HSC Biology Syllabus Notes

Module 8 / Inquiry Question 5


Overview of Week 17 Inquiry Question – How can technologies be used to assist people who experience disorders?

Learning Objective #1 – Explain a range of causes of disorders by investigating the structures and functions of the relevant
organs, for example: 

  • Hearing loss

  • Visual disorders

  • Loss of kidney function

Learning Objective #2 – 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

  • Visual disorders: spectacles, laser surgery

  • Loss of kidney function: dialysis

Learning Objective #3 – Evaluate the effectiveness of a technology that is used to manage and assist with the effects of a disorder

NEW HSC Biology Video – Technologies and Disorders

Week 17 Homework Questions

Week 17 Curveball Questions

Week 17 Extension Questions

Solutions to Week 17 Questions


Learning Objective #1 - Explain a range of causes of disorders by investigating the structures and functions of the relevant organs, for example:

- Hearing loss
- Visual disorders
- Loss of kidney function

We will first explore the structure and function of the kidney and the possible causes of kidney failure. 

Next, we will examine the eye followed by ear alongside possible reasons towards visual disorders and hearing loss respectively. 

Without further ado, let’s dive straight into materials that you will need to know for HSC Biology. 


Structure and Function of the Kidney

Each of our two kidney is made up of around a million nephrons. 

Each nephron is able to perform and involved in the processes of filtration, reabsorption, secretion and elimination. 

There are two regions of the kidney in which different sections of nephrons making up the kidney are located. 

  • These regions are the renal cortex and renal medulla (e.g. outer medulla and inner medulla).

The following diagram is of a nephron, remember about a million nephron makes up a kidney.

As depicted in the diagram below, there are blood vessels (capillaries) that are surrounding the nephron whereby substances exit the nephron’s tubule via passive or active and into the surrounding capillaries.

HSC-Biology-Nephron-Diagram-min.png

Renal Cortex

Part of Nephron in Renal Cortex of Kidney > Glomerulus

Anatomy (Structure) of Glomerulus: The glomerulus is a network of heavily convoluted blood vessels (capillaries) that surrounded by the Bowman’s Capsule. 

Function of Glomerulus: The heavily convoluted blood vessels in a small area creates a region of high blood pressure for ultrafiltration to occur. The blood is filtered through the glomerulus and the filtrate can subsequently enter the kidney tubules via the Bowman’s capsule. The filtrate in the Bowman’s Capsule is known as the glomerular filtrate.

Substances in the blood such as water, glucose, amino acids, ions (e.g. Na+, K+, Cl-) and urea are filtered into the Bowman’s capsule. 

Red and white blood cells in the blood are too big to filter through the capillaries of the glomerulus. Proteins are also not filtered into the bowman’s but remain the plasma due to their large size. 

Part of Nephron in Renal Cortex of Kidney > Bowman’s Capsule

Anatomy (Structure) of Bowman’s Capsule: A cup-shaped structure.

Function of Bowman’s Capsule: Collect the filtrate exiting the blood from the glomerulus where the filtrate in the Bowman’s Capsule is known as the glomerular filtrate.

Part of Nephron in Renal Cortex of Kidney > Proximal Tubule

Anatomy (Structure) of Proximal Tubule: A long, convoluted tube that is attached to the Bowman’s Capsule.

Function of Proximal Tubule:  The site responsible for active and passive transport of various components of the glomerular filtrate.*

* Refer to the diagram of a nephron displayed at the beginning for specifics of active & passive transport.

Part of Nephron in Renal Cortex of Kidney > Distal tubule

Anatomy (Structure) of Distal Tubule: A long, convoluted tube that is attached to the ascending loop of Henle and collecting duct. 

Function of Distal Tubule: The site responsible for active and passive transport of various components of the glomerular filtrate.*

* Refer to the diagram of a nephron displayed at the beginning for specifics of active & passive transport.



Outer Medulla

Part of Nephron in Outer Medulla > Descending Loop of Henle

Anatomy (Structure) of Descending Loop of Henle: A tubule that connects to the proximal & distal tubules of a nephron.

Function of Descending Loop of Henle: The site where water in the glomerular filter moves passively via osmosis into the nephron’s surrounding blood capillaries. 

