Lecture 3B Flashcards
Name the six places where the blood is distributed in the body under normal resting conditions. Include also the percentage of blood sent to these areas
- Cerebral (15%)
- Coronary (5%)
- Renal (25%)
- Gastrointestinal (25%)
- Skeletal muscle (25%)
- Skin (5%)
What is Ohm’s Law
Q= (delta) Pressure/Resistance
Blood flow through arteries is affected by what two major variables?
Pressure and Resistance
What is the blood flow (Q)
Quantity of blood flowing through a vessel, organ, or the entire circulation in a given period of time (L/min)
What is Poiseuille’s Law?
The relationship between Resistance, Viscosity, Vessel Length and Vessel Radius
–> R=8VL/(pie) r^4
What has the greatest influence on resistance?
Radius of the vessel
Define blood Pressure:
The force with which blood is pushed against the walls of blood vessels
Why does blood pressure fall progressively through the circulation?
Energy from heart dissipates with distance
Branching distributes pressure
What is Systolic Pressure (SP)
Highest amount of pressure reached during ventricular ejection of blood.
-First sound heard when measuring BP (top number)
What is Diastolic Pressure (DP)
The minimum amount of pressure just before ventricular ejection begins
-Last sound heard when measuring BP (bottom number)
The energy of ventricular contraction is used in two ways. Describe each
- Part of the energy of ventricular contraction provides flow during ventricular systole (Systolic propulsion)
- Remainder is stored as potential energy and released by the RECOIL of the arterial wall which propels the blood distally and provides the “diastolic runoff”. (Diastolic propulsion)
What is the “Wind Kessel” effect?
It is the pressure-storing property of the aorta released by the recoil of the arterial wall, which propels the blood distally. This helps provide a more continuous rather than pulsatile flow to the peripheral tissues.
T or F, An alteration of systolic and diastolic propulsion provides a more continuous rather than pulsatile flow to the peripheral tissues.
True
What is the Mean Arterial Pressure (MAP)
The actual pressure that propels blood to tissues; in other words, the “average” pressure in a cardiac cycle
What is the equation for MAP
2/3 DP + 1/3 SP = MAP
What is the Total Peripheral Resistance (TPR) which is also called the Systemic Vascular Resistance (SVR)
The sum of all resistance in the vasculature
What are the 3 important sources of resistance within a single vessel
- Blood Viscosity
- Vessel Length (constant)
- Vessel diameter or Radius
Blood Viscosity depends on what factors? (4)
- Concentration of the suspended medium (the formed elements)
- Velocity of flow - usually high with low viscosity
- Radius of the vessel
- RBC aggregation (Rouleaux) at lower flow velocities
In low hematocrit states such as anemia, what happens to viscosity and vascular resistance?
They both decrease
In high hematocrit states such as polycythemia and leukemia, what happens to viscosity, vascular resistance and blood pressure?
Viscosity: Increases
Vascular Resistance: Increases
Blood Pressure: Increases
In high hematocrit states, the increase in viscosity and resistance can lead to what?
Blood clotting due to decreased flow.
This entire lecture is based on Ohm’s law and Poiseulle’s law. Know them inside and out
Q=R/P
R=8VL/(pie) r^4
A two fold increase in vessel radius augments flow by what?
16 fold
A four-fold increase in vessel radius augments flow by what?
256 fold
