Lecture 2 Heart Cycle
From Iusmphysiology
Revision as of 14:51, 26 January 2011 by 134.68.83.239 (Talk)
- continued here from Lecture 1 Overview on 01/20/11.
- Prof is worried because he hasn't received an object from students.
Heart cycle
- There is lots of stuff to memorize here.
Objectives
Valves
- AV valves
- Bands of muscles called papillary muscles with chordae tendena
- From ventricles
- When vents contract, the papillary contract just before that too keep valves from popping overs.
- 1-3 mmHg pops the values opne
- Semilunar valves
- From ventricles to vessels
- Close passively
- have cusps to keep blood from flowing backward into vent
- fold out of the way when ejecting blood
- the cusp is caught by the backflow after contraction
- Open really easily
- No energy spent on these or AV valves
- 50 billion heart cycles in 70 years!
- The heart is beautifully made.
Seven steps of the heart cycle
- Start with atrial systole
Listening to the heart
- Old school: put ear to chest
- 1700s, France:
- Didn't want physicians putting faces on bodies of the people.
- Came up with heart trumpet
- Evolved into stethoscope
- 1800s, USA: a few physicians started using stethoscopes
Atrial systole
- EKG:
- Sturek talked about this, the p wave
- During atrial systole, the atrial contracts, the AV node gets turned on, and we start to react the septum and the lining of the ventrical.
- P = atria contract
- Q & R = something going on in the ventricle
- Mechanical event:
- Atria has been resting and receiving blood from appropriate vessels
- This is a passive event; the arterial and venous pressure cause the blood to enter the atria.
- Atria contract to push blood into the ventricles
- Atria has been resting and receiving blood from appropriate vessels
- Valve fxn:
- AV valves are open letting blood flow from atria to ventricles.
- Semilunar valves are closed.
- Papillary muscles are just beginning to contract to shut AV valves and resist the force of the soon-to-happen ventricular systole.
- Heart sounds:
- 4th heart sound
- It took a long time to find the 4th sound because equipment wasn't good enough to pick up this sound.
- So it's the fourth sound found.
- quite little sound; often not heard in healthy normal poeople.
- heard in heart disease and athletes with great cardiac fxn.
- Ventricular volume:
- Increased about 20% by atrial contraction
- Pretty closed to size at ventricular contraction
- End diastolic volume:
- EDV
- volume in ventricle at the end of atrial systole
- Plumped ventricle up as much as it will hold
- Atrial pressure
- has been falling since atrial systole because there is no flow from great veins and what was in the chamber is moving into the ventricle.
Isovolumetric contraction of the ventricles
- Here we move the pressure in the ventricle of a few mmHg to high pressure (that which needs to be generated in the arteries, 80-90 mmHg).
- Happens in the sound of a clap: soft and flabby to rigid
- this is pressurization of the ventricles.
- EKG:
- From peak of the R to the S of the QRS complex.
- Also, just a little bit of the ST segment
- Mechanical event:
- Isovolumetric contraction of the ventricles
- Papillary muscles are high tensed
- Pressure in ventricles ins't high enough to get through pulmonary or aortic valves
- all valves are closed
- Valve fxn:
- Heart sounds:
- first heart sound
- Heart vibrates
- heart doesn't open valves but it tenses them and they bulge
- Heart moves up in the chest because of such fast contraction
- Complex noise
- Ventricular volume:
- hasn't changed
- End diastolic volume:
- Atrial pressure
- Falling, though not much because this is such a short phase
- lowest arterial pressure
Rapid ventricular ejection
- The ventricles powerfully contract and overcome the pressure in the aorta and pulmonary artery.
- EKG:
- Continuing depolariation and contraction
- Just a wee bit of the vent starts to repolarize
- ST seg and a little T
- Mechanical event:
- vigorous pumping
- Oxytonic contraction: forces change as it contracts
- Valve fxn:
- Semilunars are open
- Heart sounds:
- More of the first heart sound
- Explosive ejection of blood into arteries causes sound.
- We sometimes call this an "opening snap" of the semilunar valves.
- Pressure is so high, it will move a crossed leg. Drop 5 lbs 3 feet and you get the same force.
- Ventricular volume:
- 70% of the volume's ejection volume is thrown out
- Stroke volume = amount of blood pumped in single cycle
- 70% of this is ejected
- We got these names because we new about steam engines in the early 1900s when we were discovering hearts.
- So the ventricular volume goes down 70%
- End diastolic volume:
- Atrial pressure
- Peaks at the end of this cycle
- We use peak as the stopping point of contraction
- stopped here at minute 26:45.
Reduced ventricular contraction
- EKG:
- Mechanical event:
- Valve fxn:
- Heart sounds:
- Ventricular volume:
- End diastolic volume:
- Atrial pressure
- EKG:
- Mechanical event:
- Valve fxn:
- Heart sounds:
- Ventricular volume:
- End diastolic volume:
- Atrial pressure
- EKG:
- Mechanical event:
- Valve fxn:
- Heart sounds:
- Ventricular volume:
- End diastolic volume:
- Atrial pressure
- EKG:
- Mechanical event:
- Valve fxn:
- Heart sounds:
- Ventricular volume:
- End diastolic volume:
- Atrial pressure
