Buscar
Estás en modo de exploración. debe iniciar sesión para usar MEMORY

   Inicia sesión para empezar

level: 7.5 The cardiac cycle

Questions and Answers List

level questions: 7.5 The cardiac cycle

QuestionAnswer
Coronary heart disease (CHD)- Type of cardiovascular disease - Occurs when coronary arteries have lots of atheromas in them - Restricting blood flow to heart - Can lead to myocardial infarction
What is the cardiac cycle- Heart undergoes a sequence of events that is repeated 70 times each min when at rest - 2 phases of the beating of heart: contraction (systole) + relaxation (diastole)
Contraction of the atria (atrial systole)- Ventricles relax - Atria contract - Decreasing volume of chambers - Increasing pressure inside chambers - This pushes blood into ventricles - Slight increase in ventricular pressure + chamber vol - AV valves are open - Semi lunar valves are shut
Contraction of the ventricles (ventricular systole)- Ventricles contract, decreasing their volume, increasing their pressure - Atria relax - Blood moves from high to low pressure into the arteries - Pressure higher in ventricles than atria, forcing AV valves shut to prevent backflow - Pressure is also higher in ventricles than aorta + pulmonary artery - Forces open SL valves + blood forced out into these arteries
Relaxation of the heart (diastole)- Ventricles + atria relax - Higher pressure in pulmonary artery + aorta closes the SL valves to prevent backflow into ventricles - Blood returns to heart - Atria fill again due to higher pressure in vena cava + pulmonary vein - Increases pressure of atria - Ventricles continue to relax, pressure falls below pressure of atria - AV valves open - Blood flows passively into ventricles from atria - The atria contract, whole process starts again
The opening + closing of the valves- Valves only open 1 way - Whether they are open or closed depends on the relative pressure of the heart chambers - Higher pressure behind valve, forced open - Higher pressure in front of valve, forced shut - Meaning blood flows only 1 direction in heart
Different types of valves- Atrioventricular valves (AV) - Semi-lunar valves (SL) - Pocket valves
Atrioventricular valves (AV)- Links ventricles + atria (left or right depending) - Prevents backflow of blood from the ventricles into the atrium
Semi-lunar valves (SL)- Link ventricles + pulmonary artery + aorta (depends) - Prevents backflow of blood from the aorta or pulmonary artery into the ventricles
Pocket valves- In veins - Ensures that when veins are squeezed - Blood flows back towards heart, rather than away
Pressure + volume changes of the heart- Mammals have closed circulatory system - Allows pressure within vessels to be maintained + regulated
Cardiac output (CO)- Volume of blood pumped by one ventricle of the heart in 1 min - Measured in dm3 min-1
What cardiac output depends on- The heart rate (rate at which heart beats) - The stroke volume (volume of blood pumped out at each beat)
Cardiac output calculation- CO = stroke volume × heart rate
Heart rate calculation60/1 cardiac cycle B.P.M
Atheroma- WBC, lipids, connective tissue build up + harden - Forming fibrous plaque - Increases risk of aneurysms + thrombosis
Cardiovascular disease and the atheroma formation- Wall of artery has many layers - Endothelium usually smooth + unbroken - If damage occurs to endothelium WBC, lipids build up + harden - Forming fatty streaks - Atheroma forms - Plaque partially blocks artery lumen - Restricts blood flow - Increasing blood pressure
Aneurysms- Balloon-like swelling in artery - Atheroma plaques damage + weaken arteries - Narrows arteries - Increasing blood pressure - Blood travels through weakened artery at high pressure, pushes inner layers through outer elastic layer - Forming swelling - May burst, causing haemorrhage (bleeding)
Thrombosis- Formation of blood clot - Atheroma plaque can rupture (burst through) endothelium of artery - Damages artery wall, leaves rough surface - Platelets + fibrin (protein) accumulate at site of damage - Or become dislodged + block blood vessels - Debris from rupture can cause blood clots elsewhere
Myocardial infarction (heart attack)- Artery becomes completely blocked, e.g. blood clot - Area of heart muscle totally cut off from blood supply - Receives no oxygen - Causes damage + death of heart muscle - Shortness of breath, chest pain - Heart failure if large areas of heart are affected
Risk factors of cardiovascular disease- High blood cholesterol and poor diet - Cigarette smoking - High blood pressure
High blood cholesterol and poor diet- Cholesterol 1 of main constituents of fatty deposits that form atheromas - Increasing blood pressure + clots - Block flow of blood to coronary arteries, cause heart attack - A diet high in saturated fat + salt increases BCL
Cigarette smoking- Has nicotine + carbon monoxide - Nicotine increases blood pressure - Carbon monoxide binds with haemoglobin, takes up the oxygen carrying capacity in the blood - Less oxygen available for cells - Can lead to heart attack, if muscle gets less O2 - Smoking decreases amount of antitoxins - So cell damage in coronary arteries - Can lead to atheroma formation
High blood pressure- Increases risk of damage to artery walls - So increased risk of atheroma formation - Increasing blood pressure + blood clots - Blocks blood flow to heart muscle, leading to heart attack - Being overweight, not exercising, excessive alcohol consumption
Coordination of heartbeat- Myogenic – begins in the muscle - SAN – Initiates the electrical activity - Pace maker - AVN – delays the signal – ‘a gate’ - Bundle of His – conducting fibres (muscle) - Purkinje Fibres – conducting fibres (muscle) - Wave of excitation