Part of Nephron in Outer Medulla > Thick region of ascending Loop of Henle

Anatomy (Structure) of Thick region of ascending Loop of Henle: A tubule that connects to the proximal & distal tubules of a nephron. 

Function of Thick region of ascending Loop of Henle: The site where sodium in the glomerular filter moves actively into the nephron’s surrounding blood capillaries.


Inner Medulla

Part of Nephron in Inner Medulla > Collecting Duct

Anatomy (Structure) of Collecting Duct: A long, convoluted tubule that is attached to the distal tubule and carries urine and other remaining substances in the glomerular filter into the renal pelvis and ureter. 

Function of Collecting Duct: Carry urine and other remaining substances that make up the glomerular filter after passing the distal tubule into the renal pelvis

Part of Nephron in Inner Medulla > Thin region of ascending Loop of Henle

Anatomy (Structure) of Thin region of ascending Loop of Henle:A tubule that connects to the proximal & distal tubules of a nephron.

Function of Thin region of ascending Loop of Henle: The site where sodium in the glomerular filter moves passively via diffusion into the nephron’s surrounding blood capillaries. 

  • NOTE: The collecting duct of the nephron serves to allow the urine to flow into the renal pelvis whereby urine can be directed accordingly to be eliminated out the individual’s body. 

  • NOTE: The nephron is not part of the renal pelvis section of the kidney. However, the renal pelvis is concerned of removing the urine that is carried out of the nephron via the collecting duct.

Diabetic Kidney Disease causes damage to kidney due to Type 1 or Type 2 Diabetes. Diabetes result in greater stress placed on nephrons to filter glucose which can result in damage over time.

High blood pressure such to conditions such as aldosterone overload can damage the glomerulus which lowers the capacity of nephrons to be able to filter blood, resulting in kidney failure. 

Kidney stones formed, due to factors like long-term high salt diet, can result the accumulation of urine in the kidney. This increasing level of pressure can damage nephrons and lead to kidney failure.

Polycystic kidney disease is a inherited disease whereby cysts (fluid-filled sacs) are formed in walls of nephrons. This can alter the shape of kidney’s nephrons, affecting their function. If left untreated, the cysts formed and altering the nephron’s shape can result in a build-up in blood pressure which can damage nephrons. This leads to kidney failure.

Structure and Function of the Eye

HSC-Biology-Structure-And-Function-of-the-Eye-min.png

Part of the eye (Name of Tissue) > Conjunctiva 

Anatomy (Structure of Conjunctiva): A transparent, mucous membrane that shields the sclera.

The function of Conjunctiva: is to protect the internal structures of the eye and helps lubricate & nourishes the eye with mucus.

  • NOTE: An infection of the conjunctiva causes a highly contagious condition called conjunctivitis.

Part of the eye (Name of Tissue) > Cornea

Anatomy (Structure of Cornea): A transparent, dome-shaped tissue wraps the front of the eye.

The function of Cornea: is responsible for protecting the internal structures of the eye and refracting light towards the eye’s retina.

Part of the eye (Name of Tissue) > Sclera

Anatomy (Structure of Sclera): This is the white part of the eye which you see in the mirror. It is a cover of the eye made of fibrin tissue.

The function of scelera: serves protects the inner parts of the eye and maintain its shape.

Part of the eye (Name of Tissue) > Choroid (Blood Vessels)

Anatomy (Structure of Choroid): A dark pigmented layer comprised of blood vessels situated between the retina and sclera. 

The function of Choroid: responsible for nourishing cells in the inner parts of the eye. It also helps to absorb light to minimise the scattering of light in the retina that would otherwise result in fake images being interpreted by the brain detected by photoreceptors on the retina.

Part of the eye (Name of Tissue) > Pupil

Anatomy (Structure of Pupil): A circular opening that is controlled by the activity of iris muscles.

The function of Pupil: responsible for permitting light to travel through to the retina. 

Part of the eye (Name of Tissue) > Retina

Anatomy (Structure of Retina): Innermost layer of the eye. Approximately 0.5mm thick lining (placed against) the back of the eye. It is composed of approx. 150 million light sensitive modified nerve cells (photoreceptors) called rods and cones. These photoreceptor nerve cells make up nerve fibres to relay stimulus to the optic nerve. Rods are more numerous than cones and are highly sensitive to shades of black and white but not to colour. Cones are colour-receptive cells. 

