9.5 Option - Communication
1. Humans, and other animals, are able to detect a range of stimuli from the external environment, some of which are useful
for communication
Students learn to:

Identify the role of receptors in detecting stimuli:
A stimuli is any change in the internal and external environment of an organism
This stimuli is picked by the organisms receptors
In the most simple form a receptor in organisms consists of single cells scattered around the body
In many organisms receptors have become more concentrated in particular areas to from sensory organs, which
contain non-sensory tissue and sensory cells. E.g. The eye

Explain that the response to a stimulus involves:
Stimulus: Any change in the internal or external environment of an organism
Receptor: The receptor detects this change, and sends messages to the brain or CNS by impulses in the nerve
Messenger: These impulses then trigger the CNS or brain to process the information and trigger new impulses
Effectors: These new impulses are transmitted to the effectors for it to produce a response
Response: A response is produced in response to the stimulus
Students:

Identify data sources, gather and process information from secondary sources to identify the range of senses
involved in communication:
Sight: Sight is a common form of communication, many animals have dangerous looking colours so as to detour
predators
Sound: This is a common form of communication, many animals use different sounds for different situations, such
as danger
Touch: Touch can be used as communication in such forms as comforting gestures. For example humans hug to
comfort or show affection
Taste: Chameleons use taste to identify if a territory is occupied. As chameleons rub their cloaca on branches to
mark there territory. Chameleons have a very poor sense of smell
Smell: Young babies are known to be capable of identifying their mother, by their smell
2. Visual communication involves the eye registering changes in the immediate environment
Students learn to:

Describe the anatomy and function of the human eye, including the:
Conjunctiva: Thin transparent membrane that is there to protect the exposed areas of the eye
Cornea: Transparent, and allows light to enter as well as helping bend or refract it. Has many nerves and is
sensitive to touch and pain
Sclera: Outermost layer of the eye at the back, opaque in colour forming the ‘white’. Tough non-elastic tissue
protecting the delicate inner layers, helps maintain shape as well as allowing a place for the attachment of muscles
for movement
Choroid: Middle of the eye containing most of the blood vessels. Posterior black to reduce scattering and reflecting
of light within the eye. Anterior continues to form the ciliary body and lens
Retina: Lines the posterior two thirds of the eye and is thin and delicate. Contains several layers of nerve cells.
Contains photoreceptors, rods and cones.
Iris: Consists of connective tissue and smooth muscles. These muscles are arranged circular and radially and control
the size of the pupil
Lens: Refracts light rays and directs them onto the retina. It is highly elastic allowing it to change shape to
accommodate to different distances

Aqueous Humor: Watery fluid in the anterior section of the eye, between the cornea and lens. It has a composition
similar to blood plasma and provides nutrients for the lens and cornea
Vitreous Humor: Jelly like material filing the remainder of the eye, behind the lens and enclosed by the retina.
Contains dissolved nutrients, refracts light and helps maintain the shape of the eye
Ciliary body: Produces aqueous humor, as well as this it controls the ciliary muscle which changes the shape of the
lens by controlling the suspensory ligaments
Optic nerve: Carries information from the eye to the brain changing light energy into nerve impulses
Identify the limited range of wavelengths of the electromagnetic spectrum detected by humans and compare this
range with those of other vertebrates and invertebrates:
Humans: Detect range lengths of 380nm to 760nm
Invertebrates: Many insects (honeybees) can detect wavelengths in the ultraviolet UV range of the spectrum. Their
light sensitive cells can detect shorter wavelengths present in the UV range. They are unable to detect some of the
longer wavelengths in the red part of the spectrum, they see red as black. Therefore bees do not have a wider
spectrum, but rather a different range
Vertebrates: Many birds are able to detect light in to the UV range of the spectrum. In addition to this birds tend to
be able to detect light most efficiently in the red. Therefore they have a wider range of detection
Students:

Plan, choose equipment or resources and perform a first-hand investigation of a mammalian eye to gather first-hand
data to relate structures to functions:
After removing the fatty tissue from the eye
Made an incision behind the cornea, and in front of the lens
Aqueous humor escapes, then studied the anterior section of the eye. Observing the pupil and the iris
Removed the lens and the vitreous humor and examined the lens
Observed print through the lens, whilst squeezing it to observe what happens
Examined the retina

Use available evidence to suggest reasons for the differences in range of electromagnetic radiation detected by
humans and other animals:
Different animals require vision in different areas of the spectrum. This allows them to live appropriately in their
habitats
For example; Honey bees are able to detect light into the UV range. This is beneficial as many flowers have UV
patterns, this helps direct bees to the pollen and nectar in the centre of the flower
3. The clarity of the signal transferred can affect interpretation of the intended visual communication
Students learn to:

Identify the conditions under which refraction of light occurs:
As light moves through a medium of a different density, the speed at which its travelling changes
Because of the light slowing down or speeding up, the light rays are bent or refracted
When light is passed through a biconvex lens, the rays are refracted towards a central point, known as the focal
point

