Page 128 - Biology Form Two

Biology for Secondary Schools

that supply blood to the heart, called of oxygen and nutrients to the brain cells.
coronary arteries. The condition can be Symptoms of stroke: Symptoms of
initiated by smoking, diabetes mellitus, stroke include sudden numbness or
hypertension and stress. This prevents weakness especially on one side of
blood from reaching some tissues of the body, abrupt confusion or trouble
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the heart. Thus, the affected tissues in understanding or speaking, and
lack adequate amounts of oxygen and unexpected poor vision in one or both
waste materials accumulate in the cells eyes. The individual also experiences
to toxic levels.
Symptoms of coronary thrombosis: sudden dizziness, loss of balance, trouble
Coronary thrombosis is characterised when walking or poor coordination, and
by uncomfortable pressure or sharp severe headaches.
pain in the chest, sometimes extending Effects of stroke: Stroke has severe
to the neck, shoulders, and arms. Other effects on the victim such as weakness
symptoms include excessive sweating, or paralysis on one side of the body,
dizziness, fainting, nausea, severe leading to difficulties in movement
indigestion, and shortness of breath. and coordination. It also causes a lack
Effects of coronary thrombosis: of sensation on one side of the body,
Coronary thrombosis can cause death speech or language problems, and loss
of some cardiac tissue or sudden human of memory. Other effects are behaviour
death. changes, exhaustion, and difficulty
Prevention of coronary thrombosis: when swallowing.
People can avoid coronary thrombosis Prevention of stroke: Stroke can be
by doing regular physical exercise, prevented by avoiding alcohol and
avoiding sudden strenuous activity smoking, maintaining blood pressure
such as aerobics, avoiding alcohol and within the normal range, and exercising
smoking, minimising intake of fatty regularly. Eating a low-fat diet and
foods, minimising intake of salt by low-salt diet (salt should not exceed 5
consuming less than 5 g of salt per day, g per day) can also help to minimise
and avoiding stress. chances of getting stroke.
Stroke
Stroke occurs when there is an Exercise 5.2
interference in the amount of blood 1. What are the differences between
flowing into the brain. Such an arteries and veins?
interference can be due to blockage or 2. Explain the role of red blood cells
rupture of an artery supplying blood to in the body.
the brain. This hinders adequate supply

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