IQ1 Homeostasis: How is an organism’s internal environment maintained in response to a changing external environment?

a) Internal Coordination Networks

- Homeostasis is the maintenance of a stable internal metabolic environment (set point). This is necessary for optimal enzyme function.

- When deviations in the external environment cause deviations in the internal environment, the hormonal/endocrine and nervous systems restore stability.

- Due to factors such as disease or trauma, sometimes this will not occur.- Elements of homeostasis include blood pH, oxygen and CO2 concentration, blood

glucose, body temperature, water balance, salt and mineral concentration, nitrogenous waste, and many more.

- The nervous system is made up of the CNS (brain and spinal cord) and PNS (branching nerves). These parts are made up of nerves, which are made of neurones.

- There are 3 types of neurones, all containing axons (conducting electricity with potassium and sodium ions), myelin (fatty insulating tissue) and dendrites (tiny filaments at the ends) connected by synapses (spaces full of neurotransmitters):

o Sensory neurones detect stimuli such as pain, pressure, temperature, taste, sound, sight, smell etc. using receptors at the ends. They store their nuclei in cell bodies attached to the side of the axon

o Motor neurones are responsible for moving; they send electrical impulses to effectors (mainly muscles) to carry out voluntary and involuntary actions

o Relay neurons (a.k.a. connector neurones, interneurons) carry information between motor and sensory neurons, and make up the spinal cord and brain

- Different sensory receptors detect different stimuli and are located in different sensory organs. These include skin (thermoreceptors, mechanoreceptors), eyes (photoreceptors), and within the body (chemoreceptors, proprioceptors/position)

- The endocrine system is made up of ‘ductless glands’ all over the body, controlled by the hypothalamus which interfaces with the (faster) nervous system.

- It secretes hormones, which target specific cells to undergo specific actions using receptors. Some hormones are lipid-soluble and pass through cell membranes to receptors inside cells, while some are water-soluble and bind to receptors outside.

- Different glands produce different hormones for different tissues. The main glands for homeostasis include:

o Pituitary: Located in the brain – produces growth hormone, oxytocin, and a variety of hormones which regulate other glands e.g. the adrenal gland

o Thyroid: Two connected glands located in the throat – produces T3 and T4, which affect digestion, metabolism, brain development and homeostasis.

o Parathyroid: Four glands located in the throat – produces PTH, which controls the body’s calcium levels.

o Adrenal Glands: Two glands above the kidneys – produces adrenaline and noradrenaline, which regulate stress responses and increase blood pressure.

o Adrenal Cortex: The ‘outer coat’ of the adrenal glands – produces cortisones which control blood pressure, energy production, and immune response.

- The pancreas is one of the most important organs of homeostasis as it controls blood glucose. It contains two types of endocrine cells – alpha cells (which produce glycogen) and beta cells (which produce insulin).

- Both of these hormones target the liver, telling it to break down and make glycogen respectively. In addition, insulin tells cells to absorb excess glucose and use it for energy.

b) Negative Feedback

- Negative feedback is where the body recognises that it is not at set point and corrects the imbalance in the opposite (negative) direction.

- Positive feedback is where the stimulus is reinforced and leads to an amplified response, e.g. labour during childbirth, milk production, ripening fruit etc.

- There are two main negative feedback loops we need to know:o Heat: Normal level is 37.5oC, controlled by the hypothalamus. Erectorpili

muscles change hair orientation, sweat glands cause evaporative cooling, shivering ups muscle metabolism, and vasoconstriction/dilation warm/cool.

o Glucose: Normal levels are 3.0 to 7.8 mmol/L, controlled by the pancreas. Insulin (beta) makes the liver absorb glucose from blood, Glucagon (alpha) makes the liver turn glycogen into glucose and release it into the blood.

c) Mechanisms and Adaptations

- There are many types of mechanisms and adaptations which assist animals and humans in maintaining homeostasis.