Rods are spread out the retina whereas cones are all packed at the fovea of the retina. 

  • NOTE: The ‘Fovea’ is the centre of the Retina. Since retina is where all the photoreceptor cells are located, the fovea is the centre of the visual field.

The function of Retina: Converts light stimuli into electrochemical message (nerve pulses) that is sent to the brain via the optic nerve for interpretation.

Part of the eye (Name of Tissue) > Iris

Anatomy (Structure of Iris): This is the coloured part of the eye that you see in the mirror. It is comprised of a pigment that has iris sphincter muscles. that is able to control the size of the pupil and amount of light that is able to travel through to the retina.

The function of Iris: use the muscles to control the size of the pupil and amount of light that is able to travel through to the retina depending on the intensity of light. 

Part of the eye (Name of Tissue) > Lens or Lenses (plural)

Anatomy (Structure of Lens): A transparent, bi-convex protein disc situated behind the pupil. 

  • NOTE: Lens is made of protein and water.

The function of Lens: responsible for refracting light towards the retina.

Part of the eye (Name of Tissue) > Aqueous Humour

Anatomy (Structure of Aqueous Humour): A transparent, watery fluid that is located between the cornea and the lens.

The function of Aqueous Humour: provides and maintains the curved shape of the eye. 

Part of the eye (Name of Tissue) > Vitreous Humour

Anatomy (Structure of Vitreous Humour): A transparent, jelly-like fluid that is located the lens and the retina.

  • NOTE: The vitreous humour is comprised of mainly water, ions, glucose and white blood cells.

The function of Vitreous Humour: is to provide an environment that helps prevent infection of the eye and transparent environment through which light can be strike the retina without hinderance. 

Part of the eye (Name of Tissue) > Ciliary Body

Anatomy (Structure of Ciliary Body): Made up of ciliary muscles and is an extension of the choroid.

The function of Ciliary Body: responsible for controlling the curvature of the lens using the using ciliary muscles. These ciliary muscles of the ciliary body is attached to suspensory ligaments which help stabilise the lens in the lens capsule. It is also responsible for producing the aqueous humour.

Part of the eye (Name of Tissue) > Optic Nerve

Anatomy (Structure of Optic Nerve): A collection or bundle of nerve fibres. It contains a ‘blind spot’ which is a region that lacks photoreceptors.

The function of Optic Nerve: Responsible conveying the electrochemical message from photoreceptors to the visual cortex of the brain.  

  • NOTE: The visual cortex of the brain has interneurons which is able to process such signal and interpret it as an image. An appropriate response is relayed to an effector in the form of an electrochemical signal via effector neurons if required.


Causes of visual disorders

Colour-blindness 

When an individual is not able to interpret the difference in any colour, they are completely colour blind. However, that is rare. 

The more common form of colour blindness is where an individual experiences difficulty interpreting some colours but is able to interpret the difference between other colours. 

  • For example, red-green colour blindness is one of the most common colour blindness.

  • It is a sex-linked, recessive visual disorder where they are not able to distinguish the difference between red and green. They will also have trouble telling the difference between blue and purple colour as they have trouble seeing red colour where blue + red = purple.

The cause of red-green colour blindness due to the dysfunctional or missing photosensitive pigment (iodopsin) in the red and/or green cone cells.

 

Each of the three photosensitive pigment detects and responds to different wavelengths of light. Respectively, the pigment in red, green and blue cones detects long, medium and short wavelengths of light in the visible light region of the electromagnetic spectrum.

These cone cells are all located in the fovea region of the retina. 

Causes: 

  • Inheriting sex-linked, recessive alleles responsible for colour-blindness from parents.

  • Injury to the eye resulting in damage to cone cells.

  • Ageing whereby the lens turns yellow which creates a yellow filter, absorbing blue light.

  • Macular degeneration, diabetic retinopathy, glaucoma, or cataracts.

  • NOTE: We will be examining cataracts shortly.

Myopia 

This is a visual disorder that results in the difficulty of objects that are far away. Myopia is also known as short-sightness which means that the affected individual can see close up objects normally but not distant objects.

There are many possibilities to why myopia may occur. We will explore two here. 

One reason could be that the cornea is has greater curvature than normal which results in a greater degree of light refraction. As a result, the image of the object that is reflecting the radiation will fall short of the retina’s fovea. As a result, the affected individual will observe a blurred image. 

