The Heart and Circulation

Question 1

Right atrium

Answer 1

receives blood from the systemic circulation, from the superior vena cavae, and the inferior vena cavae

Question 2

Right ventricle

Answer 2

Receives blood from the RA and pumps blood via the pulmonary artery to the lungs for oxygenation; the low pressure pulmonary pump

Question 3

Left atrium

Answer 3

receives oxygenated blood from the lungs and the four pulmonary veins

Question 4

left ventricle

Answer 4

• Receives blood form the LA and pumps blood via the aorta throughout the entire systemic circulation
• the high pressure systemic pump
• Walls of LV are thicker and stronger than RV and form most of the left side and apex of the heart

Question 5

What do valves provide?

Answer 5

One way flow of blood

Question 6

Artrioventricular valves

Answer 6

• Prevent back flow of blood into the atria during ventricular systole
• anchored by chordae tendinae to papillary muscles
• valves close when ventricular walls contract
• Tricuspid valve: right heart valve
• Bicuspid valve: left heart valve

Question 7

Semilunar Valves

Answer 7

• prevent back flow of blood from aorta and pulmonary arteries into the ventricles during diastole
• Pulmonary valve: prevents right backflow
• Aortic valve: prevents left back flow

Question 8

Systole

Answer 8

the period of ventricular contraction
- End systolic volume is the amount of blood in the ventricles after systole: 50 mL

Question 9

Diastole

Answer 9

• the period of ventricular relaxation and filling of blood
• End Diastolic volume is amount of blood in ventricles after diastole: 120 mL

Question 10

Atrial contraction

Answer 10

• occurs during the last third of diastole and completes ventricular filling comprising the last 20-30% of end diastolic volume

Question 11

Right coronary artery

Answer 11

• supplies right atrium, most of right ventricle, and in most individuals, the inferior wall of the left ventricle, AV node, and bundle of His
• supplies SA node 60% of the time

Question 12

Left coronary artery

Answer 12

supplies most of the left ventricle
- has two divisions: left anterior descending artery and circumflex artery

Question 13

Left anterior descending artery

Answer 13

• supplies the left ventricle and the inter ventricular septum and in most individuals, the inferior areas of the apex
• it may also give off branches to right ventricle

Question 14

Circumflex artery

Answer 14

• supplies blood to the lateral and inferior walls of the left ventricle and portions of the left atrium
• supplies SA node 40% of the time

Question 15

Veins in the heart

Answer 15

parallel arterial system
- the coronary sinus receives venous blood from the heart and empties into the right atrium

Question 16

What needs to be in balance in order to maintain a given activity level without ischemia?

Answer 16

Myocardial oxygen supply and myocardial oxygen demand

Question 17

SA Node

Answer 17

• located at the junction of the superior vena cava and right atrium
• Main pacemaker of the heart; initiates the impulse at a rate of 60-100 bpm
• Has sympathetic and parasympathetic innervation affecting both heart rate and strength of contraction

Question 18

AV Node

Answer 18

• Located at the junction of the right atrium and the right ventricle
• Has sympathetic and parasympathetic innervation
• Merges w/ bundle of His
• Intrinsic firing rate of 40-60 bpm

Question 19

Purkinje Tissue

Answer 19

• Right and left bundle branches of AV node are located on either side of IV septum
• terminate in Purkinje fibers, specialized conducting tissue spread throughout ventricles
• intrinsic firing rate of 20-40 bpm

Question 20

Conduction of heart

Answer 20

• origin is SA node –> impulse spreads throughout both atria, which contract together
• impulse stimulates AV node, is transmitted down bundle of His to Purkinje fibers; spreads throughout ventricles, which contract together

Question 21

Myocardial fibers

Answer 21

• striated muscle fiber with more numerous mitochondria
• fibers contract as functional unit
• Myocardial metabolism is aerobic
• smooth muscle tissue is found in the walls of blood vessels

Question 22

Stroke Volume

Answer 22

the amount of blood ejected with each myocardial contraction
- normal range is 55-100 mL/beat

Question 23

What influences stroke volume?

Answer 23

• Left ventricular end diastolic volume
• Contractility
• Afterload

Question 24

Left ventricular end diastolic volume

Answer 24

• amount of blood left in the ventricle at the end of diastole (aka preload)
• greater diastolic filling (preload), the greater the quantity of blood pumped (Frank Starling law)

Question 25

Afterload

Answer 25

the force the LV must generate during systole to overcome aortic pressure to open the aortic valve

Question 26

Cardiac output

Answer 26

- amount of blood discharged from left and right ventricle per minute - normal at rest: 4-5 L/min - HR x SV

Question 27

Cardiac index

Answer 27

- CO/body surface area - normal rand is 2.5-3.5 L/min

Question 28

Left ventricular end diastolic pressure

Answer 28

pressure in the left ventricle during diastole - normal range: 5-12 mmHg

Question 29

Ejection fraction

Answer 29

- percentage of blood emptied from the ventricle during systole - clinically useful measure of LV function - EF = SV/LVEDV - Normal: > 55% - < 40% = heart failure

Question 30

Atrial filling pressure

Answer 30

- difference between venous and atrial pressures - right atrial filling pressure is decreased during strong ventricular contraction, and atrial filling is enhanced

Question 31

what is right atrial filling pressure affected by?

Answer 31

changes in intrathoracic pressure - decreases during inspiration and increases during coughing or forces expiration

Question 32

When does venous return change?

Answer 32

- increases when blood volume expands - decreases during hypovolemic shift

Question 33

what occurs to diastolic filling time with increased heart rate and with heart disease?

Answer 33

it decreases

Question 34

What does myocardial oxygen demand represent?

Answer 34

- the energy cost to the myocardium - clinically measured by the product of heart rate and systolic blood pressure, know as the rate pressure produce - increases with activity and with HR and/or BP