Lecture 14

Question 1

Cardiac Output

Answer 1

Quantity of blood pumped into the aorta each minute by the heart; quantity of blood that flows through the circulation; sum of all the blood flows to all of the tissues of the body

Question 2

Cardiac Index

Answer 2

Cardiac output per square meter of body surface; just remember cardiac index is related to body size

Question 3

Flick Principle of Blood Flow

Answer 3

Used to calculate blood flow through an organ; cardiac output = O2 consumption/ concentration of O2 in the pulmonary vein - concentration of O2 in the pulmonary artery

Question 4

What is the determining factor that controls how much blood the heart pumps out?

Answer 4

The heart is a “demand” pump; heart pumps out whatever blood comes back into it from the venous system; is is the amount of blood returning to the heart that determines how much blood the heart pumps out

Question 5

Factors that Directly Affect Cardiac Output

Answer 5

Basic level of body metabolism, whether the person is exercising, age, size of the body

Young Healthy Men: 5.6 L/min
Women: 4.9 L/min
Resting Adult: 5.0 L/min

Question 6

Frank-Starling Law

Answer 6

Heart automatically pumps whatever amount of blood that flows into the right atrium; therefore, peripheral factors are more important controllers of cardiac output

Question 7

Ohm’s Law

Answer 7

Any time the long-term level of total peripheral resistance changes, the cardiac output changes quantitatively in exactly the opposite direction

Question 8

Bainbridge Reflex (Atrial Stretch Reflex)

Answer 8

Responds to changes in blood volume as detected by stretch receptors in the right atrium; contrast with baroreceptors which respond to changes in arterial pressure; not significant in humans (does occur after birth, when a large volume of the uteroplacental blood returns to the mother’s circulation and results in tachycardia)

Question 9

Factors that Cause Hypereffective Heart

Answer 9

Nervous stimulation
Hypertrophy of heart
Exercise via the nervous system

Question 10

Factors that Cause Hypoeffective Heart

Answer 10

Increased arterial pressure
Inhibition of nervous excitation of the heart
Pathological factors causing abnormal heart rhythm/rate
Coronary artery blockage
Valvular heart disease
Congenital heart disease
Cardiac hypoxia

Question 11

Cardiac Factors Causing Decreased Cardiac Output

Answer 11

Severe blood vessel blockage leading to MI
Severe valvular disease
Myocarditis
Cardiac tamponade
Cardiac metabolic derangements

Question 12

Non-Cardiac Factors Causing Decreased Cardiac Output

Answer 12

Decreased blood volume
Acute venous dilation
Obstruction of large veins
Decreased tissue mass (especially muscle mass)
Decreased metabolic rate of tissues

Question 13

Factors Affecting Venous Return to the Heart from Systemic Circulation

Answer 13

Greater the difference between the mean systemic filling pressure and the right atrial pressure, the greater the venous return

Question 14

Pressure Gradient for Venous Return

Answer 14

Difference between the mean systemic filling pressure and the right atrial pressure

Question 15

Equation for Venous Return

Answer 15

Mean systemic filling pressure - right atrial pressure/ resistance to venous return

Question 16

Resistance to venous return blood flow

Answer 16

2/3 of resistance is determined by venous resistance; 1/3 of resistance is determined by arteriolar and small artery resistance

Question 17

Local Control of Blood Flow Regulation to Skeletal Muscle

Answer 17

Large blood flow during skeletal muscle activity is due mainly to chemicals that act directly on muscle arterioles to dilate them (reduction in oxygen, adenosine, K+, ATP, lactic acid, CO2)

Question 18

Nervous Control of Blood Flow Regulation to Skeletal Muscle

Answer 18

Sympathetic vasoconstrictor nerves secrete norepinephrine and can decrease blood flow through resting muscles to as little as one-half to one-third normal

Adrenal medullae secrete norepinephrine and epinephrine; epinephrine also has a slight dilator effect

Question 19

Mass Discharge of Sympathetic Nervous System Causes…

Answer 19

Heart rate to increase, most peripheral arteries are strongly contracted except those in active muscles, coronary arteries, and cerebral arteries; muscle walls of veins are contracted which increases mean systemic filling pressure

Question 20

Coronary Blood Flow during Systole

Answer 20

Blood flow in the left ventricle falls to a low value, opposite to flow in vascular beds elsewhere in the body; inverse in right ventricle and partial compared to left

Question 21

Coronary Blood Flow during Diastole

Answer 21

Cardiac muscle relaxes and no longer obstructs blood flow through the left ventricular capillaries; inverse in right ventricle and partial compared to left

Question 22

Primary Controller of Coronary Flow

Answer 22

Local muscle metabolism

Question 23

Direct ANS stimulation acts on what?

Answer 23

Blood vessels themselves

Question 24

Indirect ANS stimulation acts on what?

Answer 24

Cardiac muscle tissue and indirectly on the coronary vessels via local control mechanisms

Question 25

Causes of Death after Acute Coronary Occlusion

Answer 25

Decreased cardiac output, damming of blood in pulmonary blood vessels and death resulting from pulmonary edema, fibrillation of heart, rupture of heart