The Heart + Cardiac Cycle Flashcards
The Human Heart’s Make Up
Consists of cardiac muscle - like smooth muscle but contracts involuntarily
=> made up of cells that are connected by cytoplasmic bridges
=> enables electrical impulses that pass through the tissue
=> has a lot of myoglobic (carries o2) + mitochondria (for energy)
Cardiac Cycle
The coordinated cycle of systole (contracting) and diastole (relaxation) that pumps blood away from the heart
=> sequence of events that take place during 1 heartbeat
Key Points to Remember
=> Blood flows from high pressure to low pressure
=> Contraction increases pressure
=> Valves (semi-lunar + A-V) are unidirectional
=> Valves open + close according to pressure gradients
(1) Diastole
=> Cardiac muscle relaxes
=> Atria fill w/ blood, increasing pressure + allowing blood to pass in to ventricles via A-V valves
=> A-V open - draining blood from atria into ventricles
=> Pressure in ventricles < aorta + pulmonary artery so semi lunar valves closes
(2) Atrial Systole
=> Cardiac muscles in atria contract, increasing pressure
=> Force blood into ventricles
=> Pressure in atria > ventricle, A-V valves open
=> Pressure in ventricles < aorta + pulmonary artery so semi-lunar valves remain open
(3) Ventricular systole
=> Atria relax + ventricles contract
=> A-V valves shut as pressure in ventricles > than atria
=> Semi-lunar valves open + blood is pushed in the aorta + pulmonary artery
=> Pressure in ventricle higher than artery
Step 1 in Cardiac Cycle
Wave of depolarisation spreads over the SAN over atria
Step 2 in Cardiac Cycle
Atria depolarizes, contracts and pump blood to ventricles
Step 3 in Cardiac Cycle
Wave reaches A/N and transmitted down the bundle of His
Step 4 of Cardiac Cycle
Wave transmitted along Purkinje fibres into ventricles
Step 5 of Cardiac Cycle
Ventricles depolarizes contract + pump blood into arteries
Step 6 of Cardiac Cycle
Atria + ventricles depolarizes and relax
Step 7 of Cardiac Cycle
Atria fill blood from vena cava + pulmonary vein
