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Phys2 Lect 2

Pressure Force per unit area
Flow volume transferred per unit time (5L/min)
Resistance Opposition to flow
Velocity Flow per cross-sectional area per unit time
How is BL FLOW related to pressure difference and resistance? PROPORTIONAL to pressure difference. INVERSELY PROPORTIONAL to resistance. Q = (P1-P2)/R
How can the pressure difference be increased? how will it affect flow? Activating B1 receptors in the ventricular myocytes will generate a greater initial pressure which will increase the pressure difference. **This will Increase flow.
How can the resistance be increased? how will it affect flow? Resistance in a BL vessel occurs via alpha1 receptors and vasoconstriction. **this will decrease flow
Cardiac Output equation CO = Paorta/TPR **TPR: total peripheral resistance (from the body)
Resistances relationship to radius and length? INVERSELY proportional to r^4. PROPORTIONAL to L. **This is energetically beneficial b/c we do not need massive ANS symp output to generate change (small change in r = large inc in Resistance).
Effect on Flow: Increased r INCREASES flow. (decreases Resistance)
Effect on Flow: Decreased r DECREASES flow. (increases Resistance)
Effect on Flow: Increased L DECREASES flow. (increases Resistance)
Effect on Flow: Decreased L INCREASES flow. (decreased Resistance).
TPR (Total Peripheral Resistance) is the sum of all resistances. How do organs being in series and parallel affect this? Series: all the resistances are added (Rt=R1+R2+R3). Parallel: (1/Rt = 1/R1 + 1/R2 + 1/R3) this greatly decreases the TPR which makes it much easier on the heart. otherwise the heart would have to be much larger.
Vasodilation's effect on flow Increasing the radius, thus increasing flow by decreasing resistance.
Vasoconstriction's effect on flow Decreasing the radius, thus decreasing flow by increasing the resistance.
Where does the main resistance to flow occur? Arterioles. **they have high ratio of smooth muscle and contain precapillary sphincters. This creates the greatest resistance and causes a large drop in pressue (100mmHg to 40mmHg)
What is the flow in the capillaries? Almost 0
At constant flow, what is the relationship between velocity and radius? Velocity is INVERSELY proportional. **Therefore velocity is at its lowest in the capillaries (<1cm/sec) b/c combined, they have the LARGEST total cross-sectional area (csa). The aorta has the lowest totatl csa and the HIGHEST velocity (23cm/sec)
Increasing cross sectional area for a given BL flow will do what to the veloctiy? DECREASE it
decreasing cross sectional area for a given BL flow will do what to the veloctiy? INCREASE it
Bernoulli Principle Total energy is conserved between potential energy and kinetic energy. *Kinetic energy: velocity. *Potential energy: BP
How will viscosity affect flow? Increasing the viscosity (via increased hematocrit) will increase the reistance and decrease flow. **Blood dopping can be dangerous for this reason.
Three different types of flow? 1.Laminar (arteries, arterioles, venules, veins). 2.Turbulent (ventricles, stenosed arteries). 3.Single-file (capillaries).
Plasma skimming and Laminar flow. In laminar flow, the middle is where the fastest flow occurs b/c there is more endothelial resistance closer to the vessel walls. **Plasma skimming occurs b/c most hematocrit will remain in the middle.
Turbulent flow Promoted by high BL flows. Fluid and cells tumble. **If heard in arteries: BRUITS (usually due to atherosclerosis)
Can high flow rates affect laminar flow? YES. if flow gets very high, laminar flow will change to turbulent flow (Bruits). **Stenosis will narrow the vessel (cross sectional area and radius) which will increase the velocity leading to turbulent flow.
Classic location of Bruits in Carotids? At the bifrication of the Carotid Artery.
Created by: WeeG



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