Identify the cornea, aqueous humor, lens and vitreous humor as refractive media:
The density of the cornea, aqueous humor, lens and vitreous humor are close to that of water
They all refract light
The greatest amount of refraction occurs when light hits the cornea, as the density between the air before it and
the cornea are of extreme differences

Identify accommodation as the focusing on objects at different distances, describe its achievement through the
curvature of the lens and explain its importance:
This is the ability of the eye to focus on objects of varying distances
The grater the distance, the smaller the curvature of the lens. This is done by:
. The cilliary muscles relax, and pull back
. As this happens they tighten the suspensory ligaments
. This stretches and elongates the lens, allowing for a slighter curve
The closer the distance the greater the curve of the lens must be to allow for quicker diffraction. This is done by:
. The cilliary muscles contract and stretch out
. This causes the suspensory ligaments to slacken
. The lens becomes more rounded allowing for greater curve of the lens

Compare the change in the refractive power of the lens from the rest to maximum accommodation:
The thinner the lens, or less curvature, that is when at rest, the less refractive power
When at maximum accommodation, the refractive power of the lens increases
Therefore, the refractive power of the lens from rest to maximum accommodation is of a greater refractive power

Distinguish between myopia and hyperopia and outline how technologies can be used to correct these conditions:
Myopia is the eyes inability to focus on distant objects, as the focal length is to short meaning the image falls short
of the retina
Myopia is caused by: Eyeball too elongated in shape, refractive power of the cornea is inadequate or the lens may
not become flat enough
Hyperopia is the eyes inability to focus on short distances, as the focal length is too long and the image does not
converge quick enough for the retina
Hyperopia is caused by: Eyeball to rounded or short, lens is to flat and cannot change enough
Both hyperopia and myopia are easily corrected through the use of spectacles, and in more recent time’s contact
lenses. As well as this there are now permanent corrections through the use of laser eye surgery
Spectacles for myopia are concave, and hyperopia are convex

Explain how the production of two different images of a view can result in depth perception:
This is the ability to accurately judge the distance of an object
Human eyes are spaced apart, they therefore take in the same image at two slightly different angles
The two images are directed to the brain where they are put together and any missing information is filled in.
Allowing you to see the image in 3D
This is called binocular or stereoscopic vision
Students:

Plan and choose equipment or resources and perform a first-hand investigation to model the process of
accommodation by passing rays of light through convex lenses of different focal lengths:
Aim: To model accommodation by passing rays of light through convex lenses of different densities, to observe the
focal length
Ray box, multiple slit slides, biconvex lenses of different densities and power pack
Placing the first convex lens 6 cm from the ray box, and measured the focal length of the light that passes through
the lens. Then did so for the second lens
Results showed that the greater the density of an object, and the greater the curvature, the greater the refractive
power and therefore shorter focal length

Analyse information from secondary sources to describe changes in the shape of the eye’s lens when focusing on
near and far objects:
Far objects: Lens elongates (becomes longer and thinner) The ciliary muscles relax, causing the suspensory
ligaments to tighten. Refractive power decreases
Near objects: Lens becomes thicker and curvature increases. The ciliary muscles contract, causing the suspensory
ligaments to shorten and slacken. Refractive power increases

Process and analyse information from secondary sources to describe cataracts and the technology that can be used
to prevent blindness from cataracts and discuss the implications of this technology for society:
Cloudy opaque film build up over the lens of the eye
Decreases visual clarity, reduces light availability to the eye
Opaque covering can eventually lead to blindness, even with capable photoreceptors
Cure: Surgical removal of the lens by making an incision on the eye ball. This lens is then replaced with a plastic
intraocular lens (IOL)
This has major implications on society, as half of the worlds blind population is bind due to cataracts. Many of
whom are from third world countries
4. The light signal reaching the retina is transformed into an electrical impulse
Students learn to:

Identify photoreceptors as those containing light sensitive pigments and explain that these cells convert light images
into electrochemical signals that the brain can interpret:
Light comes into the retin,
and moves to the back of the
retina
Detected by the rod and cone
cells in the photoreceptor cell
layer
Light moves through as
electrochemical energy
Crosses the synapse into the
bipolar cell layer (BP)
Moves through the BP an
across the synapse into the
ganglion cell layer
Moves from the ganglion cell
layer into the fibres of the
optic nerve and into the brain

Describe the differences in distribution, structure and function of the photoreceptor cells in the human eye:
Photoreceptor
Structure
Distribution
Number
Function (pigment)
Cone
Cone shaped,
Distributed in groups 6 to 7
Work better in bright light
broader than rods throughout the
million
cones distinguish colour
Contain idopsins
retina, concentrated
cones
One cone for blue, one for
in macula. There are
green, one for red.
fewer around the
The idopsin for each colour
periphery
is different
Rod
Rods are long and Evenly distributed
125 million Work better in dim light
narrow
across the retina.
rods
Higher sensitivity than cones
Contain
Absent from the
Rhodospin
fovea

