Option D - Human Physiology

Question 1

Define essentail nutrients

Answer 1

Essential nutrients are those that cannot be synthesised by the body and must be ingested as part of the diet

Question 2

Define malnutrition and state its causes

Answer 2

Malnutrition is a health condition caused by a deficiency, imbalance or excess of nutrients in the diet

It can be caused by an improper dietary intake of nutrients – e.g. overnutrition (too much) or undernutrition (not enough)
It can be caused by the inadequate utilisation of nutrients by the body – e.g. due to illness or disease

Question 3

Compare Carbohydrates, Proteins and Lipids as energy sources

Answer 3

Carbohydrates are preferentially used as an energy source because they are easier to digest and transport
Lipids can store more energy per gram but are harder to digest and transport (hence are used for long-term storage)
Protein metabolism produces nitrogenous waste products which must be removed from cells

The relative energy content of carbohydrates, proteins and fats are as follows:

Carbohydrates – 1,760 kJ per 100 grams
Proteins – 1,720 kJ per 100 grams
Fats – 4,000 kJ per 100 grams

Question 4

Cause and treatment of Phenylketonuria

Answer 4

Phenylketonuria (PKU) is a genetic condition that results in the impaired metabolism of the amino acid phenylalanine

It is an autosomal recessive disease caused by a mutation to the gene encoding the enzyme phenylalanine hydroxylase
Phenylalanine hydroxylase (PAH) normally converts excess phenylalanine within the body into tyrosine
In people with PKU, the excess phenylalanine is instead converted into phenylpyruvate (also known as phenylketone)
This results in a toxic build up of phenylketone in the blood and urine (hence phenylketonuria)

Untreated PKU can lead to brain damage and mental retardation, as well as other serious medical problems

Infants with PKU are normal at birth because the mother is able to break down phenylalanine during pregnancy
Diagnosis of PKU is made by a simple blood test for elevated phenylalanine levels shortly after birth

PKU is treated by enforcing a strict diet that restricts the intake of phenylalanine to prevent its build up within the body

This low-protein diet should include certain types of fruits, grains, vegetables and special formula milk
This diet should be supplemented with a medical formula that contains precise quantities of essential amino acids
Patients who are diagnosed early and maintain this strict diet can have a normal life span without damaging symptoms

Question 5

Which fatty acids are essential

Answer 5

Alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid) cannot be synthesised by the body

Foods rich in essential fatty acids (omega-3 and omega-6) include fish, leafy vegetables and walnuts

Question 6

Explain the relationship between LDLs, HDLs and fats in the blood.

Answer 6

Low density lipoproteins (LDLs) carry cholesterol from the liver to the body (hence raise blood cholesterol levels)
High density lipoproteins (HDLs) carry excess cholesterol back to the liver for disposal (hence lower blood cholesterol levels)

The mix of fatty acids consumed as part of a diet directly influences the levels of cholesterol in the bloodstream:

Saturated fats increase LDL levels within the body, raising blood cholesterol levels
Trans fats increase LDL levels and lower HDL levels, significantly raising blood cholesterol levels
Cis-polyunsaturated fats raise HDL levels, lowering blood cholesterol levels

Question 7

What is the Consequence of high cholesterol?

Answer 7

High cholesterol levels in the bloodstream lead to the hardening and narrowing of arteries (atherosclerosis)

When there are high levels of LDL in the bloodstream, the LDL particles will form deposits in the walls of the arteries
The accumulation of fat within the arterial wall leads to the development of plaques which restrict blood flow
If coronary arteries become blocked, coronary heart disease (CHD) will result – this includes heart attacks and strokes

Question 8

Define vitamin

Answer 8

Vitamins are chemically diverse carbon compounds that cannot be synthesised by the body, many function as cofactors, antioxidants or hormones

Question 9

Discuss Vitamin C in Mammals

Answer 9

Ascorbic acid is made internally by most mammals from monosaccharides – but it is not produced by humans

Consequently, human must ingest vitamin C as part of their dietary requirements in order to avoid adverse health effects

In mammals it functions as a potent antioxidant and also plays an important role in immune function, the synthesis of collagen (a structural protein) and in the synthesis of lipoproteins

Question 10

Discuss vitamin D in humans

Answer 10

Vitamin D is involved in the absorption of calcium and phosphorus by the body – which contribute to bone mineralisation

Insufficient amounts of this vitamin cause the onset of diseases such as osteomalacia (where bones soften) or rickets (where bones are deformed)

