HSC Biology Module 8: Non-infectious Disease and Disorders

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Module 8: Non-infectious Disease and Disorders

Contents

Homeostasis

Construct and interpret negative feedback loops that show homeostasis by using a range of sources, including but not limited to:

NEGATIVE FEEDBACK LOOP

Stimulus → receptor detects stimulus → hypothalamus receives signal → signal sent to effector → effector responds and counteracts stimulus → effectors stop response once original state is restored.

– temperature

AKA thermoregulation

BODY TEMPERATURE RISES TOO HIGH

 

NEGATIVE FEEDBACK LOOP

Stimulus → receptor detects stimulus → hypothalamus receives signal → signal sent to effector → effector responds and counteracts stimulus → effectors stop response once original state is restored.

– temperature

AKA thermoregulation

BODY TEMPERATURE RISES TOO HIGH

BODY TEMPERATURE DROPS TOO LOW

– glucose

  • Glucose levels change based on consumption of carbohydrates.
  • Increased carbohydrates → increased glucose.

GLUCOSE LEVELS RISE TOO HIGH

GLUCOSE LEVELS DROP TOO LOW

Investigate the various mechanisms used by organisms to maintain their internal environment within tolerance limits, including:

– trends and patterns in behavioural, structural and physiological adaptations in endotherms that assist in maintaining homeostasis

BEHAVIOURAL ADAPTATIONS

Adaptation How adaptation maintains homeostasis
Animal moves to shade in hot environments. Maintains stable temperature e.g. kangaroos are most active at dawn/dusk when there is the most shade.
Animal burrows underground in hot environments. Maintains stable temperature e.g. white-throated wood rate burrows tunnels to cool down.
Animal licks forearms. Cools down body temperature through evaporative cooling e.g. kangaroos and lions.
Panting in hot temperatures. Quick breathing evaporates water from the tongue → cools blood vessels e.g. dog.
Animals huddle together in cold temperatures. Decrease body surface exposed to cool temperature e.g. male emperor penguins.

STRUCTURAL ADAPTIONS

Adaptation How adaptation maintains homeostasis
Liver: homeostatic organism (maintains correct sugar and amino acid levels). – WHEN SUGAR LEVELS ARE TOO HIGH: Liver converts excess sugar into glycogen OR fat stored in adipose tissue.- WHEN SUGAR LEVELS ARE TOO LOW: Liver coverts glycogen into sugar.

-WHEN AMINO ACIDS ARE TOO HIGH: Liver converts amino acids to ammonia which is excreted.

Organism surface area:volume ratio. Low surface area:volume → heat conservation (animals in cold environments) e.g. bilby. 

High surface area:volume → heat loss (animals in hot temperatures) e.g. snake.

Body insulation e.g. fur, feathers, blubber. Trap air/heat against/within skin to increase heat retention in cool environments.
Countercurrent circulation. Arteries carrying warm blood run close to veins carrying cool blood to maximise heat transfer between vessels e.g. penguins.

 

PHYSIOLOGICAL ADAPTATIONS

Adaptation How adaptation maintains homeostasis
Thirst. Prompting body to drink water protects organism from dehydrating and maintains correct solute concentrations.
Metabolism. Helps maintains constant body temperature (higher metabolism heats body).
Hibernation. Body temperature drops and metabolism is slowed down to conserve energy during colder temperatures when food sources are low e.g. pygmy possum.
Vasodilation. Blood vessels dilate to transfer heat from body to surrounding environment → cools body.
Vasoconstriction. Blood vessels constrict to retain heat within body → heats body.

 

– internal coordination systems that allow homeostasis to be maintained, including hormones and neural pathways

HOW DO SIGNALLING MOLECULES WORK?

Cells detect change from stable state → signalling molecules released → neighbouring cells receive message until the signal reaches effector cells → response triggered.

Internal coordination system Description
Endocrine system (hormones) Hormones are signalling molecules (above) transported via:-       Circulatory system (blood)

–       Diffusion through extracellular fluid

The 3 types of hormones are:

–       Lipid hormones e.g. prostaglandins

–       Peptide hormones e.g. insulin AND protein hormones e.g. growth hormone

–       Amino acid-derived hormones e.g. adrenaline

Hormones are produced by endocrine glands e.g. pituitary gland.

