
What is flow (Q) proportional and inversely proportinal to? Provide the equation
- proportional to driving pressure gradient (ΔP) and
- inversely proportional to resistance (R)
What is important when talking about rate of flow and pressure?
Rate of flow depends on the pressure difference, NOT the absolute pressure
* The greater the pressure difference between two points, the greater the flow; the greater the resistance, the less the flow
In our body with its anatomy, how do we have a nice driving pressure difference?
Coming out of the aorta, the P is 85mm (driving force) then the vena cava pressure is 0mm therefore pressure can go from high to low
- When will the tube offer greater resistance (R)?
- What law describes the determinants of resistance? (give equation)
- length (L) increases or if the radius (r) is decreased and higher viscosity (η)= MORE RESISTANCE
- Poiseuille’s law describes the determinants of resistance
What is the dominant varibale that determines resistance? Explain why
Radius is the dominant variable that determines resistance because radius is raised to the fourth power; for example, doubling the vessel radius increases flow by a factor of 16
Physiologic control of vascular resistance is achieved by what?
altering the blood vessel diameter through vasoconstriction and vasodilation
- Vascular smooth muscle actively controls what?
- Explain the new sock and old sock
- What are the difference btw arteries and veins?
- Vascular smooth muscle actively controls the diameter of arteries and veins
-
New sock: all the arteries, arteriole because of lots of smooth muscle+elasticity to stretch and recoil (maintain driving force)
* Arteries are the blood pressure reservoir -
Old sock: veins and venules because low pressure and will just take the volume of blood without most resistance.
* Veins are the blood volume reservoir
What are the vascontrictors that are both nonreceptor mediated and receptor mediated with there mechanism of action?
What are the vasodilators that are direct and receptor mediated with their mechanism of action
The series and parallel arrangement of blood vessels within an organ affects what?
vascular resistance in the organ
* general rule of thumb; adding similar-sized arteries in parallel reduces resistance, whereas losing similar-sized arteries in series raises vascular resistance
- Disease can cause loss of parallel flow cause what?
- Long-term aerobic training such as distance running, in which the arteriolar and capillary network increase their numbers in parallel causes what?
- Disease can cause loss of parallel flow thus increasing resistance
- Long-term aerobic training such as distance running, in which the arteriolar and capillary network increase their numbers in parallel, thereby reducing resistance to blood flow
Explain the distribution of pressure, flow velocity and blood volume
- Aorta: highest BP, velocity but low cross sectional area
- Arteries: high BP and velocity but a little more cross sectional area than aorta
- Arterioles: Biggest drop of pressure and velocity with an increase of cross section
- Capillaries: have lower BP, velocity but the highest cross section
- Venules: Lower BP, higher velocity and lower cross section than capillaries
- Veins: Lower BP, higher velocity and lower cross section than venules
- Vena cava: higher velocity but the lowest BP and cross section
- Where is pressure the highest and lowest?
- Why the largest pressure drop in arterioles?
- What is the MAP and why?
Pressure is highest in the central arteries and lowest in the central veins. The largest pressure decrease occurs across the arterioles, indicating that they are the site of highest vascular resistance.
What is the regulation of MAP? (include equation)
- Mean arterial pressure will increase when?
- What does it also predict?
- Mean arterial pressure will increase if the cardiac output, TPR, or both increase.
- It also predicts that at a constant mean arterial pressure, blood flow through any portion of the vascular tree will increase if TPR decreases.
What are the other factors that influence resistance (and thus flow)? (3)
- Vessel length
- Blood viscosity
- Vessel compliance
What happens with vessel length and BP+flow?
- Blood pressure decreases over distance as potential energy is lost through friction between blood and blood vessel walls and between blood cells.
- Pressure and flow decline with distance - arterial vs. venous pressure
- What elevates viscosity the most?
- What happens with increased and decreased viscosity?
- RBC count and albumin concentration elevate viscosity the most
- Decreased viscosity with anemia and hypoproteinemia speed flow
- Increased viscosity with polycythemia and dehydration slow flow
- What is compliance?
- What if a structure has low complience? Where do we see this?
- Compliance describes the distensibility of a structure and is defined as the volume change produced by a given pressure change
- If a structure has low compliance (i.e., it is stiff), applying a normal pressure change (ΔP) will produce a small volume change (ΔV).
- Vessel compliance is seen in certain heart diseases and also decreases with aging
What is the equation for complance? Explain how you would manipulate it
- What do the pace markers cells have?
- Cardiac cells have what? What does this allow?
- Pace markers cells have automaticity and rhythmicity to initiate cardiac function
- Cardiac cells have nexi (gap junctions to move ions) to have functional syncytium (to allow contraction together)
How can the ANS modulate the cardiac function?
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