Outline the role of rhodopsin in rods:
Rhodopsin is made up of two parts, a retinal molecule that is derived from vitamin A and a protein called opsin
Light strikes the rhodopsin pigment, and it changes from a resting state to an excited state. This is due to the
activation of the retinal
When the retinal becomes activated, the rhodopsin splits into an opsin part and a free retinal part. Rhodopsin is
said to be bleached
The activated pigment causes a change in electrical charges of the membrane of the cone
This starts an electrical impulse triggering the release of neurotransmitter
The neurotransmitter then stimulates the bipolar cell, triggering an impulse (electrochemical signal)
The bipolar cell transmits the electrochemical signal to the ganglion cells which in turn carry it to the brain
Rhodopsin is then regenerated to be used again

Identify that there are three types of cones, each containing a separate pigment sensitive to either blue, red or green
light:
Cones allow us to see in colours. This is due to the cone cells containing one of three different pigments
This makes each more sensitive to light in one of three wavelengths:
1. Short wavelengths of ‘blue light’ 455nm
2. Medium wavelengths of ‘green light’ 530nm
3. Long wavelengths of ‘red light’ 625 nm
The sensitivity of cones also allows it to detect light to some extent of either side of their peak sensitivities. This
allows for an overlap in some colours, and therefore allows for the cones to detect a range of colours from the
spectrum

Explain that colour blindness in humans results from the lack of one or more of the colour-sensitive pigments in the
cones:
The cones have three different types of pigment, to detect different colours
If a particular pigment is missing then the cones are unable to detect that colour
Subsequently the person is said to be ‘colour blind’ therefore human colour blindness is caused by the absence of
one or more pigments
Students:

Process and analyse information from secondary sources to compare and describe the nature and functioning of
photoreceptor cells in mammals, insects and in one other animal:
Planarians (free-living aquatic flatworms): Have a basic cup-shaped structure lined with pigment cells
This pigment cup may contain fluid, being the only refractive part of the eye
Each eye has fewer photoreceptors resulting in very poor visual acuity. The simple image that forms is unclear and
not inverted. The role is therefore to detects light in the environment and where it comes from
Insects: Have more compelxe structures called compound eyes
They detect light, movement and colour
Made up of 8000 units called Ommatidia, which sees only part of an object
When put together a mosaic type picture is formed. Ommatidia are larger than rods and cones and as a result
there are fewer. This results in a blurred image by human standards
However the time taken for one ommatidium to receive a light stimulus, generate and impulse and then
regenerate is far quicker than the mammalian eye. This results in a far more efficient flicker vision. This makes the
insect far more efficient at detecting movement

Process and analyse information from secondary sources to describe and analyse the use of colour for
communication in animals and relate this to the occurrence of colour vision in animals:
Colour can be used as an essential form of communication in breeding. E.g. The male satin bowerbird (Aus) builds a
bower of grass twigs and decorates it with brightly coloured objects. This attracts the female, he then performs a
dance. If the female suitably impressed, they copulate and the female then flies off to build a nest and lay eggs
Visual displays can also be used as warning mechanisms, the peacock displays its colourful feathers when they are
threatened
-
Food recognition, colouration of flowers is linked to attracting pollination by birds and bees. They are also visited at
night, suggesting flowers may have ultraviolet markings on them, attracting birds and bees
Colour is the most important form of communication with birds. Birds are therefore capable of seeing both well
into the ultraviolet range and the normal, red, green and blue ranges.
Bees however rely on UV, and are sensitive to UV, green and blue
5. Sound is also a very important communication medium for humans and other animals
Students learn to:

Explain why sound is a useful and versatile form of communication:
Sound bends around objects, and travels around corners. It moves through all substances, solids, liquids and gases
An animals reliance on sound is therefore always supported by its environment
Animals to don’t have to be in visual or direct contact to communicate, like other senses. When the other senses
are impaired or absent, sound can be used as the primary from of communication
Sounds may be varying pitch, loudness and tone. A complete message can be conveyed in a short space of time.
Sound will travel long distances

Explain that sound is produced by vibrating objects and that the frequency of the sound is the same as the frequency
of the vibration of the source of the sound:
Sound is produced by a vibrating object that forms a compression wave in a medium
The frequency of the sound produced is the same as the frequency of the vibration of the source of the sound

Outline the structure of the human larynx and the associated structures that assists the production of sound:
Larynx is a hollow box, housing the vocal cords. It consists of a framework of nine cartilages, joined by membranes
and ligaments. These form a box, the voice box, in which sound can be produced and resonate.
Sound is produced by: The lunges produce air; this air must be strong enough to push open the vocal cords. This
achieved by the relaxing of the diaphragm to form a dome shape, and the internal intercostals muscles so that the
pressure inside the chest cavity is higher than the outside of the body. This means air is forced out in attempt to
equalise the air pressure.
Students:

Plan and perform a first-hand investigation to gather data and identify the relationship between wavelength,
frequency and pitch of a sound:
Used an audio generator and a CRO
Selected a frequency of 20Hz and recorded the sound waves. Then did so at 200Hz and
Results showed that as frequency is increased, there is an increase in pitch, and a decrease in wave lengths

Gather and process information from secondary sources to outline and compare some of the structures used by
animals other than humans to produce sound:
Grass hopers produce sound by rubbing one part of their body along another. The scrape a row of pegs on their
back legs, along the hard edges of their front legs
-
Catfish, when alarmed or travelling in a shoal, vibrate a bone against their swim bladder producing a noise similar
to a giant aerator
-
Birds produce sound through syrinx. Elastic membranes of connective tissue inside the syrinx open and close as the
bird exhales. The pressure of their air entering the syrinx, the size of the syrinx, and elasticity of the folds
determine how the sound is produced
6. Animals that produce vibrations also have organs to detect vibrations
Students learn to:
 Outline and compare the detection of vibrations by insects, fish and mammals
Feature
Fish
Mammal
Name of structure that
Lateral line
Ear
detects vibrations
Type of vibration detected
Pressure waves
soundwaves
Insect
Tympanum
Soundwaves
How it works
Mechanoreceptors with hair
cells in capula, detect
changes in water pressure
This causes and impulse to
the brain
Outer, middle and inner ear.
Tympanic membrane between
the outer ad middle ears
converts the soundwave into
mechanical vibrations. Inner
ear has the cochlea which has
hair cells which generate an
impulse. The impulse is sent to
the brain
Tympanum is an internal air
chamber enclosed by
tympanic membrane
Soundwaves cause the
tympanic membrane to
vibrate and attached nerve
fibres are generated and
travel to the brain
Similarity
Receptors detect vibrations.
Nerve fibres send the info to
the brain
Lateral line provides fish
with info about changes in
the direction and speed of
water
Receptors detect vibrations.
Nerve fibres send the info to
the brain
Ear provides info about
changes in direction and pitch.
Has cochlea and opens to
outside
Receptors detect vibrations.
Nerve fibres send the info to
the brain
Tympanum provides
information about changes
in direction of sounds and
detects certain pitch. No
cochlea. Has tympanic
membrane
Difference

Describe the anatomy and function of the human ear, including:
Part of ear
Anatomy
Pinna
Forms outer ear
Composed of cartilage
Tympanic membrane
Taut membrane consisting of three
layers, outer layer continuous with
outer layer of auditory canal
Ear ossicles:
-Hammer
-Anvil
-Stirrup
Bones
Hammer lies towards the side of
the head
Anvil is attached to the hammer
and the long process is attached to
the stirrup
The footplate of the stirrup rests
on the oval window
Membrane between the middle
ear and inner ear.
Oval window
Round window
Membrane located in the round
window niche at the base end of
the lower canal of the cochlea
Function
Helps collect and localise sound
waves
Produces ear wax, to prevent dirt
entering the ear and making it
water repellent
Transmits sound through
vibrations in the membrane, the
pars tensa provides the active
vibrating area in response to
sound
The hammer vibrates with the
tympanic membrane passing the
vibrations to the anvil
Anvil gives the sound a small boost
of 2.5dB
Stirrup gives the sound a boost of
20dB
Holds the fluid of the cochlea. As
the footplates of the stirrup
vibrates the oval window vibrates,
sending waves through the
perilymph
The round window allows the
release of the hydraulic pressure
of the perilymph that is caused by
the vibration of the stirrup on the
oval window
Cochlea
Snail shaped structure containing
three canals filled with fluid
The lowest canal contains
perilymph as well as the upper
canal
The middle canal contains
endolymph
Middle canal holds the organ of
corti
Organ of corti
Contains inner and outer hair cells
Inner hair cells have a nerve fibre
attached
A collection of nerve cells-nerve
tissue. It leads from the cochlea to
the brain
Auditory nerve
-
Vibration wave patterns from the
stirrups footplates set up a
vibration in the membranes and a
travelling wave pattern in the
perilymph and endolymph of the
cochlea.
This is transmitting the vibration
along
Middle canal holds the organ of
corti
The hair cells convert the
vibrations into electrochemical
energy.
The transmission of neural energy
from the cochlea to the brain
The ear is responsible for: Sound transmission, balance and pressure

Outline the role of the Eustachian tube:
The Eustachian tube helps to equalise the pressure on either side of the tympanic membrane by bringing in air
from the mouth

Outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations
that occur:
External ear:
- Auditory canal; sound is transmitted as a wave to the tympanic
membrane
Middle ear:
- Outer layer of tympanic membrane; Vibrations from the tympanic membrane are
conveyed through this chamber via the movement of the interconnecting ear ossicles
Inner ear:
- Stapes;
vibrate the oval window setting up a pressure wave in the perilypmh of the upper canal
- Reissener's membrane the moves transferring energy to the endolymph of the middle canal
- This vibrates the basilar membrane stimulating the hair cells of the organ of corti
- The hair cells send messages along nerve fibres to the brain where they are interpreted
- The pressure waves contine to the round window at the end of the lowest canal

Describe the relationship between the distribution of hair cells in the organ of Corti and the detection of sounds of
different frequencies:
There are thin fibres of various lengths in the basilar membrane of the organ of corti. Each of these vibrate at
different frequencies
When the cochlea vibrates at a frequency, the vibration is detected by the fibre of the corresponding length
Hair cells run along the length of the basilar membrane and the hair cells associated with the stimulated fibres are
then bent
Thus different frequencies of sound will activate the basilar membrane at different locations and this will, in turn,
activate different sets of hair cells
Hair cells are arranged along the basilar membrane from those stimulated by low frequencies at the apex to those
stimulated by high frequencies at the base

Outline the role of the sound shadow cast by the head in the location of sound:
When sound waves are coming from directly in front or behind or above the head, both ears receive the sound
equally and the sound will be the same for both ears.
When sound is coming from one side the receptors in the ear closest to the sound will be stimulated slightly earlier
and also more intensely
The brain locates the sound as coming from one side of the head
The head is said to cast a Sonic shadow or sound shadow on the sound coming into an ear from the opposite side
of the body
Students:
 Gather and process and analyse information from secondary sources on the structure of a mammalian ear to relate
structures to functions:
Refer to: Describe the anatomy and function of the human ear, including.....


Process information from secondary sources to outline the range of frequencies detected by humans as sound and
compare this range with two other mammals, discussing possible reasons for the differences identified:
The range of sound detected by humans is from 20 to 20000Hz (0.02 KHz to 20KHz)
The human ear is most sensitive to frequencies of 2000 to 4000 Hz which corresponds with speech
-
The frequency range for dolphins is less than 1Khz to greater than 100KHz
Lower frequency sounds travel further in aquatic mediums
Because they surface they need to be capable of detecting higher frequency sounds
They require a greater range of frequencies as they have a greater reliance on sound, as opposed to other senses
such as visual which is limited in their environment. They also use these higher frequencies to detect there
locations, know as echolocation
-
The Kangaroo rat is a nocturnal animal. The frequency ranges from 0.03KHz to about 50KHz
Need for a greater sensitivity to sound due to visual constriction
Their predators produce low frequency sounds, by detecting these sounds they can be aware of predators around
them
Process information from secondary sources to evaluate a hearing aid and a cochlea implant in terms of:
Position and type of energy
transfer occurring
Hearing aid
-Battery operated hearing device,
that amplifies vibrations so that
they can physically stimulate the
nerves of the cochlea
Uses the normal auditory pathway,
and consists of microphone,
amplifier and earphone
-Positioned inside the curve of the
Cochlea implant
-Battery operated hearing device,
that electrically stimulates the
nerves of the cochlea by bypassing the normal auditory
pathway
Consists of implanted receiver
package, electrode array, speech
processer and the headset
pinna and ear canal
-Sound waves are picked up and
magnified by the amp, this is
channelled to the auditory canal
by the earphone, then follows the
normal auditory pathway
Conditions under which the
technology will assist hearing
Limitations of each technology
For people with a ruptured
tympanic membrane or damaged
ossicles
For people with adequate residual
hearing
Able to detect fewer sounds than
cochlear implant
-receiver package and electron
array are implanted in the ear, and
headset and speech processer are
worn externally
-Sound waves are picked up by the
mic, and converted into electrical
code by the speech processor,
code is sent by cable to head set,
transmitted to the implant, which
transforms the signal into
electrical impulses which stimulate
the cochlear nerves
For profoundly or totally deaf
people who receiver no benefits
from a conventional hearing aid
Damaged hair cells in cochlea
Requires surgery
Post-op side effects
Expensive and ongoing costs
7.Signals from the eye and ear are transmitted as electro-chemical changes in the membranes of the optic and auditory
nerves
Students learn to:

Identify that a nerve is a bundle of neuronal fibres:
A nerve is a bundle of neuronal fibres

