Hemodynamics/Systemic Circulation Flashcards
What is the equation for calculating the Velocity of blood flow (generally)?
V = F/A
F = flow (ml/min) A = area (cm2)
What are the 2 factors that determine the rate of blood flow?
- pressure that pushes it
2. resistance to flow
What is the equation for Ohms law, which can calculate the flow of blood between 2 points along a vessel?
F = (change in Pressure)/Resistance
So using Ohms law (F = ΔP/R), if you increase pressure, will you increase or decrease flow rate?
Increase
So using Ohms law (F = ΔP/R), if you increase resistance, will you increase or decrease flow rate?
Decrease
If you increase the resistance in a vessel (like from atherosclerosis or a clot), what will happen to the organ DOWNstream from that vessel?
ISCHEMIA UP IN THIS BITCH
Let’s get weird. Give me the Poiseuilles law for blood flow.
F = (πΔPr^4)/(8nL)
ΔP= change in pressure r = radius of vessel n = viscosity of the blood L = length of tube
In Poiseuilles law, the radius of the vessel is to the 4th power. What does this mean as far as subtle changes to radius size on blood flow?
Subtle changes (inc or dec) causes a massive change in blood flow
Using Poiseulles law, if u increase the viscosity of the blood, do u increase or decrease blood flow rate?
Decrease!
remember n is on the bottom
also, making blood more viscous (thick) will be more sludgy.
So what factor can we actually test to determine the blood’s viscosity?
Hct
This feature of blood vessels allows them to accomodate the polsatile output of the heart and average them out, giving a smooth and continuous flow to the blood.
Distensibility
This is the point when blood vessels completely collapse because pressure falls below a critical level.
Critical closing pressure
This is the measurement of blood flow through a vessel for a given pressure.
Conductance (C = 1/R)
What is the R(total) for resistance of blood flow if vessels are arranged in series?
R(total) = R1 + R2 + R3 +R4…
So if you remove a series circuit from a vessel, will resistance go up or down?
Down!
Ex:
X = 2 + 2 + (2) –> X = 6
Remove 1: X = 2 + 2 –> X = 4
What is the R(total) for resistance of blood flow if vessels are arranged in parallel?
1/R(total) = 1/R1 + 1/R2 + 1/R3 + …..
So if you remove a parallel circuit from a vessel, will resistance go up or down?
Up!
Ex:
1/X = 1/2 + 1/2 + (1/2) –> X = 0.67
Remove 1: 1/X = 1/2 + 1/2 –> X = 1
This si the streamline blood flow of blood at a steady rate.
laminar flow
This is disorderly flow where blood flows cross-wise, forming whirls, causing increased resistance.
Turbulent flow
Turbulent flow increases directly in proportion to which 3 factors?
velocity of flow, diameter of the vessel, and density of the blood
Turbulent flow increases inversely proportional to which factor?
viscosity of blood
This device is where there is a recorder that is connected to a needle/catheter that’s directly inserted into an artery to measure blood pressure.
Transducer
What % deviation can a sphygmomanometer give when being compared to the measurements by a transducer?
10% deviation. it’s indirect.
This is the difference between systolic and diastolic pressures.
Pulse pressure
What is the pulse pressure if the systolic is 120mmHg and the diastolic is 80mmHg?
40
If there is a narrowed pulse pressure, what is that a sign of?
Increased resistance.
This is the avg of the arterial pressure over a period of time, determined by 60% of the diastolic and 40% of the systolic.
Mean arterial pressure (MAP)
What is the equation for MAP?
MAP = (1/3 systolic pressure) + (2/3 diastolic pressure)
What is the eqn for stroke volume?
SV = CO x HR
If stroke volume is increased, it leads to an increase in this factor, which is the greeater difference between systole and diastole.
Pulse pressure
Generally, this is the ability of the vessel to distend with increasing pressure.
Compliance.
What will happen to compliance if the vessel is hardened in atherosclerosis?
It’ll increase
An increase in compliance will cause an increase or decrease in pulse pressure?
Increase
This is the sum of all systemic vascular pressure within the body.
Total peripheral resistance.
Will exercise increase or decrease TPR? Basically, will peripheral dilations increase or decrease it?
Decrease
Why is a low TPR good for blood pressure?
increased flow to the tissues –> increased venous load back to the heart –> high/normal BP
What is the approximate MAP in the aorta?
~100mmHg
What is the approximate MAP in capillaries?
~17mmHg
What is the approximate MAP in veins?
~0 mmHg
What is the approximate MAP in pulmonary artieries?
~16
Is the velocity of blood flow directly or inversely proportional to vascular area?
Inversely.
the larger the vessel (like aorta) = the slower the flow.
True or False: lipids and gases can cross the plasma membrane without using pores.
Truf.
What is the equation for Ficks law of diffusion?
Diffusion = (Partial Pressure*Area)/Thickness
What is the starling eqn?
