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Learning Outcomes
What you need to
know
Unit 3
Tick off each piece of information once you have learned it.
A) MAMMALIAN NUTRITION
REQUIREMENT OF FOOD
 The main food groups are carbohydrates, proteins, fats,
vitamins and minerals.
 To maintain good health, human beings consume a balanced
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diet from the main food groups.
Carbohydrates, fats and proteins all contain the chemical
elements carbon, hydrogen and oxygen.
Protein also contains nitrogen.
Carbohydrates are made up of simple sugars
Proteins are made up of amino acids
Fats are made up of fatty acids and glycerol.
FOOD TESTS
 The test for starch is to use iodine. The colour change is
from brown to blue/black
 The test for glucose is to use Benedict’s reagent. The colour
change is from blue to brick red.
 The test for protein is to use Biuret’s reagent. The colour
change is from blue to lilac.
 The test for fat is the translucent spot test.
ENERGY CONTENT OF FOOD
 Different food groups have different energy contents e.g
fat contains more energy than protein and carbohydrate.
THE NEED FOR DIGESTION
 Digestion involves the breakdown of large, insoluble food
molecules into smaller, soluble food molecules to allow
absorption into the blood stream through the lining of the
small intestine.
THE MOUTH, SALIVARY GLANDS AND OESOPHAGUS
 Mechanical breakdown of food happens in the mouth.
 Saliva contains amylase which digests starch into maltose
 Mucus in the saliva comes from salivary glands and it helps
lubricate the mouth and food to aid swallowing.
 Peristalsis occurs along the whole length of the alimentary
canal, not just the oesophagus.
 Peristalsis is like a wave-like motion.
 Circular muscles form a ring that contracts and squeezes the
food from behind and circular muscles in front relax and
allow the food to pass.
THE ROLE OF THE STOMACH
 Food is churned in the stomach by the action of longitudinal
and circular muscles to mix food with gastric juices.
 Protein is broken down by pepsin.
 The stomach contains gastric glands with mucus-secreting
cells, enzyme secreting cells and acid secreting cells.
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THE ROLE OF THE SMALL INTESTINE IN THE ABSORBTION
AND SECRETION OF FOOD
 Fat digestion by enzyme lipase.
 Further protein digestion by trypsin.
 Absorption of food is by diffusion
 The small intestine is very long with a folded inner lining on
which there are many villi.
 A large surface area is provided for absorbing digested
food.
 The lining of each villus (epithelium) is only 1 cell thick
allowing nutrient molecules to pass through easily.
 A blood capillary network and a central lacteal is present in
each villus to allow efficient transport of substances.
 Glucose and amino acids are absorbed into the epithelial cells
and then pass directly into the blood capillaries.
 The products of fat digestion are also absorbed into the
epithelial cells but do not pass into the blood capillary. They
pass into the lacteal instead.
 Blood rich in amino acids and glucose from the small intestine
is transported in the hepatic portal vein to the liver.
 Enough glucose is released into the blood circulation for use
as an energy source.
 Excess glucose is converted in the liver to glycogen and is
stored there until needed.
 Enough amino acids are released into the blood circulation to
be used in protein synthesis during growth and tissue repair.
 Excess amino acids are broken down in the liver to urea.
kidneys deal with this later)
 The process of breaking down amino acids is called
deamination. This happens in the liver
 Some of the products of fat digestion (fatty acids and
glycerol) are used as an energy source.
 Excess fatty acids and glycerol are converted to fat and
stored in the body’s fatty tissue until required.
THE ROLE OF THE PANCREAS, LIVER AND GALL BLADDER
 The pancreas produces lipase, trypsin and amylase.
 The liver stores excess glucose as glycogen and is the site of
deamination
 The gall bladder stores bile which emulsifies fats to aid
digestion.
THE ROLE OF THE LARGE INTESTINE, RECTUM AND ANUS
 Material that passes into the large intestine consists of
undigested material, bacteria and dead cells.
 Large intestine absorbs water from this leaving faeces which
are passed into the rectum and expelled by the anus.
B) CONTROL OF THE INTERNAL ENVIRONMENT
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THE STRUCTURE OF THE HUMAN URINARY SYSTEM
 Includes the kidneys, renal artery, renal vein, ureter, bladder
and urethra.
THE ROLE OF THE MAMMALIAN KIDNEY
 Osmoregulation is the regulation of water content in organisms.
 The kidneys are the main organs for osmoregulation.
 Water is gained through drinking, food and metabolic water.
 Water is lost through sweat, breath, faeces and urine.
PRODUCTION OF UREA AND ITS REMOVAL IN URINE
 Urea is the waste product from the breakdown of excess amino
acids in the liver (deamination).
 Urea is transported in the blood to the kidney where it is
filtered out and excreted from the body in urine.
STRUCTURE AND FUNCTION OF THE KIDNEY
 The kidneys are organs of filtration and reabsorption.
 Each kidney contains about a million microscopic functional units
called nephrons.