Identify neurones as nerve cells that are the transmitters of signals by electro-chemical changes in their membranes:
Nerve impulses are electrical in nature and chemical as it passes across the synapse
Nerve impulses transmit a signal due to the exploitation of a property all cells have, an electrochemical potential
across their membranes
This is a difference in electrochemical charge across the cell membrane
This difference is due to the concentration of ions (charged particles). That is high concentration of Na+ (sodium) in
the extracellular fluid (outside the cell) and low concentration in the cytoplasm (inside)
The potential is maintained by a Na+-K+ pump, a specialised protein in the membrane. This actively transports Na+
outwards, and keeps K+ inside, held by negatively charged biological molecules
-
Therefore at resting potential there is a higher concentration of sodium ions (Na+) outside the axon membrane
than inside it. This due to the membrane being impermeable to Na+ due to sodium ion channels being shut
There is a higher number of K+ inside than outside, although a small do move out
Therefore, the inside is more negatively charged than the outside, which is more positively charged
-
A nerve impulse then reaches the resting nerve fibre, caused by a neurotransmitter
This stimulates the membrane to become permeable to sodium ions
Small number of Na+ rushes in, and the resting potential is reversed
That is the inside is now positive and the outside is negative, this is an action potential
The nerve impulse is passed along the membrane, as it only occurs at the nodes of ranvier. The nerve impulse
jumps from one node to the next (except at unmyelinated fibres here it is slower)
-
One node of renvier notifies the next by:
Some of the diffused Na+ diffuses down the cytoplasm inside the membrane and myelin sheath to the next node
This Na+ causes the membrane to become permeable to Na+, initiating an action potential
As the nerve impulse passes, the resting potential is quickly restored by the Na+-K+ pump actively transporting Na+
outwards and K+ inwards
-
Whilst the nerve impulse is electrical down the axon it is chemical across the synapse. This happens by:
-
When the nerve impulse reaches the axon branches and synaptic knobs, this causes the release of
neurotransmitter molecules from small vesicles in which they are stored
Neurotransmitters are chemicals stored in vesicles in axon branches, that can transmit a signal across the synapse,
for example adrenalin (epinephrine)
Once the neurotransmitter is released from the vesicle into the synapse, it travels across the synapse to the
membrane dendrites of the next neuron. There is stimulates the membrane to become permeable to sodium (by
opening the sodium ion channels) thus initiating a nerve impulse in the next neuron
Once the neurotransmitter has acted, it is degraded by an enzyme into its component molecules and returned to
the axon branch to be resynthesised and stored
-
-

Define the term ‘threshold’ and explain why not all stimuli generate an action potential:
Threshold is the amount of positive change in membrane potential which is required before an action potential is
produced
The depolarisation must reach a threshold which is at least 15mV more positive then the resting potential of -70mV
No action potential is produced if the depolarisation is below this level
This is one reason as to why not all stimuli generate an action potential

Identify those areas of the cerebrum involved in the perception and interpretation of light and sound:
Cerebrum
Sound

Visual (light)
Explain, using specific examples, the importance of correct interpretation of sensory signals by the brain for the
coordination of animal behaviour:
If sensory signals are not received or properly interpreted, the bodies responses to the stimulus in the environment
can become impaired
For example:
MS; this is when the immune systems destroys the myelin sheaths. Resulting in a short circuit in nerve impulses.
This then causes muscle control problems and visual disturbances.
Alcohol; Impairs the transmission of messages. By blocking nerve impulses by reducing the plasma membranes
permeability to sodium ions, if there is no sodium entry, there is no action potential. This results poor coordination,
lack of concentration, retarded reflexes and blurred vision
Students:

Performa a firsthand investigation using stained prepared slide and/or electron micrographs to gather information
about the structure of neurones and nerves:

Perform a firsthand investigation to examine an appropriate mammalian brain or model of a human brain to gather
information to distinguish the cerebrum, cerebellum and medulla oblongata and locate regions involved in speech,
sight and sound perception:
Cerebrum
Auditory
Medulla oblongata
Cerebellum
Visual
Speech

