10 - Hemodynamics Flashcards
4 functions of microcirculation
- Delivery of oxygen and nutrients
- Distribution of salt and water over blood and extracellular fluid volume
- Removal of Co2 and other waste products
- Create a barrier between blood and tissues
Which organ gets the most blood flow?
The liver
Artery:
Mean diameter
Mean wall thickness
Thickest layer of wall
Artery:
Mean diameter - 4.0mm
Mean wall thickness - 1mm
Thickest layer of wall - Smooth muscle → elastic tissue → fibrous tissue → endothelium
Arteriole:
Mean diameter
Mean wall thickness
Thickest layer of wall
Arteriole:
Mean diameter - 30.0um
Mean wall thickness - 60.um
Thickest layer of wall - Smooth muscle → endothelium
no elastic tissue or fibrous tissue
Arteriole:
Mean diameter
Mean wall thickness
Thickest layer of wall
Arteriole:
Mean diameter - 30.0um
Mean wall thickness - 60.um
Thickest layer of wall - Smooth muscle → endothelium
no elastic tissue or fibrous tissue
capillary:
Mean diameter
Mean wall thickness
Thickest layer of wall
capillary:
Mean diameter - 8.0um
Mean wall thickness - 0.5um
Thickest layer of wall - Only has endothelium
How is the diameter of the capillary related to the size of red blood cells? Monocytes?
The mean diameter of a capillary is 8.0um
RBC are typically 6-8um
Monocytes are 12-20um
Venule:
Mean diameter
Mean wall thickness
Thickest layer of wall
Venule:
Mean diameter - 20.0um
Mean wall thickness - 1.0um
Thickest layer of wall - Fibrous tissue → endothelium (wall has only endothelium and fibrous tissue - no elastic tissue or smooth muscle)
Vein:
Mean diameter
Mean wall thickness
Thickest layer of wall
Vein:
Mean diameter - 5.0mm
Mean wall thickness - 0.5mm
Thickest layer of wall - smooth muscle → elastic tissue → fibrous tissue → endothelium
Velocity of blood flow depends on ________
Velocity of blood flow depends on the total cross-sectional area
What regulates how much blood flows into the capillary bed?
Response to metabolic needs
Precapillary sphincters
Local and CNS regulators
What is myogenic response? What does it cause?
Myogenic response is the intrinsic capacity of the vasculature to respond to an increase in hoop stress with vasoconstriction
Causes autoregulation of blood flow
The hoop stress, or tangential stress, is the stress around the circumference of the pipe due to a pressure gradient
Which breakdown product of ATP can modulate vascular tone?
Adenosine
- links hypoxia (low oxygen in blood) to vasodilation
What are two vasoconstrictors?
Adrenergic system
Angiotensin II
What is an example of a vasodilator?
Nitric oxide
What are 6 chemical vasoconstrictors?
- Norepinephrine (alpha receptor)
- Serotonin
- Substance P
- Endothelin
- Vasopressin
- Angiotensin II
Name the physiological role of each of the following vasoconstrictors
- Norepinephrine (alpha receptor)
- Serotonin
- Substance P
- Endothelin
- Vasopressin
- Angiotensin II
Name the physiological role of each of the following vasoconstrictors
- Norepinephrine (alpha receptor)
- Baroreceptor reflex
- Serotonin
- platelet aggregation
- sm mm contraction
- Substance P
- pain
- increase capillary permeability
- Endothelin
- paracrine mediator
- Vasopressin
- Increase blood pressure in hemorrhage
- Angiotensin II
- increase blood pressure
Name the source for each of the following vasoconstrictors:
- Norepinephrine (alpha receptor)
- Serotonin
- Substance P
- Endothelin
- Vasopressin
- Angiotensin II
Name the source for each of the following vasoconstrictors:
- Norepinephrine (alpha receptor)
- sympathetic neurons
- Serotonin
- Neurons
- GIT
- platelets
- Substance P
- Neurons
- GIT
- Endothelin
- Vascular endothelium
- Vasopressin
- Posterior Pituitary
- Angiotensin II
- plasma hormone
What type of chemical is each of the following vasoconstrictors?
