05a: Circulation and P Flashcards
The pressure in all distensible vessels is determined by its:
- Compliance
2. Volume (contained within it at any moment)
Compliance of veins is determined by product of their (X) and (Y).
X = distensibility (specific compliance) Y = volume
Since veins have (X) times the distensibility as arteries and carry (Y) times the volume. Hence, their compliance is (Z) times that of arteries.
X = 5-6 Y = 3-4 Z = 15-24
Define distensibility (with an equation).
Percent change in V as a function of P;
(delta V/V)/delta P
At relaxed volume, the cross-section of vein looks (X) shape. With volume and small P increases, shape changes to (Y). The cross-sectional area and circumference of vessel (increase/decrease).
X = biconcave Y = elliptical then circular;
CS Area increases BUT no change in circumference of vessel
When higher V and P changes (increase/decrease) (X) of vein, its distensibility finally begins to decrease.
Increase;
X = circumference
Change in volume in artery during given time period is determined by:
Flow in - Flow out
During the period of the entire cardiac cycle, SV is (greater/smaller) than runoff volume.
Equal!
In steady state, the time averaged volume in artery (increases/decreases).
Doesn’t change
In steady state, the time averaged pressure in artery (increases/decreases).
Doesn’t change
During systole, flow into artery is (greater/smaller) than flow out, causing (increase/decrease) in P and V.
Greater;
Increase
During diastole, flow into artery is (greater/smaller) than flow out, causing (increase/decrease) in P and V.
Flow into artery is ZERO!
Decrease (“diastolic run off” to pump out rest of blood from systole)
During diastole, it’s the (X) property of the arteries that provides driving force to propel blood out.
X = elastic recoil
T/F: Since pressure in aorta is relatively constant, it’s possible to approximate MAP.
False - despite constantly changing P of aorta, MAP can still be approximated
MAP equation…
Pd + (1/3)(PP)
Pulse pressure equation…
Ps-Pd
In an aortic pressure curve, the peak pressure is (X).
X = aortic systolic P
List the key physiological factors that affect arterial blood volume.
- CO (HR and SV)
2. Peripheral resistance
The pulse pressure is predominantly determined by (X) and (Y) characteristic of (Z) vessel.
X = SV Y = compliance Z = aorta
The actual systolic P that will be attained is actually dictated by which other P?
Diastolic P (prior to ejection)
List the factors that influence aortic systolic P.
- SV
- Ejection velocity
- Aortic distensibility
List the factors that influence aortic diastolic P.
- Aortic distensibility
- HR
- Peripheral resistance
List the changes in factors that, at given (X) P, will increase pulse pressure by (increasing/decreasing) systolic P.
X = diastolic;
Increasing;
- Increase SV
- Increase ejection velocity
- Decrease in aortic distensibility
An increase in peripheral resistance will (increase/decrease) pulse pressure by (increasing/decreasing) (diastolic/systolic) P. What’s being directly affected in this case?
Decrease;
Increasing;
Diastolic P;
Rate of “run-off” (decline of arterial V and P) is decreased
An increase in HR will (increase/decrease) pulse pressure by (increasing/decreasing) (diastolic/systolic) P. What’s being directly affected in this case?
Decrease;
Increasing;
Diastolic P;
Time for run-off (decline of arterial V and P) is decreased
Vessels downstream of aorta experience (increase/decrease) in systolic P and (increase/decrease) in diastolic P, causing (increase/decrease) in Pulse P.
Increase;
Decrease;
Increase
Vessels downstream of aorta experience (increase/decrease) in mean P.
Always decrease (loss of E due to friction)
(X) is the primary factor propelling blood through venous system. Explain what it is.
X = vis a tergo
Pressure difference between peripheral venous pressure (Pv) and RA pressure (Pra)
Standing perfectly still for prolonged time may cause fainting, because it compromises which secondary factor influencing (X).
X = venous return (decreased)
Skeletal muscle pumps
Describe how (inspiration/expiration) helps in venous return.
Inspiration;
Descent of diaphragm increases intra-abdominal P, increasing pressure gradient that drives venous return
Venomotor tone is factor in venous return because (increase/decrease) in venous wall tension, resulting in increase (P/compliance) helps increase venous return.
Increase;
P
Ventricular ejection aids in venous return by which mechanism?
Reaction force pulls heart downward, decreasing RA pressure
When considering flow of fluid between two points at different levels above the ground, it’s crucial to consider difference in (X) between the two points. Which components make up (X)?
X = TOTAL fluid E
- Lateral P
- KE
- Gravitational PE
T/F: Fluid flowing between two points at different levels above ground will always flow from high to low lateral pressures.
False
Upon standing, (arterial/venous) pressure in foot is (increased/decreased) by larger value.
Both increase by same amount!
Upon standing, (arterial/venous) (X) pressure in head is (increased/decreased) by larger value.
X = lateral;
Both decreased by same amount!
T/F: SV decreased with decrease in respiratory rate.
True
T/F: SV decreased with hypotension.
False
An individual in which HR, TPR and compliance are kept constant, and increase in stroke volume results in (increase/decrease) pulse pressure and (increase/decrease) in MAP.
Increase in both
Because (veins/arteries) are compliant, standing leads to (X) and (rise/fall) in VR. In the absence of (Y), this would lead to fall in (Z) and fainting.
Veins; X = venous distension/pooling Fall; Y = reflex response for BP Z = MAP
What causes (veins/arteries) in head and neck to collapse?
Veins;
If they have pressure below atmospheric pressure
T/F: A patient with aortic stenosis is likely to have a lower than normal fluid velocity through the aortic valve.
False
T/F: A patient with aortic stenosis is likely to have a higher than normal pulmonary venous pressure.
True
