Lecture 3: Mechanics and CO Flashcards
Ventricular Systole
start w/ close AV valve, pressure inside incs, muscle depol, cnontraction
ventricular diastole
vent. muscles repol., drop in pressure, ventricle fills
* *** This takes less time as HR incs
Atrial Systole
very short,
vent filling largely passive due to this
Stroke Volume
difference in blood between end diasoltic and syst. vols.
vol moved out per stroke
Equal for right and left
Cardiac Output
vol. of blood pumped out per minute
CO (l/min) = SV (L/beat) X HR (beat/min)
Cardiac Output at rest
HR =75 bpm, SV= 0.07 L/min, CO= 5.25 L/mon`
Determinatnts of Stroke Volume
1) aortic (pulm art) bp (amount blood out)
2) end diastolic vol (per load): blood at start
3) active or passive contractility (how hard contraction of muscle)
active = from nervous system
Passive= from heart.
hypertension:
high bp/get less blood out/slower flow
so heart contracts harder
Afterload
pressure required to open semilunar valves
Aortic BP
vents cant eject blood to aorta till pressure in vent passes pressure in artery
inc in pressure= major impact on work of heart and SV
Preload
End Diastolic Volume
cardiac chambers can only pump what they get
SV cant inc unless rate of cardiac filling incs.
ECG
represents large movement of charge
During QRS…
pressure in left vent goes way up, AV valve closes
pressure difference in LA and LV due to…
LA blood going to LV
active contractility
stim. symp nerves to heart
controled by norepinephrine
inc rate of pacemaker
inc force of muscle contraction (cardiac)
passive contractility
chnage lenght of cardiac muscle fibers (Frank Starling mechanism)
