Unit 1 - CV System The Heart PART B

Question 1

The rate of blood flow (F) to tissues & organs is determined by (4 things):

Answer 1

a. Pressure gradients (ΔP)
b. Resistance to blood flow caused by friction
c. Poseuille’s Law
d. Velocity of Flow

Question 2

Pressure definition

Answer 2

in a fluid is the force exerted by the fluid on its container

Question 3

Pressure gradients (ΔP) definition

Answer 3

differences in pressure b/t 2 locations in the CV system

Question 3

Blood flows from areas of _____ pressure to areas of _____ pressure, (_____ the pressure gradient)

Answer 3

HIGH

LOW

DOWN

Question 4

Over the entire CV system, pressure is HIGHEST closest to the _______, & ________ as you move further away from this pump

Answer 4

VENTRICLES

DECREASES

Question 5

Pressure is highest in ________

Answer 5

ventricles & aorta

Question 6

Lowest pressure in the __________

Answer 6

vena cava & atria

Question 7

If fluid is NOT moving, the pressure it exerts is called ________, & force is exerted _____ __ ___ ______

Answer 7

HYDROSTATIC PRESSURE

EQUALLY IN ALL DIRECTIONS

Question 8

The pressure created in the ventricles is called the _____ _______, b/c __________

Answer 8

DRIVING FORCE

it is the force that drives blood through the blood vessels

think: squeezing water balloon

Question 9

Pressure ____ continuously as blood moves FARTHER from the heart

Answer 9

FALLS

Question 10

In a system in which fluid is flowing, pressure FALLS over distance as __________

Answer 10

energy is lost b/c of friction

Question 11

Blood flow is _______ proportional to the size of the pressure gradient (F ∝ Δ P)

Answer 11

DIRECTLY

Question 12

Blood flow is DIRECTLY proportional to the size of the pressure gradient (F ∝ Δ P), therefore:

Answer 12

• the GREATER the pressure difference b/t the 2 locations, the HIGHER the flow
• the SMALLER the pressure difference, the LOWER the flow
• WITHOUT a pressure gradient (ΔP = 0), there is NO flow

Question 13

The GREATER the pressure difference b/t the 2 locations, the _______ the flow

Answer 13

HIGHER

Question 14

The SMALLER the pressure difference, the _____ the flow

Answer 14

LOWER

Question 15

WITHOUT a pressure gradient (ΔP = 0), there is _____ flow

Answer 15

NO

Question 16

When fluid-filled container EXPANDS, pressure exerted on the fluid ______,
therefore, when heart RELAXES & EXPANDS, pressure in the fluid-filled chambers _______

Answer 16

DECREASES

FALLS

Question 17

The MEAN BLOOD PRESSURE of the systemic circulation ranges from a high of 93 mm Hg in the _____ to a low of a few mm Hg in the ______ ______

Answer 17

AORTA

VENAE CAVAE

Question 18

Fluid flows only if there is a ________ pressure gradient (ΔP)

Answer 18

POSITIVE

Question 19

If the tube has NO pressure gradient, then ____ flow

Answer 19

NO

Question 20

Flow depends on the ______ ______, not on the _______ _______.

Answer 20

PRESSURE GRADIENT (ΔP)

ABSOLUTE PRESSURE (P)

Question 21

Blood flow takes the path of _____ resistance

Answer 21

LEAST

Question 22

Resistance definition

Answer 22

tendency of the CV system to oppose blood flow

Question 23

Resistance to blood flow (vascular resistance) caused by ______

Answer 23

friction (of blood cells in contact with vessel walls & with each other)

Question 24

What 4 things is vascular resistance determined by?

Answer 24

1. Vessel length (L) 2. Internal vessel radius (r) 3. Blood viscosity (ŋ) 4. The equation: R = 8Lŋ/πr^4

Question 25

Vessel length (L)

Answer 25

LONGER blood vessels INCREASE resistance analogy: don't need to suck as hard on a short straw as on a long one

Question 26

Internal vessel radius (r)

Answer 26

- DECREASING radius (vasoCONTRICTION), INCREASES resistance - INCREASING radius (vasoDILATION), DECREASES resistance analogy: drinking milkshake through a fat straw is much easier than through a skinny cocktail straw

Question 27

Vasoconstriction

Answer 27

DECREASES blood flow through a vessel

Question 28

Vasodilation

Answer 28

INCREASES blood flow through a vessel

Question 29

Blood viscosity (ŋ)

Answer 29

- friction b/t molecules in a flowing fluid

Question 30

Blood viscosity (ŋ) is proportional to ______

Answer 30

HEMATOCRIT (the proportion of the blood volume that is RBC's)

Question 31

INCREASING hematocrit, _______ viscosity, which _______ resistance to blood flow

Answer 31

INCREASES INCREASES analogy: water (low viscosity) vs honey (high viscosity) moving through a tube - drinking water through a straw is easier than drinking a thick milkshake

Question 32

What do L & r determine?

Answer 32

the SA of the vessel in contact with the blood

Question 33

The MORE SA in contact with the blood, the ______ the resistance

Answer 33

HIGHER

Question 34

Explain F = ΔP/R

Answer 34

an INCREASE in R, causes a DECREASE in blood flow (F) (& vice versa)

Question 35

Describe the equation: R = 8Lŋ/πr^4

Answer 35

- where 8 & π are CONSTANTS - however, in humans, L (vessel length) does NOT change (an exception is the lengthening of blood vessels that occurs in obesity), & ŋ (viscosity) is RELATIVELY constant - So R (resistance) is MAINLY determined by changes to vessel radius (R ∝ 1/r^4)

Question 36

What is the exception to L (vessel length) not changing in humans?

Answer 36

an exception is the lengthening of blood vessels that occurs in obesity

Question 37

A SMALL change in the RADIUS, produces a _____ change in _______. For example, ______

Answer 37

LARGE RESISTANCE For example, INCREASING the radius of a vessel by a factor of 2 (e.g. from 2mm to 4mm) DECREASES the resistance by a factor of 16X

Question 38

Poseuille's Law:

Answer 38

Equation that combines the effects that pressure gradients & the factors determining resistance have on blood flow F = ΔP/R = ΔPπr^4/8Lη

Question 39

Velocity of Flow

Answer 39

the distance a fixed volume of blood travels in a given period of time

Question 40

Velocity (AKA velocity of flow)

Answer 40

measure of HOW FAST blood flows past a part

Question 41

Formula for Velocity of Flow explained

Answer 41

v = Q/A - Q = Flow rate (the volume (HOW MUCH) of blood that passes a given point in the system per unit time) - A = cross-sectional area of the tube

Question 42

Velocity ______ when cross sectional area DECREASES

Answer 42

INCREASES

Question 43

Velocity ______ when cross sectional area INCREASES

Answer 43

DECREASES

Question 44

Velocity is ______ in NARROW sections

Answer 44

FASTER

Question 45

Velocity is ______ in WIDER sections

Answer 45

SLOWER

Question 46

If flow rate (Q) = 12 cm^3/min, that is identical along the length of the vessel that means...

Answer 46

that in 1 min, 12cm^2 of fluid flow past point X in the narrow section, & 12cm^3 of fluid flow past point Y in the wide section