- Structural adaptations such as ear size, fur, etc. (anatomical), physiological adaptations such as hibernation, sweating etc. (metabolic), and behavioural adaptations such as burrowing. Only endotherms can maintain homeothermy!

- Nocturnalism is an example of an adaptation which contains all three types – structural adaptations such as eyes that see in the dark, physiological adaptations such as endothermy, and behavioural adaptations such as sleeping in the day.

- One example of hot and cold adaptations are Arctic and Fennec foxes:

Arctic Foxes (cold) Fennec Foxes (hot)Small ears Large earsRounded body Slender bodyShort legs Long legsThick fur Short fur

- Counter-current flow is an adaptation for the extremities of animals which live in very cold temperatures (arctic duck feet, orca tongues, etc.) where the veins and arteries are intertwined so that the cold vein blood is warmed by the artery blood.

- An Australian native endotherm which is an example of homeostatic adaptations is the bilby, which maintains homeothermy through large ears, long tail, and small size (structural), burrowing (behavioural), and nocturnalism (all three).

d) Plant Water Balance

- To maintain optimum osmotic levels for efficient metabolism, plants regulate water though the process of transpiration.

- However, plants also need to maintain optimum temperature, and they do this through evaporative cooling, leading to water loss.

- Plants in hot climates thus have a wide variety of structural and physiological adaptations to prevent excess water loss.

- These include deep root systems, thin needle-like, curled, or vertically-hanging leaves with thick waxy cuticles, sunken stomata with stomatal hairs which only open in the morning, hard fruit and small flowers, water storage in trunks, and loss of leaves/limbs in very dry periods.

IQ2 Cause and responses: Do non-infectious or infectious diseases cause more deaths?

Non-infectious diseases (non-communicable diseases) are not pathogenic and are usually preventable through lifestyle.

a) Genetic Diseases- Genes code for proteins, and when a protein is being produced and functioning the

gene is being expressed.- Mutations lead to the expression of faulty proteins or the absence of a protein, as

one or more of the amino acids making up the protein is wrong.- This is caused by a deletion, substitution, or addition of chromosomes or of base

pairs in the DNA code.- Humans have 23 pairs of chromosomes, and a map of them is called a karyotype.

- We studied genetic diseases in our depth study:Cystic Fibrosis: 508th position, a whole PHE amino acid goes missing due to a triple-base deletion. This damages the protein CFTR, causing it to be folded wrong and fail to reach the surface of the cell where it is needed to remove chloride from the cells. This means that the mucus on the cell surface does not attract water and thus is not washed away, causing damage to the lungs, pancreas, and digestive system.

- 3p Deletion Syndrome is a chromosome rearrangement disorder caused by a partial deletion of the p arm of chromosome 3. It leads to slow growth, small head/jaw, droopy eyelids, malformed ears/nose, widely spaced eyes, polydactyly (extra digits), cleft palate seizures, weak muscle tone, intestinal issues, heart defects, and learning difficulties/developmental delay. It also increases the risk of OCD and autism.

- Down Syndrome is a genome disorder caused by a trisomy (extra chromosome) 21. It leads to learning difficulties/developmental delay, low muscle tone, small head, ears and mouth, upward slanting eyes, and irregular spacing between toes.

- Turner Syndrome is a genome disorder caused by a missing X chromosome. It leads to infertility, stunted growth, broad chest, low hairline/ears, heart issues, webbed neck, and puberty which is late and/or ineffective (no secondary sex characteristics).

b) Environmental Diseases- Humans interact with many environments throughout their lives, and some can be

dangerous and cause disease. Not all of these dangers are known!- Some environmental diseases can damage the DNA and lead to future genetic

diseases, while others only affect the person exposed to that environment.

- Environmental diseases are caused by exposure to chemical or physical agents in the ambient and/or workplace environment:

o Lifestyle diseases are caused by people’s choices, such as smoking, alcohol, food choice, and exercise (or lack of it). These include heat disease, lung cancer, type 2 diabetes, and obesity.

o Chemical exposure can be due to lack of knowledge about the chemical’s danger, such as with asbestos and mesothelioma, or it can be accidental such as lead poisoning.

o Allergens are elements which only cause disease/immune response in certain individuals, and this can range from mild hay-fever to anaphylaxis. Allergens include food, plant materials, and the most common allergen, dust.

o Other elements of the physical environment can also cause disease – for example UV radiation causing skin cancer etc.

Disease Cause SymptomsMesothelioma Lung cancer caused by

breathing asbestos particulateCough, chest pain and shortness of breath

Melanoma Skin cancer caused by UV New, unusual skin growthObesity Lifestyle disease caused by

overeating/lack of exerciseHigh weight, difficulty moving, back and joint pain

Asthma Allergy-related asthma is caused by allergens

Restricted windpipe, difficulty breathing

- Mesothelioma: Similar to a tumour which forms in the lungs, it is treated with chemotherapy, radiotherapy, and surgery as well as a variety of new treatment methods which are in development. It predominately occurs in men who mined asbestos (81%) and to a lesser extent their wives, and onset is mainly in those over 65. To prevent this disease and manage it at a national level, asbestos safety laws have been put into place and using it in buildings has been outlawed.

c) Nutritional Diseases- Nutritional diseases are diet related and can be caused by deficiencies in diet, poor

diet, and psychological conditions that lead to inappropriate diet.- There are two main types of nutritional diseases:

o Undernutrition, including malnourishment and vitamin deficiencieso Over-nutrition, mainly leading to obesity

- Diabetes II: When the effectiveness of pancreatic cells in producing working insulin is decreased – at first, insulin is produced but receptors fail to pick it up, making the insulin ineffective, and this then develops into pancreatic scarring where no insulin is

produced at all. It is treated and managed through lifestyle alterations, insulin injections, etc.

- Scurvy: Vitamin C is essential to produce collagen, used for wound healing. As such, vitamin C deficiency leads to scurvy, where teeth fall out and wounds don’t heal.

d) Cancer- Cancer is caused by changes in the DNA of a cell which prevent the cell from ceasing

division. As such, cancer cells divide uncontrollably and cannot function correctly.- Most cancers start in a specific organ in the form of a malignant tumour (tumours

can also be benign/non-cancerous), but they can metastasise to different places.- Metastasis occurs when cancer enters the lymph nodes and/or bloodstream.- The study of cancer is known as oncology, and is carried out by oncologists.

o Carcinoma: cancer of the epithelial tissue, e.g. skino Sarcoma: cancer of the connective tissue, e.g. bone, fat, muscle, blood vesselo Leukaemia: cancer of the bone marrow and thus blood cellso Lymphoma: cancer of the immune system or lymphatic system

- Breast Cancer: it is the most common new cancer diagnosis. 13.2% of all breast cancer cases in Australia occurred in 2018, most cases (18,087) are female but a small percentage (148) are males, in Japan breast cancer rates are quite low but ethnically Japanese people have normal rates when living in other countries. It is treated using chemotherapy, radiotherapy, surgery, and new treatments involving the immune system.

IQ3 Epidemiology: Why are epidemiological studies used?

- Epidemiological studies can identify the causes of disease and the ways in which the disease can be cured or managed.

- All epidemiological studies require long time periods, large sample sizes (ideally thousands), data collection both on the participants and on the disease, randomised participant selection, control measures, statistical analysis, and ethical management.

- Incidence is the percentage of the population who gets a disease in a certain time period, and prevalence is the percentage of the population who has a disease in a certain time period. These are often similar, but chronic diseases can have low incidence but high prevalence (hard to get, hard to cure).

- Mortality is the amount of people who die from a disease in a certain period of time.

- Data can be examined globally or regionally, and can be presented using incidence, prevalence, mortality, or even severity.

IQ4 Prevention: How can non-infectious diseases be prevented?

- Non-infectious diseases are major causes of death and disability in the developed world, and as such prevention measures are necessary.

- These are often run by the government, and usually consist of educational public health programs such as ‘Slip Slop Slap’ and Quit Smoking, backed up by legislation.

- Educational programs are designed to inform the public about risk factors for non-infectious diseases. They may be targeted at a specific group, or everyone.

- As well as informing, these programs are persuasive and aim to alter behaviours.

- Successful public health campaigns have a strong evidence base (proof of what causes the disease), a limited number of evidence-based interventions (e.g. Slip Slop Slap), communication of accurate information to the public/healthcare workers, effective performance management with real-time monitoring (epidemiology), and partnership between public/private sectors (political commitment).

- Genetic technologies can also be used to prevent some genetic diseases which are not exacerbated by environmental or lifestyle factors and hence cannot be treated using public health campaigns. Some preventative technologies include:

o Pre-Implantation Testing: Embryos are created using IVF, then at the three-day mark a cell is removed for analysis. If the embryo has the disease it is destroyed, and if it is healthy it is implanted and grows.

o Recombinant DNA Technology: Genes from one species are implanted into another, for example human genes implanted into goats, bacteria, and rice. These animals then produce human proteins, which can replace the proteins of people with genetic defects (e.g. insulin from E. coli for diabetics).

o Monoclonal Antibodies: Mice are exposed to antigens, they produce specific antibody-generating B-cells, the B-cells are removed and fused with tumour cells to form hybridomas, and the hybridomas multiply to create huge quantities of very specific antibodies that can then be used in humans.

o Gene Therapy: A gene is inserted into a cell using a viral vector to cure or treat a disease, but this can be ineffective. See the depth study!

IQ4 Technologies and Disorders: How can technologies assist people with disorders?

a) Ears- Sound energy and how sound travels as compression waves through a medium- Frequency is the number of sound waves that pass a given point in a given time

(wavelength), and amplitude is the difference between the highest and lowest air pressure caused by a sound wave. Frequency controls pitch (high frequency high pitch) and amplitude controls volume (high amplitude loud).

Structure Function LocationOuter Ear (Pinna, Ear Canal)

Funnels sound into the middle ear, amplifying faint sounds; protects the middle ear

Sides of the head

Tympanic Membrane

Thin flattened cone of skin which detects and transmits air vibrations into the middle ear bones

Between outer and middle ear

Ossicles (Malleus, Incus, Stapes)

Bones which transmit and amplify sound into the middle ear – the malleus is connected to the eardrum and the stapes impacts the oval window

Within the middle ear

Oval Window A smaller ‘second eardrum’ at the outer rim of the cochlea, which vibrates to transmit sound into the cochlea fluid; there is also another even smaller version of it to release the pressure of vibrations

Between middle and inner ear

Cochlea A spiral-shaped, fluid-filled organ lined with mechanoreceptors designed to detect precise pitch and volume of sound and transmit it as electrical nerve impulses down the optic nerve to the brain

Within the inner ear (labyrinth)

- Sound waves are funnelled by the pinna through the ear canal, where they cause the eardrum to vibrate. This vibration is amplified by the middle-ear bones and passed via a membrane into the cochlea, where it causes the liquid inside to move. The moving liquid is detected by mechanoreceptors which send signals via the auditory nerve to the brain.

- Mechanoreceptors in the ear are tiny hair-cells (stereocilia) located in the basal membrane of the cochlea or ‘inner ear’. The shortest and stiffest hairs are located at the outer end of the cochlea and detect high-frequency sounds, while the longer and more flexible hairs towards the inner end of the cochlea detect low-frequency sounds.

- Hearing loss can be mild to profound, and can occur at birth or later in life, and can vary from ear to ear. There are many causes and types of hearing loss, divided into three main categories:

o Conductive hearing loss is caused by dysfunction of the middle ear (eardrum or ossicles), usually due to a perforated eardrum, an ear infection, damage to the ossicles, or a growth in the middle ear space.

o Sensorineural hearing loss is caused by dysfunction of the inner ear (cochlea or auditory nerve), usually due to age, exposure to loud noise, a genetic condition, or a serious disease such as measles, mumps, or meningitis.

o Mixed hearing loss is caused by a combination of problems in the middle and inner ear, usually due to a genetic condition or syndrome.