Vitamin D can be naturally synthesised by the body when a chemical precursor is exposed to UV light (i.e. sunlight)
The vitamin D may be stored by the liver for when levels are low (e.g. during winter when sun exposure is reduced)
Individuals with darker skin pigmentation produce vitamin D more slowly and hence require greater sun exposure

Question 11

Role of minerals in humans and plants

Answer 11

Minerals in Human Development

Major constituents of structures such as teeth and bones (e.g. Ca, P, Mg)
Important components of body fluids (e.g. Na, K, Cl)
Cofactors for specific enzymes or components of proteins and hormones (e.g. Fe, P, I)

Minerals in Plant Development

Magnesium is an important component of chlorophyll (required for photosynthesis)
Potassium is an inorganic salt found within the sap of a plant (maintains water potential)
Calcium is important for plant root and shoot elongation

Question 12

Explain apetite control

Answer 12

SHormones send messages to the appetite control centre of the brain (within the hypothalamus)
Hormonal signals will either trigger a feeling of hunger (promote feasting) or satiety (promote fasting)

Stretch receptors in the stomach and intestine become activated when ingested food distends these organs
Adipose tissue releases hormones in response to fat storage
The pancreas will release hormones in response to changes in blood sugar concentrations

Hormones will either stimulate or inhibit the appetite control centre to promote sensations of hunger or satiety

Hormones that trigger a hunger response include ghrelin (from stomach) and glucagon (from pancreas)

Hormones that trigger a satiety response include leptin (from adipose tissue) and CCK (from intestine)

Hint: Ghrelin Grows Hunger ; Leptin Lowers Hunger

Question 13

Explain how obesity increases chances of hypertension and type II diabetes

Answer 13

Individuals who are overweight or obese are more likely to suffer from hypertension (abnormally high blood pressure)

Excess weight places more strain on the heart to pump blood, leading to a faster heart rate and higher blood pressure
High cholesterol diets will lead to atherosclerosis, narrowing the blood vessels which contributes to raised blood pressure
Hypertension is a common precursor to the development of coronary heart disease (CHD)

Individuals who are overweight or obese are also more likely to suffer from type II diabetes (non-insulin dependent)

Type II diabetes occurs when fat, liver and muscle cells become unresponsive to insulin (insulin insensitivity)
This typically results from a diet rich in sugars causing the progressive overstimulation of these cells by insulin
Hence overweight individuals who have a high sugar intake are more likely to develop type II diabetes

Question 14

Explain starvation with reference to anorexia

Answer 14

Starvation

Starvation describes the severe restriction of daily energy intake, leading to a significant loss of weight

As the body is not receiving a sufficient energy supply from the diet, body tissue is broken down as an energy source
This leads to muscle loss (as muscle proteins are metabolised for food) and eventually organ damage (and death)

In severe anorexia, the body begins to break down heart muscle, making heart disease the most common cause of death

Blood flow is reduced and blood pressure may drop as heart tissue begins to starve
The heart may also develop dangerous arrhythmias and become physically diminished in size (atrophy)

Question 15

What are exocrine glands and provide a few examples

Answer 15

Exocrine glands secrete to the surface of the body or the lumen of the gut

Salivary glands – secrete saliva which contains amylase (breaks down starch)
Gastric glands – secretes gastric juices which includes hydrochloric acid and proteases (breaks down protein)
Pancreatic glands – secretes pancreatic juices which include lipase, protease and amylase
Intestinal glands – secretes intestinal juices via crypts of Lieberkuhn in the intestinal wall
Sweat glands - secrete sweat for cooling

Question 16

Explain how gastric secretions are controlled

Answer 16

Nervous Mechanism:

The sight and smell of food triggers an immediate response by which gastric juice is secreted by the stomach pre-ingestion
When food enters the stomach it causes distension, which is detected by stretch receptors in the stomach lining
Signals are sent to the brain, which triggers the release of digestive hormones to achieve sustained gastric stimulation

Hormonal Mechanism:

Gastrin is secreted into the bloodstream from the gastric pits of the stomach and stimulates the release of stomach acids
If stomach pH drops too low (becomes too acidic), gastrin secretion is inhibited by gut hormones (secretin and somatostatin)
When digested food (chyme) passes into the small intestine, the duodenum also releases digestive hormones:
Secretin and cholecystokinin (CCK) stimulate the pancreas and liver to release digestive juices
Pancreatic juices contain bicarbonate ions which neutralise stomach acids, while the liver produces bile to emulsify fats

