Lecture 21- Vascular Foundations I: the circulatory system

Question 1

CV system transports substances entering the body:

Answer 1

oxygen, nutrients, water

Question 2

CV system substances leaving the body:

Answer 2

metabolic waste, heat, CO2

Question 3

CV system substances moved around the body:

Answer 3

wastes, hormones, immune cells and antibodies

Question 4

The arteries are described as a “…”

Answer 4

pressure reservoir
(maintains the pressure); elastic
–> stretches to accomodate
–> snaps back to maintain pressure

Question 5

Arterioles are described as “…”

Answer 5

adjustable screws that can tighten or loosen
–> main site of blood pressure regulation (through vasoconstriction or vasodilation

Question 6

exchange between O2 and CO2 takes place at

Answer 6

exchange epithelium in the capillaries

Question 7

Veins are describes as a “…”

Answer 7

volume reservoir; compliant
stretches but does not snap back

Question 8

blood flow= flow rate=

Answer 8

volume/time= cardiac output (L/min)

Question 9

there is a — times increase in cardiac output with sympathetic stimulation

Answer 9

5

ex. at rest CO= 5.8 L/min,
during exercise CO= 25.6 L/min

Question 10

why is variable distribution of blood flow to tissues possible?

Answer 10

due to parallel arrangement of arterioles

Question 11

pressure — with distance due to —

Answer 11

decreases with distance due to friction

heart contracts –> creates a driving pressure –> blood flows out

Question 12

resistance to blood flow increases as radius of a blood vessel —

Answer 12

decreases

Question 13

resistance in a blood vessel: vasodilation vs. vasoconstriction

Answer 13

vasodilation= decreased resistance
vasoconstriction= increased resistance

Question 14

arterioles ONLY receive — input

Answer 14

sympathetic input

Question 15

“white water rafting”

Answer 15

in the aorta, blood flow is very turbulent and high velocity

Question 16

“lazy floating down the river”

Answer 16

in arteries, it is more calm.
wide, lazy, floating down the river, slow velocity

Question 17

pressure — as we move away from the heart

Answer 17

decreases

Question 18

velocity of blood flow (cm/min)

Answer 18

= distance traveled by a fixed volume of blood per unit time (cm/min)

Question 19

when does velocity of blood increase or decrease?

Answer 19

increases as flow rate (L/min) increases

decreases as CSA of blood vessels increase (larger tubes= slower flow)

Question 20

explain why pressure drops with distance from the heart?

Answer 20

as blood flows through circulation it loses pressure, which creates a pressure gradient

pressure is lost due to FRICTION:
- friction within the blood
- friction between blood and vessel walls

Question 21

blood and laws of fluid flow (3)

Answer 21

flow is prop to pressure gradient
F ∝ ΔP

flow is inversely prop to resistance
F ∝ 1/R

together…
F ∝ ΔP/R

Question 22

very low pressure in the veins…

Answer 22

• need help to be pumped back up
• skeletal muscle pump
• valves prevent backflow

Question 23

what would happen if valves aren’t working properly?

Answer 23

varicose veins, edema, blood pooling

Question 24

venous return (VR)=

Answer 24

the flow of blood into the right atrium from the peripheral vessels

• skeletal muscle pump helps maintain VR

Question 25

blood flow is slowest through the…

Answer 25

capillaries

• capillaries have greatest CSA
• exchange is happening at the capillaries so we want it to be slow to ensure O2 and CO2 is properly exchnaged

Question 26

what determines the velocity of blood flow through that vessel type?

Answer 26

the TOTAL cross sectional area of the vessels

Question 27

capillaries have the smallest individual diameter but they have the…

Answer 27

largest total cross sectional diameter

…therefore slowest velocity!!!

Question 28

precapillary sphincter

Answer 28

ring of smooth muscle that can tighten or relax to close off capillaries in response to local signals

–> or maximize response when needed

Question 29

metarterioles

Answer 29

= bypass

divert blood flow if sphincters are closed

they also allow larger materials (ex. WBCs) to bypass narrow capillaries and reach venous circulation

Question 30

capillary density is related to….

Answer 30

your bodies’ needs

Question 31

single layer of flattened epithelial cells: movement of…

Answer 31

-diffusion of gases
- osmosis (water)
- movement of materials through larger pores

Question 32

do proteins leak out of capillaries?

Answer 32

no

Question 33

about —-L per day of fluid is filtered out of capillaries

Answer 33

3L/day

-excess tissue fluid is picked up by lymphatic vessels and returned to venous system

Question 34

lymph is dumped back in at the…

Answer 34

subclavian vein

-but also checked by lymph nodes, spleen etc. first