Present information from secondary source to graphically represent a typical action potential:
Option- Communication
1.2.1
Receptors are used to detect changes in the ambient environment, and concert them into nervous impulses so the brain is able
to detect them.
1.2.2
The response to a stimulus involves firstly there being a stimulus, which is a change in the ambient environment, which the
receptor detects. This is then transported to the central nervous system through the peripheral nervous system. Once the CNS
has received the message and decided how to counteract the change, it then sends this response back through the PNS to the
effecter glands and muscles, which perform this response.
1.3.1
Mechanoreceptors: detect sound waves and pressure on skin
Thermoreceptors: Temperature
Photoreceptors: light, colour and movement
Chemoreceptors: detect dissolved molecules (taste) and molecules in air (touch)
2.2.1
The purpose of the eye is to allow the entry of light, organize rays into a clear image, convert light signals into electrochemical
impulses and prevent leakage of light within the eye. To do this, there are several components:
-
Conjunctiva: The protective layer on the outside of the eye
Cornea: the outer eye which is the first change in density
Sclera: Is posterior on the outside of the eye (the white part) which is tough and elastic, maintaining the shape.
Choroid: Contains most blood vessels. Is black at the back, restricting light leakage
Retina: The retina is the point that the light hits which is the image that is interpreted to the brain. Contains
photoreceptors.
Iris: The Iris is a protective boundary which expands or contracts in to restrict the amount of light that enters the eye
Lens: is the accommodative component of the eye which changes in curvature through a refractive medium
Aqueous and vitreous humour: Are refractive mediums which maintain the shape of the eye
Ciliary body: involves muscles and ligaments which contract or loosen in order to change the curvature of the lens
Optic nerve: is the nerve which transmits the message received by the retina to the brain
2.2.2
Humans are trichromatic organisms, that is, they are able to detect light from the red, green and blue ranges of the spectrum.
This is due to the wavelengths of light which they are able to see, ranging from roughly 380- 780. In comparison, other
organisms are able to detect light in different ranges of the spectrum. Some invertebrates such as bees are able to detect light in
the ultraviolet range of the spectrum, although they are not capable of detecting light in the red range of the spectrum, while
vertebrates such as wombats are able to detect light from the infrared range of the spectrum, without being able to detect
ultraviolet wavelengths. Some organisms are only able to detect a dichromatic range of colours, while others are able to detect a
tetrachromatic range of colours.
2.3.1
We got a sheep’s eye, a scalpel, scissors, gloves and tweezers. We then cut away the fatty tissue and cut roughly along the
equator of the eye, to avoid the lens. We then cut the lens out and observed that, the optic nerve, aqueous humour and several
other features such as the retina.
2.3.2
The reason behind differences of electromagnetic radiation which is detected among various organisms is evolutionary. Due to
the variation and adaptation, organism’s behaviours require them to detect different ranges of light which cater to their needs.
Natural selection states that over time, they will adapt to enable them to detect light in the required range of the spectrum.
3.2.1
There must be a change in density, speed and the surface must be transparent.
3.2.2
The refractive medium in the eye is the cornea, aqueous humour, lens and the vitreous humour.
3.2.3
Accommodation is the eyes ability to detect light at different distances. For far objects, the ciliary muscles loosen, causing the
ligaments to contract, and hence, pull the lens taut so the thin curvature enables decreased refraction. For close objects, the
muscles contract which causes the ligaments to loosen so that the curvature of the lens increases to increase the amount of
refraction.
3.2.4
A lens at rest refracts the light inwards, although, in comparison to a lens at maximum accommodation, the light is refracted
inwards at a much steeper angle.
3.2.5
Myopia is the inability to focus on distant objects as the lens suffers from an inability to flatten out; therefore the light rays
focuses in front the retina. It is corrected with a concave lens in the form of contacts or glasses which refract the light outwards
slightly before it reaches the eye so the light has to converge from a wider point
Hyperopia is the inability to focus on close objects as the lens is incapable of compressing, therefore, the light rays focus behind
the retina. It is corrected with a convex lens in the form of glasses or contacts so that it refracts the light inwards slightly, giving
it more time to converge upon reaching the eye.
3.2.6
Two different images of a view enable an object to be detected from different angles. In doing this, the eye is able to see the
object in 3 dimensions as the images are put together as one, filling in any missing information. This is called binocular vision.
3.3.1
We gathered a ray box, and a multi light slide and two biconvex lenses of different curvatures. We then turned on the ray box
and measured 10cm back from it, where we positioned one of the lenses on top of a piece of paper. By tracing the lens and the
rays until the point of convergence, and then doing the same, keeping all variables consistent, we were able to compare the two
results. The results were obtained by measuring the focal length.
Accuracy: used ruler and traced the beams
Validity: kept all variables constant, except for the curvature of the lens
Reliable: repeat
3.3.3
Cataracts are a disease which affects the protein in the lens, causing it to become opaque. This results in blurred vision. To fix
this, an operation known as phacomulsification is used, this involves the insertion of a rod which vibrates and breaks the lens.
The lens is then sucked out and replaced with a plastic lens that is completely transparent and functional. This technology
provides a safe and fairly easy way of allowing the elderly members of society a chance to see clearly, while maintaining a
normal lifestyle.
4.2.1
