Lecture 29 - Cardiovascular System: Physiology of Blood Flow and Blood Pressure

Question 1

How will pressure gradient help with blood flow?

Answer 1

It will produce a force that moves fluid in the direction of lower pressure. Larger pressure gradient creates more force

Question 1

What affects rate of blood flow?

Answer 1

Blood flow through a vessel is function of the opposing forces of pressure and resistance

Question 2

How does resistance affect blood flow?

Answer 2

Resistance slows down the velocity/volume flow rate of blood caused by the friction between the walls of the tube and the fluid

Question 3

T/F? Vessel resistance does not increase linearly with vessel length

Answer 3

False - it does increase linearly with vessel length. The longer the vessel, the more surface that’s in contact with blood, causing more friction

Question 4

T/F? Vessel luminal diameter is inversely related to resistance

Answer 4

True - smaller diameter = larger resistance; more blood will be in contact with the smaller vessel wall

Question 5

Does vessel diameter or vessel length have a larger impact on resistance?

Answer 5

Vessel diameter - change in diameter of a vessel will always produce a larger change in resistance than an equivalent change in length

Question 6

What is viscosity?

Answer 6

A measure of resistance due to interactions among the molecules in the moving fluid

The more the molecules and materials suspended in the fluid interact with each other, the more viscous it is, causing internal friction -> slows down overall flow

Question 7

How does turbulent (non-laminar) flow affect resistance?

Answer 7

It increases resistance

Laminar flow is when liquid is moving unidirectionally in smooth layers. In turbulent, these layers are disrupted and movement is not unidirectional, decreasing overall flow

Question 8

How does turbulent flow occur?

Answer 8

Occurs due to shifts or changes in the geometry of the vessel wall:
- branch points
- tight curves
- irregular surfaces

Question 9

Describe arterial pressure

Answer 9

It fluctuates with the changes in pressure due to the cardiac cycle - it is the highest during and just after ventricular systole, and lowest during diastole

Question 10

How is blood pressure reported?

Answer 10

Systolic pressure/diastolic pressure

Question 11

What is pulse pressure?

Answer 11

Difference between systolic pressure and diastolic pressure

Question 12

What is mean arterial pressure (MAP)

Answer 12

Diastolic pressure plus 1/3 pulse pressure

Question 13

How is blood pressure measured?

Answer 13

Measured through a cuff (sphygmomanometer) that tracks how much external pressure it takes to block blood flow

Question 14

What do elastic arteries do?

Answer 14

They help buffer pulse pressure, reducing the variability in blood flow and pressures in capillaries

Arteries with larger amounts of elastic tissue stretch when blood is forced into them with high pressure, temporarily reducing blood flow rate

Question 15

Why does average blood pressure decline as it passes through the systemic circuit?

Answer 15

Pressure reduces due to the resistance the blood flow encounters throughout the length of the vessel. The further the vessels are from the ventricle (source of the pressure gradient), the lower the average pressure within them

Question 16

Where is the largest pressure drop-off?

Answer 16

Arterioles - this shows that these vessels provide the highest total resistance to volume flow

Question 17

Where is the cross-sectional area of all blood vessels largest and smallest in?

Answer 17

Largest - capillaries; smallest - elastic arteries

Capillaries have tiny vessels and have relatively high resistance because of its small individual diameter - but its parallel arrangement makes the overall resistance more moderate

Question 18

Where is the velocity of blood flow the highest? Lowest?

Answer 18

Highest - arteries; lowest - capillaries

Question 19

4 factors that affect blood flow through circuits and cardiac output

Answer 19

1. Cardiac output affects pressures
2. Pressures affect blood flow
3. Blood flow affects venous return
4. Venous return affects cardiac output

Question 20

How does gravity affect blood flow

Answer 20

It can oppose or enhance blood flow depending on the location of the heart

Ex. arteries supplying blood to the head must generate enough pressure to pusch blood directly against the force of gravity. Arteries supplying blood to regions below the heart get an assiset from the force of gravity

Question 21

How do veins in limbs help prevent backflow of blood due to gravity?

Answer 21

Valves

Question 22

T/F? Skeletal muscle contractions work with valves to provide a secondary pump that helps propel blood toward the trunk

Answer 22

True - muscles contracting around the vein compress the vein, providing extra pressure which helps squeeze blood upward towards the heart, countering the force of gravity