Cardiovascular Structure and Function

Question 1

Pulmonary circulation

Answer 1

• right side of the heart
• delivers blood to lungs for oxygenation
• heart and lungs

Question 2

Systemic circulation

Answer 2

• left side of heart
• move oxygenated blood throughout the body
• heart and body

Question 3

Heart wall layers

Answer 3

Pericardium
- double walled membranous sac (encloses heart)
- prevents displacement of heart, serves as physical barrier, and elicits reflexes
- two layers = parietal and visceral pericardia separated by pericardial cavity containing pericardial fluid (reduce friction)

Myocardium
- thickest layer
- made of cardiac muscle
- anchored to fibrous skeleton
- contractile force for blood flow

Endocardium
- internal lining of myocardium
- connective tissue and squamous cells
- continuous with endothelium → lines arteries, veins, and capillaries → creates continuous, closed circulatory system

Question 4

Chambers of the heart

Answer 4

• left atrium
• right atrium
• left ventricle (larger than right to eject blood)
• right ventricle

Question 5

Valves of the heart

Answer 5

atrioventricular valves
- right side = tricuspid (3 cusps)
- left side = mitral (2 cusps)

semilunar valves
- pulmonic
- aortic

Question 6

Cardiac cycle

Answer 6

each ventricular contraction + relaxation = one cardiac cycle
(1) atrial systole
(2) isometric ventricular contraction → ventricular volume remains constant as pressure increases rapidly
(3) ejection
(4) isovolumetric ventricular relaxation → both sets of valves are closed → ventricles relaxed
(5) passive ventricular filling → atrioventricular valves are forced open → blood rushes into relaxing ventricles

Question 7

Diastole

Answer 7

• during relaxation
• blood flows intro atria
• atrioventricular valves open
• blood begins to fill ventricles
• atrial systole squeezes any blood remaining in atria out into ventricles

Question 8

Systole

Answer 8

• ventricular contraction following diastole
• push blood out through semilunar valves into pulmonary artery (right ventricle) and aorta (left ventricle)
• blood enters systemic circulation

Question 9

Direction of blood flow

Answer 9

Deoxygenated blood enters the right side of the heart via the superior or inferior vena cava → Coronary sinus collects blood from coronary vessels → Enters right atrium → Passes through tricuspid valve → Enters right ventricle → Pushed through pulmonary valve → Pulmonary trunk → Pulmonary arteries → Arterioles → Capillaries → Alveoli → Blood collects oxygen from alveoli and removes carbon dioxide → Oxygenated blood travels through pulmonary venules → Veins → Enters left atrium → Passes through mitral valve → Enters left ventricle → Pushes through aortic valve → Aorta → Travels to organs and tissues to provide oxygen and nutrients → Deoxygenated blood returns to the right side of the heart via the superior or inferior vena cava

Question 10

Cardiac action potentials

Answer 10

transmission of electrical impulses → necessary for the continuous, rhythmic repetition of the cardiac cycle (systole and diastole)

Question 11

Conduction system sequence

Answer 11

SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers

Question 12

Depolarization

Answer 12

electrical activation of the muscle cells caused by the movement of electrically charged solutes (ions) across cardiac cell membranes

Question 13

Repolarization

Answer 13

deactivation of muscle cells caused by movement of electrically charged solutes (ions) across cardiac cell membranes

Question 14

Electrocardiogram

Answer 14

sum of all cardiac action potentials

P wave: atrial depolarization

PR interval: onset of atrial activation to onset of ventricular activation
- Time for SA node activation to travel through atrium, AV node, His-Purkinje system to activate the ventricular myocardial cells

QRS complex: sum of all ventricular muscle cell depolarization

ST interval: entire ventricular myocardium is depolarized

QT interval: “electrical systole” of the ventricles

T wave: ventricular repolarization

Question 15

Automaticity

Answer 15

property of generating spontaneous depolarization to threshold → enables the SA and AV nodes to generate cardiac action potentials without any stimulus

Question 16

Rhythmicity

Answer 16

regular generation of an action potential by the heart’s conduction system → SA node sets the pace

Question 17

Heart rate

Answer 17

beats per minute

Question 18

Intercalated disks

Answer 18

thickened portion of the sarcolemma that contain two junctions (desmosomes and gap junctions) that allow electrical impulses to spread from cell to cell

Question 19

Myocardial contractility

Answer 19

change in developed tension at a given resting fiber length (contractility = ability of the heart muscle to shorten)

Question 20

Cardiac output

Answer 20

volume of blood flowing through either the systemic or pulmonary circuit per minute (L/min)

Question 21

Ejection fraction

Answer 21

• amount of blood ejected from ventricle
• stroke volume / end-diastolic volume
• normal stroke volume = 40-60 ml/beat
• normal end-diastolic volume = 70-80 ml/m^2
• normal ejection fraction = 60-75%

