The Heart Flashcards
What does the heart pump for
Both the pulmonary and systemic circulatory systems. The double pump works synchronously keeping oxygenated blood and deoxygenated blood Seperate.
Cardiac muscle is myogenic meaning it does need electrical stimulation from nerves or hormones and contracts by itself
What are 4 chambers of heart
Left/right atria
Left/right ventricles
Walls of ventricles thicker than walls of atria due to much bigger contraction
Left ventricle thicker than right as it sends blood around entire body
What does the septum do?
Stops oxygenated and deoxygenated blood from mixing so fully oxygenated blood gets pumped around body for max efficiency
Also maintains differences in pressure
What are valves and their types?
Valves stop blood from flowing back, so blood flows in one direction only. They are held by tendinous cords attached to papillar muscles, that contract to prevent valves from turning inside out.
Semilunar valves are found in aorta and pulmonary artery (open when pressure > in ventricle)
Atrioventricular found between atria and ventricle (open when pressure > in atria)
What is the cardiac cycle?
- Deoxygenated blood returns from body via vena cava to right atrium which fills with blood. Oxygenated blood returns from lungs via pulmonary curb to left atrium which fills with blood. Heart is relaxed (distole)
- Atrioventricular valves open due to pressure, blood flows into ventricles.
- Atria contract in atrial systole forcing more blood into ventricles
- Ventricles contract in ventricular systole
- Right ventricle forces blood into pulmonary artery, left forces into aorta. Semilunar valves open from pressure, atrioventricular as pressure drops
- Atria and ventricles relax, blood flows into heart via vena cava, this is one cardiac cycle
How is cardiac cycle controlled?
- An electrical impulse travels from sinoatrial node (a specialised tissue known as pacemaker that generates electrical excitation) to the walls of the atria, causing atrial cystole
- Impulse reaches AV node which delays it by about 0.1 second, allowing ventricle to fill with blood
- Bundle branches carry singles from AV node to heart apex
- The signal spreads through the ventricle walls causing them to contact in ventricular systole, starting from purkinje fibre as it allows blood to exit from ventricles
SEE NOTES FOR ECG
What is an ECG
A measure of the electrical activity of the heart, where electrodes are placed around the body.
A P-wave is the electrical excitation sweeping over the atria causing atrial systole
The QRS wave is the excitation sweeping over the ventricles causing ventricular systole.
The T wave is the recorder wave where heart is relaxed in diastole
What does it mean by the heart being myogenic
It produces its own excitation causing cardiac muscle to fontwzft in a coordinated fashion.
Heart rate is controlled by nerves and hormones
Nerves allow rapid adjustment to small changes and hormones like adrenaline are slower acting but long lasting
What happens to ventricular pressure during cardiac cycle?
Atrial systole: blood follows into left ventricle, pressure increases
Ventricular systole: there is a large increase as muscles are thick, then semilunar valve opens once pressure is higher than in arteries
Diastole: semilunar valves closed due to decrease in pressure, ventricular diastole so pressure falls, however at end some blood flows into ventricle when AV valve opens
What happens to the atrial pressure during cardiac cycle?
Atrial systole: atria contracts, AV valves are open
Ventricular systole: AV valve closed as pressure decreases, then atrial diastole happens and atria fills with blood
Diastole: AV valve opens due to increased in pressure, and blood flows into ventricles so decrease
What happens to aortic pressure during cardiac cycle?
Atrial systole:
Ventudcluar: blood flows into aorta as semilunar valve opens, so pressure increases
Diastole: decrease as no more blood enters aorta as semi lunar valve closes, so aortic pressure decreases