Nervous system (neural pathways) Sensory neurons carry impulses from receptors to CNS → interneurons pass impulse from sensory neurons to motor neurons → motor neurons carry impulse to effector → response maintains homeostasis. 

MECHANISMS OF NEURAL PATHWAYS:

–       Neural pathways are extremely DIRECT for max. speed of conduction.

–       Neurons have a high concentration of mitochondria to provide enough energy to maintain a balance of ions across the cell membrane.

–       Neurons secrete neurotransmitters (signalling molecules) → stimulate cellular responses.

–       Receptors are uniquely suited for function e.g. photoreceptors for vision and thermoreceptors for temperature.

Osmoregulation Maintenance of water balance via osmosis → maintains ion concentration → maintains pH → optimal enzyme functioning.

 

DIVISIONS OF PERIPHERAL NERVOUS SYSTEM:

– mechanisms in plants that allow water balance to be maintained

Mechanism How it works
Stomata opening/closing. WATER LEVELS HIGH: stomata open to increase photosynthesis.WATER LEVELS LOW: stomata close to reduce water loss by evaporation.
High numbers of stomata (found in hydrophytes). Maximise loss of water since they live in freshwater environments.
Few numbers of stomata (found in xerophytes). Reduces water loss since they live in dry environments.
Leaves hanging vertically. Reduce sun exposure → reduces water loss by evaporation OR overheating e.g. eucalyptus leaves.
Extensive root systems. Maximise surface area for water absorption from soil (for plants in dry environments).

 

Causes and Effects

Investigate the causes and effects of non-infectious diseases in humans, including but not limited to:

– genetic diseases

Example Cause Effect
Phenylketonuria Mutation in gene coding for enzyme phenylalanine hydroxylase. Body cannot convert phenylalanine to tyrosine without enzyme → increase in concentration of phenylalanine.RESULTS IN:

– MENTAL RETARDATION

– FADED SKIN/HAIR COLOUR.

– SMALLER HEAD SIZE.

– SEIZURES.

 

– diseases caused by environmental exposure

Example Cause Effect
Immediate hypersensitivity (allergic reaction type I) Immune system mistakes harmless substances (e.g. pollen, dust) as harmful antigens. Mild effects e.g. itchy skin, teary eyes.Severe effects AKA anaphylaxis → vomiting, difficulty breathing, unconsciousness, death.

 

– nutritional diseases

Example Cause Effect
Scurvy Deficiency of vitamin C. Swelling of body parts and fatigue.

 

– cancer

Cause Effect
Carcinogens: factors that mutate DNA. Causes rapid cell proliferation and slows down cell apoptosis (programmed cell death) → enables cancer cells to divide very quickly.

 

Collect and represent data to show the incidence, prevalence and mortality rates of non-infectious diseases, for example:

Incidence: number of new cases each year.

Mortality: number of deaths.

– nutritional diseases

EXAMPLE: SCURVY

Incidence and mortality rates decrease as knowledge of nutrition becomes widespread e.g. importance of fruit/vegetable nutrients → decreases prevalence.

– diseases caused by environmental exposure

EXAMPLE: CANCER

Mortality rates decrease as public health programs are created to control/prevent disease e.g. slip slop slap campaign encouraged use of sunscreen to prevent UV rays mutating DNA e.g. regular screening for cancer is encouraged e.g. Quit campaign raised awareness of effects of smoking to decrease chance of mutating DNA → decreases prevalence.

Epidemiology

Analyse patterns of non-infectious diseases in populations, including their incidence and prevalence, including but not limited to:

– nutritional diseases

  • Unbalanced diet that lacks or is excessive in nutrients → malnutrition → increases incidence + prevalence e.g. undernutrition = underweight and micronutrient diseases AND overnutrition = obesity.
  • Over time as knowledge/education increases about the importance of a balanced diet and intake of vital nutrients, prevalence of disease decreases.

– diseases caused by environmental exposure

  • UV radiation is a mutagen (environmental risk) → increases incidence + prevalence of cancer.
  • As knowledge about environmental risks increases, campaigns are created and public awareness is increased → incidence and prevalence decrease.

