CARDIAC CYCLE Flashcards
What are the five leading causes of death?
- ischaemic heart disease (CVD)
- cerebrovascular disease (CVD)
- dementia and Alzheimer’s
- chronic lower respiratory disease
- lung cancer
What is the path of blood through the heart?
DEOXYGENATED BLOOD to vena cava → right atrium → right ventricle → pulmonary artery → lungs → OXYGENATED blood → left atrium (via pulmonary vein) → left ventricle → aorta → rest of body
What are the four major systemic arteries?
- Aorta
- Femoral
- Brachial
- Carotid
What are the two major systemic veins?
- Jegular
- Vena cava (inferior and superior)
What is the difference between the superior vena cava and inferior vena cava?
- Superior carries blood from all parts of the body above the diaphragm
- Inferior carries blood from all parts below diaphragm
What are the vessel types in order of blood flow?
Arteries -> arterioles -> pre-capillary sphincter -> capillary -> venule -> vein
What are the four valves of the heart?
The mitral valve (AV) = left atrium and left ventricle.
The tricuspid valve (AV) = right atrium and right ventricle.
The aortic valve (SL) = left ventricle to the aorta
The pulmonary valve (SL) = right ventricle and pulmonary artery.
How is a heart beat initiated?
- SA generates an action potential
- AP through atria to AVN = atrial contraction
- Small delay (about 100ms) = ensures atria is empty + ventricles fill with blood before ventricular contraction
- AP travels though Bundle of His and then out to the Purkinje Fibres = ventricular contraction from base up
Describe atrial contraction?
- Atria contract when a wave of electrical activity (depolarisation) from SA node arrives at the muscle
- The pressure in atria increases = blood is pushed into ventricles (through open AV)
- The SL valves remain closed because V pressure is lower than in the aorta and pulmonary arteries
- Volume of blood in ventricles reaches the max point in the cycle End-Diastolic Volume
- Ventricles remain relaxed at this stage (action potential is being delayed by the AV node, so hasn’t reached the ventricles)
Describe ventricular contraction (systole)?
- The AP reach ventricles = contraction
- There’s a rise in the pressure inside the ventricles (VP greater than AP)
- AV valves close (no backflow into atria)
- When there’s a higher pressure, the aortic valves (SL) open - takes blood out for systemic circulation
- Ventricle pressure falls (VP is less than AP) = aortic valve closes = prevents backflow of blood from the arteries
- The volume of the blood in the ventricles is at its lowest = end-systolic volume
Describe diastole (between atrial/ ventricular contraction)?
- This is after ventricular contraction, so the atria/ventricles have minimum blood immediately
- The pressure in the ventricles is low
- aortic and pulmonary valves remain closed = arterial pressure remains ↑
- When the VP decrease below AP, the AV valves open = blood from atria to ventricles
- As blood enters ventricles - wall begins to stretch - pressure doesn’t change
- When VP = AP, no more blood will enter
What’s diastolic pressure and what systolic pressure?
- Diastolic pressure (DP) – the minimum arterial pressure (happens during diastole)
- Systolic pressure (SP) – the maximum arterial pressure (during systole)
What is meant by end diastolic volume?
The volume of blood in ventricle at diastole (after filling) - max vol in cardiac cycle
What is meant by end systolic volume?
The volume of blood in ventricle at systole (after emptying) - lowest vol in cardiac cycle
How to calculate MEAN ARTERIAL PRESSURE ?
MAP = DP + 1/3(SP-DP)