- Norepinephrine (alpha receptor)
- Serotonin
- Substance P
- Endothelin
- Vasopressin
- Angiotensin II
- Norepinephrine (alpha receptor)
- neurotransmitter
- Serotonin
- paracrine
- neurotransmitter
- Substance P
- paracrine
- neurotransmitter
- Endothelin
- paracrine
- Vasopressin
- neurohormone
- Angiotensin II
- hormone
What are 9 vasodilators?
- Nitric oxide (NO)
- Bradykinin (via NO)
- Adenosine
- ⤓O2 ; ⤒CO2 ; ⤒H+ ; ⤒K+
- Histamine
- Epinephrine (beta2 receptors)
- Acetylcholine (via NO)
- Natriuretic peptides (example - ANP)
- Vasoactive intestinal peptide (VIP)
What is the physiological role of the following vasodilators:
- Nitric oxide (NO)
- Bradykinin (via NO)
- Adenosine
- ⤓O2 ; ⤒CO2 ; ⤒H+ ; ⤒K+
- Histamine
- Epinephrine (beta2 receptors)
- Acetylcholine (via NO)
- Natriuretic peptides (example - ANP)
- VIP
What is the physiological role of the following vasodilators:
- Nitric oxide (NO)
- paracrine mediator
- Bradykinin (via NO)
- increase blood flow
- Adenosine
- increase blood flow to match metabolism
- ⤓O2 ; ⤒CO2 ; ⤒H+ ; ⤒K+
- increase blood flow to match metabolism
- Histamine
- increase blood flow
- Epinephrine (beta2 receptors)
- increase blood flow to skeletal muscle, heart, liver
- Acetylcholine (via NO)
- erection of clitoris or penis
- Natriuretic peptides (example - ANP)
- reduce blood pressure
- Vasoactive intestinal peptide
- digestive secretion
- relax smooth muscle
Source of the following vasodilators
- Nitric oxide (NO)
- Bradykinin (via NO)
- Adenosine
- ⤓O2 ; ⤒CO2 ; ⤒H+ ; ⤒K+
- Histamine
- Epinephrine (beta2 receptors)
- Acetylcholine (via NO)
- Natriuretic peptides (example - ANP)
- VIP
Source of the following vasodilators
- Nitric oxide (NO)
- Endothelium
- Bradykinin (via NO)
- multiple tissues
- Adenosine
- Hypoxic cells
- ⤓O2 ; ⤒CO2 ; ⤒H+ ; ⤒K+
- Cell metabolism
- Histamine
- Mast cells
- Epinephrine (beta2 receptors)
- Adrenal medulla
- Acetylcholine (via NO)
- Parasympathetic neurons
- Natriuretic peptides (example - ANP)
- Atrial myocardium
- Brain
- Vasoactive Intestinal Peptide (VIP)
- Neurons
Type of chemical each of the following vasodilators:
- Nitric oxide (NO)
- Bradykinin (via NO)
- Adenosine
- ⤓O2 ; ⤒CO2 ; ⤒H+ ; ⤒K+
- Histamine
- Epinephrine (beta2 receptors)
- Acetylcholine (via NO)
- Natriuretic peptides (example - ANP)
- VIP
- Nitric oxide (NO)
- paracrine
- Bradykinin (via NO)
- paracrine
- Adenosine
- Neurohormone
- ⤓O2 ; ⤒CO2 ; ⤒H+ ; ⤒K+
- Paracrine
- Histamine
- Paracrine
- Epinephrine (beta2 receptors)
- neurohormone
- Acetylcholine (via NO)
- neurotransmitter
- Natriuretic peptides (example - ANP)
- hormone, neurotransmitter
- VIP
- neurotransmitter;
- neurohormone
What conversion inhibits platelet aggregation
Conversion of GTP to cGMP by Soluble guanylate cyclase
What regulates how much blood streams into the capillary bed
The blood entering some capillary beds is controlled by small muscles called precapillary sphincters
Located between arterioles and capillaries and contain muscle fibers that allow them to contract
What is renal autoregulation?
Renal blood flow (RBF) autoregulation is a vital homeostatic mechanism that protects the kidney from elevations in arterial pressure that would be transmitted to the glomerular capillaries and cause injury
What regulates how much blood streams into the capillary bed:
Active hyperemia
Hyperaemia (also hyperemia) is the increase of blood flow to different tissues in the body
Active hyperemia is hyperemia due to local or general relaxation of arterioles
Describe how active hyperemia is accomplished and what triggers it:
- Increase in tissue metabolism → increase release of metabolic vasodilators into ECF → Dilation of arterioles → decrease resistance = Increase bloodflow → O2 and nutrient supply to tissue increases as long as metabolism is increased
What is reactive hyperemia?