Investigate the treatment/management, and possible future directions for further research, of a non-infectious disease using an example from one of the non-infectious diseases categories listed above

CANCER (CAUSED BY ENVIRONMENTAL EXPOSURE)

Treatment

  • Chemotherapy: deliberately kill cells that are cancerous. Negative side effects = killing healthy cells.
  • Radiation therapy: deliberately damages cell DNA → kills cells. Negative side effects = killing healthy tissue.
  • Surgery: removes tumours. Negative side effects: difficult to remove all cancerous cells in 1 surgery.
  • Monoclonal antibody therapy: mass production of antibodies which are injected into body to aid the immune response.

Management

  • Cancer vaccines.
  • Slip slop slap campaign (1981).
  • Regular screening for cancer → early detection → treatment.
  • Quit (educational program) → raise awareness of effects of smoking on mutating DNA.

Possible future directions for future research

  • Personalised cancer vaccines.
  • Cell therapy e.g. genetically engineering T-cells from the patient to kill cancer antigen.

Evaluate the method used in an example of an epidemiological study

FEATURES OF EPIDEMIOLOGICAL STUDY

  • Descriptive studies: Patterns of disease e.g. frequency, age, gender, occupation, location and time period.
  • Analytical studies:
  1. i) Case control studies: compare people with disease to those without.
  2. ii) Cohort studies: get 2 groups that are free of the disease, expose 1 group to factor potentially causing disease.
  • Intervention studies: Test the effectiveness of treatment/campaign to change behaviour of population to decrease incidence of disease.

EXAMPLE: LUNG CANCER

  • Descriptive studies: Age, sex, smoking habits, diet, occupation and drinking habits.

 

  • Analytical studies:

i) Case control study by Richard Doll (1947) to compare smoking habits of patients with and without lung cancer → showed people with lung cancer were smokers suggesting a link.

ii) Cohort study by A Hill (1951) where 1 group of doctors were smoker and the others were non-smokers over 10 years → showed smokers had lung cancer and more cigarettes = more chance of lung cancer.

  • Intervention studies: Quit campaign decreases number of people smoking was studied.

EVALUATION

Positives: large sample size, control of variables (e.g. age, gender), large sample size, long period, accurate/reliable studies.

Evaluate, using examples, the benefits of engaging in an epidemiological study

EXAMPLE: LUNG CANCER

Epidemiological study → understanding of cause/effects of lung cancer → prevent exposure to mutagens that cause lung cancer (e.g. smoking) + early detection/treatment.

Prevention

Use secondary sources to evaluate the effectiveness of current disease-prevention methods and develop strategies for the prevention of a non-infectious disease, including but not limited to:

NON-INFECTIOUS DISEASE: CANCER

– educational programs and campaigns

  • Quit educational program.
  • Slip slop slap campaign.

RAISE AWARENESS OF EFFECTS OF SMOKING/UV RAYS ON MUTATING DNA AND CAUSING CANCER.

Effectiveness: high (reduced mortality/incidence rates drastically).

Prevention strategies: stop smoking and prevent exposure to sun.

– genetic engineering

  • Genetically engineering other animals (e.g. mice) to produce high volumes of monoclonal antibodies.

Effectiveness: average (technology has not reached full potential and is not a foolproof method of eradicating cancer).

Technologies and Disorders

Explain a range of causes of disorders by investigating the structures and functions of the relevant organs, for example:

– hearing loss

THE EAR

Outer ear Pinna Collects sound waves and channels into ear canal.
Outer ear Auditory canal Sound waves travel through.
Boundary between outer and middle ear Tympanic membrane (eardrum) – stretched across end of auditory canal Vibrates from sound and passes on these vibrations.
Middle ear Ear ossicles – Hammer (malleus) anvil (incus) stirrup (stapes) 3 bones that transmit vibrations from eardrum to oval window.
Middle ear Oval window – thin membrane Amplify and pass vibrations.
Boundary between middle and inner ear Round window Thin membrane which bulges to allow vibrations to escape from cochlea → prevents wave reflections within cochlea (ringing).
Inner ear Cochlea – contains basilar membrane Fluid-filled spiral where sound vibrations are transmitted → produces pressure waves → stimulates OOC.
Inner ear Basilar membrane – covered in fibres that get longer the further down the membrane For each frequency, only certain sections of fibres vibrate.
Inner ear Organ of Corti – contains hair cells Stimulated by pressure wave → nerve impulse.
Auditory nerve Transmits nerve signals from OOC to brain.