Hearing Aids

- It fits over the outside of the ear and contains a microphone which amplifies sound coming into the outer ear.

Bone Conduction Implants

- The outer part contains a microphone which amplifies sound into vibrations, and the inner part transmits those vibrations through the skull bone to the inner ear (cochlea), bypassing the outer and middle ear. They are best for someone with conductive hearing loss.

- These are usually effective (almost 100%), but can lead to infections or occasionally chronic pain. In addition, head trauma can damage the implants.

Cochlea Implants

- The outer part contains a microphone which amplifies sound into vibrations, and the inner part contains a sensor which detects the vibrations and an electrode which passes through the cochlea to interface with the auditory nerve. They are best for someone with sensorineural hearing loss.

- They are very effective at restoring hearing unless the auditory nerve is damaged. They are available to almost everyone with hearing loss in Australia, but less so worldwide. They also completely remove any remaining hearing so the patient is completely dependent on the implant, and they require a lot of practice/training for the brain to make sense of the signals.

b) Eyes- Light enters the eye through the transparent cornea and passes through the pupil to

the lens, which focuses the light through the vitreous chamber onto the retina at the back of the eyeball. Here, the light is absorbed by pigment and detected by photoreceptors, sending signals down the optic nerve to the brain.

Structure Function LocationExtrinsic Muscles Six muscles which hold the eye in place and allow it to

move, letting us look in different directionsOutside the eyeball

Sclera and Choroid The two outer layers of the eye, which protect and ‘hold in’ its contents and contain blood vessels – the sclera is what is usually referred to as the ‘white’ of the eye

Sclera: outermostChoroid: second-outermost

Cornea A transparent extension of the sclera containing no blood vessels; it protects the iris/pupil and the cornea-air interface refracts light, allowing our eyes to focus

Iris (and Pupil) The iris is a ring of muscle which controls the size of the pupil – a hole which lets light in to the retina and which works like a camera aperture

Aqueous Humour A water-like liquid which replaces the function of blood vessels in the cornea

Between the lens and the cornea

Lens A transparent biconvex disk of ‘crystalline’ matter through which light passes and is focused onto the retina

Ciliary Body The muscles which hold the lens in place and control its shape (accommodation), contracting for distance vision

Behind the iris

Vitreous Humour A clear, colourless liquid slightly more viscous than water, which replaces the function of blood vessels in the lens

Behind the lens, filling the eyeball

Retina A thin layer of cells including (inner to outer) pigmented cells, transparent nerve cells, and photoreceptors

Coating the inside & back of the eye

Fovea/Macula The area of the retina where photoreceptors, especially cones, are most densely packed – ideal for focusing

Centre of the retina

Optic Nerve The main nerve which carries information from eye to brain, and which passes through the retina at the ‘blind spot’ because the retina is very poorly designed XD

Beside the fovea

- The lens refracts light to focus on the more photoreceptor-dense parts of the retina

(e.g. fovea), and is flexible in order to ‘accommodate’ for close/distant vision.- Accommodation is caused by the ciliary body, which expands and contracts to

change the shape of the lens and ensure light from both up close and far away are equally focused. Distant vision relaxed muscles, flat lens, and vice versa.

- There are two main types of photoreceptors found in the eye, ‘rods’ and ‘cones’:o Cones are responsible for colour vision and detail, but only work in bright

light. Humans have three types of cones – red, green, and blue – and these are mainly located around the centre of the retina and in the fovea.

o Rods are more effective than cones in low light, but cannot detect colour or great detail. They are more common at the edges of the retina (peripheral).

- Myopia (short-sightedness) occurs when light focuses in front of the retina, and Hyperopia (long-sightedness) occurs when light focuses behind the retina. Both are caused by a misshapen eye or lens.

