PSL 431 Exam 4 Questions with
Correct Answers
List the two factors that affect blood flow rate and describe this relationship in an
equation - ANSWER-- blood flow rate (F) is directly proportional to the pressure
gradient (delta P) and inversely proportional to vascular resistance (R)
- F = delta P / R
How does pressure gradient (delta P) effect flow rate? - ANSWER-- delta P exists
between the beginning and the end of a vessel; ↑ ΔP = ↑ F
- vasculature creates resistance blood flow that leads to a ↓ in pressure
Explain how this equation is related to Ohms Law (V = IR) - ANSWER-- Current =
flow rate
- Voltage = change in pressure
- Substitute this in, and we get out flow rate equation
Explain, in detail, why the pressure at the beginning of a vessel is higher than the
pressure at the end of a vessel. - ANSWER-- Resistance against the wall of a vessel
creates a drop in pressure
Explain, in general, how blood vessels create resistance (R) to blood flow. -
ANSWER-- opposition to blood flow due to friction between moving blood and the
vascular wall
If the driving pressure for blood blow (i.e., ΔP) were held constant, explain what
would happen to F if R were to increase. - ANSWER-- if ΔP is constant, then ↑ R = ↓
F
Discuss how a constant F is sustained when R increases. - ANSWER-- if ↑ R, ΔP
must correspondingly ↑ in order to maintain a constant F
- To increase pressure, we can increase cardiac output
List the three factors that affect R and describe the relationship of these factors in an
equation. - ANSWER-1) directly proportional to blood viscosity (η) , 2) directly
proportional to vessel length (L), and
3) inversely proportional to vessel radius (r);
- that is: R ∝ ηL/r^4
Explain, in detail, how blood viscosity affects R. - ANSWER-- friction developed
between molecules of a fluid sliding over each other while flowing
- ↑ fluid thickness = ↑ η
- for example, an ↑ in RBCs with blood doping -> ↑ blood thickness -> ↑ η
, Explain, in detail, how blood viscosity and vessel length affect R. - ANSWER-- ↑
surface area (SA) of the blood vessel that the blood meets = ↑ R
- vessel surface area is a function of L and r; if r is constant, ↑ L -> ↑ SA -> ↑ R
Explain, in detail, how blood vessel radius (or diameter) affects R. - ANSWER-- ↑ r
(or diameter) = ↓ R
- ↑ r -> ↓ SA of the blood vessel that the blood meets -> ↓ R -> ↑ F
- R = ηL/r^4, therefore a ↑ r (2x) -> ↓ R (16x)
- F = ΔP/R, therefore (if ΔP is constant) -> ↑ F (16x)
Explain why vessel radius has such a profound impact on R. - ANSWER-- Very small
changes in radius have a huge effect on resistance (to the 4th power)
Explain why vessel radius has such a profound impact on F. - ANSWER-- Very small
changes in radius have a huge effect on flow (to the 4th power)
Histologically compare/contrast elastic arteries, muscular arteries, and arterioles -
ANSWER-- Elastic arteries have a lot of elastic fibers in their wall
- Muscular arteries distribute blood, muscle wall is very thick
- Arterioles are resistance vessels
Name the three tunics - ANSWER-1) tunica intima (endothelium and scant CT),
2) tunica media (smooth muscle and CT*),
3) tunica adventitia (CT - collagen and elastin)
Explain how large, elastic arteries serve as both pressure reservoirs and blood flow
conductors. - ANSWER-- elastic arteries rapidly conduct blood to muscular arteries
which distribute blood to the various organs, whose blood flow is regulated by
arteriole resistance
o Vasodilation or vasoconstriction of arteries
- large arteries (e.g., aorta, pulmonary trunk) also serve as pressure reservoirs as
they are compliant, or distensible (i.e., expand w/ ↑ pressure), and exhibit elastic
recoil
Describe the Windkessel effect and how it is responsible for maintaining diastolic
blood pressure and flow. - ANSWER-- the pressure and volume that is ejected into
the circulation during systole is "stored" by the elasticity of the vessel walls, and
during diastole, pressure and flow are maintained by the elastic recoil of these same
vessel walls
Compare/contrast systolic (SBP) and diastolic blood pressure (DBP). - ANSWER--
force exerted by blood against a vessel wall
- systolic blood pressure (SBP) is the maximal arterial BP when the heart is
contracting and
- diastolic blood pressure (DBP) is the minimum arterial BP when the heart is
relaxing
Explain how the measurement of pulse rate at the wrist is related to BP. -
ANSWER-- The "thud" you feel in your pulse is the jump in blood pressure from 80 to
120. Using this, we can get our pulse
