8 Flashcards
How many chambers
4
Which way does blood flow
One direction
Arterial blood flows…
Away from heart
Venous blood flows…
Towards the heart
The hearts pump the ____ amount - are in _____
The hearts pump the same amount - are in series
- two pumps in series working together
Contraction of heart
- pressure of contraction shuts AV valve
- pressure drops and valves flop open for passive filling
- valves keep it unidirectional
- right and left pumps contract simultaneously
- atria contract first… ventricles contract second
- valves open and close to direct blood
What do AV valves do?
- control flow between the atria and ventricles
- tricapsid and bicapsid
What do the aortic and pulmonary valves do?
- control flow from the ventricles out to the circulatory vessels
Blood movement through the heart is gated by…
….valves
Valves open and close to…
.. direct blood
Structure of muscle in heart
- sarcomere is key contractile element
- actin = thin
Cellular mechanism of cardiac contraction
- Ca2+ levels go up, and more Ca2+ is released from the SR
- myosin binds to actin to form cross-bridges
- myosin pulls on actin to shorten the sarcomere and generate force
- every myocyte activated during each heart beat
- so how can we increase force of contraction ??
How many myocytes are activated each heart beat?
All of them- everyone is recruited
How to increase the force of cardiac contraction
- every cardiomyocyte is activated during each heart beat
- extent of X-bridges formed not maximised at rest
- increase cytosolic Ca2+ level
- increase number of cross-bridges formed
- increase force of contraction
(Don’t activate more fibres like skeletal - all are already activated so we increase the calcium)
Cellular mechanism of cardiac relaxation
- decrease in cytosolic Ca2+ levels - Ca2+ pumped back into the SR
- cross bridges release when ATP binds to myosin
- reduction is force means the heart can relax
- all cardiac myocyres relax each beat
REQUIRES ATP
Diastole
- relaxation
- falling pressure
Systole
- contraction
- rising pressure
Cardiac cycle
Main phases of the cardiac cycle
-lubb sound is the AV valve closing
- isovolumetric ventricular = contraction and building pressure but not ejecting (systole)
- ventricular ejection - pulse - Dupp sound of closing semilunar
- myosin heads release - relaxation - isovolumetic ventricular relaxation
- pressure falls in ventricle and valve opens
- pressure up in systole
- down in diastole
Features of a blood pressure trace
- pulsatile change in pressure in the major arteries linked to ejection of blood
- periods of systole (rising pressure) and diastole (falling pressure)
- diastole is typically longer then systole
- systemic arterial pressure is much higher then the pulmonary arterial pressure - need more pressure as its going further
Feautres of blood pressure trace
- systolic pressure is the highest point on the trace
- diastolic pressure is the lowerst point on the trace
- pulse pressure is the difference between the highest and lowest points
- mean pressure is the average across the full cycle - pulled down by diastolic pressure - about a third of the pulse pressure
- hypertension is high blood pressure, while hypotension is low blood pressure
