CV Physiology Flashcards
Systemic circulation
path of oxygen rich blood from LV through aorta, pumped to all organ systems, back to heart (RA)
Pulmonary circulation
path of partially oxygen-depleted blood from RV through lungs and back to the heart (LA)
Semilunar valves
origin of pulmonary artery and aorta
one-way valves that open during systole to allow blood to enter pulmonary and systemic circulations
Atrioventricular valves
atria and ventricles are separated into 2 functional units by connective tissue and by AV valves
tricuspid and mitral valves
one-way valves that open during diastole to allow blood into ventricles
Valves…
prevent backflow of blood
what opens a valve is a difference in pressure
Cardiac Cycle
repeating pattern of contraction and relaxation of the heart
includes all mechanical and electrical events of the heart
divided into 5 phases
Systole
contraction phase
Diastole
relaxation phase
Phases of Cardiac Cycle
- atrial systole
- isovolumetric contraction
- ejection
- isovolumetric relaxation
- rapid inflow and diastasis
Phase 1 Cardiac Cycle
Atrial Systole
- Mitral valve is already open, ventricle has been filling with blood before atrial contraction
- P wave, atrial depolarization
- Atrial contraction pushes 10-20% more blood into ventricle
- S4 sound, always abnormal, vibration sound
Phase 2 Cardiac Cycle
Isovolumetric ventricular contraction
- QRS complex, ventricular depolarization
- contraction of ventricles causes ventricular pressure to rise
- S1 sound: LUB
- Ventricular P > atrial P, so AV valves closes
- EDV
Isovolumetric
- ventricles are not filling with blood because AV valves closed
- ventricles are not ejecting blood because ventricular pressure is less than aortic pressure, so semilunar valves are still closed
occurs during phase 2
End-diastolic volume
volume of blood in ventricle before ejection
about 120 mL
Phase 3 of Cardiac Cycle
Ejection
- Contraction of ventricles causes ventricular pressure to rise above aortic pressure
- Ventricular pressure > atrial pressure, AV valves are closed
- Ventricular repolarization (T wave)
- Stroke volume is about 80 mL
T wave
ventricular reploarization
LV pressure starts to fall
Stroke volume
volume of blood ejected during one contraction
resting SV = 80 mL
Phase 4 of Cardiac Cycle
Isovolumetric ventricular relaxation
- ventricles are fully repolarized and relaxed
- ventricular pressure falls below aortic pressure, AV closes
- S2 sound–DUB
- ESV–volume of blood in ventricles is constant
- phase lasts until pressure in ventricles falls to pressure in atria
Phase 5 Cardiac Cycle
Rapid inflow and diastasis
- ventricular pressure < atrial pressure, which opens AV valves
- ventricular pressure is low, chamber is relaxed
- Rapid ventricular filling occurs (S3 sounds)
- cycle returns to phase 1, with active rapid filling
longest phase of cardiac cycle
Diastasis
reduced ventricular filling and longest phase of cardiac cycle
S3 sound…
sometimes normal in <40 yrs
abnormal leads to heart failure
Left ventricular pressure volume loop
1–> 2 Isovolumetric contraction
2–> 3 ventricular ejection
3–>4 isovolumetric relaxation
4–>1 ventricular filling
Isovolumetric contraction…
pressure increases
all valves closed
ventricular volume remains constant
Ventricular Ejection
aortic valve opens
pressure remains high
volume decreases to 70 mL
Isovolumetric relaxation
Ventricle relaxes
aortic valve closes
volume remains constant at 70 mL
Ventricular filling
pressure rises
mitral valve opens
volume increases
Preload
end-diastolic volume (EDV)
Ejection fraction
portion of blood pumped out of ventricle with each contraction (SV/EDV), often expressed as a percentage
healthy/normal = 55-70%
systolic heart failure <40%
Afterload
pressure against which the heart has to work to eject blood
strictly speaking = aortic pressure
more broadly = systemic BP
Contractility
intrinsic ability of myocardial cells to develop force
Increased preload
Increased afterload
Increased Contractility
S1 Sounds
Closing of AV valves when ventricles contract at systole
LUB sounds
mitral and tricuspid
S2 Sounds
Closing of semilunar valves when ventricles relax at diastole, sometimes can be split during breathing
DUB sounds
aortic and pulmonic
Heart murmurs
abnormal heart sounds produced by abnormal patters of blood flow in heart
caused by turbulent blood flow–> defective heart valves and septal defects
Defective heart valves
causes murmur
stenotic = valves do not open fully
Regurgitant/insufficient/incompetent = valves do not close tightly
Causes of incompetent heart valves
Congenital
Damage by antibodies (rheumatic endocarditis)
damage to papillary muscles
Septal Defects
holes in the septum between left and right sides of heart
- usually congenital
- can occur in either septa, blood goes from left to right
- result is increased blood and pressure on right side of heart, leading to pulmonary HTN and edema
Cardiac muscles
myocardial cells are striated, actin/myosin are arranged in sarcomeres, short, branched, interconnected cells. Have gap junctions
cardiac muscle can produce action potentials spontaneously
Gap junctions
each cell is joined to adjacent cell by electrical synpase
helps depolarization to spread quickly
Functional Synctium
adjacent cardiac muscle cells are all connected
results in myocardium behaves like a single, large muscle cell
no graded contractions like those in skeletal muscle, electrical impulses spreads to all cells
How can myocardial contractility be increased?
increased EDV/frank-starling mechanism
epinephrine/norepinephrine (increases Ca)
Types of heart cells
Contractile cells
conducting/automatic cells
Contractile cells
produce the force of contraction
the pump
Conducting/automatic cells
contribute little to no force generation in heart
include SA node, AV node, bundle of His, purkinje fibers
Depolarization
occurs when there is a net movement of positive ions into the cell (inward current)
Hyperpolarization
occurs when there is a net movement of positive ions out of the cell (outward current)
Mechanisms that can produce in membrane potential
change in driving force for a permeant ion
opening and closing of ion channels
Automaticity
automatic nature of the heartbeat
Sinoatrial node
group of myocardial cells in RA
demonstrate spontaneous depolarization
functions as pacemaker, has fastest firing rate
don’t maintain stable resting membrane potential
SA nodes initiate the SINUS rhythm
