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3.2 Transport in Animals

Transport ­ the movement of substances such as oxygen, nutrients, hormones, waste and heat
around the body

Three factors influence the need for transport systems:
1) Size
2) Surface area/volume ratio
3) Level of metabolic activity
Features of a good transport system:

A fluid or medium…

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Small blood vessels that distribute the blood from arteries to the capillaries
They have a layer of smooth muscle which contracts to increase resistance to flow and
reduces the rate of blood flow
Constriction of arteriole walls is used to divert blood to regions of the body that are…

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Oncotic pressure ­ the pressure created by the osmotic effects of the solutes and causes the
movement of tissue fluid into the blood (it has a negative figure and is also measured in kPa)

Structure of the Heart

Blood Pressure

Atria ­ These chambers have relatively thin walls as they…

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The intercalated discs facilitate synchronised contraction
The Cardiac Cycle

What Happens
Diastole The muscular walls of all four chambers relax. Elastic recoil causes
the chambers to increase in volume which allows blood to flow in
from the veins
The pressure in the ventricles rapidly drops below the pressure of

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The pressure in the ventricles is now greater than that of the
arteries and so the semilunar valves open to allow blood to flow
into the arteries as the ventricles contract.

Blood enters the aorta and pulmonary artery in a rapid spurt but must be delivered in an even

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spreads out through the walls of both ventricles.
This means that they contract from the apex upwards, forcing the blood in the correct direction.

Wave P shows the excitation of the atria
QRS indicates the excitation o the ventricles
T shows diastole

Sinus rhythm ­ normal
Bradycardia ­ slow…

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After the first oxygen binds to the haemoglobin the haemoglobin undergoes a slight
conformational change which allows other oxygen molecules to more easily bond to its remaining
haem groups.

Fetal haemoglobin lies to the left of the normal haemoglobin dissociation curve as fetal
Haemoglobin has a higher oxygen affinity that…

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Carbon dioxide concentration increases

The following increase in cell cytoplasm acidity causes changes in the tertiary structure of the
haemoglobin and reduced its affinity for oxygen
This causes the dissociation of the oxygen to the tissues in order to provide them with it for

This ensures that tissues that…


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