AQA AS Bio unit 1:The heart and Heart disease

HideShow resource information
  • Created by: AmaniF
  • Created on: 27-05-13 17:59
Preview of AQA AS Bio unit 1:The heart and Heart disease

First 439 words of the document:

Risk Factors and The heart
Risk Factors increase the probability of suffering from a disease.
There are risk factors which we can control e.g. diet, and some that we can't e.g. age.
You need to know the risk factors for CHD
Age and sex - Men are more likely than women to get CHD
Genetic Factors - CHD tends to run in families.
Smoking - Nicotine makes the arteries constrict which causes an increase in blood pressure
High Blood Pressure - Arteries develop thicker walls, narrowing the lumen which increases
the rate of blood flow. This can damage the lumen so an atheroma could develop.
High concentration of LDL. Low-density-lipoproteins are involved in the formation of
The Heart - Blood flow
The direction of blood flow in the heart goes as follows:
Vena Cava >> Right atrium >> Right Ventricle >> Pulmonary artery >> Pulmonary vein >> Left Atrium >>
Left Ventricle >> Aorta
The blood flow is controlled by pressure and by the semi-lunar valves and atrio-ventricular valves.
When the pressure in the ventricle is higher than that of the pressure in the atrium, the
atrio-ventricular valves shut. When the pressure in the ventricle is higher than that of the pressure in
the arteries, the semi-lunar valves open. The pressure in the ventricle increases when it decreases in
volume because of the muscular walls.
The heart goes through 3 different stages.
Atrial systole >> Ventricular systole >> Diastole
In atrial systole, the atria contract. In ventricular systole, the ventricles contract and the atria relax. In
Diastole, the muscles of the ventricles relax.
Controlling the heartbeat
The hearts muscle is myogenic which means that it can beat without outside influence. It does this by
using a 'pacemaker' which sends an electrical impulse across the heart. The impulse starts at the
sinoatrial node (SAN) which is located at the top of the right atrium. The electrical impulse travels
across to the left atrium, which allows them both to contract at the same time. To travel to the
ventricles, the impulse passes through the atrioventricular node (AVN). This is a group of insulating,
fibrous cells, which stop the impulse for a short amount of time. From here, the impulse is carried
down the bundle of His. This bunch of fibres goes down to the apex then travel back up the walls of
the ventricle again.

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Coronary Heart disease
CHD refers to any condition that interferes with the coronary arteries that supply blood to the heart.
Fatty deposits build up in an artery when the endothelium becomes damaged and inflamed. The
endothelium may be damaged by high blood pressure or viral infection. A lipid core starts to build up
underneath the damaged surface. After this, the wall is repaired, but it leaves a lump with a rough
surface called a plaque.…read more


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »