3-Cardiac Cycle Flashcards
excitation-contraction coupling
stim for muscle contraction = depolarizing impulse
-electric events precede mechanical events
-slower/inc time delay in cardiac than skeletal muscle
-calcium induced calcium release
calcium cycling
- Ca entry thru voltage Ca channels
- diffuse to ryanodine receptor on SR membrane
- Ca released from SR
- troponin interaction = contraction from shortening sarcomere (actin/myosin
- Ca channels close (phase 3) = dec intracell Ca bc no more enters cell
- Ca sequestered to SR by SERCA pump and out of cell by Ca exchanger (NCX) and pump
sympathetic stim excitation-contraction
- beta adrenergic act of muscle
- inc cAMP and PKA
- enhance act of Ca channels
- inc intracell Ca and release from SR
- enhance myosin ATPase activity
- inc toponin C ‘iontropy’
- inc Ca reupatake ‘lusitropy’
inotropy
force of contraction
lusitropy
rate of relaxation
phases of cardiac cycle
- atrial systole
- isovolumic (ventricular) contraction
- ejection - rapid + reduced
- isovolumic (vent) relaxation
- filling- rapid + reduced
ventricular systole is what parts
contraction
isovolumic contraction + ejection
ventricular diastole
aka relaxation
isovolumic relaxation + ventricular filling + atrial systole
things on Wigger’s diagram
- ECG
- muscle tension
- pressures- aortic, LV, LA
- valves
- phonocardiogram/heart sounds
- LV volume
- aortic flow
atrial systole wave components
follows P wave + includes SOME of QRS complex
LV pressure and volume during atrial systole
pressure slightly inc bc atrial kick adds last 20% of volume to ventricle = end diastolic volume, total filling volume
valves during atrial systole
aortic valve closed
mitral valve open-blood entering ventricle
sounds during atrial systole
S4
always abnormal - from forcing blood into non compliant/stiffened ventricle
isovolumic contraction - waves
begins during portion of QRS
pressure/volume
isovolumic contraction
LV pressure inc from ventricular muscle contraction
-volume stays the same
valves - isovolumic contraction
-aortic closed
-mitral closed passively bc pressure differential across valve, mitral>aortic
sounds-isovolumic contraction
S1
first heart sound from closing mitral valve vibrating chordae tendinae and blood
rapid ejection pressure/volume
LV pressure inc more from isovolumic contraction bc still contracting
LV volume dec fastest of any phase
rapid ejection valves
-aortic is open from pressure of other phases, need to overcome aortic pressure
-mitral closed
rapid ejection sounds
none 0 zilch
phase of AP corresponding to rapid ejection
phase 2, ventricle contracting
reduced ejection waves
just before T when relaxation begins in ventricular myocardium, Ca channels close
reduced ejection pressure and volume
LV pressure falls as muscle cells relax
LV volume dec but slower/reduced than rapid ejection
-vol at end of phase = end systolic volume, residual volume after ejection
reduced ejection valves
-aortic open as blood ejected
mitral closed
isovolumic relaxation pressure & volume
LV pressure dramatically dec since myocytes complete relax
LV vol not change
isovolumic relaxation valves
both aortic and mitral closed
isovolumic relaxation sounds
S2
closure of semilunar valves = vibrations of fluid and tissue
rapid filling ECG
isoelectric line, flat
myocytes are relaxed
rapid filling pressure & volume
LV pressure low (lower than LA pressure) so passive move blood from atrium to ventricle
LV volume inc rapidly
rapid filling valves
aortic closed
mitral open
rapid filling sounds
S3
from ventricles filling fast
can be healthy or pathologic
reduced filling ECG
isoelectric line still
-myocytes relaxed
ends with P wave
reduced filling pressure & volume
LV pressure low
LV volume inc but slower/reduced
reduced filling valves
aortic closed
mitral open
reduced filling sounds
natta
differences with right heart pump
all other cycle cards about left heart
-R same events just lower pressure
-only gets to 20 mmHg vs 120 on L
resistance of pulmonary circ lower than systemic circ
waves of atrial pressure curve
- a wave = contraction, H ascent before as venous return inc pressure, X descent after a wave
- c wave = early systole, tricuspid valve bulges into RA from isovolumic contraction of vent, X’ descent after
- v wave= venous return then open AV valve, isovolumic relaxation of vent, Y descent
low yield for exam, importnat 2nd year
stroke volume is
end diastolic vol - end systolic vol
amount blood ejected by heart in one beat
ejection fraction is
stroke volume (end diastolic-systolic) / end diastolic vol
x 100
proportion of blood ejection with each contraction, index of cardiac fxn 65-70% normal
fractional shortening is
(end diastolic-end systolic diameter) / end diastolic diameter
x100
index of cardiac contractility/myocyte shortening
relationship b/t HR and cycle duration
inverse- as HR inc CC dec
diastole duration changes the most, not uniform over all phases
bookends of systole
S1 = close AV valve
S2 = close semilunar
heart sounds during inspiration
S2 split into A2 and P2
P2 is delayed (comes after A2), inc venous return
A2 is earlier than during expiration, dec venous return
aortic valve closes before pulmonic
wide splitting
A2 and P2 are farther apart
-pulmonic stenosis
pulmonic valve closes slower than normal
paradoxical splitting heart sounds
aka reverse, P2 before A2
-aortic stenosis, during expiration
aortic valve close slower than normal
narrow splitting
higher resistance in pulmonary circ
-hypertension, age?
blood flow
closed circulation
- vena cava
- R atrium
- tricuspid valve (AV)
- R ventricle
- pulmonic valve (semilunar)
- pulmonary circulation- to lungs
- L atrium
- mitral valve (AV)
- L ventricle
- aortic valve (semilunar)
- aorta
- systemic circulation
regurgitant murmur
from blood flow across valve when it should NOT be
-regurgitant valves don’t close
stenotic murmur
blood flow turbelently across valve when it normally should be
-stenotic valves don’t open
ejection murmur
type of systolic (b/t S1 and S2)
from aortic or pulmonic valve stenosis
pansystolic/holosystolic murmur
type of systolic
from regurgitant AV valve or VSD
late murmur
type of systolic murmur
from mitral valve prolapse
early murmur
type of diastolic (after S2 before S1)
from regurgitant aortic or pulmonic valve
-if aortic then lower forward stroke volume bc blood goes back into ventricle
mid-late murmur
type of diastolic murmur
from stenotic AV valve
what phases is mitral valve open
ventricular filling so
1. atrial systole
2. rapid filling
3. reduced filling