- Astigmatism occurs when light does not focus properly on the retina, and is caused by a misshapen cornea or eyeball.

- Cataracts occur when the lens becomes cloudy or even opaque, preventing light from passing through. It is often caused by age.

- Glaucoma occurs when the pressure in the aqueous humour in the eye becomes too high, distorting the retina and putting pressure on the optic nerve. It is usually caused by a blockage in the fluid drainage channel.

- Detached Retina occurs when the retina separates from the sclera, leading to distortion and ‘floaters’ in the vision.

- Macular degeneration occurs when the macula/fovea cells degrade over time, leading to a loss of sharpness in vision. It is often caused by age.

- Glasses and Contacts work in exactly the same way, refracting light so that once it passes through the eye lens it focuses in the right place. Convex lenses are used for hyperopia to focus the light in, and concave lenses are used for myopia to spread the light out. Glasses and contacts can also be used for astigmatism.

- Laser surgery is a more permanent and effective method of refracting light before it hits the lens through reshaping a layer of the cornea called the stroma. This is done by cutting a ‘flap’ in the outer layer of the cornea then vaporising part of the stroma.

- 92-98% of people who have undergone laser surgery are satisfied, but there are some downsides: 10% have conjunctival bleeding, 95% have dry eyes, and some have chronic pain, flap slippage, or over/under-correction which means follow-up surgery is needed. Some also experience glare problems due to scarring.

c) Kidneys- The main function of the kidneys is to remove nitrogenous waste (ammonia) from

the blood, which is formed when amino acids break down (deamination).- Ammonia cannot be stored in the body, so the kidneys also convert it to urea. They

also filter out electrolytes and hormones, and regulate water levels in the blood.

- The ultrastructure of the kidney is the part which is visible to the naked eye, and is made up of the cortex and medulla.

- The microstructure is the close-up part which actually does the filtration, known as nephrons. There are a million in each kidney, and they contain a the glomerulus, Bowman’s Capsule, convoluted tubules, and the loop of Henle.

- Ultrafiltrationo Blood flows through the afferent arteriole, through the glomerulus

capillaries, and back out through the efferent arteriole.o All small molecules (water, salts, glucose, urea, amino acids, hormones) are

sucked out of the glomerulus by the Bowman’s Capsule.- Reabsorption

o These small molecules flow through the proximal convoluted tubule (PCT) where amino acids and glucose return to the efferent via active transport.

o The remaining filtrate passes through the descending loop of Henle, where water returns to the efferent passively via osmosis.

o It then travels up the ascending loop, where salts pass into the efferent first passively, then actively. This leaves fairly pure urea.

o In the distal convoluted tubule (DCT), hormones (aldosterone etc.) regulate active transport which moves water and salts into or out of the efferent as needed to establish homeostasis.

o The remaining filtrate (urine) then passes into the collecting duct. Here is the last chance for water to pass back into the blood to prevent dehydration, as anti-diuretic hormone (ADH) causes aquaporins to open and release water.

- Loss of kidney function can be acute or chronic.- Acute kidney function loss is caused by damaged tissue (due to drugs/infection/

radioactive dye/etc.) or obstruction to urine leaving (due to kidney stones/prostate issues/etc.) and can lead to chronic conditions.

- Chronic kidney function loss has many possible causes, including damaged blood vessels (due to hypertension/diabetes/etc.), kidney infections/autoimmune attacks (glomerulonephritis), polycystic kidney disorder (benign tumours on the kidney), urine reflux, and kidney stones.

- During dialysis, blood is pumped through dialysis tubing and the urea, nitrogen, and other waste products flow out into the dialysate due to the osmotic gradient.

- Dialysis does not effectively do the job of the kidney, and eventually the build-up of toxins in the body will cause damage. As such, it is only a temporary solution while waiting for a transplant. However, transplants can also cause problems such as rejection and constant immunosuppression.