Question 17

Outline the use of proton pump inhibitors

Answer 17

The low pH environment of the stomach is maintained by proton pumps in the parietal cells of the gastric pits

These proton pumps secrete H+ ions (via active transport), which combine with Cl– ions to form hydrochloric acid
Certain medications and disease conditions can increase the secretion of H+ ions, lowering the pH in the stomach

Proton pump inhibitors (PPIs) are drugs which irreversibly bind to the proton pumps and prevent H+ ion secretion

This effectively raises the pH in the stomach to prevent gastric discomfort caused by high acidity (e.g. acid reflux)
Individuals taking PPIs may have increased susceptibility to gastric infections due to the reduction of acid secretion

Question 18

Explain the formation of stomach ulcers

Answer 18

Stomach ulcers are inflammed and damaged areas in the stomach wall, typically caused by exposure to gastric acids

There is a strong positive correlation between Helicobacter pylori infection and the development of stomach ulcers

Helicobacter pylori is a bacterium that can survive the acid conditions of the stomach by penetrating the mucus lining

H. pylori anchors to the epithelial lining of the stomach, underneath the mucus lining
An inflammatory immune response damages the epithelial cells of the stomach – including the mucus-secreting goblet cells
This results in the degradation of the protective mucus lining, exposing the stomach wall to gastric acids and causing ulcers
The prolonged presence of stomach ulcers may lead to the development of stomach cancer over many years (20 – 30 years)
H. pylori infections can be treated by antibiotics (previously, stomach ulcers were considered stress related and not treatable)

Question 19

Explain dehydration by cholera

Answer 19

Vibrio cholerae is a bacterial pathogen that infects the intestines and causes acute diarrhoea and dehydration

The associated disease – cholera – can kill within hours unless treated with oral rehydration therapies

V. cholerae releases a toxin that binds to ganglioside receptors on the surface of intestinal epithelium cells

This toxin is internalised by endocytosis and triggers the production of cyclic AMP (a second messenger) within the cell
Cyclic AMP (cAMP) activates specific ion channels within the cell membrane, causing an efflux of ions from the cell
The build up of ions in the intestinal lumen draws water from cells and tissues via osmosis – causing acute diarrhoea
As water is being removed from body tissues, dehydration will result if left untreated

Question 20

State the different cells that are found in gastric pits

Answer 20

The gastric pits are lined by a number of different cell types which contribute to the overall function of the stomach:

Goblet cells – secrete mucus to form a protective layer around the stomach lining
Parietal cells – secrete hydrochloric acid which is responsible for creating a low pH environment in the stomach
G cells – secrete gastrin (stimulates release of stomach acids to increase stomach acidity)
Chief cells – secrete pepsinogen (inactive protease precursor which is activated by acidity to form active pepsin)

Question 21

State the main functions of the liver

Answer 21

The liver functions to process the nutrients absorbed from the gut and hence regulates the body’s metabolic processes

It is responsible for the storage and controlled release of key nutrients (e.g. glycogen, cholesterol, triglycerides)
It is responsible for the detoxification of potentially harmful ingested substances (e.g. amino acids, medications, alcohol)
It produces plasma proteins that function to maintain sustainable osmotic conditions within the bloodstream
It is responsible for the breakdown of red blood cells and the production of bile salts

Question 22

Describe the strucutre of the liver

Answer 22

The liver is composed of smaller histological structures called lobules, which are roughly hexagonal in shape

Each lobule is surrounded by branches of the hepatic artery (provide oxygen) and the portal vein (provide nutrients)
These vessels drain into capillary-like structures called sinusoids, which exchange materials directly with the hepatocytes
The sinusoids drain into a central vein, which feeds deoxygenated blood into the hepatic vein
Hepatocytes also produce bile, which is transported by vessels called canaliculi to bile ducts, which surround the lobule

Question 23

Explain the role of the liver in the metabolism in carbohydrates, proteins and lipids

Answer 23

Carbohydrate Metabolism

Excess glucose in the bloodstream (e.g. after meals) is taken up by the liver and stored as glycogen
When blood glucose levels drop, the liver breaks down glycogen into glucose and exports it to body tissues
When hepatic glycogen reserves become exhausted, the liver synthesises glucose from other sources (e.g. fats)
These metabolic processes are coordinated by the pancreatic hormones – insulin and glucagon

Protein Metabolism

The body can not store amino acids, meaning they must be broken down when in excess
Amino acid breakdown releases an amine group (NH2), which cannot be used by the body and is potentially toxic
The liver is responsible for the removal of the amine group (deamination) and its conversion into a harmless product
The amine group is converted into urea by the liver, which is excreted within urine by the kidneys
The liver can also synthesise non-essential amino acids from surplus stock (via transamination)

