AS UNIT 1 - HEART STRUCTURE & FUNCTION

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Describe the typical graph showing heart beat and function. How is the heart structure adapted to cope with the differing demands of blood flow.

Describe the typical heart beat - use systole, diastole, Bundle of His, Purkinje and any other relevant key words or phrases.

Posted: 13-12-09 21:25 by Mike McNicholas

and ... During a cardiac cycle, the pressure of blood in the aorta is higher than the pressure of blood in the pulmonary artery. Explain what causes this difference in pressure. (2 marks)

Explain the link between atheroma and the increased risk of aneurism. (4 marks)

Cigarette smoking and a diet high in saturated fat increase the risk of myocardial infarction. Explain how. (6 marks)

Posted: 13-12-09 21:29 by Mike McNicholas

a) during the cardiac cycle, the pressure and the volume of blood in the atrium and the ventricals changes.

at the beginning of the cycle, the aortic pressure decreases in the time period of around 0.1 of a second, as the semlunar valve opens this pressure increases from 14.8 kPa and peaks off at about 17 kPa, this then decreases as the semilunar valve closes at around 0.4 seconds in to the cycle, and then the pressure decreases slowly untill the start of the next cycle.

whilst this is happening the atrial pressure decreases as the atrioventricular valve closes, this pressure drops to around 3 kPa and steadily increases back to around 2 kPa, this is when the atrioventricular valve opens and the pressure decreases again, and then steadily increases untill the start of the next cycle.

at the same time the ventricular pressure increases from just over 2 kPa to around 17kPa with in the space of 0.2 of a second, this is because the atrioventricular valve has closed, this pressure then drops to below 0 kPa with in 0.1 of a second and then levels back off to restart the cycle at 2kPa.

during the whole of the cycel the ventricular volume rises as the atria contract and the ventricles fill with blood and then drops suddenly as the bloos is forced out into the aorta when the semilunar valve opens. the volume increases again as the ventricles fill with blood.

the heart structure is adapted to support the differing demands of blood flow, this structure involves different valves, and different thicknesses in heart muscle tissue. the pressure in the heart is maintained because mamals have a closed circulatory system.

a typical heart beat has many stages:

the heart relaxes at the end of one typical heat beat for a moment, this is known as diastole, blood returns to the atria of the heart through the pulmonary vein (from the lungs) and the vena cava (from the body).

a wave of electrical activity spreads out from the SAN ( sinoatrial node) across the right atria then the left atria causing them to contract.

this stage of the heart beat is also known as atrial systole, it is where the atrial walls contract forcing the remaning blood out of them.

this electrical activity reaches the atrioventricular none (AVN) which is situated just above the right ventrical.

- the AVN conveys a wave of electrical activity down the bundle of his fibers down the central septum to the base of the heart, these electrical waves are released at the apex (purkinje fibers) causing the ventricles to contract from the base upwards.

- this stage of the heart beat is known as the ventrivular systole, this alllows the ventricles to refill with blood after a short delay.

Posted: 13-12-09 23:04 by Adam Helstrip

The reason for the higher blood pressure in the aorta during the cardiac cycel compared to that in the pulmanory artery, is because the aorta has a greater distance to transport oxygenated blood round the whole of the body, where as the pulmanory artery only has to transport deoxygenated blood to the lungs.

atheroma is a fatty deposit that forms with in the wall of an artery. fatty streaks then begin to form, this causes a build up of white blood cells that have taken up low density lipoprotiens. these fatty streaks enlarge and then eventually cause an irregular patch, this is called atheromatous plaque. This build up of plaque (cholesterol) bulge in to the lumen of the artery causing it to narrow so that blood flow through it is reduced. this could lead to risk of an aneurysm because an atheroma leads to the formation of thrombosus which weakens the artery walls. these weakened points swell up like a balloon like blood filled structure, this is called an aneurysm. these aneurysms frequently burst which cause blood loss to the region which the artery supplys. a brain aneurysm is known as a cerebrovascular accident, or a stroke.

cigarette smoking and a diet high in saturated fat can increas the risk of myocardial infraction, this is caused by a reduced supply of blood to the heart. blockages in the conoary arterys are the main cause of this. smoking cigarette can contrabute to this, this is because when u smoke cigarettes a fatty deposit is left in the artery. this is also known as cholesterol, the result of this is a blockage of the arteries increasing blood pressure and this could lead on to a heart attack.

carbon monoxide from cigarette smoke combines with the haemoglobin in the red blood cells, this reduces the oxygen carrying capacity of the blood. to supply the equivalent quantity of oxygen to the tissues, the heart must work harder, and this can lead to raised blood pressure and increase the risk of CHD and strokes, in addition this may lead to lack of oxygen being supplied to the heart muscle during exercise and cause chest pains and in more severe cases, cause a heart attack.

nicotine in the blood increases the production of adrenaline, this increases the blood pressure, and can also make the red blood cells mroe 'sticky' this leads to a higher risk of thrombosis and a heart attack ( myocardial infraction).

a poor diet may contain high salt levels, this raises the blood pressure and this contributes to a heart attack, also high levels of saturated fat in the diet increase the amount of low density lipoprotiens, this raises the blood cholesterol concentration and can lead to a blockage in the arteries which also cause high blood pressure and increase the risk of a heart attack.

Posted: 14-12-09 17:54 by Adam Helstrip

I agree with everything adam has said was right even though in the mock i didn't know what aneurysm was . and there was spelling mistakes which shouldn't have been made silly! :P

but the paragraph which explains why the aorta has a higher pressure in my opinion is wrong. I'm not sure it may be right, but i thought it would have higher blood pressure because the aorta is the artery that leads to the body so it's attached to the left side of the heart, which is more muscular, so it can pump blood harder to the rest of the body, as it would be hard for a weak pump to push blood to the toes for example.

nice one though loads of good detail taught me about aneurysm :D

Posted: 14-12-09 22:35 by Issa

well its not wrong, it just needed a little bit adding to it, also, not every one can spell everything correctly :P but if were nit picking at stuff, your punctuation is shocking xD

Posted: 15-12-09 14:38 by Adam Helstrip

This was soo helpful . Man appreciates it. :)

Posted: 20-02-18 10:17 by Bshamsi