Hyperemia = is the increase of blood flow to different tissues in the body
Reactive hyperemia refers to the temporary increase (‘hyper’) of blood flow (‘emia’) to an area as a result of (or reaction to) ischemia, or an arterial blockage (‘isch’, meaning to stop or block, ‘emia’, meaning blood flow)
What triggers reactive hyperemia and what is the response?
Decrease tissue bloodflow due to occlusion → Metabolic vasodilators accumulate in ECF → Dilation of arterioles (but occlusion prevents BF) → Remove occlusion → Decrease resistance creates increase BF → as vasodilators wash away, arterioles constrict and bf returns to normal
What type of capillary would you find in the brain?
continuous capillaries
What type of capillary bed would you find in the liver/spleen/bone marrow?
Discontinuous capillaries
What type of capillary bed would you find in the kidney - glomerulus / intestine?
Fenestrated
What are continuous capillaries?
- continuous capillaries have a continuous endothelial lining.
- They have tight junctions (leaky junctions) between their endothelial cells along with intercellular clefts through which small molecules, like ions, can pass.
- Continuous capillaries are generally found in the nervous system, as well as in fat and muscle tissue.
Discontinuous capillaries are in the _____ and _____ with very large _____ that allow passage of ______
Discontinuous capillaries are in the spleen and liver (sinusoids) with very large pores that allow passage of cells
What are fenestrated capillaries?
Fenestrated capillaries are characterized by the existence of pores within the endothelial cells and form specialized regions of the capillary bed in the mucosa of the intestinal tract, in the pancreas, in endocrine organs, in the choroid plexus and in the ciliary processes of the eye
Endothelial cell junctions of Continuous capillaries allow ___ and _____ to pass
Endothelial cell junctions of Continuous capillaries allow water and small dissolved solutes to pass
How do compounds move from the capillary to the interstitium (and back)?
Starling law
Net ultrafiltration = filtration - absorption
= permeability x (hydrostatic pressure gradient - colloid osmotic pressure gradient)
= Kf (deltaP - delta pi)
= Kf [(Pcap-Pinterst) - (picap - piinterst)]
What is plasma colloid osmotic pressure
Oncotic pressure
Oncotic pressure, or colloid osmotic-pressure, is a form of osmotic pressure induced by the proteins, notably albumin, in a blood vessel’s plasma (blood/liquid) that displaces water molecules, thus creating a relative water molecule deficit with water molecules moving back into the circulatory system within the lower venous pressure end of capillaries
What happens to the excess water and solutes that filter out of the capillary
Picked up by the lymph vessels and returned to the circulation
How do you calculate net pressure in systemic capillaries?
Net pressure = Hydrostatic pressure - colloid osmotic pressure (oncotic pressure)
effect of Hydrostatic pressure (Pcap) on fluid movement
hydrostatic pressure Pcap forces fluids out of the capillary
Effect of Colloid osmotic pressure (oncotic pressure) on direction of movement
Colloid osmotic pressure of proteins within the capillary (oncotic pressure) pulls fluid into the capillary
What is nephrotic syndrome?
How does it affect oncotic pressure?
Massive loss of plasma proteins due to leak of the glomerular capillary filter;
Very very low oncotic pressure (eg 5mmHg)
How do you calculate net pressure in capillary?
Net pressure = hydrostatic pressure - colloid osmotic (oncotic) pressure
How do you calculate diffusion rate?
Diffusion rate = [(△P)(area)(Solubility)]/ [(distance)(MW)]
What are the 3 layers of blood vesels
- Tunica intima
- endothelial layer
- Tunica media
- vascular smooth muscle
- elastic tissue
- Tunica Adventitia
- collagen
- vasa vasorum
Three steps to ventricular contraction:
- Ventricle contracts
- semilunar valve opens
- Aorta and arteries expand and store pressure in elastic walls
What is the windkessel effect
Windkessel effect is a term used in medicine to account for the shape of the arterial blood pressure waveform in terms of the interaction between the stroke volume and the compliance of the aorta and large elastic arteries and the resistance of the smaller arteries and arterioles
Three steps to ventricular relaxation
- Isovolumic ventricular relaxation
- Semilunar valve shuts
- Elastic recoil of arteries sends blood forward into the rest of the system
Fluid flows only if there is a _________ gradient
Fluid flows only if there is a positive pressure gradient
How do you calculate change in pressure?