Fat Metabolism

The liver is the major site for converting excess carbohydrates and proteins into fatty acids and triglycerides
It is also responsible for the synthesis of large quantities of phospholipids and cholesterol
These compounds are then stored by the liver or exported to cells by different types of lipoproteins
Low density lipoprotein (LDL) transports cholesterol to cells, for use in the cell membrane and in steroid synthesis
High density lipoprotein (HDL) transports excess cholesterol from cells back to the liver (for storage or conversion)
LDL is considered ‘bad’ as it raises blood cholesterol levels, while HDL lowers cholesterol levels and is therefore ‘good’
Surplus cholesterol is converted by the liver into bile salts, which can be eliminated from the body via the bowels

Question 24

Explain how the liver carriers out detoxification

Answer 24

The detoxification of compounds by the liver typically involves two sets of chemical pathways:

Toxins are converted into less harmful chemicals by oxidation, reduction and hydrolysis reactions
These reactions are mediated by a group of enzymes known as the cytochrome P450 enzyme group
These conversions produce damaging free radicals, which are neutralised by antioxidants within the liver
The converted chemical is then attached to another substance (e.g. cysteine) via a conjugation reaction
This renders the compound even less harmful and also functions to make it water soluble
The water soluble compounds can now be excreted from the body within urine by the kidneys

Question 25

List the function of plasma proteins

Answer 25

There are a number of different types of plasma proteins, each serving different specific functions:

Albumins regulate the osmotic pressure of the blood (and hence moderate the osmotic pressure of body fluids)
Globulins participate in the immune system (i.e. immunoglobulins) and also act as transport proteins
Fibrinogens are involved in the clotting process (soluble fibrinogen can form an insoluble fibrin clot)
Low levels of other plasma proteins have various functions (e.g. α-1-antitrypsin neutralises digestive trypsin)

Question 26

Define plasma proteins

Answer 26

Plasma proteins are proteins present in the blood plasma and are produced by the liver (except for immunoglobulins)

The proteins are produced by the rough ER in hepatocytes and exported into the blood via the Golgi complex

Question 27

Explain how redblood cells are recycled

Answer 27

Kupffer cells are specialised phagocytes within the liver which engulf red blood cells and break them down

Kupffer cells break down haemoglobin into globin and iron-containing heme groups
Globin is digested by peptidases to produce amino acids (which are either recycled or metabolised by the liver)
Heme groups are broken down into iron and bilirubin (bile pigment)

The released iron must be complexed within a protein in order to avoid oxidation to a ferric state

Iron can be stored by the liver within a protein shell of ferritin
Iron can be transported to the bone marrow (where new haemoglobin is produced) within the protein transferrin

Question 28

Explain and outline Jaundice

Answer 28

Jaundice is a condition caused by an excess of bile pigment – bilirubin – within the body

Bilirubin is produced as part of the natural breakdown of haemoglobin by the liver
Normally, the liver conjugates this bilirubin to other chemicals and then secretes it in bile
When there is an excess of bilirubin, it may leak out into surrounding tissue fluids

Jaundice may be caused by any condition which impairs the natural breakdown of red blood cells, including:

Liver disease – impaired removal of bilirubin by the liver may cause levels to build within the body
Obstruction of the gall bladder – preventing the secretion of bile will cause bilirubin levels to accumulate
Damage to red blood cells – increased destruction of erythrocytes (e.g. anemia) will cause bilirubin levels to rise

The main consequence of jaundice is a yellowish discoloration of the skin and whites of the eyes (sclera)

Question 29

How is the cardiac muscle adapted to its function

Answer 29

The heart is composed of cardiac muscle cells which have specialised features that relates to their function:

Cardiac muscle cells contract without stimulation by the central nervous system (contraction is myogenic)
Cardiac muscle cells are branched, allowing for faster signal propagation and contraction in three dimensions
Cardiac muscles cells are not fused together, but are connected by gap junctions at intercalated discs
Cardiac muscle cells have more mitochondria, as they are more reliant on aerobic respiration than skeletal muscle

These structural features contribute to the unique functional properties of the cardiac tissue:

Cardiac muscle has a longer period of contraction and refraction, which is needed to maintain a viable heart beat
The heart tissue does not become fatigued (unlike skeletal muscle), allowing for continuous, life long contractions
The interconnected network of cells is separated between atria and ventricles, allowing them to contract separately