Another reason that a person may have myopia is that the affected individual may have an elongated eye ball in the horizontal direction. This can also result in image falling short of the retina’s fovea.

In order to see far away objects, the refraction of light should not be as high.

The exact cause of myopia is not completely certain. However, if parents have myopia, the chances of the children having myopia is higher. That being said, the genes that are known to cause myopia are not suffice to explain the inheritance patterns of myopia. Therefore, environmental factors such as constant up-close reading exercises and playing video games have seen to have some degree of correlation to myopia through research studies.

 

Hyperopia 

This visual disorder is also known as long-sightness. This effectively means that the affected individual can see distant objects normally but not close objects.

Here, the degree of light refraction is inadequate resulting in the image of the object being focused behind the retina rather than on the retina’s fovea. This will result in a blurry image observed by the individual.

Again, some reasons could include that the: 

  • Cornea not having enough curvature

  • Lens not having enough curvature

  • Eyeball is shorter than normal

In order to observe objects that are close to the eye, there must be adequate refraction of light.

Causes: Not completely certain. This is because there are limited studies pertaining to hyperopia. However, ageing of the lens resulting in protein accumulated in the lens could play a factor. There is minimal association between genes and hyperopia and so the inherited factor is small. There is possibility environmental factors that contribute towards hyperopia. 

This condition is most common amongst Native and African Americans and Pacific Islanders for uncertain reasons. 

So, if an individual has a perfect pair of eyes, how can he or she see distant and close objects?

Well, here is where accomodation takes place! 

Accomodation helps focus light onto the retina’s fovea to produce a clear image at varying distances by adjusting the curvature or shape of the lens. 

Each of our eyes are able to perform accomodation by adjusting the shape or curvature of our lens. This will therefore affect the focal length (or the distance to between the lens and the focal point). 

As we have explored in the structure & function of the eye in the previous section, the ciliary muscles and suspensory ligaments that are connected to the sclera are able to adjust the curvature of the lens. 

As the ciliary muscles contract, the lens come more round. Vice versa, when the ciliary muscles relax, the lens becomes less round. 

The more round the lens, the greater the refractive power of the lens and the shorter the focal length. This is important for focusing objects at close distances.

Vice versa, the less round the lens, the less refractive power of the lens and the longer the focal length. This is useful for seeing objects that are far away.

  • NOTE: Hyperopia and Myopia is when there are problems with performing accomodation.

Cataracts

This is a condition that is caused as a natural result of ageing whereby light is prevented from striking the retina. 

This is because when the cells of the lens die, the protein of the cell will accumulate in the lens capsule which result in the lens being opacity rather than transparent. 

These protein absorb the incoming light radiation and prevent light from passing through and striking the photoreceptor cells on the retina. 

Other than ageing, cataracts can also be caused by excessive exposure to ultraviolet radiation, high intake of alcohol, salt and steroids. 

These three visual disorders that we explored would be suffice for answering questions in HSC Biology. 

  • If you wish to study another condition, feel free to research about Glaucoma.


Structure and Function of the Ear

HSC-Biology-Structure-And-Function-of-the-Ear-min.png

Outer Ear

Part of the Outer Ear > Pinna

Anatomy (Structure) of Pinna: The fleshy section of the outer ear and what you see in the mirror.

Function of Pinna: Gather and direct sound into the ear canal in the appropriate direction. It also protects the inner parts of the ear from substances in the ambient environment (e.g. dust, chemicals, etc)

  

Part of the Outer Ear > Ear Canal

Anatomy (Structure) of Ear Canal: The tube that connects the pinna to the tympanic membrane. 

Function of Ear Canal: Directs sound directly to the tympanic membrane. It is also responsible in manufacturing and secreting ear wax to shield the ear from any substances that enter the canal, protecting the inner parts of the ear.

 

Part of the Outer Ear > Tympanic Membrane

Anatomy (Structure) of Tympanic Membrane: This is commonly referred to as the eardrum that expands at the end of the ear canal. It is sensitive membrane that is located between the external and middle ear. 

Function of Tympanic Membrane: The eardrum converts pressurised sound waves into mechanical energy as it oscillates at the same frequency as the sound that enters the ear canal. The air-tight membrane also protects the middle ear from any substances in outer ear.

