Cardio 2 Flashcards
Define systole. (Ventricules)
Contraction & emptying
Define diastole.
Relaxation & filling
majority of cardiac cycle
Define cardiac output.
Total volume of blood ejected by heart per min
Define stroke volume.
Volume of blood ejected by ventricle on each beat
Describe what the cardiac cycle is.
-events that occur from the beginning of one heartbeat to the next
-initiated by spontaneous generation of AP in sinus node
>AP travels from SA node through atria & through AV bundle into ventricles
>delay of cardiac impulse from atria into ventricle
Describe the reciprocal of the heart rate.
-total duration of cardiac cycle (systole & diastole)
>if HR is 80bpm the duration = 1/80 = 0.0125 min per beat
What are the phases of the cardiac cycle?
- Atrial systole
- Isovolumic contraction [ventricular systole]
- Ventricular ejection [ventricular systole]
- Isovolumic relaxation [ventricular diastole + atrial systole]
- Rapid influx [ventricular diastole + atrial systole]
- Diastasis [ventricular diastole + atrial systole]
When does atrial diastole occur?
During ventricular systole & 2/3 of ventricular diastole
What does the atria function as?
-primer pump for ventricles
-blood flows from veins into atria
(AV valves open)
-80% of blood flows through atria into ventricles before atria contract
Describe the atrial systole.
-forces blood into ventricles
>atrial contraction = +20% filling of ventricles
-ventricle pumps more blood than required
>atria fail = ventricle works
>clinical signs after exercise
Describe the Isovolumic (isometric) contraction.
-outflow of blood from ventricles during systole begins with Isovolumic contraction
-as ventricular contraction begins = ventricular pressure rises
>cause AV valves to close = pressure >80mmHg
-high pressure allows semilunar valves to open
>against pressure in aorta & pulmonary artery
*no emptying during this phase
*cardiac muscle tension increase
*no shortening of muscle fibers
Describe the role of AV valves.
-prevent back flow of blood from ventricles to atria during systole
-open = forward pressure gradient
-close = backward pressure gradient
when AV valves close = LUBB 1st heart sound
Describe what happens when AV valves are open.
atrial pressure greater than ventricular pressure
1. Blood returns to heart & fills atria = pressure against AV valve as they are forced open
2. Ventricles fill & AV valve flaps hang limp in ventricles
3. Atria contract = more blood into ventricles
Describe what happens when the AV valves are closed.
atrial pressure less than ventricular pressure
1. Ventricles contract, force blood against AV valve
2. Atrioventricular valves close
3. Papillary muscles contract & chordae tendinae tighten = prevent valve flap from going into atria
Describe the role of chorda tendinea.
-AV valves attached to papillary muscles by chorda tendinea
-dont help valves to close
-pull vanes of valves in toward ventricles during systole
>prevent bulging back toward atria
[chorda tendinea rupture or papillary muscle paralysis = severe/lethal cardiac incapacity]
Describe the ventricular ejection phase.
-high pressure = opens semilunar valves & blood is ejected out of ventricles
-60% volume ejected = ejection fraction
>70% of ejected blood flows during first third of ejection = rapid ejection
>80% is ejected during next two thirds = slow ejection
Describe diastole.
-L & R intraventricular pressures decrease rapidly
>helps close semilunar valves
>AV valves remain closed
-volume doesn’t change = isovolumic/isometric relaxation
Describe the semilunar valves during diastole.
-prevent back flow of blood from aorta & pulmonary arteries into ventricles during diastole
-resist physical stress
-no support by chordae tendinae
-smaller openings = rapid ejection
-high pressure in arteries during systole = closed
[semilunar close = DUBB 2nd heart sound]
Describe what happens when the semilunar valves are open VS closed.
OPEN:
-ventricles contract & intraventricular pressure rises = blood pushed against semilunar valves = open
CLOSED:
-ventricles relax & intraventricular pressure falls = blood flows back from arteries, filling cusps of semilunar valves = close
Describe the phase of rapid filling of the ventricles.
-systole is over
-ventricular pressure falls
-pressure inside atria forces AV valves open
>blood flows into ventricles
-2nd phase of diastole
-lasts 1/3 of ventricular diastole
Describe the diastasis phase.
-middle third of diastole = small amount of blood flows into ventricles
-blood empties into atria from veins & passes through atria directly into ventricles
-3rd phase of diastole
-persists until SA node initiates AP leading to atrial contraction again
Describe the last third of diastole.
-atria contract
-begins a new cycle
Describe what happens during diastole.
-fillings of ventricles increase volume of ventricle
>volume = end diastolic volume
>fraction of volume that’s ejected = ejection fraction (60%)
Describe what happens during systole.
-ventricles empty & volume decreases
-volume of blood ejected by ventricle = stroke volume
-remaining volume in each ventricle = end systolic volume
-cardiac output = total volume ejected by heart per min
What happens when the heart rate increases?
-duration of each cardiac cycle decreases (including contraction & relaxation phases)
-great percentage of decreasing occurs during diastole
-fast HR = doesn’t remained relaxed long enough to allow complete filling of cardiac chambers before next contraction