Correct Answers
List the two factors that affect blood flow rate and describe this relationship in an
equation - ANSWER-- blood flow rate (F) is directly proportional to the pressure
gradient (delta P) and inversely proportional to vascular resistance (R)
- F = delta P / R
How does pressure gradient (delta P) effect flow rate? - ANSWER-- delta P exists
between the beginning and the end of a vessel; ↑ ΔP = ↑ F
- vasculature creates resistance blood flow that leads to a ↓ in pressure
Explain how this equation is related to Ohms Law (V = IR) - ANSWER-- Current =
flow rate
- Voltage = change in pressure
- Substitute this in, and we get out flow rate equation
Explain, in detail, why the pressure at the beginning of a vessel is higher than the
pressure at the end of a vessel. - ANSWER-- Resistance against the wall of a vessel
creates a drop in pressure
Explain, in general, how blood vessels create resistance (R) to blood flow. -
ANSWER-- opposition to blood flow due to friction between moving blood and the
vascular wall
If the driving pressure for blood blow (i.e., ΔP) were held constant, explain what
would happen to F if R were to increase. - ANSWER-- if ΔP is constant, then ↑ R = ↓
F
Discuss how a constant F is sustained when R increases. - ANSWER-- if ↑ R, ΔP
must correspondingly ↑ in order to maintain a constant F
- To increase pressure, we can increase cardiac output
List the three factors that affect R and describe the relationship of these factors in an
equation. - ANSWER-1) directly proportional to blood viscosity (η) , 2) directly
proportional to vessel length (L), and
3) inversely proportional to vessel radius (r);
- that is: R ∝ ηL/r^4
Explain, in detail, how blood viscosity affects R. - ANSWER-- friction developed
between molecules of a fluid sliding over each other while flowing
- ↑ fluid thickness = ↑ η
- for example, an ↑ in RBCs with blood doping -> ↑ blood thickness -> ↑ η
, Explain, in detail, how blood viscosity and vessel length affect R. - ANSWER-- ↑
surface area (SA) of the blood vessel that the blood meets = ↑ R
- vessel surface area is a function of L and r; if r is constant, ↑ L -> ↑ SA -> ↑ R
Explain, in detail, how blood vessel radius (or diameter) affects R. - ANSWER-- ↑ r
(or diameter) = ↓ R
- ↑ r -> ↓ SA of the blood vessel that the blood meets -> ↓ R -> ↑ F
- R = ηL/r^4, therefore a ↑ r (2x) -> ↓ R (16x)
- F = ΔP/R, therefore (if ΔP is constant) -> ↑ F (16x)
Explain why vessel radius has such a profound impact on R. - ANSWER-- Very small
changes in radius have a huge effect on resistance (to the 4th power)
Explain why vessel radius has such a profound impact on F. - ANSWER-- Very small
changes in radius have a huge effect on flow (to the 4th power)
Histologically compare/contrast elastic arteries, muscular arteries, and arterioles -
ANSWER-- Elastic arteries have a lot of elastic fibers in their wall
- Muscular arteries distribute blood, muscle wall is very thick
- Arterioles are resistance vessels
Name the three tunics - ANSWER-1) tunica intima (endothelium and scant CT),
2) tunica media (smooth muscle and CT*),
3) tunica adventitia (CT - collagen and elastin)
Explain how large, elastic arteries serve as both pressure reservoirs and blood flow
conductors. - ANSWER-- elastic arteries rapidly conduct blood to muscular arteries
which distribute blood to the various organs, whose blood flow is regulated by
arteriole resistance
o Vasodilation or vasoconstriction of arteries
- large arteries (e.g., aorta, pulmonary trunk) also serve as pressure reservoirs as
they are compliant, or distensible (i.e., expand w/ ↑ pressure), and exhibit elastic
recoil
Describe the Windkessel effect and how it is responsible for maintaining diastolic
blood pressure and flow. - ANSWER-- the pressure and volume that is ejected into
the circulation during systole is "stored" by the elasticity of the vessel walls, and
during diastole, pressure and flow are maintained by the elastic recoil of these same
vessel walls
Compare/contrast systolic (SBP) and diastolic blood pressure (DBP). - ANSWER--
force exerted by blood against a vessel wall
- systolic blood pressure (SBP) is the maximal arterial BP when the heart is
contracting and
- diastolic blood pressure (DBP) is the minimum arterial BP when the heart is
relaxing
Explain how the measurement of pulse rate at the wrist is related to BP. -
ANSWER-- The "thud" you feel in your pulse is the jump in blood pressure from 80 to
120. Using this, we can get our pulse