Middle Ear

Part of the Middle Ear > Ear Ossicles

Anatomy (Structure) of Ear Ossicles: The three small bones located in the middle ear with their names being the malleus (Hammer), the incus (Anvil) and the stapes (Stirrup).

Function of Ear Ossicles: Converts the mechanical energy of the tympanic membrane to the oval window. During this conversion, the stress due to vibration on the tympanic membrane is reduced whilst transferring vibration to the oval window.

Part of the Middle Ear > Oval Window

Anatomy (Structure) of Oval Window: A thin membrane located between the middle and inner ear.

Function of Oval Window: Transfers themechanical energy from ossicles to the fluid in the cochlea.

Part of the Middle Ear > Round Window

Anatomy (Structure) of Round Window: A membrane that is located below the oval window. 

Function of Round Window: A membrane that moves in and out to adjust for pressure differences due to mechanical energy in the cochlea. This adjustment in pressure helps eliminate the constant “ringing” in the ear.

Inner Ear

Part of the Inner Ear > Cochlea

Anatomy (Structure) of Cochlea: Circular, snail-like chamber occupied with fluid.

Function of Cochlea: The fluid in the cochlea as a medium convert mechanical energy received from the oval window into electrochemical energy and transfer it to the hair cells in the Organ of Corti.

Part of the Inner Ear > Organ of Corti (INSIDE COCHLEA)

Anatomy (Structure) of Organ of Corti: An organ comprised of millions of cochlear hair cell receptors located inside the cochlea. These receptors are attached to nerve cells.

Function of Organ of Corti: These hair cell receptors are coded to be responsive and be activated when exposed to electrochemical energy of specific range of frequency and transfers the mechanical energy into electrochemical signals which are be carried to the auditory nerve via the nerve cells attached to hair cells.

Part of the Inner Ear > Auditory Nerve

Anatomy (Structure) of Auditory Nerve: A collection or bundle of nerve fibres.

Function of Auditory Nerve: Carry electrochemical signals to the auditory cortex brain.

  • The auditory cortex of the brain has interneurons which is able to process such signal and interpret it as sound. An appropriate response is relayed to an effector in the form of an electrochemical signal via effector neurons if required.

The Eustachian tube is situated between the OUTER AND INNER ear. 

The Eustachian tube is a tube that connects the throat with the inner ear. It serves to equalise the pressure between the outer and inner ear so that it maintains an equal pressure on both sides of the eardrum. This prevents shifting the position of the eardrum to a undesired position. A damaged eustachian tube can result in discomfort and dizziness.

Causes of Hearing Loss

There are two main types of hearing loss, these being: Conductive hearing loss and Sensorineural hearing loss.

  • The former deals with problems pertaining to hinderance of sound waves into the inner ear due to problems in the outer or middle ear.

  • The latter deals with problems in the inner ear or the auditory nerve.

  • Fun Fact: The other types of hearing loss which are mixing hearing loss and central hearing loss. However, they are less common than the two mentioned above.

Causes of conductive hearing loss:

  • Malformation of structures in the outer and/or middle ear.

  • Hardening of the stapes bone (Otosclerosis) due to extra bone growth – Inherited Disorder.

  • Ear infections

  • Wax accumulation in ear canal

Causes of Sensorineural hearing loss: 

  • The exposure to abnormally loud noise can damage and kill cochlear hair cells resulting in sensorineural hearing loss. Similarly, repeated exposure to loud noise can also damage and kill hair cells in the cochlea. These loud noises could also damage the auditory nerve resulting in difficulty of neurons transmitting stimulus (sound waves) to the relevant part of the brain where the sound can be interpreted or ‘heard’.

  • Mutation of the CABP2 Gene affecting the transmission of message between hair cells synapses. However, the exact mechanism of such mutation causing hearing loss is not fully understood.

  • Ageing result in the damage to cochlear hair cells due to exposure to loud sounds in lifetime.




Learning Objective #2 - 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
- Visual disorders: Spectacles, Laser Surgery
- Loss of kidney function: Renal Dialysis

Hearing Loss: Cochlear Implants, Bone Conduction Implants, Hearing Aids

Hearing aids are battery-powered electrical devices that are used to amplify the sound in the ambient environment such that the affected individual, who are hearing-impaired, can hear better. 

If both ears are affected, we need one hearing aid for each ear.