Question 22

Preload

Answer 22

volume and associated pressure generated n the ventricle at the end of diastole

determined by:
- amount of venous return entering the ventricle during diastole
- the blood left in the ventricle after systole

Question 23

Laplace law

Answer 23

the relationship by which the amount of tension generated in the wall of the ventricle (any chamber or vessel) to produce a given intraventricular pressure depends on the size (radius and wall thickness) of the ventricle

Question 24

Frank-starling law of the heart

Answer 24

the length-tension relationship of preload to myocardial contractility (stroke volume)

Question 25

Afterload

Answer 25

resistance to ejection of blood from the left ventricle → the load the muscle must move after it starts to contract

aortic systolic pressure

Question 26

Stroke volume

Answer 26

volume of blood ejected per beat during systole

depends on force of contraction which depends on myocardial contractility (degree of myocardial fiber shortening)

Question 27

Cardiovascular control center

Answer 27

primary = brain stem in the medulla

secondary = hypothalamus, cerebral cortex, thalamus, interneurons

Question 28

Baroreceptor reflex

Answer 28

facilitates blood pressure changes and heart rate changes

mediated by tissue pressure receptors in the aortic arch and carotid arteries

Question 29

Bainbridge reflex

Answer 29

distention of atria stimulates atrial receptors which activates bainbridge reflex to increase heart rate

Question 30

Blood vessel wall layers

Answer 30

Tunica externa
Tunica media
Tunica intima

Question 31

Elastic arteries

Answer 31

thick tunica media with more elastic fibers than smooth muscle fibers

ex: aorta and its major branches and the pulmonary trunk

Question 32

Muscular arteries

Answer 32

• medium and small sized arteries
• farther from the heart than elastic arteries
• more muscle fibers than elastic arteries because they need less stretch and recoil
• distribute blood to arteries through the body and help control blood flow because smooth muscle can be stimulated to contract or relax

Question 33

Lumen

Answer 33

internal cavity of the vessel

Question 34

Endothelium

Answer 34

lining of the blood vessel

Question 35

Veins

Answer 35

thin walled
fibrous
larger diameter
more numerous than arteries
some have valves for one-way flow

Question 36

Muscle pump

Answer 36

venous return to heart

Question 37

Blood flow

Answer 37

amount of fluid moved per unit of time (L/min)

regulated by pressure, resistance, velocity, turbulent v laminar flow, and compliance

Question 38

Blood velocity

Answer 38

distance blood travels in a unit of time (cm/sec)

directly related to blood flow
inversely related to the cross-sectional area of the vessel in which the blood is flowing

Question 39

Pressure

Answer 39

the force exerted on the liquid per unit area (mm Hg)

Question 40

Resistance

Answer 40

opposition to force

diameter and length of the blood vessels

Question 41

Laminar flow

Answer 41

fluid flows in long, smooth-walled tubes

Question 42

Turbulent flow

Answer 42

blood flows in vessel turns, over rough surfaces, whorls and eddy currents

produces noise → causes murmur to be heard on auscultation

resistance increases with turbulence

Question 43

Vascular compliance

Answer 43

increase in volume a vessel can accommodate for a given increase in pressure

Question 44

Systolic blood pressure

Answer 44

arterial blood pressure during ventricular contraction (systole)

Question 45

Diastolic blood pressure

Answer 45

arterial blood pressure during ventricular filling (diastole)

Question 46

Baroreceptors

Answer 46

stretch receptors located in the aorta and carotid sinus → respond to changes in smooth muscle fiber length by altering their rate of discharge and supply sensory information to the cardioinhibitory center in the brain stem

Question 47

Arterial chemoreceptors

Answer 47

specialized areas within the aortic and carotid arteries are sensitive to concentrations of oxygen, carbon dioxide, and hydrogen ions (pH) in the blood

important for control of respiration and blood pressure

Question 48

Antidiuretic hormone (ADH)

Answer 48

causes reabsorption of water by the kidney → increases blood plasma volume → increases blood pressure

released by posterior pituitary

Question 49

Natriuretic peptides

Answer 49

help regulate sodium excretion (natriuresis), diuresis, vasodilation, and antagonism of renin-angiotensin system

Question 50

Coronary perfusion pressure

Answer 50

difference between the pressure in the aorta and pressure in the coronary vessels of the right atrium

Question 51

Systolic compressive effect

Answer 51

when coronary arteries are compressed by ventricular compression during systole

Question 52

Myoglobin

Answer 52

protein present in heart muscle that binds oxygen during diastole and releases it when blood levels of oxygen drop during systole

Question 53

Autoregulation

Answer 53

automatic self-regulation

allows individual vessels to regulate blood flow by altering their own arteriolar resistances

maintains constant blood flow at perfusion pressures (mean arterial pressure)

Question 54

Poiseuille law

Answer 54

relationship among blood flow, pressure, and resistance

Question 55

Renin-angiotensin system

Answer 55

regulates blood pressure