SNAB Topic 1 Unit 1 Notes - Lifestyle, health and risk NOTES

SNAB Topic 1 Unit 1 Notes - Lifestyle, health and risk notes

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Unit One ­ Topic 1: Lifestyle, health and risk [BIOLOGY REVISION NOTES]
BIOLOGY AS REVISION NOTES
TOPIC 1: UNIT 1
SNAB specification
Made by Nabilah Chowdhury
Copyrighted
References: Various internet sources, sources from GetRevising, SNAB text book
(CIS 1.1 / Sp. 1.6) TRANSPORT IN ANIMALS 19/10/13
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Unit One ­ Topic 1: Lifestyle, health and risk [BIOLOGY REVISION NOTES]
Surface area to volume ratio:
Singled cell organisms have a large surface area to volume ratio (can exchange molecules
across their outer surfaces)
Large multi-cellular organisms have a smaller surface area to volume ratio (outer surface
isn't large enough to allow substances to diffuse in)
Circulatory Systems
OPEN CIRCULATORY SYSTEM-
In invertebrates (e.g.…read more

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Unit One ­ Topic 1: Lifestyle, health and risk [BIOLOGY REVISION NOTES]
FISH (SINGLE CIRCULATORY SYSTEM) MAMMAL (DOUBLE CIRCULATORY SYSTEM)
Deoxygenated blood is pumped to gills Vena cava vein carries blood into the right atrium
CO2 from blood is released into water whilst O2 is right ventricle CONTRACTS pulmonary artery
taken into blood lungs
Blood leaves the gill In the lungs the blood becomes oxygenated
As the oxygenated blood is travelling around the Oxygenated blood travels to the pulmonary vein
body, blood pressure is reduced…read more

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Unit One ­ Topic 1: Lifestyle, health and risk [BIOLOGY REVISION NOTES]
This means that the slightly ­ve charge of the O atom is attracted to the slightly +ve charge of the H atom
(in another molecule). The hydrogen bonding holds the molecules together in a loose pattern thus it is a
liquid at room temp, unlike other small atoms.
Solvent Properties
Ionic (charged) molecules dissolve easily in water b/c their charges are attracted to the slightly +ve
or ­ve ends of the water molecule.…read more

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Unit One ­ Topic 1: Lifestyle, health and risk [BIOLOGY REVISION NOTES]
ARTERY
Endothelium
Carries blood AWAY from heart ­ High B.P
narrow lumen ­ maintains high B.P
thicker walls ­ contains more collagen
fibres + connective tissue for strength
more elastic fibres - stretch + recoil
more smooth muscle - to contract+
constrict artery
no valves
VEIN
Carries blood TO heart ­ Low B.P
wider lumen ­ eases B.…read more

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Unit One ­ Topic 1: Lifestyle, health and risk [BIOLOGY REVISION NOTES]
CAPILLARY
Walls are only 1 cell thick - short diffusion
pathway
Has flattened endothelium and lumen
THE HEART (CIS 1.7 ­ 1.…read more

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Unit One ­ Topic 1: Lifestyle, health and risk [BIOLOGY REVISION NOTES]
When veins are bringing blood back to the heart, they have barely enough pressure. They need the
assistance of skeletal muscles to aid with blood flow.
Muscles contract when respiring / moving.
When muscles contract, they narrow the lumen thus increase the B.P
When muscles relax, the lumen widens thus decreasing B.P
There is no pulse and pressure is low.
Valves prevent backflow.
THE CARDIAC CYCLE (CIS 1.7/Sp. 1.…read more

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Unit One ­ Topic 1: Lifestyle, health and risk [BIOLOGY REVISION NOTES]
(CIS 1.15/Sp. 1.11) ATHEROSCLEROSIS
Blocked arteries narrowing higher B.P artery bursts infarction heart attach / stroke
In the arteries supplying the heart, this causes a heart attack (myocardial infarction).
In the arteries supplying the brain, it causes a stroke.
An infarction is when tissue dies due to a lack of oxygen which is usually the result of a lack of
blood ­ ischaemia.
Only arteries get atherosclerosis b/c of the high B.…read more

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Unit One ­ Topic 1: Lifestyle, health and risk [BIOLOGY REVISION NOTES]
Platelets are cells with no nucleus. But when platelets come in contact with the damaged
vessel their shape changes into a "spiky" shape ­ they stick to each other and the collagen in
the wall: a platelet plug is formed. They then release more substances that activate even
more platelets to their aid.…read more

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Unit One ­ Topic 1: Lifestyle, health and risk [BIOLOGY REVISION NOTES]
Artery narrows --> less flexible blood
cant stretch against wall so instead it
builds up behind the narrowed artery
bulges = aneurysm
(CIS 1.23) RISK
Probabilities
E.g. 24,000 people died in 2005. The population was 72,200,000. What is the average risk in:
Percentage: 24,000 / 72,200,000 = 0.033%
Fraction: 72,200,000 / 24,000 = 1 in 3008 people
These averages make the assumption that everyone has the same chance of the outcome = WRONG.…read more

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