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Why must flow be equal in the two circuits of the body (systemic and pulmonary)?
Because they are connected in series by left and right heart.
What is the approximate pressure in the R ventricle, pulmonary artery, L atrium, Capillaries?
What is the approximate pressure in the L ventricle, Aorta, Mean Art. BP, R atrium?
- 0 (Central Venous pressure).
What maintains higher pressure in the systemic circuit?
- Higher resistance
- Lower compliance.
Where does the major drop in pressure occur (when going from systemic to venous), why?
- Greateast resistance.
How are (flow) velocity and cross-sectional area related?
Velocity inversely related to cross sectional area.
What are the two largest blood reservoirs in the body?
- Systemic Veins
- Pulmonary system
- Due to: High Compliance.
What is the Poiseuille equation?
- Q= (Pu-Pd)/R
- Q: flow
- Pu: Pressure upstream
- Pd: Pressure downstream
- R: Resistance of vessels in between.
What are the three determinants of Resistance in a vessel?
- R (proportional to): vL/r^4
- v: Viscosity of blood
- L: Length of vessel (unchanging phsiologically)
- r: Radius of vessel -- resistance inversely proportional to the 4th power of radius -- Most important determinant of resistance.
What are the two types of flow?
What number helps determine laminar vs. turbulent flow?
Reynold's number: (d*vel*dens)/vis.
Where would turbulent flow first appear in anemia, why?
Aorta: Largest diameter, Highest velocity, decreasing blood viscosity.
What is the main factor determining capillary pressures?
- Arteriolar resistance
- Increased resistance: Decreased cap pressure
- Decreased resistance: Increased cap pressure (and flow).
Are the bodies organs connected in series or parallel?
What is the advantage of connection in parallel?
- Lower total resistance
- Individual regulation of blood flow (with changing internal resistance).
What is the LaPlace relationship?
- T (proportional to) Pr
- T: wall tension
- P: pressure
- r: radius
- Aorta has largest wall tension because of largest radius and pressure.
- dV: change in volume
- dP: change in pressure.
What is the inverse of compliance?
Elasticity: tendency to rebound.
What is the main factor affecting systolic BP?
- Stroke volume
- Increased SV: increased systolic BP (and vice versa).
What is the main factor affecting diastolic BP?
- Total peripheral resistance (TPR) -- arteriolar constriction/dilation
- Increased tPR: increased diastolic (and vice versa).
Mean Pressure equals?
- MP= diastolic + 1/3 pulse pressure
- Closer to diastolic than systolic.
What two variables determine Mean Arterial Pressure (MAP)?
- MAP= CO x TPR
- CO: Cardiac Output
- TPR: Total peripheral resistance.
What is the function of the baroreceptor reflex?
Short term regulation of BP.
What is the function of the RAAS?
Long term regulation of BP.
Where are the main receptors of the baroreceptor reflex?
- Carotid sinus
- Also in the aortic arch.
What is the Fick principle?
- Calculates blood flow through an organ
- Q= uptake/(A-V)
- Q: Flow
- uptake: O2 consumption of that organ
- A: Arterial O2 conc
- V: Venous O2 conc.
What is the cardiac index?
- CI= CO/BSA
- CO: Cardiac output
- BSA: Body Surface Area.
What are the two theories explaining intrinsic regulation (autoregulation) of blood flow?
- Metabolic hypothesis (more support): Tissue releases a vasodilatory substance to regulate flow
- Myogenic hypothesis: Increased pressure increases stretch, leading to contraction of arteriole.
What is a major characteristic of an autoregulating tissue?
Blood flow is independent of blood pressure.
What are the autoregulating tissues?
- Cerebral circulation
- Coronary circulation
- Skeletal muscle vasculature during exercise.
Why are the kidneys not a true autoregulating tissue?
Blood flow is partially regulated through hormonal and neuronal influences.
What is the main mechanism controlling flow in extrinsically regulated tissues?
Tonic changes in sympathetic adrenergic activity (alpha).
What are two circulations with mainly extrinsic regulation?
- Cutaneous circulation
- Resting skeletal muscle.
Where is the lowest venous PO2 found in the resting individual?
- Coronary circulation
- Only increase in blood flow can increase oxygen delivery to tissue (given maximal O2 extraction at rest).
Increased cardiac pump function (work) occurs with?
- Exercise: Increased volume work
- Increased BP: Increased pressure work
Which has a higher O2 cost, pressure work or volume work?
What is the main factor regulating cerebral blood flow (in normal conditions)?
- Arterial PCO2, directly proportional to cerebral blood flow
- Abnormal conditions: Large decrease in arterial PO2 increases cerebral blood flow (normal or elevated arterial PO2 have no effect).
The cutaneous circulation is controlled by, varies by?
- Almost entirely by sympathetic adrenergic nerves
- Varies mainly by need for temp. exchange
- Constriction: causes elevated temp
- Dilation: causes lower temp.
What is the pulmonary response to exercise?
- Increased CO -> increased pulm pressure
- Vessel dilation
- Apical recruitment
- --> decreased resistance --> little/no change in pulm pressure.
What is the pulmonary response to hemorrhage?
- Decreased CO -> decreased pulm pressure
- Vessel constriction
- --> Inreased resistance --> little/no change in pulm pressure.
What are the shunts in fetal circulation?
- Ductus Arteriosus: Pulmonary artery -> descending aorta
- Foramen Ovale: R atrium -> L atrium
- Ductus venosus: Umbilical vein -> IVC.
What percentage of fetal CO goes to placenta?
How does foramen ovale close?
- Increased TPR due to loss of placental circulation
- Decreased pulmonary resistance due to lung expansion
- Reversal of flow.
What produces the S1 heart sound, when is a split heard?
- Closure of mitral and tricuspid valves
- Audible split heard: RBBB, delay in closure of tricuspid valve.
What produces the S2 heart sound, when is a split heard?
- Closure of aortic (A2) and pulmonic (P2) valves
- Inspiration: Decreased pulmonic resistance, increased R heart output, delayed closure of P2.
What causes a widening of S2 split?
What causes fixed splitting of S2?
- Atrial septal defect
- L -> R shunt.
What causes paradoxical splitting of S2?
- Advanced aortic stenosis.
- Occurs righ after opening of AV valves
- children: normal, rapid expansion of compliant ventricles
- adults: volume overload, sigh of cardiac disease.
- Atrial contraction against stiff ventricle
- examples: concentric hypertrophy, MI.
What are the waves in the jugular venous pulse tracing?
- a wave: atrial contraction, highest deflection, PR interval
- c wave: tricuspid bulge into atrium with ventricular contraction
- x descent: atrial relaxation
- v wave: atrial filling
- y descent: ventricular filling when tricuspid valve opens.
Draw a mental Pressure-Volume loop?
Seriously, do it.
What are the causes of an ejection murmur?
Aortic or pulmonic stenosis.
What are the causes of a pansystolic murmur?
- Mitral or tricuspid regurtitation/insufficiency
- Ventricular septal defect (VSD).
What is the cause of a late systolic murmur?
Mitral valve prolapse (mid systolic click).
What are the causes of early diastolic murmurs?
What are the causes of mid to late diastolic murmurs?
Mitral or tricuspid stenosis.
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