Unformatted text preview: omes scarred, less flexible, and thicker. This
reduces the amount of alveolar expansion possible
and reduces the diffusion efficiency across the gas
exchange surface. 4. Many restrictive diseases are caused by inhalation
of dusts and pollutants associated with particular
occupations, e.g. asbestos workers, coal miners,
beryllium miners, cement workers etc. 5. In an asthma attack, histamine is released from
sensitized mast cells. The histamine causes airway
constriction, accumulation of fluid and mucus, and
inability to breathe. The Effects of High Altitude (page 173) 1. (a) Less oxygen is available for metabolic activity
so people become breathless and often dizzy.
Associated effects are headache, nausea,
tiredness and coughing.
(b) Altitude sickness or mountain sickness. 2. (a) Heart and breathing rates increase.
(b) Increased breathing rate increases the rate
at which new air is brought into the lungs
(compensating for lower oxygen). Increased
heart rate pumps blood more rapidly to tissues to
improve oxygen delivery. 3. (a) Any two of: RBC concentration in the blood may
increase, the blood may become thicker, over a Biozone International 2009 Photocopying Prohibited 29
long period of time, capillary networks increase in
(b) Increased RBCs and blood concentration
increase the amount of oxygen that can be
Increased capillary density increases the amount
and efficiency of oxygen delivery to tissues. 2. See diagram. CS
PS Pyloric sphincter
and small intestine The Human Diet (page 177) Nutrients are required as (a) and (b) in any order:
(a) An energy source
(b) As the raw materials for metabolism, growth, and
repair. 2. (a) The new food pyramid distinguishes between
“healthy” and “unhealthy” fats, and “healthy” and
“unhealthy” (refined) carbohydrate sources. This
is contrary to the older pyramid, which placed all
fats together as to be avoided, and recommended
that all carbohydrates form the base of the food
pyramid. The new pyramid recommends a high
intake of plant oils which correlates with reduced
rates of heart disease.
(b) Evidence: Althoug...
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- Winter '13