Lecture 8: THE HEART AS A PUMP Flashcards
How is the heart in the mammalian cardiovascular system?
Four chambered (atria and ventricle on each side)
How does the blood flow in the mammalian cardiovascular system?
In one direction
Where does arterial blood flow?
Away from the heart (not always oxygenated)
Where does venous blood flow?
Towards the heart (not always deoxygenated)
The heart is …
Two pumps that lie in series
What is the first part of the heart series?
Right atrium
What comes after the right atrium?
Right ventricle
What comes after the right ventricle?
Lungs
What comes after the lungs?
Left atrium
What comes after the left atrium?
Left ventricle
What comes after the left ventricle?
All organs
What goes through the two circuits?
Equal flow
What happens when the atria contract?
AV valves are open to allow the ventricle to fill while the semilunar valves are closed so that pressure builds up in the ventricles
What happens when the ventricles contract?
AV valves close so as the ventricles contract it puts force on the blood and makes sure the blood doesn’t flow backwards.
What happens when pressure gets great enough?
The semilunar valves open and ejection of the blood occurs
What contracts simultaneously?
Right and left pumps
What contracts first?
Atria
What contracts second?
Ventricles
What do valves do?
Open and close to direct blood
What is the thin filament?
Actin (light coloured)
What is the thick filament?
Myosin (blue coloured)
How are calcium levels during relaxation?
Low
What happens after relaxation (calcium levels)?
Ca2+ levels go up and more ca2+ is released form the sarcoplasmic reticulum (SR)
What happens when calcium levels rise?
Myosin binds to actin to form cross bridges
What happens after myosin binds to actin to form cross bridges?
Myosin pulls on actin to shorten the sarcomere and generate force (head changes position)
What is activated during every beat?
Every cardiomyocyte
How can the force of contraction be increased?
Increasing cytosolic calcium levels, increasing number of cross bridges formed
What happens during relaxation (calcium levels)?
Decrease in cytosolic calcium levels as calcium is pumped back into the SR
When do cross bridges release?
When ATP binds to myosin
What does a reduction in force mean?
The heart can relax
What do all cardiomyocytes do each beat?
Relax
What is diastole?
Relaxing and falling pressure
What is systole?
Contracting and rising pressure
When does the cardiac cycle begin?
All four chambers are relaxed and partly filled with blood ready to contract
What is the first phase of the cardiac cycle?
Atrial systole
What happens in atrial systole?
Atria contract and fill the ventricles with blood. AV valves open and semilunar valves closed
What is the phase after atrial systole?
Ventricular systole (isovolumetric contraction)
What happens in ventricular systole (isovolumetric contraction)?
The volume of the bold in the ventricles remains the same as the atria relax and ventricles begin to contract. Both valves are closed
What is the phase after ventricular systole (isovolumetric contraction)?
Ventricular systole (ventricular ejection)
What happens in ventricular systole (ventricular ejection)?
Semilunar valves open when the pressure build up so that blood can be released into the arteries
What phase is after ventricular systole (ventricular ejection)?
Isovolumetric ventricular relaxation
What happens in isovolumetric ventricular relaxation?
Blood has been pushes out and semilunar valves snap shut. AV valves open, heart relaxes and falling pressure of the blood
What phase is after isometric ventricular relaxation?
Ventricular diastole
What happens in ventricular diastole?
All chambers relax and the atria begin to fill passively
Which circuit has higher pressure?
Systemic
What is the highest blood pressure?
Systolic blood pressure
What is the lowest blood pressure?
Diastolic blood pressure
What is the mean pressure?
The average pressure across the whole pulse and almost always closer to diastole because the heart spend more time in this phase
What is pulse pressure?
The difference between the highest and lowest points
What is hypertension?
High blood pressure
What is hypotension?
Low blood pressure
What is the pressure in the systemic circulation?
High (110mmHg)
What is the pressure in the pulmonary circulation?
Low (25mmHg)
How is the flow equal in both circuits?
Resistance - the pulmonary circuit has less resistance than the systemic circuit
What is flow equal to?
Pressure difference/resistance