These devices are attached onto the external ear so that it can amplify the frequencies at which the affected individual has difficulty hearing in. 

The device directs sounds in the ambient environment directly into the ear canal. 

The three main components of a hearing aid are:

  • Microphone – used to detect sound waves in the ambient environment and transform sound waves into electrical signals

  • Amplifier – used to amplify the electrical signal

  • Receiver – responsible in converting electrical signal into sound waves.

The benefits of hearing aids is that are to restore hearing to affected individual with cochlear hair cell receptors having abnormally low sensitivity. 

This low sensitivity of cochlear hair cell receptors can be as a result of ageing, exposure to loud noise (causing damage to hair cells but not complete damage). Also, hearing aids can also help with loss of hearing due to ear infection and head trauma. 

This low sensitivity would mean that the sound from the environment is required to be amplified using a hearing aid so it reaches the threshold in which the cochlear hair cell receptors are activated. This would mean that they can detect and send the stimulus (sound) to the auditory nerve.

Some limitations of the hearing aid are that it does not heal hearing-impaired individuals so that normal hearing is restored. Also, if the cochlear hair cell receptors are completely damaged or dead, no amount of amplification from the hearing aid will help.

Cochlear Implant ('The Bionic Ear')

So what is the resolution when the cochlear hair cell receptors are completely damaged or dead? 

Well, we still have a saving grace. That is the cochlear implant. 

The use of this electric device is that it is able to directly stimulate the auditory nerve itself which means it can bypass the necessary activation of cochlear hair cell receptors as well as any damages in the outer, middle and inner ear.

This means that even if the hair cells are dead, the device can help deaf individual to hear!

Unlike the hearing aid, the cochlear implant requires surgical implantation. 

The actual implantation process of the bionic ear involves the installation of 22 electrodes in the cochlea, hence the term ‘cochlear implant’.

There are five parts to the cochlear implant:

  • Microphone – worn behind the ear to detect the sound waves.

  • Speech processor – filters and sorts the sound detected by the microphone then converting the sound into an electrical signal.

  • Transmitter – receives the signal from the speech processor, converts signal into a radio wave and convey it to the receiver/stimulator.

  • Receiver/stimulator – converts radio signals into electrical signals

  • Electrodes – receives the electrical signal and relay it to the brain via the auditory nerve. Depending on which electrode that receives signal and gets activated, the frequency and pitch of the signal transmitted to the brain via the auditory nerve will vary. The 22 electrodes are located at different areas of the cochlea.

    • NOTE: The Amplitude or volume of sound depends on the size of the electrical signal or impulse.

 

LIMITATIONS OF THE COCHLEAR IMPLANT:

  • The cost of the cochlear implant is high – ranging from $30k to $50k in the absence of insurance.

  • The actual sound frequencies will be different to that in the environment which means there is often long period of time of learning, therapy and adjusting to sounds after the surgical implantation. This can sometimes take years and will depend on when the person became deaf. The longer the timeframe between deaf and installation of cochlear implantation, the longer the time required for learning new sounds.

Bone Conduction Implants

So what if the person’s outer and middle ear structures are not functionally normally to detect and convey sound waves or vibrations to the inner ear? 

Well, bone conduction implants can help.

Bone conduction implants involves a microphone to detect sound waves which are relayed to an external sound processor involved in transforming sound waves into vibrations. These vibrations are sent to the connected implant which in the temporal bone. The sound waves are then transferred from the temporal bone (part of skull) directly to the cochlea. 

Therefore, the bone conduction implant bypass the structures of the external and middle ear and directly stimulates the cochlea in the inner ear.

For instance, in the event where the eardrums are damaged, bone conduction implants can be used as long cochlea is functional.

Eardrums can be damaged by exposed to loud sound waves for extended periods of time. Damage to the eardrum can also occur with ageing where the long exposure of sound and high volume sound waves can damage the eardrum overtime.

Less stress is therefore applied to the ears are it does not involve applying pressure to structures in the external (outer) and middle ear.

The background noise received by external sound processor in the implantable hearing used in bone conduction is lower than normal microphones in hearing aids which is generally advantageous for the person with the bone conduction implant. This is because it removes ‘junk noises’ in the environment. 

  • However, in some situations, we may not want that (e.g. small vibrational sounds produced that during dangerous events).