 Each nephron has several parts; a glomerulus (knot of blood
vessels) which is enclosed in a Bowman’s Capsule, which leads into
a tubule surrounded by a network of blood capillaries.
 Several kidney tubules share a collecting duct.
FILTRATION
 Blood containing waste products enters the kidney by the renal
artery.
 The renal artery splits into a million branches each supplying a
glomerulus.
 Each glomerulus is a coiled knot of blood capillaries surrounded
by a Bowman’s capsule.
 Blood enters a glomerulus at high pressure
 The blood is filtered by the glomerulus.
 Small molecules are allowed to pass through (glucose, water, salts
and urea).
 Large molecules are stopped from leaving the bloodstream (blood
cells and plasma protein).
 The glomerular filtrate passes into the Bowman’s capsule and into
the tubule.
REABSORPTION
 Useful substances are then reabsorbed (all glucose, some salt
and much water) into the capillaries surrounding the tubule.
 The process of reabsorbtion is so effective that about 99% of
the water originally in the glomerular filtrate is reabsorbed.
 The final urine left over contains excess, unwanted water, urea
and excess salts.
 Blood capillaries surrounding the tubules unite to leave the
kidney as the renal vein.
 The renal vein contains purified blood.
NEGATIVE FEEDBACK CONTROL BY ADH
 Osmoreceptors in the hypothalamus are stimulated by a change
in water concentration in the blood.
 A decrease in water concentration triggers an increase in the
release of antidiuretic hormone (ADH) from the pituitary gland.
 ADH increases the permeability of the kidney tubules and
collecting duct, resulting in more water being reabsorbed into
the blood stream.
 As the water concentration of the blood rises, less ADH is
released resulting in less water being reabsorbed.
 Blood water concentration low -> small volume of concentrated
urine produced.
 Blood water concentration high -> large volume of dilute urine
produced.
OSMOREGULATION IN MARINE AND FRESHWATER BONY FISH
 Marine bony fish have hypotonic tissues
 They lose water by osmosis and have a dehydration problem
 They overcome this problem by drinking water and excreting
excess salts.
 A small volume of concentrated urine will be produced.
 Freshwater bony fish have hypertonic tissues
 They gain water by osmosis and have an influx problem
 They overcome this problem by excreting copious and very dilute
urine.
C) CIRCULATION AND GAS EXCHANGE
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THE STRUCTURE AND FUNCTION OF THE HEART AND BLOOD
VESSELS
 The heart is a muscular organ that is divided into 4 chambers:- 2
atria and 2 ventricles. (left and right)
 The left ventricle wall is very thick and muscular since it has to
pump blood all round the body.
 The right ventricle wall is less thick since it just pumps blood to
the lungs
 The heart has 4 heart valves.
 2 of the valves are between the atria and ventricles. On the left
hand side is the bicuspid valve. On the right hand side is the
tricuspid valve.
 The 2 other heart valves are at the origins of the pulmonary
artery and the aorta – these are the semi-lunar valves.
 The valves ensure that blood is only able to flow in one direction.
They prevent backflow of blood.
 Since the heart wall is made of muscle it must get its own supply
of oxygenated blood.
 The heart is supplied by the coronary arteries. (a branch of the
aorta).
 If a coronary artery becomes blocked, the heart does not get a
supply of oxygen and this may result in death of the tissue
THE PATHWAY OF BLOOD THROUGH THE HEART AND ASSOCIATED
VESSELS
 Blood arrives at the heart via the vena cava.
 This blood is low in oxygen (deoxygenated.)
 From the vena cava it enters the right atrium then the right
ventricle.
 It exits the heart by the pulmonary artery where it is carried to
the lungs to pick up oxygen.
 The blood becomes oxygenated.
 From the lungs it goes back to the heart via the pulmonary vein.
 It enters the left atrium, then the left ventricle.
 The blood leaves the heart in the aorta where it is delivered to
the rest of the body.
BLOOD VESSELS
 Blood leaves the heart in arteries, flows through capillaries and
returns to the heart in veins.
 The pulse indicates that blood is pumped through arteries.
ARTERIES
 Artery walls are very thick and muscular since they have to
withstand blood travelling at high pressure.
VEINS
 Veins have valves present to stop the blood flowing backwards.
 Veins are wider and have thinner muscular walls
CAPILLARIES
 Capillaries are 1 cell thick, they are long, narrow and thin to
provide a large surface area.
 Capillaries carry food and oxygen to every cell.
 Gaseous exchange happens at each cell (oxygen in, carbon dioxide
out) and waste is removed back into the blood.
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You need to know the names and positions of these vessels;
Pulmonary artery; pulmonary vein; aorta, vena cava; hepatic vein;
mesenteric artery; hepatic portal vein; renal artery and renal
vein.
