The Heart Flashcards
Describe the Cardiac Cycle (Impulses)
A wave of depolarisation starts at the sinoatrial node (SAN) and spreads across the atrium to the atrioventricular node (AVN). After a brief delay, it is transmitted down the bundle of His and into the lower Purkinje fibres. The heart is described as myogenic as it beats independently.
What sound does the heart make, and what causes it?
The heart makes a ‘lub-dub’ sound, caused by the valves closing. The ‘lub’ happens when the Atrioventricular valves close, and the ‘dub’ happens when the Semilunar valves close.
Describe the differences between Arteries, Veins and Capillaries?
Arteries: Thick walls, smaller lumen, high pressure, heart to body.
Veins: Thin walls, larger lumen, low pressure, body to heart.
Capillaries: Tiny walls & lumen (1 cell), low pressure, arteries to organs to veins.
What is a Capillary?
Capillaries are tiny, one cell wide vessels branching off of Arteries & Veins, which carry blood to the important organs and parts of the body from the main channels.
What are the main causes of most CVDs?
Smoking, poor diet, high blood pressure, obesity, lack of exercise.
Describe the Cardiac Cycle (Blood)
Deoxygenated blood is pumped from the heart to the lungs via the pulmonary arteries. Oxygen diffuses/dissolves through the lungs into the blood, making it oxygenated. This blood is then pumped into the heart via the pulmonary vein, and out through the Aorta into the rest of the body. After depositing its oxygen into the main body organs etc, the deoxygenated blood returns to the heart via the vena cava, and is pumped through the heart and into the pulmonary arteries again, to repeat the cycle.
What happens during Atrial Systole?
Atria contract, pushing blood down into the ventricles.
What happens during Atrial Diastole?
Atria relax, AV valves close to prevent backflow of blood from ventricles. Atria filling.
What happens during Ventricular Systole?
AV valves close, semilunar valves open, ventricles contract to push blood out into the body.
What happens during Ventricular Diastole?
AV valves open, passive ventricular filling or ordinary filling, depending on atrial systole/diastole. Semilunar valves closed.
What happens during Cardiac Diastole?
Both atria and ventricles are relaxed. Passive atria & ventricular filling.
- What is the pulmonary circuit?
2. What is the systemic circuit?
- The system of blood vessels which go from the heart to the lungs and back to the heart.
- The system of blood vessels which go from the heart to the body and back to the heart.
Name the structure which separates the left & right ventricles.
The septum.
What’s the name for the arteries which supply the heart muscles with blood?
Coronary arteries.