Visual Disorders: Spectacles & Laser Surgery

Spectacles (glasses) can be worn outside the eye so that it can adjust the refraction of light prior to the radiation striking the eye and undergoing refraction.

For people affected with myopia, each of the lens of the spectacle will have a concave shape so that it can diverge the light radiation prior to the light striking the eye. 

  • NOTE: Remember that myopia is when the individual refracts too much of the light (e.g. having a cornea of too high of a curvature)

Once the light strikes the cornea and passes through to the lens of the individual’s eye, the light will be refracted more and more towards the retina. 

However, it’s the spectacle’s lens that corrects and allow the focal point of the radiation to hit the fovea of retina for people with myopic conditions.

The opposite is true for people with hyperopic conditions (suffering from hyperopia) where the structures of their eye (e.g. the cornea) does not refract enough light so that the focal point of the radiation does not hit the retina. 

As a result, each lens of the spectacle would be convex. This allows the light to be refracted as it strikes the spectacle’s lens so that so the eventual focal point of the light radiation will hit the fovea of the retina after passing through the different structures of the eye. 

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Apart from spectacles, contact lenses can be used which are placed on top of the cornea. These lens can help adjust the refraction of light so that light is focused on the fovea of the retina, producing a clear image. These are generally more expensive than spectacles over the long term, making them a disadvantage. However, there are soft, sport contact lenses that are stable – more suitable for sporty individuals who may not want spectacles falling off during sport.

Glasses with coloured lens and coloured contact lenses could be used to act filters to help treat colour-blindness. The glasses only work if the necessary pigment protein are present in the cones that allow the affected individual to detect different colour wavelengths. If they are completely absent, the glasses will not work. Other than wearing these glasses, there is currently no other treatments available to cure ‘colour blindness’. 

These contact lenses can be implanted in front of the lens of the eye through surgery (rather than on top of cornea which does not require surgery). 

In the event of infection, surgically contact lenses can be removed like normal replaceable contact lenses used by people without colour blindness.

Laser Refractive Surgery: Laser In Situ Keratomileusis (LASIK)

Laser In Situ Keratomileusis (LASIK) is a type of laser refractive eye surgery used to restore vision defects such as myopia and hyperopia. It is a permanent treatment and more risky than wearing glasses.  Individuals with extreme form of refractive errors (hyperopia or myopia) are not suitable for LASIK. Instead, a contact lens can be implanted in front of the eye lens to help correct more extreme conditions that laser sugery cannot rectify. Pro is that you can now play sports without glasses falling off!

People under the age of 20 may not be suitable for this technology as their eye has not yet fully developed. 

Also, people who eye disorder or disease may not be recommended to undergo LASIK due to the nature of surgery by worsen the eye’s health condition. 

People over the age of 40 may be advised to use reading glasses over LASIK due to natural ageing of the eye, making it harder to see close objects. Here, LASIK may not be useful (won’t have permanent effect) as refractive power changes as time goes on, limiting the effectiveness laser surgery in terms of restoring vision for a long period of time.

This technology involves the use of a microkertaone which is a surgical equipment that is used to lift the corneal tissue so that a laser used to modify and correct the cornea so that the cornea has the correct refractive index or power. 

For instance, the laser can remove tissues above or below the cornea. This reduces the curvature of the cornea which lowers the refractive power which can be used to treat myopia.

Fun Fact: Sometimes an ultraviolet radiation is used.

To treat hyperopia, the laser can be concentrated at an area so that the heat produced can be used to remove some of the connective tissues surrounding the cornea to increase the curvature of the cornea.

Healing time: Less than 24 hours typically.

Laser Eye Surgery for Cataracts

To treat cataracts, laser eye surgery can be used. 

This involves using a laser to create a small cut on the edge of the cornea and inserting a ultrasonic probe into the lens capsule. 

The probe then powered to reduce ultrasound that is able to decompose the proteins in the lens. These proteins and dead lens cells are removed via suction, leaving the lens capsule behind. 

After that, intraocular or bionic lens is inserted into the lens capsule whereby the intraocular lens has the same capabilities of refracting light onto the retina as the normal lens.  

Due to improvements with technology and technique, cataract surgery can be performed at a cost of lower than $25 in some countries. The Fred Hollows Foundation helps fund cataract surgery for many individuals in Africa and Asia helping to decrease the population suffering from blindness due to cataracts. 

