18-2: Blood flow and blood pressure

Question 1

blood flow

Answer 1

amount of blood that passes through a blood vessel or organ in a given period of time (mL/min). determined by 2 factors: resistance and blood pressure

Question 2

resistance

Answer 2

opposition to blood flow resulting from friction between blood and walls of vessels.

3 important sources:
viscosity
vessel length
vessel diameter

Question 3

When resistance increases, blood flow _.

Answer 3

decreases

Question 4

viscosity

Answer 4

thickness of blood, related to the ratio of blood cells to plasma

Question 5

Resistance increases when viscosity _; therefore blood flow _.

Answer 5

increases (eg. polycythemia, dehydration); decreases

Question 6

The longer a blood vessel, the __ resistance as blood flows through it; therefore, blood flow _.

Answer 6

more; decreases

Question 7

How does an extra pound of fat affect blood pressure?

Answer 7

requires miles of small vessels to service it, greatly increasing resistance, and therefore pressure to maintain flow

Question 8

The smaller the diameter of the vessel, the __ resistance; therefore blood flow _.

Answer 8

greater (more fluid in contact with the walls); decreases

Question 9

What is the major determinant of peripheral resistance?

Answer 9

arterioles

Question 10

blood pressure

Answer 10

the pressure (force per unit area) exerted by the blood on the walls of the blood vessel as it flows through

Question 11

Blood flows from areas of _ pressure to areas of _ pressure

Answer 11

high to low

Question 12

Pressure differences are related to _ and _; when blood pressure increases, blood flow _.

Answer 12

cardiac output and resistance; increases

Question 13

Blood pressure is highest in the __; the steepest drop occurs in the _; is _ in the capillaries; and continues to _ through the veins, finally reaching 0 _.

Answer 13

aorta; arterioles (greatest resistance to blood flow); low; drop; when it enters the right atrium

Question 14

What are the two pumps aiding venous return?

Answer 14

respitory pump and skeletal muscle pump

venous pressure is too low to keep blood flowing back to heart - the two pumps increase the pressure gradient to ensure adequate venous return

Question 15

respiratory pump

Answer 15

inhaling causes: (1) chest to expand, and pressure in thoracic veins to DROP; (2) abdomen to compress and pressure in abdominal veins to RISE

Blood flows back up towards the heart from high to low pressure, with valves preventing backflow

Question 16

muscular pump

Answer 16

as skeletal muscles surroudning deep veins contract, they squeeze the vein pushing blood forward towards the heart; valves prevent blood from flowing back down

Question 17

What are the major factors affecting blood pressure?

Answer 17

cardiac output
blood volume
peripheral resistance

Question 18

What is the main determinate of blood pressure?

Answer 18

cardiac output - amount of blood pumped into aorta each minute

Question 19

If cardiac output increases (due to __ stroke volume or __ heart rate), then blood pressure __.

Answer 19

increased SV/increased HR; increases

Question 20

If cardiac output decreases (due to __ SV or __ HR), then blood pressure __.

Answer 20

decreased SV/decreased HR; decreases

Question 21

What is the avg blood volume in an adult?

Answer 21

5 L

Question 22

A hemorrhage results in ___ blood pressure.

Answer 22

decreased (due to the decrease in blood volume)

Question 23

High salt intake results in __ blood pressure.

Answer 23

increased (due to increase in blood volume)

Question 24

As blood volume decreases, blood pressure __; as blood volume increases, blood pressure ___.

Answer 24

decreases; increases

Question 25

peripheral resistance

Answer 25

all factors that oppose blood flow (eg. friction, vessel diameter)

Question 26

As peripheral resistance increases, blood pressure ___; if resistance decreases, blood pressure ___.

Answer 26

increases (to maintain blood flow); decreases