Principles of Cardiac Output

Question 1

Cardiac Output (CO)

Answer 1

the amount of blood pumped by each ventricle per minute

Question 2

Stroke Volume (SV)

Answer 2

the amount of blood pumped by each ventricle per beat
- 70 mL

Question 3

Equation for CO

Answer 3

Heart Rate (HR) x Stroke Volume (SV)

Question 4

Cardiac Reserve

Answer 4

the difference in resting CO and maximal CO

Question 5

SV equation

Answer 5

SV = EDV - ESV

Question 6

Ejection Fraction

Answer 6

each ventricle pumps about 60% of its blood with each contraction

Question 7

3 factors for regulating stroke volume

Answer 7

Preload
Frank-Starling Law
Contractility

Question 8

Preload

Answer 8

the degree to which muscles are stretched before contracting

high preload = higher (SV) stroke volume

Question 9

Frank-Starling Law

Answer 9

a length-tension relationship - cardiac muscle cells are stretched to their optimal length for maximal contraction

• higher EDV = higher SV
• increased venous return = increased preload

Question 10

Contractility

Answer 10

the contractile strength achieved at a given muscle length

• increase with rises in Ca2+ from extracellular fluid or sarcoplasmic reticulum
• increase contractility will increase SV and decrease ESV

Question 11

Positive Ionotropic Agents

Answer 11

increases contractility

• epinephrine, norepinephrine, throxine, glucagon, high levels of extracellular Ca2+

(things that increase heart rate)

Question 12

Negative Ionotropic Agents

Answer 12

decreases contractility

• acidosis, rising extracellular K+ levels, and CA2+ channel blocker

(things that decrease heart rate)

Question 13

Sympathetic Nervous System (SNS)

Answer 13

• activated by emotional and physical stressors - epinephrine is released, SA Node depolarizes more rapidly
• increases heart contractility and speeds heart relaxation via enhanced Ca 2+ movement

Question 14

Parasympathetic Nervous System (PNS)

Answer 14

• reduces heart rate, mediated by acetylcholine
• acetylcholine hyperpolarizes the membranes of its effector cells by opening K+ channels

Question 15

Atrial (Bainbridge) reflex

Answer 15

• autoimmune reflex initiated by increased venous return and increases atrial filling
• stretching of the atrial walls increases heart rate by stimulating the SA Node and the atrial stretch receptors
• Stretch receptors activation triggers reflexive adjustments of autonomic Output to the SA Node – increased HR

Question 16

Epinephrine

Answer 16

increases both heart rate and contractility

Question 17

Thyroxine

Answer 17

increases heart rate, enhances the effects of epinephrine and norepinephrine

Question 18

Hypocalcemia

Answer 18

depresses heart function

Question 19

Hypercalcemia

Answer 19

stimulates heart functions and can increase risk of arrythmia

Question 20

Hypokalemia

Answer 20

weakens heart contraction

Question 21

Hyperkalemia

Answer 21

alters the heart’s electrical activity, can increase risk of heart block and cardiac arrest

Question 22

Age

Answer 22

HR is 140-160 BPM in fetuses then declines

Question 23

Gender

Answer 23

HR is typically faster in females

Question 24

Exercise

Answer 24

HR increases secondary to activation of the SNS
- HR will be lower in highly trained athletes

Question 25

Temperature

Answer 25

heat increases HR cold decreases HR

Question 26

Congestive Heart Failure

Answer 26

secondary to a weakened myocardium, the heart becomes and inefficient pump; circulation is not adequate to meet the tissues needs

Question 27

Causes of weakened myocardium

Answer 27

...

Question 28

What side of the heart is failing when peripheral congestion is seen?

Answer 28

right side

Question 29

Pulmonary Congestion

Answer 29

fluid leaks from pulmonary blood vessels into lung tissue symptoms- shortness of breath/dyspnea on exertion

Question 30

what side of the heart is failing when pulmonary congestion is seen?

Answer 30

left side

Question 31

peripheral congestion

Answer 31

blood stagnates in the organs and tissues symptoms- swelling in the distal extremities

Question 32

Diuretics

Answer 32

increases excretion of Na+, H2O by the kidneys

Question 33

Digitalis

Answer 33

increases heart contractility

Question 34

4 primitives of heart chambers

Answer 34

- Sinus Venosus - Atrium - Ventricle - Bulbus Cordis

Question 35

Sinus Venosus

Answer 35

receives all venous blood from the embryo - becomes the smooth walled portions of the atria, the coronary sinus and the SA Node

Question 36

Atrium

Answer 36

becomes the pectinate muscle ridged parts of the atria

Question 37

Ventricle

Answer 37

the strongest part of the embryonic heart - becomes the left ventricle

Question 38

Bulbus Cordis

Answer 38

has cranial extension - truncus arteriosus - becomes the pulmonary trunk, part of the aorta, and most of the right ventricle

Question 39

what gestational age is the fetal heart contracting?

Answer 39

22 days

Question 40

Foramen Ovale

Answer 40

a hole in the interatrial septum, a bypass for the lungs - becomes the Fossa Ovalis in adults

Question 41

Ductus Arteriosus

Answer 41

a shunt between the pulmonary trunk and the aorta, another bypass for the lungs - becomes the ligamentum arteriosum in adults

Question 42

2 basic types of congenital heart defects

Answer 42

1. mixing of O2 rich and O2 poor blood - inadequately oxygenated blood reaches the body's tissues ex: septal defects, patent ductus arteriosus 2. narrowed valves/vesseks increase the heart's workload ex: coarctation of the aorta

Question 43

Tetralogy of Fallot

Answer 43

a serious condition in which cyanosis appears within minutes of birth - encompasses both types of defects

Question 44

4 features of Tetralogy of Fallot

Answer 44

1. narrowed pulmonary trunk/pulmonary valve stenosed 2. hypertrophied right ventricle 3. ventricular septal defects 4. aorta receiving blood from both chambers

Question 45

Explain how a highly trained aerobic athlete could have a resting HR as low as 30-40 bpm.

Answer 45

Aerobic exercise can clear fatty deposits from blood vessels and slow the development coronary heart disease