Cardiovascular Structure and Function Flashcards
Pulmonary circulation
- right side of the heart
- delivers blood to lungs for oxygenation
- heart and lungs
Systemic circulation
- left side of heart
- move oxygenated blood throughout the body
- heart and body
Heart wall layers
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
Chambers of the heart
- left atrium
- right atrium
- left ventricle (larger than right to eject blood)
- right ventricle
Valves of the heart
atrioventricular valves
- right side = tricuspid (3 cusps)
- left side = mitral (2 cusps)
semilunar valves
- pulmonic
- aortic
Cardiac cycle
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
Diastole
- 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
Systole
- ventricular contraction following diastole
- push blood out through semilunar valves into pulmonary artery (right ventricle) and aorta (left ventricle)
- blood enters systemic circulation
Direction of blood flow
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
Cardiac action potentials
transmission of electrical impulses → necessary for the continuous, rhythmic repetition of the cardiac cycle (systole and diastole)
Conduction system sequence
SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers
Depolarization
electrical activation of the muscle cells caused by the movement of electrically charged solutes (ions) across cardiac cell membranes
Repolarization
deactivation of muscle cells caused by movement of electrically charged solutes (ions) across cardiac cell membranes
Electrocardiogram
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
Automaticity
property of generating spontaneous depolarization to threshold → enables the SA and AV nodes to generate cardiac action potentials without any stimulus
Rhythmicity
regular generation of an action potential by the heart’s conduction system → SA node sets the pace
Heart rate
beats per minute
Intercalated disks
thickened portion of the sarcolemma that contain two junctions (desmosomes and gap junctions) that allow electrical impulses to spread from cell to cell
Myocardial contractility
change in developed tension at a given resting fiber length (contractility = ability of the heart muscle to shorten)
Cardiac output
volume of blood flowing through either the systemic or pulmonary circuit per minute (L/min)
Ejection fraction
- 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%
Preload
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
Laplace law
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
Frank-starling law of the heart
the length-tension relationship of preload to myocardial contractility (stroke volume)
Afterload
resistance to ejection of blood from the left ventricle → the load the muscle must move after it starts to contract
aortic systolic pressure
Stroke volume
volume of blood ejected per beat during systole
depends on force of contraction which depends on myocardial contractility (degree of myocardial fiber shortening)
Cardiovascular control center
primary = brain stem in the medulla
secondary = hypothalamus, cerebral cortex, thalamus, interneurons
Baroreceptor reflex
facilitates blood pressure changes and heart rate changes
mediated by tissue pressure receptors in the aortic arch and carotid arteries
Bainbridge reflex
distention of atria stimulates atrial receptors which activates bainbridge reflex to increase heart rate
Blood vessel wall layers
Tunica externa
Tunica media
Tunica intima
Elastic arteries
thick tunica media with more elastic fibers than smooth muscle fibers
ex: aorta and its major branches and the pulmonary trunk
Muscular arteries
- 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
Lumen
internal cavity of the vessel
Endothelium
lining of the blood vessel
Veins
thin walled
fibrous
larger diameter
more numerous than arteries
some have valves for one-way flow
Muscle pump
venous return to heart
Blood flow
amount of fluid moved per unit of time (L/min)
regulated by pressure, resistance, velocity, turbulent v laminar flow, and compliance
Blood velocity
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
Pressure
the force exerted on the liquid per unit area (mm Hg)
Resistance
opposition to force
diameter and length of the blood vessels
Laminar flow
fluid flows in long, smooth-walled tubes
Turbulent flow
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
Vascular compliance
increase in volume a vessel can accommodate for a given increase in pressure
Systolic blood pressure
arterial blood pressure during ventricular contraction (systole)
Diastolic blood pressure
arterial blood pressure during ventricular filling (diastole)
Baroreceptors
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
Arterial chemoreceptors
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
Antidiuretic hormone (ADH)
causes reabsorption of water by the kidney → increases blood plasma volume → increases blood pressure
released by posterior pituitary
Natriuretic peptides
help regulate sodium excretion (natriuresis), diuresis, vasodilation, and antagonism of renin-angiotensin system
Coronary perfusion pressure
difference between the pressure in the aorta and pressure in the coronary vessels of the right atrium
Systolic compressive effect
when coronary arteries are compressed by ventricular compression during systole
Myoglobin
protein present in heart muscle that binds oxygen during diastole and releases it when blood levels of oxygen drop during systole
Autoregulation
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)
Poiseuille law
relationship among blood flow, pressure, and resistance
Renin-angiotensin system
regulates blood pressure