As a result, they are able to return to live a productive life which allows them to exit poverty and starvation. The previously affected individuals can subsequently to work such as growing crops and fishing and perform other work that allows them to be independent and not be a burden (both financially and lifestyle) to their families. 

Loss of Kidney Function: Renal Dialysis

So what option is available if both of a person’s kidneys do not work? 

There is a technique called renal dialysis. 

This involves a machine whereby a semi-permeable dialysis tubing is attached to an artery where the patient’s blood is pumped into the tubing. 

This tubing runs through a dialysis fluid inside the dialysis machine whereby the dialysing fluids is absent of urea. This means that urea present in the patient’s blood will diffuse into the dialysis fluid due to concentration difference. 

  • NOTE: Recall from Preliminary HSC Biology, solute (e.g. urea) moves from high concentration to low concentration

During this process, other excess solute such as salts (e.g. NaCl) are also removed from the blood.

The dialysing fluid contains a glucose concentration that is approximately equal of the patient’s blood glucose level. This reduces the loss glucose from the patient’s blood.

The machine continuously removes dialysing fluid as nitrogenous waste (e.g. urea) concentration rises.

The dialysing fluid flows in the opposite of blood that is present in the dialysing tubing so increase the concentration difference between urea in the blood and in the dialysing fluid. This thereby facilitates diffusion of urea out the blood. 

We will explore some of the limitations of renal dialysis in the following learning objective. 

Learning Objective #3 - Evaluate the effectiveness of a technology that is used to manage and assist with the effects of a disorder

This learning objective essentially requires us to compare the advantages and limitations of technologies that are designed to manage or treat disorders. 

We have already discussed the limitations of each technology in the above sections. So, here we will recap on some of the advantages of some of the technologies that we mentioned which you can select to use in your HSC Biology exam response. 

Technology: Renal Dialysis

Effectiveness of Renal Dialysis: 

Renal Dialysis is performed two to three times per week at a hospital or at home. This important as it helps drive the patient salt and water balance (osmoregulation) to a safe, normal level on a frequent basis when dialysis is performed. 

This is critical to avoid excess accumulation of nitrogenous waste that is toxic to cells. This is because high concentrations of urea in the blood results in a condition known as uraemia. 

High concentrations of urea can directly damage cells, resulting in cell death. Urea of high levels can interfere with cell signalling whereby the production of blood cells in our bone marrow is hindered, resulting in anaemia. It can also lower the effectiveness of platelets in clotting blood. 

So, the routine removal of urea from the patient’s blood prevents the above disorders and symptoms.

However, renal dialysis has limitations. Some of these are that:

  • Renal Dialysis is a slow process requiring several hours and so it takes time away from daily life.

  • The patient is also required to be undergo dialysis on a regular basis as the removal of nitrogenous waste only occurs when patient is attached to the dialysis machine.

  • The technology does not restore kidney function.

 

All in all, renal dialysis is effective in performing its role of acting as an ‘artificial kidney’ for patients suffering from dysfunctional kidneys. This allows the patient to perform everyday functions without experiencing many symptoms that the absence of renal dialysis would otherwise render performing certain daily activities difficult. This include breathing normally. So, the advantages outweighs the disadvantages. 

Laser Eye Surgery, Spectacles, Cochlear Implant, Hearing Aids

  • The technology allows individuals to be independent, meaning they will be less of a burden to their families.

  • The technology improves the quality of life of being able to restore sight/hearing to patients. This allows them communicate efficiently with the environment (including with other people).

  • EXAMPLE: They can now engage in social sports with the any cohort due to eye surgery and/or spectacles.

  • EXAMPLE: They can enjoy music and play instruments due to cochlear implant and/or hearing aids.

  • The technology also means that the affected individual is not required to be put in special classrooms or schools whereby they are isolated from major social circles.

Statistics on effectiveness of technologies:

  • “The Fred Hollows Foundation [dealing with cataracts laser eye surgery] now works in more than 25 countries and has restored sight to over two million people worldwide.“ – Source: Fred Hollows Foundation.

  • “As of December 2012, approximately 324,200 Cochlear Implants have been implanted worldwide.” – Source: National Institutes on Deafness and Other Communication Disorders, 2017. This effectively means that the technology has restored hearing to over 300,000 people.