Topic 1 Flashcards
Atrial Systole
- atria contract while the ventricles relax.
- This decreases the volume inside the atria which increases the pressure
- increased pressure forces the atrioventricular valves open and pushes blood into the ventricles.
Ventricular Systole
- ventricles contract while the atria relaxed
- This decreases the volume inside the ventricles which increases the pressure
- this forces the atrioventricular valves closed and causes the semi-lunar valves to open.
- closure of atrioventricular valves prevents the back-flow of blood into the atria.
- Blood is forced out of the ventricles and into the arteries (the aorta and the pulmonary artery).
Cardiac Diastole
- atria and ventricles relaxed so the pressure is low in both chambers.
- pressure is higher in the arteries than in the heart chambers –> semi-lunar valves are forced closed –> prevents blood flowing back into the ventricles
- Blood is returned to the heart and the atria fill with blood.
Arteries
- thick, muscular, elastic walls to carry blood at high pressure
- folded endothelium allows for elastic recoil
- narrow lumen to maintain high blood pressure
Veins
- Valves to prevent the backflow of blood
- wide lumen and thin walls –> blood is at low pressure
Capillaries
- one cell thick for short diffusion pathway
- pores to allow for exchange of substances
How blood clots form
blood vessel is damaged –>
protein called thromboplastin is released from damaged blood vessel –>
this triggers the conversion of prothrombin into thrombin (an enzyme) –>
thrombin catalyses conversion of fibrinogen, a soluble protein, into insoluble fibrin fibres –>
fibres tangle together and form a mesh –>
platelets and red blood cells get trapped and form a blood clot
how blood clots cause heart attacks
the coronary artery becomes blocked –> blood supply is cut off and no oxygen is received by that area
how blood clots cause strokes
artery leading to brain becomes blocked –> reduction in the amount of blood and therefore oxygen that can reach the brain
Atheroma formation
endothelium is damaged e.g. by high blood pressure –>
inflammatory response - white blood cells/macrophages move to the area –>
these white blood cells + lipids from the blood clump together under the endothelium to form fatty streaks –>
more white blood cells, lipids and connective tissue build up and harden to form a fibrous plaque called an atheroma –>
this partially restricts the artery, increasing blood flow, increasing blood pressure
atheromas lead to thrombosis by….
… breaking through the endothelium and damaging the artery wall –> triggering thrombosis (blood clot formation)
Lifestyle factors that increase risk of CVD
lifestyle:
diet- increases blood cholesterol which increases atheroma formation
high bp: risks damage to the artery walls which increases atheroma formation
Smoking: Carbin monoxide reduces the amount of oxygen that is transported in the blood,
if the heart doesn’t receive enough oxygen = heart attack
if the brain doesn’t receive enough oxygen = stroke
Factors beyond your control that increase risk of CVD
- Genetics: such as alleles which make them more likely to have high blood pressure or blood cholesterol
- Age: Plaques can build up in the arteries very slowly over time
- Gender
Antihypertesives
strengths, weaknesses and what they are
- beta-blockers: reduce strength of the heartbeat
- vasodilators: widen blood vessels
- diuretics: reduce blood volume
ALL REDUCE BLOOD PRESSURE
strengths:
- can be given in combination since all work differently
- blood pressure can be monitored at home so patients can see if they working
weaknesses:
- palpitations, abnormal heart rhythms, fainting and headaches due too low blood pressure
Statins
REDUCE BLOOD CHOLESTEROL
- reduce the amount of LDL cholesterol produced inside the liver
- which reduces atheroma formation
strengths:
- reduce CVD risk
weaknesses:
- muscle and joint pain, increased risk of diabetes