INTERNAL STRUCTURE OF THE LUNGS AND FEATURES WHICH
MAKE THEM EFFICIENT GAS EXCHANGE STRUCTURES
 Structure to include trachea, bronchi, bronchioles and alveoli
(airsacs)
 Alveoli have a large surface area
 Alveoli have thin walls
 Alveoli have moist surfaces
 Alveoli have a good blood supply
 These features allow efficient gas exchange
 Oxygen diffuses from the alveoli into the blood stream
 Carbon dioxide diffuses from the blood stream into the alveoli.
FEATURES OF CAPILLARY NETWORK WHICH ALLOW EFFICIENT GAS
EXCHANGE IN THE TISSUES
 Capillaries have a large surface area
 Capillaries are in close contact with the tissue cells
 Capillaries have very thin walls.
COMPOSITION AND FUNCTIONS OF THE BLOOD
 Oxygen is carried in red blood cells
 Carbon dioxide is carried in the blood plasma
 (some carbon dioxide is also carried in the red blood cells)
 The concentration of carbon dioxide carried dissolved in the
plasma is limited by the increase in acidity that carbon dioxide
causes in the blood
 Soluble foods is carried dissolved in the blood plasma
FUNCTION OF HAEMOGLOBIN IN THE TRANSPORT OF OXYGEN
 Haemoglobin combines with oxygen to form oxyhaemoglobin at
high levels of oxygen in the lungs.
 Oxygen is released at low level of oxygen in the tissues.
FUNCTIONS OF MACROPHAGES AND LYMPHOCYTES IN DEFENCE
 Phagocytosis is the process by which bacteria are engulfed and
destroyed by macrophages.
 The macrophage will engulf a bacterial cell and then digest it.
 Phagocytosis is an example of non-specific immune response since
it provides general protection against a wide range of microorganisms.
 Antibody production is an example of specific immune response
as they are specific to a particular antigen.
 An antigen is a molecule that is recognised as alien to the body
by the body’s lymphocytes.
 The presence of an antigen in the body stimulates the
lymphocytes to produce antibodies.
 An antibody is a Y-shaped molecule. Each arm has a
receptor site whose shape is specific to a particular antigen.
 When an antibody meets its complementary antigen, they
combine at their specific sites like a lock and key and the antigen
is rendered harmless. It will then be engulfed by phagocytosis.
D) SENSORY MECHANISMS AND PROCESSING OF INFORMATION
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STRUCTURE AND FUNCTION OF THE BRAIN
 Structures to include the cerebrum, cerebellum, medulla and
hypothalamus.
 The cerebrum is the site of conscious responses and higher
centres
 The cerebellum is the centre of balance and co-ordination of
movement
 The medulla is the site of the vital centres such as breathing
and heart rate.
 The hypothalamus is the centre for regulation of water
balance and temperature.
DISCRETE AREAS OF CEREBRUM RELATED TO SENSORY/MOTOR
FUNCTION
 The location of sensory and motor strips as discrete areas of
the cerebrum is required to be known.
THE BRAIN, SPINAL CORD AND NERVES
 Nerves carry impulses from the senses to the central nervous
system and impulses from the central nervous system to the
muscles.
REFLEX ACTION AND THE REFLEX ARC
 The reflex arc is made up of receptor, sensory neurone, relay
fibre, motor neurone and effector.
 Transmission of a nerve impulse through a reflex arc results
in a reflex action.
 A reflex action is a rapid, involuntary, automatic response to
a stimulus
 A reflex action protects the body from damage.
THE ROLE OF THE CENTRAL NERVOUS SYSTEM
 The CNS sorts out information in the form of impulses from
the senses.
 The CNS sends messages in the form of impulses to muscles
which can then make the appropriate response.
TEMPERATURE REGULATION AS A NEGATIVE FEEDBACK
MECHANISM
 The hypothalamus contains the body’s temperature-monitoring
centre.
 It receives nerve impulses from heat and cold receptors in
the skin.
 It also has its own central thermoreceptors which monitors
the temperature of the blood.
 The central thermoreceptors detect changes in the body’s
core temperature.
 The hypothalamus responds to this info by sending motor
nerve impulses to effectors.
OVERHEATING
 The skin helps to correct overheating of the body by: Increased rate of sweating
 Vasodilation - the arterioles leading to the skin become
dilated which allows a large volume of blood to flow through
capillaries near the skin surface. Heat can be lost as
radiation.
OVERCOOLING
 The skin helps to correct overcooling of the body by: Decreased rate of sweating
 Vasoconstriction - The arterioles leading to the skin become
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constricted which allows only small volume of blood to flow
through capillaries near the skin surface. Little heat is lost
by radiation
Contraction of erector muscles - This is when the hairs on
the skin are raised by the erector muscles contracting. It
traps a wider layer of air between the body and the
environment. Provides insulation.
SHIVERING
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When the hypothalamus detects a drop in body temperature,
nerve impulses to the skeletal muscles cause them to undergo
brief repeated contractions – shivering.
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Shivering generates heat energy and helps to return the body
temperature to its normal level.