Questions 20+

Question 1

What are three other major collateral pathways other than the Circle of Willis?

Answer 1

• ECA to ICA Collaterialization by going through the Opthalmic and its branches
• The Right and Left ECA crossover at the midline to collateralize
• Anterior communicating arteries crossover to collateralize each other

Question 2

Define the Arterial System:

Answer 2

• This is a multi-branched elastic conduct that carries blood away from the heart to the distant tissues of the body.
• The arterial tree oscillates with each heartbeat, each heart beat pumps 70 ml of blood into the Aorta
• The amount of blood ejected with each heartbeat is known as the stroke volume
• The amount of blood ejected from the LV into Aorta each minute is known as the Cardiac Output

Question 3

What is the stroke volume and how much is it for a resting pt?

Answer 3

Stroke Volume: the amount of blood ejected with each heartbeat

-Each heartbeat pumps about 70ml/beat of blood into the Aorta

Question 4

What is the Cardiac Output and how do we calculate it ?

Answer 4

-The amoutn of blood ejected from the LV into the Aorta each min is known as the Cardiac Output
-The normal cardiac output in a resting patient is5.25 L/min
Formula - CO = SV x HR

Question 5

What is the Cardiac Output for a resting patient?

Answer 5

5.25 L/min

Question 6

If my patient has a heart rate of 7t beats per min. and a stroke volume of 75 ml, what is the CO?

Answer 6

Answer:

Question 7

What two criteria must be met for blood to flow?

Answer 7

1) A pressure gradient (or change in pressure)

2) A route for blood flow
- Vessels
- Arteries
- Veins

Question 8

What creates an Arterial Reservoir?

Answer 8

• The elastic walls of the arteries expand during systolic phase and excess blood volume creates potential energy
• The wall stretches since the capillaries cannot trasmit a large volume of blood all at once.
• This stretching of the vessel wall creates an Arterial Reservoir

Question 9

Blood flow in the arteries because of the pressure gradient created by ______

Answer 9

heart –> arteries

Question 10

What creates potential energy in the arteries?

Answer 10

-The elastic walls of the arteries expand during systolic phase. Excess blood volume creates potential energy (pressure) more stretch systolic

Question 11

What creates kinetic energy in the arteries?

Answer 11

During diastolic pressure the walls of the arteries become stretched and the potential energy is converted into kinetic energy

Question 12

What are the three different types of energy in the body?

Answer 12

-Potential Energy

-Kinetic Energy

-Hydrostatic Pressure

Question 13

Define each of the three types of enrgy found in the body:

A) Potential Energy

Answer 13

Potential Energy - Also called Pressure Energy. This is the main form of energy found in the body

• It is present when blood flows during systolic phase
• It is usually measured in mmHg (millimeter of Mercury)
• This is what we measure when we take BP

Question 14

Define each of the three types of energy found in the body:

B) Kinetic Energy

Answer 14

Kinetic Energy - this is the ability of blood to do work as result of velocity

Question 15

Define each of the three types of energy found in the body:

C) Hydrostatic Pressure

Answer 15

Hydrostatic Pressure - also called gravitational pressure
-This is the pressure exerted by a fluid due to its height in circulatory system

Question 16

Define the resistance to flow:

Answer 16

The main form of resistance to blood flow is the blood viscosity, which is the thickness of the blood.

R = change in P / Q

Change in P = P1 - P2

Viscosity is Q; R = P1 - P2 / Q

Question 17

Define the hematocrit:

Answer 17

Hematocrit is the percentage of RBC per unit volume blood
-Viscosity is related to the hematocrit

-Decreasing the hematocrit = thinner blood = decreased resistance to flow

Question 18

What is the formula to calculating resistance?

Answer 18

Formula: R = P1 - P2 / Q

Change in P = P1-P2

R = Change in P /Q

R = 8 x n x L / πxr⁴

Question 19

What does each variable in the resistance formula mean and what are the relationships?

Answer 19

R = Resistance to flow: unitless
P1 = Proximal Pressure:mmHg
P2= Distal Pressure:mmHG

Change in P (Triangle) = Change in Pressure: measure gradient: mmHg

Q = Velocity flow rate: L/min or ML/min

*Direct relationship Increases gradient

Question 20

Energy is lost as a result of two things:

Answer 20

1) Change in flow direction for blood EXL: turture vessel, vessle bifurcation

2) Increased Friction for Example:
- increased hematocrit
- narrowing of vessle; vasoconstriction stenosis

Question 21

Define Poiseuille’s Law:

Answer 21

It defines the relationship between pressure vessle radius, viscosity, and vessle length to volumeric flow rate
-Used to determine flow in a long straight tube with no stenosis

Question 22

Formula for Poiseuille’s Law

Answer 22

Q = Change in P (π)(r⁴)/ 8 nl

or

Q = (P1-P2) πr⁴/ 8 nl

Question 23

What are the relationships in the formula?

Answer 23

Q = volumetric flow rate of simply flow units
i.e. Volume/time ; ML/min

P1= Proximal Pressure : units mmHg
P2= Distal Pressure: units mmHg
π= 3.14 constant units
L = Vessel lenght : unit mm or cm
λ= viscosity constant ; 0.035 poise: kg/ms or mg/cm
r = radius of vessle; units: mm or cm

Question 24

When do we use this formula?

Answer 24

-When there is normal flow in a long straight tube with no stenosis