NOTE: OOC = organ or corti

DISORDERS

  • Auditory processing disorders: brain cannot understand speech.

CAUSE: birth defect or physical injury to brain.

  • Conductive hearing loss: sound is not correctly transmitted from the outer to middle ear.
  • CAUSE: malformation of outer/middle ear, fluid in middle ear, ear infection, faulty Eustachian tube that doesn’t equalise ear pressure, tumours in middle ear, excess earwax.
  • Sensorineural hearing loss: damaged cochlea disrupts pathways from inner ear to brain.
  • CAUSE: exposure to loud noises damage the cochlea hair cells, physical injury to head, tumours in the pathway from the inner ear to brain, aged hair cells over time, drug abuse.
  • Mixed hearing loss: conductive AND sensorineural hearing loss

– visual disorders

THE EYE

Part Structure Function
Eyelid Muscle + skin. Protection.
Conjunctiva Thin, transparent membrane. Protection.
Cornea No blood vessels.Transparent: allow light.

Curved: bends light → converges → lands at the back of eyeball.

Sclera Outermost layer that is tough, non-elastic tissue:·         At the back it is opaque. It continues to the front as transparent cornea. Maintain shape and is site of attachment.
Choroid Middle layer that has blood vessels:·         At the back it is black: absorbs light and reduce scattering of light within eye.

·         At the front it forms the ciliary body, lens and iris.

·         Blood vessels: nourish the retina.

Retina Covers back 2/3 of eye, very thin, contains nerve cells, nerve tissue (e.g. Ganglion cells, bipolar neurons).2 types of photoreceptors:

·         Rods

·         Cones

Photoreceptors respond to light and convert into nerve impulses.
Fovea Centre back, containing cone cells (no rod cells) and blood vessels. Gives sharp image.
Iris Situated between lens and behind cornea and contains melanin. 

Made of connective tissue and smooth muscle:

·         Circular muscle.

·         Radial muscles.

Control size of pupil and amount of light entering eye. 

Circular muscles contract → pupil smaller → less light.

 

Radial muscles contract → pupil larger → more light.

 

This is because too much bright light can damage eye → pupils constrict to prevent this. In dim light pupils dilate allowing maximum amount of weak light.

Pupil Opening. Light enters to reach retina.
Lens Biconvex and transparent: Refracts light and directs them onto retina where image is formed.Elastic: Change shape for near or far vision (accommodation).
Aqueous humor Transparent, watery fluid at front between cornea and lens. Refracts light, maintains shape and provides nutrients for lens and cornea.
Vitreous humor Clear, jelly-like substance. Maintains shape and transparency allows light to refract and pass through.
Ciliary muscles Attached via suspensory ligaments to the lens. Adjust the curvature of lens.
Suspensory ligaments Adjust curvature of lens.
Ciliary body Secretes aqueous humor.
Optic nerve Bundle of neurons. Transmits nerve impulses from retina to brain.

DISORDERS

  • Myopia: short sightedness (distant objects fall in front of retina).

CAUSE: eyeball is elongated and lens is not flat enough when ciliary muscles contract.

 

  • Hyperopia: long sightedness (near objects fall behind the retina).

CAUSE: eyeball is too round, refractive power of cornea is too great and lens is too flat.

 

  • Cataracts: blurry/cloudy vision.

CAUSE: protein in eye starts to denature and becomes translucent.

 

  • Glaucoma: causes blindness.

CAUSE: fluid builds up in eyes and disrupts functioning of optic nerve → impacts transmission from optic nerve to brain.

– loss of kidney function

THE KIDNEY

Structure Function
Renal hilum Provides space for renal artery/vein/ureter
Renal capsule Provides stiff outer shell to maintain shape of soft inner tissue and protect from damage.
Glomerulus Bundle of capillaries surrounded by Bowman’s capsule.
Renal cortex Contains Bowman’s capsule, proximal and distal tubule.
Renal pyramids Form the renal medulla to the renal cortex.Aligned with bases facing outwards to renal cortex.