Question 30

What is cardiac output

Answer 30

Cardiac output describes the amount of blood the heart pumps through the circulatory system in one minute

Equation: Cardiac Output (CO) = Heart Rate (HR) × Stroke Volume (SV)

Question 31

Discuss the use of artifical pacemakers

Answer 31

An artificial pacemaker is a medical device that delivers electrical impulses to the heart in order to regulate heart rate

Artificial pacemakers are typically used to treat one of two conditions:

Abnormally slow heart rates (bradycardia)
Arrhythmias arising from blockages within the heart’s electrical conduction system

Question 32

Explain the treatment of Fibrillation

Answer 32

Fibrillation is the rapid, irregular and unsynchronised contraction of the heart muscle fibres preventing the optimal flow of blood

Fibrillation is treated by applying a controlled electrical current to the heart via a device called a defibrillator

This functions to depolarise the heart tissue in an effort to terminate unsynchronised contractions
Once heart tissue is depolarised, normal sinus rhythm should hopefully be re-established by the sinoatrial node

Question 33

Outline the endocrine system

Answer 33

The endocrine system is comprised of ductless glands that release chemicals into the blood to regulate body functions

A hormone is a chemical messenger that is transported indiscriminately via the bloodstream to act on distant target cells
Hormones are specific and will only activate cells or tissues that possess the appropriate target receptor

Question 34

Explain how the hypothalamus controls hormone secretion

Answer 34

The hypothalamus is the section of the brain that links the nervous and endocrine systems in order to maintain homeostasis

It receives information from nerves throughout the body and other parts of the brain and initiates endocrine responses
It secretes neurochemicals (called releasing factors) into a portal system which target the anterior lobe of the pituitary gland
It also secretes hormones directly into the blood via neurosecretory cells that extend into the posterior pituitary lobe

Pituitary Gland

The pituitary gland lies adjacent to the hypothalamus and is in direct contact due to a portal blood system

The pituitary gland receives instructions from the hypothalamus and consists of two lobes (anterior and posterior lobe)

Anterior Lobe

The hypothalamus produces releasing factors, which are released into portal vessels by neurosecretory cells
The releasing factors cause endocrine cells in the anterior pituitary to release specific hormones into the bloodstream

Posterior Lobe

The posterior lobe releases hormones produced by the hypothalamus itself (via neurosecretory cells)
These neurosecretory cells extend into the posterior lobe from the hypothalamus and release hormones into the blood

Question 35

Why may athletes use human growth hormone?

Answer 35

Growth hormones an anabolic peptide hormone that stimulates growth

It acts directly to reduce the formation of adipose cells (i.e. less nutrients stored as fat)
It acts indirectly via insulin growth factor (IGF) – produced by the liver – to increase muscle mass and bone size

Question 36

Explain how lactation is controlled by hormones

Answer 36

Prolactin is responsible for the development of the mammary glands and the production of milk

It is secreted by the anterior pituitary in response to the release of PRH (prolactin releasing hormone) from the hypothalamus
The effects of prolactin are inhibited by progesterone, which prevents milk production from occurring prior to birth

Oxytocin is responsible for the release of milk from the mammary glands (milk ejection reflex)

It is produced in the hypothalamus and secreted by neurosecretory cells that extend into the posterior pituitary
Oxytocin release is triggered by stimulation of sensory receptors in the breast tissue by the suckling infant
This creates a positive feedback loop that will result in continuous oxytocin secretion until the infant stops feeding

Question 37

Explain oxygen dissociation curves

Answer 37

As each O2 molecule binds, it alters the conformation of haemoglobin, making subsequent binding easier (cooperative binding)

This means haemoglobin will have a higher affinity for O2 in oxygen-rich areas (like the lung), promoting oxygen loading
Conversely, haemoglobin will have a lower affinity for O2 in oxygen-starved areas (like muscles), promoting oxygen unloading

Because binding potential changes with each additional O2 molecule, the saturation of haemoglobin is not linear (sigmoidal shape)

Question 38

How does fetal hemoglobin differ from adult hemoglobin?

