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Home , Arteriole, Pulse pressure

CIRCULATORY SYSTEM

Learning Objectives 1.Describe the functions of , , , & . 2.Describe the relationship between pressure, flow, and resistance in regulating peripheral circulation. 3. Define systolic, diastolic and mean arterial pressures 4. Explain the myogenic response, active and reactive hyperemia and reflex control of vessel resistance. 5. Explain the factors that alter trans- movement of fluid and solutes . 6. Explain the difference between capacitance and distributing vessels and the relationship between lymphatic and blood circulations. CIRCULATORY (CV) SYTEM RULES FOR CV SYSTEM

1. Bulk flow from high to low pressure states. 2. Resistance opposes blood flow. Resistance depends on: a. length of the tube () b. radius of the tube (to 4th power!)- most important! c. viscosity of the blood 3. Flow rate is the volume of blood that passes a given point per unit time (L/min). This is determined by pressure gradients and resistance. 4. Velocity of the blood is how far a volume of blood travels per unit of time (mm/sec). This is determined by cross sectional area, if the flow rate is constant. PRESSURE & PULSATILTY

120

80 (BP) maintained in by Blood compliance of elastic Pressure arteries. (mmHg)

10 Pulsatility & blood pressure capillary Vena Cava diminishes in arterioles due Distance from to resistance. BLOOD PRESSURES

Mean Arterial (MAP)

MAP = DP + 1/3 (SP – DP)

Pulse Pressure (PP) = SP –DP

Where DP = diastolic pressure SP = systolic pressure REGULATES BLOOD FLOW TO AN ORGAN

Arteries distribute blood to individual organs!

FLOW (F) = (P2-P1)/Resistance

CO = Q. = (MAP- P vena cava)/Total Peripheral Resistance = MAP/TPR

.Q organ = (MAP – Venous P)/Resistance of organ = MAP/R organ

ARTERIOLES REGULATE BLOOD WITHIN ORGANS

1. LOCAL CONTROL: Myogenic response = change in wall tension Hyperemia = change in ECF metabolites active = increased metabolism increases ECF metabolites (K+, CO2, H+) reactive hyperemia = increased metabolites during ischemia causes higher flow in reperfusion

2. REFLEX CONTROL: Sympathetic innervation (NorEpi at α 1 AR) (, ) ARTERIOLES ACT AS “NOZZLES”

Dynamic changes in arterioles Artery Arteriole Capillary ( or ) 80 regulate downstream pressures &

flow rates across capillary beds.

40 Pressure Green = vasodilation of arteriole (mmHg) Blue = basal state of arteriole 20 Red = vasoconstriction

EXCHANGE ACROSS CAPILLARY

Arteriole Capillary

Lymph is formed by the slight mismatch between filtration and absorption in the blood capillaries.

3L per day of is returned to the blood.

Lymph drainage not in CNS. Lymph node GENERAL CONCEPTS

1. Heart consists of two pumps that drive the unidirectional flow of blood through the pulmonary and systemic circulations. 2. Vascular system is a conduit for blood flow and a dynamic system that controls the distribution of the blood to the organs of the body. 3. Arteries are low resistance conduits that maintain pressure during diastole and distribute blood to organs. 4. Arterioles are the dominant site of resistance to blood flow within the organ. 5. Capillaries are the site of exchange. Balance between hydrostatic and oncotic forces determines the direction of fluid movement either into or out of the capillaries. 6. Veins are the low resistance conduits for venous return and volume reservoirs. GENERAL CONCEPTS

6. Sympathetic nervous system (SNS) constricts of veins leading to increased venous return, and thereby increased SV and CO.

7. The lymphatic system provides a one-way route for the return of interstitial fluid to the cardiovascular system.

8. Disease states that alter the hydrostatic and oncotic pressures can result in edema. These disease states include , liver disease, kidney disease and protein malnutrition.