Change in pressure = flow x resistance = Q x R
How do you calculate resistance? (ie what is the Poiseuille equation)
Resistance = (8ηl) / (∏r4)
η (eta) = viscosity
l = length of vessel segment
r = radius of vessel
Normal vessel resistance =
Anemic Vessel Resistance =
Polycythemia vessel resistance =
- Normal vessel resistance = 45
- Anemic Vessel Resistance = 15
- lower than normal RBC’s
- Polycythemia vessel resistance = 65
- Higher than normal RBC’s
Two blood vessels that run in parallel have a lower resistance than two blood vessels that run in a serial manner. True or false?
True
- total resistance of the system arranged in series is equal to the sum of the individual resistances
- When resistances are arranged in series, the total flow through each level of the system is the same
- total resistance in a parallel arrangement is less than any of the individual resistances.
How does velocity of flow change with vessel diameter?
The narrower the vessel, the faster the velocity of flow
How do you calculate Velocity of flow?
Velocity (v) = (Flow rate (Q)) / (Cross sectional Area (A))
What is hoop stress?
Mechanical stress defined as the result of forces acting perpendicular to the axis
aka wall tension
How do you calculate hoop stress?
Hoop stress = wall tension
Hoop stress = (pressure x radius) / (Thickness of vessel)
What is shear stress? What denotes shear stress?
Shear stress, denoted by tau, is defined as a stress which is applied parallel to a face of a material, as opposed to a normal stress which is applied perpendicularly
What is turbulent flow?
- In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between those layers.
Turbulent flow typically occurs at ______ or ______ and leads to a(n) _______ in resistance and a(n) ______ in NO formation
Turbulent flow typically occurs at bifurcations or uneven surfaces and leads to a(n) increase in resistance and a(n) decrease in NO formation (prone to atherosclerosis)
How can Turbulent flow be predicted?
By using the “Reynold’s Number”
Re = Velocity.diameter.density / viscosity
If Re >2000 turbulent flow can occur
What is wall tension?
Hoop stress
Ventricular wall tension is based on the thickness of the ventricular myocardium. The law of Laplace states that ventricular wall tension is proportional to ventricular radius and intraventricular pressure. Patients with coronary artery disease will have decreased blood and oxygen supply to the myocardium.
What is Laplace’s law?
The law of Laplace states that ventricular wall tension is proportional to ventricular radius and intraventricular pressure.
Wall tension = hoop stress = pressure x radius/vessel thickness
Formula for Vascular compliance
Vascular compliance = (increase in volume) / (increase in pressure)
What does a high compliance mean ?
A high compliance means that you can put a lot of volume in without much increase in pressure
How does venous compliance compare to arterial compliance?
Venous compliance is much higher than arterial compliance
(lower pressure in veins)
compliance = increase in volume / increase in pressure
What is incisura and what is it caused by?
a downward notch in the curve recording aortic blood pressure that occurs between systole and diastole and is caused by backflow of blood for a short time before the aortic valve closes
What is the pulse wave velocity?
Measurement of the time needed for the pressure wave to travel from one place to the other (eg carotid to radial)
What is pulse wave analysis?
Analysis of the pattern of the pulse wave to yield correlates to arterial stiffness
= can inform us about structural abnormalities of the vascular wall
Define systolic blood pressure:
Systolic pressure measures the pressure in your arteries when your heart beats.
Define diastolic blood pressure
diastolic blood pressure measures the pressure in your arteries when your heart rests between beats
How do blood pressure cuffs work?
- When cuff pressure >120mmHg arterial blood flow is stopped = no sound can be heard from brachial artery
- Cuff pressure between 80 and 120mmHg korotkoff sounds are created by pulsatile blood flow through the compressed artery
- Cuff pressure <80mmHg = blood flow is silent when artery is no longer suppressed
How do you calculate mean arterial pressure
Mean arterial pressure = (Diastolic x2 + Systolic) / 3
How do you calculate pulse pressure?
Pulse pressure = systolic pressure - diastolic pressure
what is distensibility?
the capacity to swell as a result of pressure from inside.