Answer 38

The haemoglobin of the foetus has a slightly different molecular composition to adult haemoglobin
Consequently, it has a higher affinity for oxygen (dissociation curve is shifted to the left)
This is important as it means fetal haemoglobin will load oxygen when adult haemoglobin is unloading it (i.e. in the placenta)
Following birth, fetal haemoglobin is almost completely replaced by adult haemoglobin (~ 6 months post-natally)

Question 39

Explain the transport of CO2

Answer 39

When CO2 enters the erythrocyte, it combines with water to form carbonic acid (reaction catalysed by carbonic anhydrase)
The carbonic acid (H2CO3) then dissociates to form hydrogen ions (H+) and bicarbonate (HCO3–)
Bicarbonate is pumped out of the cell in exchange with chloride ions (exchange ensures the erythrocyte remains uncharged)
The bicarbonate in the blood plasma combines with sodium to form sodium bicarbonate (NaHCO3), which travels to the lungs
The hydrogen ions within the erythrocyte make the environment less alkaline, causing haemoglobin to release its oxygen
The haemoglobin absorbs the H+ ions and acts as a buffer to maintain the intracellular pH
When the red blood cell reaches the lungs, bicarbonate is pumped back into the cell and the entire process is reversed

Question 40

Why does ventilation rate increase with exercise?

Answer 40

Exercise increase respiration and thus formation of CO2 whic dissolves to form Carbonic acid which may then lose protons (H+) to form bicarbonate (HCO3–) or carbonate (CO32–)
The released hydrogen ions will function to lower the pH of the solution, making the blood plasma less alkaline

Central chemoreceptors in the medulla oblongata detect changes in CO2 levels (as changes in pH of cerebrospinal fluid) and impulses are sent to the respiratory control centre in the brainstem

Signals are sent to the diaphragm and intercostal muscles to increase the rate of ventilation (this process is involuntary)
As the ventilation rate increases, CO2 levels in the blood will drop, restoring blood pH (also O2 levels will rise)

Peripheral chemoreceptors in the carotid and aortic bodies also detect CO2 levels, as well as O2 levels and blood pH

Question 41

How does the blood maintain its pH

Answer 41

This pH range is, in part, maintained by plasma proteins which act as buffers

Amino acids are zwitterions – they may have both a positive and negative charge and hence can buffer changes in pH
The amine group may take on H+ ions while the carboxyl group may release H+ ions (which form water with OH– ions)

Question 42

What is the Bhor shift

Answer 42

Carbon dioxide lowers the pH of the blood (by forming carbonic acid), which causes haemoglobin to release its oxygen

This is known as the Bohr effect – a decrease in pH shifts the oxygen dissociation curve to the right

Question 43

Discuss the possible benefits of high altitude training

Answer 43

At high altitudes, air pressure is lower and hence there is a lower partial pressure of oxygen (less O2 because less air overall)

This makes it more difficult for haemoglobin to take up and transport oxygen (lower Hb % saturation)
Consequently, respiring tissue will receive less oxygen

Over time, the body may begin to acclimatise to the lower oxygen levels at high altitudes:

-Red blood cell production will increase in order to maximise oxygen uptake -and transport
-Red blood cells will have a higher haemoglobin count with a higher affinity for oxygen
-Vital capacity will increase to improve rate of gas exchange
-Muscles will produce more myoglobin and have increased vascularisation to improve overall oxygen supply
-Kidneys will begin to secrete alkaline urine (removal of excess bicarbonates improves buffering of blood pH)
-People living permanently at high altitudes will have a greater lung surface area and larger chest sizes

Professional athletes will often incorporate high altitude training in order to adopt these benefits prior to competition. Athletes may commonly either train at high altitudes (live low – train high) or recover at high altitudes (live high – train low)

Question 44

Causes and treatments of emphysema

Answer 44

Causes

The major cause of emphysema is smoking, as the chemical irritants in cigarette smoke damage the alveolar walls

The damage to lung tissue leads to the recruitment of phagocytes to the region, which produce an enzyme called elastase
This elastase, released as part of an inflammatory response, breaks down the elastic fibres in the alveolar wall
A small proportion of emphysema cases are due to a hereditary deficiency in this enzyme inhibitor due to a gene mutation

Treatments

There is no current cure for emphysema, but treaments are available to relieve symptoms and delay disease progression

Bronchodilators are commonly used to relax the bronchiolar muscles and improve airflow
Corticosteroids can reduce the inflammatory response that breaks down the elastic fibres in the alveolar wall
Elastase activity can be blocked by an enzyme inhibitor (α-1-antitrypsin), provided elastase concentrations are not too high
Oxygen supplementation will be required in the later stages of the disease to ensure adequate oxygen intake
In certain cases, surgery and alternative medicines have helped to decrease the severity of symptoms

Question 45

Define malnutrition

Answer 45

Malnutrition is a health condition caused by a deficiency, imbalance or excess of nutrients in the diet