Other circulation Flashcards
When is flow highest in the left coronary artery and the right coronary artery? Why?
Peak flow in RCA = highest during systole
Peak flow in LCA = highest during diastole
The left ventricle = highly capillarized; when LV contracts during systole >> capillaries get compressed >> increased resistance to flow; thus peak is during diastole when there isn’t resistance to flow
Describe the effect of increased heart rate on left coronary perfusion
If heart rate increases, LV has less filling time therefore flow is decreased (i.e. spending less time in diastole)
Why is the endocardium most at risk for damage if there are perfusion problems? (i.e. explain the relationship between left ventricular pressure, internal pressure and tissue hydrostatic pressure)
When the left ventricle contracts, it exerts pressure on itself (internal pressure) that is equal to the tissue hydrostatic pressure.
What are the factors that influence coronary flow?
Metabolites
Nervous control (symp/parasymp)
Shear stress/Flow-induced vasodilation
Myogenic response
Systolic compression
What are the metabolites that control coronary bloodflow and what is their action?
Adenosine (vasodilation; increases flow/reduces tone)
O2, CO2, H+, K+
How does the sympathetic nervous system regulate coronary blood flow? What about the oarasympathetic system?
Sympathetic: catecholamine binding to alpha receptors (vasoconstriction - increases tone/decreases flow); binding to beta receptors (vasodilation - increases flow/decreases tone)
Parasympathetic: acetylcholine (vasodilation - decreases tone/increases flow)
What is the effect of systolic compression on coronary flow? What about shear stress and the myogenic response?
Systolic compression: constriction = reduced flow b/c increased resistance
Myogenic response: dilation and constriction (depends)
Shear stress/Flow: vasodilation via Nitric Oxide release
What is the relationship between coronary flow and O2 consumption rate?
Directly proportional. A decrease/increase in coronary flow = a decrease/increase in O2 consumption rate by the same factor
T/F: Vasodilator metabolites influence the flow rate but their release is not influenced by flow.
Falsehood. Removal of vasodilators is proportional to the flow rate and vice versa. They influence flow and are influenced by flow.
Describe the autoregulation of coronary blood flow
Even as pressure changes, autoregulation works to keep flow rate constant (so the flow rate can change in either direction depending on the body’s needs)
What’s the difference between active and reactive hyperemia?
Active hyperemia: increased blood flow induced by increased metabolism and increased dilator production
Reactive hyperemia: increased blood flow as a reaction to an ischemic injury (the blood flow/O2 delivery was cutoff and so when flow is returned, the rate goes up sharply)
T/F: Metabolic vasodilation only occurs in the capillaries/tertiary arterioles, which are the highest sight of resistance. How do the coronary arteries dilate? What about the arteries between the coronary arteries and the arterioles?
True.
Large vessels dilate as a result of the myogenic response
Arteries: flow-induced vasodilation
Describe the impact of mild coronary artery stenosis (diffuse, non-flow limiting) on blood flow at rest and during exercise
@ rest: diffuse plaque doesn’t impact arterial resistance and flow
during exercise: arterioles and downstream vessles vasodilate, but plaque prevents flow b/c endothelia are covered by the plaque >> no shear stress >> no flow induced vasodilation
Describe the role of metarterioles and precapillary sphincters in blood flow in the capillary beds
Precapillary sphincters help to control flow in the capillaries
Metarterioles can branch into the capillary beds/link arterioles and venules directly (so they’re just conduits for blood flow)
What’s the difference between hydrostatic and oncotic pressure in the capillaries? How is capillary pressure affected by changes in arterial pressure and venous pressure influence capillary hydrostatic pressure?
Hydrostatic pressure: blood pressure in the capillaries
Oncotic pressure: pressure driven by protein concentration in the plasma
Arterial pressure increases >> Pc increases; arterial resistance increases >> Pc decreases; venous resistance increases >> Pc increases
Major plasma proteins
Albumin
Globulin
Fibrinogen
How do you calculate net fluid movement? What does it mean if Jv is positive? Negative?
Net fluid movement (Jv) = Kf [(Pc - Pi) - (πc -πi)] OR Kf [(Pc+πi) - (Pi+πc)] (no matter which equation, it’s filtration - absorption)
Positive net water movement = filtration
Negative net water movement = absorption
Between the arterial side and venous end, where is Pc the highest/lowest? At which location does absorption/filtration take place?
Pc higher at the arterial end; filtration at that end
Pc lowest at the venous end; filtration at that end
What is the effect of increasing capillary permeability?
(You’d think: a more permeable capillary = increased plasma protein levels = increased capillary oncotic pressure = increased absorption)
But actually (or at least, over time): plasma proteins leak out >> decrease capillary osmotic pressure >> increased filtration out of the capillary
Describe the effect of increasing venous pressure/ venous constriction
Increased venous pressure >> increased capillary hydrostatic pressure >> fluid movement out of the capillary (filtration) and into the interstitial space where it collects and results in edema
How would you help to treat edema?
Give pt a diuretic >> increases fluid excretion
What are the effects of low serum protein levels? (as is the case in severe liver disease, starvation and nephrotic syndrome)
Decreased capillary osmotic pressure >> fluid leaves capillary and goes into interstitial space (fluid collects in peritoneal cavity)
Effect of hydrostatic pressure increase in lungs
What is the net fluid movement in the kidney?
Increased capillary hydrostatic pressure >> increased filtration >> increased fluid retention in the interstitial space of the lungs
Net fluid movement in the kidney (intrarenal) = highly positive b/c kidney does a lot of filtration
Describe the effect of muscle contraction on blood flow in skeletal muscle
Muscle contraction improves venous return b/c with each contraction, blood gets pushed back up to the heart b/c the valves in the veins don’t allow backflow