Each apex (tip) connects to a minor calyx.

Minor calyx/major calyx Small, hollow tube that collects urine. 

Minor calyces merge to from 3 large major calyces which form the renal pelvis at centre of kidney.

Renal medulla Loop of Henle and collecting tubules.
Renal pelvis Formed from major calyces.Exits kidney at renal hilum where urine drains into ureter.
Bowman’s capsule Cup-like sack for filtration – collects filtrate and sends it throughout rest of nephron.

 

DISORDERS

  • Glomerulonephritis: results in kidney failure.

CAUSE: infected glomeruli = red blood cells/proteins are not filtered out of urine and exit body = excess fluid moves into body via osmosis.

 

  • Diabetic nephropathy: incorrect filtering in Bowman’s capsule.

CAUSE: type 1 and 2 diabetes allows large substances to pass Bowman’s capsule with urine.

 

  • Reflux nephropathy: urine escapes the bladder.

CAUSE: faulty valves cannot prevent urine from escaping the bladder → concentrated urine enters kidney → kidney damage.

 

  • Polycystic kidney disease: cysts grow inside kidney → prevent correct functioning.

CAUSE: genetics.

Investigate technologies that are used to assist with the effects of a disorder, including but not limited to:

– hearing loss: cochlear implants, bone conduction implants, hearing aids

COCHLEAR IMPLANTS

  • Sensorineural hearing loss.
  • NEGATVIES: surgery, expensive, side effects include infection, maintenance costs, background noise amplified, visible.

BONE CONDUCTION IMPLANTS

  • Conductive hearing loss.
  • POSITIVES: device feels weightless, comfortable, no blocking of ear canal = clean ear = prevents infection.
  • NEGATIVES: surgery, risk of infection/inflammation, expensive.

HEARING AIDS

  • Conductive, sensorineural and mixed hearing loss.
  • POSITIVES: inexpensive, no surgery, no side effects.
  • NEGATIVES: uncomfortable, amplifies background noises, residual hearing (buzzing) when removed, sometimes visible.

– visual disorders: spectacles, laser surgery

SPECTACLES

  • Myopia: Glasses with concave lens → bend rays outwards → diverge before they reach the eye → extends focal length → image falls on retina instead of in front.

  • Hyperopia: Glasses with convex lens → bends rays inwards → converge before they reach the eye → shorter focal length → image falls on retina instead of behind.

LASER SURGERY

  • Myopia: decreases curvature of cornea.
  • Hyperopia: increases curvature of cornea.

– loss of kidney function: dialysis

DIALYSIS

  • Renal dialysis: removes metabolic wastes by diverting blood out of artery into tubes with artificial semi-permeable membranes (coiled to increase SA). Tubes submerged in dialysis fluid (dialysate) which flows in opposite direction to maximise diffusion.
  • Positives and negatives discussed in next dot point.

2 types of renal dialysis:

Haemodialysis Peritoneal dialysis
Blood flows out into dialyser and back in. Semi-permeable membrane inside abdomen of body has sterile glucose solution (similar to dialysate) pumped. Blood vessels flow on outside of the membrane and substances diffuse in/out.

Evaluate the effectiveness of a technology that is used to manage and assist with the effects of a disorder

EXAMPLE: RENAL DIALYSIS FOR KIDNEY FAILURE

POSITIVES: removes waste, replicates filtration function of kidney, replicates principle of passive transport, no surgery needed.

NEGATIVES:

  • time consuming
  • limited wastes are removed e.g. Na+ do not diffuse out fast enough and accumulate in blood → strict diet
  • dialysate needs to be constantly replace to maintain the correct concentration gradient
  • does not replicate reabsorption and secretion function of kidney
  • waste needs to be regularly discarded
  • is not continuous (unlike the kidney)

OVERALL RENAL DIALYSIS IS VERY EFFECTIVE IN PERFORMING THE MAIN FUNCTION OF THE KIDNEY (REMOVING UREA), HOWEVER DOES NOT PERFORM ADDITIONAL FUNCTIONS E.G. SALT REGULATION.

Overall positive impact on the patient, however there are some difficulties using this technology (discussed above).

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