The Heart and Circulation Flashcards
Right atrium
receives blood from the systemic circulation, from the superior vena cavae, and the inferior vena cavae
Right ventricle
Receives blood from the RA and pumps blood via the pulmonary artery to the lungs for oxygenation; the low pressure pulmonary pump
Left atrium
receives oxygenated blood from the lungs and the four pulmonary veins
left ventricle
- 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
What do valves provide?
One way flow of blood
Artrioventricular valves
- 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
Semilunar Valves
- 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
Systole
the period of ventricular contraction
- End systolic volume is the amount of blood in the ventricles after systole: 50 mL
Diastole
- the period of ventricular relaxation and filling of blood
- End Diastolic volume is amount of blood in ventricles after diastole: 120 mL
Atrial contraction
- occurs during the last third of diastole and completes ventricular filling comprising the last 20-30% of end diastolic volume
Right coronary artery
- 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
Left coronary artery
supplies most of the left ventricle
- has two divisions: left anterior descending artery and circumflex artery
Left anterior descending artery
- 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
Circumflex artery
- 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
Veins in the heart
parallel arterial system
- the coronary sinus receives venous blood from the heart and empties into the right atrium
What needs to be in balance in order to maintain a given activity level without ischemia?
Myocardial oxygen supply and myocardial oxygen demand
SA Node
- 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
AV Node
- 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
Purkinje Tissue
- 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
Conduction of heart
- 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
Myocardial fibers
- 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
Stroke Volume
the amount of blood ejected with each myocardial contraction
- normal range is 55-100 mL/beat
What influences stroke volume?
- Left ventricular end diastolic volume
- Contractility
- Afterload
Left ventricular end diastolic volume
- 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)
Afterload
the force the LV must generate during systole to overcome aortic pressure to open the aortic valve
Cardiac output
- amount of blood discharged from left and right ventricle per minute
- normal at rest: 4-5 L/min
- HR x SV
Cardiac index
- CO/body surface area
- normal rand is 2.5-3.5 L/min
Left ventricular end diastolic pressure
pressure in the left ventricle during diastole
- normal range: 5-12 mmHg
Ejection fraction
- percentage of blood emptied from the ventricle during systole
- clinically useful measure of LV function
- EF = SV/LVEDV
- Normal: > 55%
- < 40% = heart failure
Atrial filling pressure
- difference between venous and atrial pressures
- right atrial filling pressure is decreased during strong ventricular contraction, and atrial filling is enhanced
what is right atrial filling pressure affected by?
changes in intrathoracic pressure
- decreases during inspiration and increases during coughing or forces expiration
When does venous return change?
- increases when blood volume expands
- decreases during hypovolemic shift
what occurs to diastolic filling time with increased heart rate and with heart disease?
it decreases
What does myocardial oxygen demand represent?
- 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
