Chapter 20 Cardiac Output & Venous Return

Question 1

______ __________—the volume of blood pumped out of the heart per minute. Therefore, it takes into account both HR (bpm) and SV

Answer 1

Cardiac Output (CO)

Question 2

_______ __________—the volume of blood returning from the superior and inferior vena cava into the Right Atrium each minute.

Answer 2

Venous Return (VR)

Question 3

the most influence on CO is _____ ______ (the volume of blood returning to the heart has the most influence on how much will be pumped out).

Answer 3

VR

Question 4

the most influence on CO AND VR is Total Peripheral

Resistance

Answer 4

KNOW THIS!

Question 5

CO varies depending on several factors:

1. Size of the body (surface area—so height and weight)
2. Level of body metabolism at rest (basal metabolic rate or BMR)
3. Metabolic rate during exercise
4. Age—the decline in CO with age is indicative of decline in activity level and declining muscle mass

Answer 5

KNOW THESE 4 FACTORS

Question 6

Effect of Exercise on CO:

CO is __________ proportional to tissue O2 use.

Answer 6

directly

Question 7

_____ ______ _______ is an autoregulatory mechanism that signals the heart to automatically pump out the SAME amount of blood that was returned to the right atria.

Answer 7

Frank-Starling Mechanism (Law)

So with an increase in VR, there is the same increase in CO

Question 8

The stretched right atrium initiates the \_\_\_\_\_ \_\_\_\_\_
which passes information via the vagus nerves to the 
vasomotor center (VMC) located in the medulla of the brain. This vagal nerve stimulus signals the sympathetic nervous system to increase HR.

Answer 8

Bainbridge Reflex

Question 9

The increase in HR prevents ________ of the blood in the veins, atria and pulmonary system

Answer 9

‘damming”

Question 10

Under normal resting conditions, \_\_\_ is controlled by 
peripheral circulation (the sum of all local tissue blood flows)  which determines VR. Therefore, \_\_\_ is the “sum of all local  blood flow regulations.”

Answer 10

CO

CO

Question 11

CO varies inversely with _________

Answer 11

TPR:

↓ TPR →↑ CO (left of 100)
Beriberi, Hyperthyroidism, anemia, etc.

↑ TPR →↓ CO (right of
100) Removal of arms & legs, hypothyroidism

Question 12

Ohm’s Law:

_____ = arterial pressure/ TPR

Answer 12

CO

Question 13

Chronic Conditions that Cause↓TPR

\_\_\_\_\_\_\_\_—caused by insufficient 
vitamin B1 (thiamin) in the diet. This 
vitamin is needed in the metabolic 
pathway so if ATP isn’t made, the 
cell’s reaction is to need more 
nutrients, thus more blood so local 
blood vessels dilate which ↓TPR.

Answer 13

Beriberi

Question 14

Chronic Conditions that Cause↓TPR

_____________—tissue
metabolism increases so O2 need
increases. To increase local blood
flow, blood vessels dilate which ↓TPR.

Answer 14

Hyperthyroidism

Question 15

Chronic Conditions that Cause↓TPR

\_\_\_\_\_\_\_\_\_\_—decrease in blood viscosity 
and with decrease in RBCs is a 
decrease in O2 delivery. To increase 
O2 delivery, local blood vessels dilate 
which ↓TPR.

Answer 15

Anemia

Question 16

Factors Related to Hypereffective Heart 1 OF 2
(increased plateau)

1. Nervous System Excitation:

a) Sympathetic Stimulation
b) Parasympathetic Inhibition

The effect of these two systems is
to ↑ HR from resting (72 bpm) up
to max HR (180-200 bpm) and ↑
force of contraction .

Answer 16

KNOW

Question 17

Factors Related to Hypereffective Heart 2 OF 2
(increased plateau)

2. Hypertrophy—as with skeletal 
muscle, long-term aerobic exercise 
will increase the mass and 
contractile strength of the heart 
muscle (myocardium).

Answer 17

KNOW

Question 18

Factors Related to Hypoeffective Heart 1 OF 2
(decrease the plateau)

1. Low Pumping Effectiveness:

When the heart becomes
severely damaged, the ability to
pump blood to the tissues is
severely compromised.

Answer 18

KNOW

Question 19

Factors Related to Hypoeffective Heart 2 OF 2
(decrease the plateau)

2. Interference with VR

Anything that ↓VR will lead to a
↓CO

EX. Decreased blood volume—results most
often from hemorrhaging. Not enough
blood in peripheral vessels to come back to
the heart

Answer 19

KNOW

EX. Acute venous dilation—results from
fainting

EX. Decrease in tissue mass (skeletal muscle)—
results from aging and inactivity. Results in
decrease in O2 need so decrease in blood
flow.