Cardiac - Pt 2 Flashcards
What are the phases of the Nodal Action Potential?
Phase 4
Phase 0
Phase 3
What is the main characteristic of Phase 4 in the Nodal Action Potential?
- Possesses an unstable membrane potential caused by the the “Funny Current”
The “Funny Current” is caused by….
- Due to the Na+ influx from voltage-gated, non-selective cation channels.
- These channels open in response to the previous action potential.
What is the main characteristic of Phase 0 in the Nodal Action Potential curve?
- It is the rapid depolarization of the cell.
- This is due to Voltage-Gated L-type Ca2+ channels opening, and Ca2+ rushing into the cell.
What type of channels cause the upstroke in the nodal action potential?
The opening of Voltage-gated, L-type Ca2+ channels
What cation(s) is responsible for the Ventricular Upstroke?
What cation(s) is responsible for the Nodal upstroke?
- Na+/Ca2+
- Ca2+
What is the main characteristic of Phase 3 in the Nodal Action Potential?
Repolarization occurs via potassium rushing out of the cell down its electrochemical gradient.
What causes the absolute refractory period in ventricular cardiac cells?
The inactivation of Na+ voltage gated channels (just like in muscle cells)
What is the Supranormal period in the nodal action potential curve?
- The cell is hyper excitable, to where even a weak stimulus could cause an AP.
What do the Chordae Tendineae do for Semilunar valves in the heart?
Where are they attached?
- First - the chordae tendineae supports AV valves so they do not open backwards. Not, semilunar valves
- They are attached to the AV valves and papillary muscles
What happens to the AV valves when ventricular pressure exceeds Atrial pressure?
AV valves close
Why does the mitral valve close before the Tricuspid Valve during a heart contraction?
Because the pressure gradient caused by the Left Ventricle is greater than the pressure gradient caused by the right ventricle.
T/F
Chordae Tendineae help to close AV valves?
False
The chordae Tendineae only support the AV valves from swinigng upward into the atria
What is the Frank-Starling relationship?
- “States that the volume of blood ejected by the bentricle depends on the volume present in the ventricle at the end of diastole”
T/F
As heart filling increases, stretch increases, and less systolic force will be generated during contraction - resulting in a decreased stroke volume
FALSE
This is opposite of the Frank Sterling Law.
When stretching increases, more systolic foce will be generated and it will increase stroke volume
T/F
Heart Sounds are caused by valves?
False
They are caused by turbulence of blood vibrating chamber walls!
What is the normal cadence of “heart sounds?”
What is the cause of each of these sounds?
- Lub (s1)
- AV valves closing, so its actually the blood coming into the ventricle that makes the sound
- Dub (s2)
- Semilunar valves close…beginning of ventricular diastole
- Pause
What are the 2 “abnormal” heart sounds?
What causes each of these sounds?
- S3
- physiologically or pathologically present. Children or extreme athletes
- S4
- Normally just pathological. Stiffened ventricle.
- Coincides with atrial contraction.
Which heart sounds can be split?
S1 and S2
How is S2 split physiologically?
- Happens during Inspiration
- Inspiration => decrease in thoracic pressure => increase in venous return => increase RV EDV => Increase RV Stroke Volume (cuz Frank Starling) => prolonged ejection time => delayed closure of pulmonary valve = splitting of S2 during inspiration.
Why does the left side of the heart contract before the right side?
Because the left side’s bundle branches are larger in diameter = faster conduction of contraction.
Left or Right?
Which side has a longer isovolumetric conctration time?Why?
- The left side has a long isovolumetric time because the LV needs to build up enough pressure to overcome the diastole pressure of the attached artery.
- The pressure needed to overcome the attached Aorta is much greater than the pressure that the RV needs to overcome the diastole pressure of the pulmonary trunk
If the right ventricle is not pumping enough blood into the pulmonary system…what observation could a dentist make?
- The jugular could be enlarged, meaning that blood is backing up since not enough is pumped out to the pulmonary trunk each beat
The contraction (systole) and relaxtion (diastole) of all four heart chambers once is….
1 cardiac Cycle, or 1 heart beat.
What are the 4 cardiac Cycle Phases?
- Ventricular Filling
- Isovlumetric Contraction
- Ventricular Ejection
- Isovolumetric Relaxation
What are the 3 subphases of Ventricular Filling - from the Cardiac Cycle?
-
Rapid Ventricular Filling
- 90% of blood from Atria -> Ventricle is passive
-
Reduced Ventricular FIlling
- This happens because the Atrium has recoiled after being stretched during atrial filling.
-
Atrial Systole
- 10% of blood remaining is “kicked” into ventricle by atrial contraction
T/F
10% of the blood passed from the Atrium to the Ventricle is moved passively?
FALSE
Almost 90% of blood movement from Atrium to Ventricle is passive.
What is “Isovolumetric Contraction?”
It is the time point during the cardiac cycle when the ventricle pressure is rising above Atrial pressure due to contraction, but the ventricular pressure has not overcome the semilunar valve….so there is not actual “muscle movement for contraction”
Think Isometric vs isotonic
Ventricular ejection happens when…
What is Ventricular ejection’s 2 subphases?
- Ventricular pressure exceeds aorta/pulmonary trunk pressure (or the pressure on the semilunar valves)
- Rapid ejection
- Reduced Ejection
- I’m guessing this is the recoil of the muscle being stretched??
Atrial Systole accounts for around []% of the time spent in ventricular filling and contributes less than [] % of total blood moved from atria to ventricle
20%
5%
For most of ventricular filling the atria are in [] as well
Diastole
The volume of blood in the LV at the end of ventricular filling is known as the [] [] []
End Diastolic Volume
T/F
During Isovolumetric contraction - the semilunar valves are closed and the AV valves are open?
FALSE
- Half right - the semilunar valves remain closed because Ventricle pressure still does not exceed aortic/pulmonary artery pressure.
- HOWEVER, the AV valves are shut because ventricular pressure has exceeded atrial pressure.
End Diastolic volume - End Systolic volume =
Stroke Volume
The maximal pressure in the aort typically reaches [] mmHg
120 mmHg
What pressure threshold does the LV have to meet in order to eject blood into the Aorta? Remember the maximal pressure in the aort is typically 120mmHg
- 80 mmHg
- This is because the Aorta goes through a diastole phase as well. As the Aorta is lowering in pressure, the ventricle is rising in pressure.
- This pressure loop usually meets around 80 mmHg and the ventricle is then able to eject its blood.
What is the end systolic volume?
- The ventricle will not eject all of its blood during ventricular ejection - some of it will remain.
- This remainder is the end systolic volume.
Isometric Relaxation:
- Pressure in the arteries is now [] than in the ventricles so the [] valves shut
- During ventricular systole, the atria have been in []
- As the atria fill, intra-atrial pressure [] and eventually the [] valves open
- greater; semilunar
- diastole
- increases; AV
What causes the dicrotic notch in the Aorta Pressure graph?
The semilunar valve buldges into the ventricle after the aorta has been filled…so it drops aortic pressure slightly.