NFP = Pc-Pif - πp+πif
or, the way I like it:
NFP = (Pc + πif) - (Pif + πc)
basically,
NFP = (pressures pushing fluid into if) - (pressures pushing into capillary)
Use the starling eqn to figure out the NFP for this ex:
At arteriole end of capillary, Pc is 30 mm Hg, πc is 28 mm Hg, πif is 4 mm Hg and Pif is 0 mm Hg
NFP = (30 + 4) - (0 + 28) = +6 mmHg
which means 6mmHg of pressure INTO the interstitial fluid
super important guys. huge for physio questions. physiologists love this shit cuz it applies to renal and cardio and everything inbetween.
What is the composition of the walls of the systemic capillaries to allow fluid to travel between the interior and exterior of the capillary?
unicellular layer of endothelial cells and are surrounded by a very thin basement membrane on the outside with pores and channels
What tissue connects the endothelial cells of the lymphatic capillaries to the surrounding connective tissue?
anchoring filaments
When fluid enters the terminal lymphatic capillaries, what does the lymph vessels do to pump the fluid into the blood circulation?
Contract
At the terminal lymphatic capillaries, the endothelial cells overlap each other, forming this structure to allow fluid to be passed to the interior of the lymphatic capillary.
Valves
How does edema develop in venous obstruction?
Blockage within a vein causes a buildup of pressure and fluid behind the obstruction, causing fluid leakage (edema)
How does edema develop in lymphatic obstruction?
Blockage within a lymphatic duct causes a buildup of pressure and fluid behind the obstruction, causing edema
How does edema develop in increased capillary permability?
After hours of cellular hypoxia and lack of nutrients, the permeability of capillaries increases and large quantities of fluid begin to transude into the tissues, causing edema
How does edema develop in tissue injury?
Histamine causes vasodilation that increases porosity. This allows for fluid and plasma protein to leak into tissues and cause edema.
How does edema develop in malnutrition?
A reduction in plasma proteins because of malnutrition causes the plasma colloid osmotic pressure (πc) to fall, leading to increased capillary filtration (NFP!) throughout the body as well as extracellular edema.
Where are the 2 locations for the baroreceptors in the body?
carotid arteries and arch of the aorta
Describe the pathway from the carotid baroreceptors to the vasodilation of the veins sand arterioles.
carotid baroreceptors –> Herrings nerves –> CN IX –> tractus solitarium –> inhibition of vasoconstrictor center of medulla –> excitaton of peripheral vagus PANS center –> vasodilation of veins and arterioles –> decreased HR and ionotropy of heart
True or False: the barorecepotrs in the aortic arch, via X, are more important in regulating gradual change rather than sudden changes in BP.
False. it’s the opposite dawg.
This is the reflex to increase the HR when the central venous pressure is high.
Bainbridge reflex
Gib me the pathway of the brainbridge reflex, starting in the atrium and then finally increasing HR.
R’s in atrium stretched by inc in venous BP –> increase SANS –> hypothalamus stops production of ADH –> kidneys dilate arterioles to inc urine volume
basically,
GET THIS FLUID OUT OF MEEEEE
True or False: if there is a decrease in O2, there is an increase in arterial pressure.
True
GET THIS O2 IN MEEEEEEEEEE
True or False: if there is a decrease in CO2, there is an decrease in arterial pressure.
True
GET THIS CO2 OUT OF MEEEEEEEEE
Story time?
I went to a catholic school during all of elementary school. During mass one day, the priest was giving his sermon. There was just our 5th grade class and random church-goers in the church cuz it was a Thursday afternoon. I had the bright idea to let off a very uncomfortable fart that was brewing within. Thought it was gonna be SBD. Ended up being the most wretched, curdling, disgusting rumbling fart trumpet ever, as it vibrated off the wooden pews. Priest stopped his sermon and looked over. Felt like I was in a movie. Put my head down and accepted my defeat. No getting out of that one.
Give me the pathway of how renin from the JG cells of the kidney cause an increase in BP.
Renin released in response to hypoTN –> converted to angiotensin I –> lungs –> angiotensin II by ACE –> inc salt and water retention by constricting renal arterioles + aldosterone secretion
When is ANF released by the atrial walls of the heart?
In response to stretch, as is the case with heart failure.
How does ANF cause a decrease in BP by acting on the kidneys?
Tells the kidneys to increase their excretion of salt and water
This is the reflex when there is an increase in intracranial pressure that compresses the blood vessels of the brain, which then stimulates increases in BP and blood flow, which will decrease the HR by baroreceptor reflex
Cushings reflex
True or False: sustained changes in BP cause baroreceptors to “reset” to a new pressure.
True!
This occurs when there is decreased blood flow for seconds to hours because of an obstruction, results in marked increase blood flow when the obstruction is removed.
Reactive hyperemia
This is increased blood flow to an area based on increased need.
Active hypermia
This is the theory that states that when metabolite (CO2, H+, adenosine, K+) levels are high, that means that cells are using resources up, which stimulate the vessels to relax to allow more blood flow and nutrients to come in.
Vasodilator metabolite theory