Photoreceptor cells are found in the retina which contains light sensitive pigments. These receptor cells detect light at the cones
and rods which simulates an electrical charge that travels throughout elongated cells in the photoreceptor cells. As this electrical
charge travels through the cones and rods to the foot, a chemical that exists in the synapse allows this charge to transfer over it
and on to the bipolar cell layer where it continually travels through the ganglion cell layer and the optic nerve fibres to reach the
brain.
4.2.2
STRUCTURE
DISRIBUTION
-
CONES
Shorter and conical shaped
Contains outer, inner and conducting
segments
Contains cell body and foot
Visual pigment is iodopsin
Fewer around he peripheral of the
-
RODS
Long and narrow shaped
Contains outer, inner and conducting
segments
Contains cell body and foot
Visual pigment is rhodopsin
Evenly distributed along retina
-
-
retina
Most concentrated in the macula
Roughly 6-10 million
-
Detects bright light
Detects colour
-
FUNCTION
-
Detects movement
Many rods per bipolar layer
Are very sensitive, responding to low
intensity
Detects black and white
Roughly 125 million
Detects movement
Are very sensitive, responding to low
intensity
Detects black and white
4.2.3
Rhodopsin exist in a deactivated or an activated form. They are used to detect black and white shades of light which simulates
the change in electrical charge. From here, electrical charges are continuous, carried over the synapse by the neurotransmitter.
The rhodopsin joins back together to detect a new light source.
4.2.4
There are different types of iodopsin, each are sensitive to different ranges of light. In the human eye, there are three different
types of iodopsin which are pigment sensitive to blue, red or green light. Rhodopsin and iodopsin contain a retinal molecule and
a protein called opsin. The types of opsin distinguish between what each is sensitive to.
4.2.5
As there are various types of opsin which are sensitive to different ranges along the spectrum, the absence of one of these
would result in the inability to detect a colour. Red green colour blindness is the absence of red and green sensitive opsin, or
poorly working opsin.
4.3.1
Eyes vary in structure and function over a variety of animals from complex to simple.
Simple Light Receptors: organisms such as planarians involve a cup shape of pigment cells that contain a refractive fluid. As it is
so simple, the purpose of there eyes are to detect light sources rather than clear images.
Compound eyes: Insects have a collection of roughly 8000 detection units called ommatadia. Each ommatadia detects a sector
of vision, which, when combined, produces a mosaic type of picture which is blurred. The purpose of this is to detect light,
movement and colour, while being more beneficial over humans in the sense that they have a broader range of vision.
4.3.2
Animals of varying species use colours as a form of communication. The purpose of certain animals to detect certain colours is to
allow them to detect certain signals.
Humans use colours as a form of signaling in every day life. They are used in mapping, for survival such as different
colours in war and as a form of display such as looking pale shows illness.
Other animals use light for many reasons such as:
-
To distinguish between species, sex type, maturity and readiness
As a warning mechanism (e.g. peacocks exposing their feathers)
Food recognition (bees attracted to ultraviolet markings
5.2.1
Sound can travel around bends and through all mediums, allowing it to be very versatile. It is used for communication, but also
for functioning. When visual, tactile and olfactory senses are impaired or insufficient in a particular environment, sound can be
used and detected. Whales emit sound and listen for the echo to detect distances of objects which is known as echolation.
5.2.2
Sound originates from something which vibrates rapidly enough to organize the movement of molecules into compression
waves. It must travel through particles that can be compressed, where it moves back and forwards in the same direction as the
flow of energy. Frequency is determined by cycles per second, called a hertz, and distinguishes between pitches. Wavelength is
the distance between two adjacent compressions which coincides with frequency (low frequency has short wavelengths).
Amplitude is the displacement of a particle and determines the volume.
BASICALLY: sound is produced by a vibrating object that forms a compression wave in a medium. The frequency of the sound
produced is the same as the frequency of the vibration of the source of sound.
5.2.3
The larynx consists of nine cartilages joined by membranes and ligaments which form a hollow box where sound can be
produced and resonates.
5.3.1
We used a Cathode Ray Oscilloscope (CRO), an audio generator and a power pack. We powered up the audio generator and
CRO, then selected a sine wave output of 20Hz, and identified there being 4 crests. We drew the diagram and changed it to
200Hz, then 2000Hz, where the amounts of crests increased each time. From this we concluded, the higher the frequency, the
higher the pitch, the shorter the wavelength.
5.3.2
ANIMAL
GROUP
Insects
EXAMPLE
Grasshopper
Fish
Sea catfish
Birds
Storks
Mammals
Eastern Horse
Shoe Bat
6.2.1
FEATURE
Name of
structure
Type of
vibration
detected
How it works
Similarity
Differences
6.2.2
-
NAME OF
STRUCTURE
Tymbals
Wings
MAIN FEATURES- STRUCTURE AND FUNCTION
-
Underwater
microphones
Syrinx
Throat
Stridulation: rubs front of wing against rough
part of another wing
Ribbed membranes at the base of the
abdomen buckle and produce a pulse sound
Vibrate the bone against the swim bladder
Elastic membranes of connective tissue inside the
syrinx open and close as the bird exhales
Movement of the air in the trachea and nasal sacks.
FISH
Lateral line
MAMMAL
Ear
INSECT
Tympanum
Pressure waves
Sound waves
Sound waves
Mechanoreceptors with hair
cells detect changes in water
pressure causing an impulse to
the brain. Bony fish detect
vibrations through the skull to
the hairs in an inner ear
Have an outer, middle and
inner ear which collects and
directs the sound waves from
the air, converting it to
vibrations, and then
electrochemical energy which
sends nervous impulses to the
brain
The tympanum which is
enclosed by a tympanic
membrane (eardrum) receive
vibrations from sound waves
and send nerve impulses to
the brain via the nerve fibres.
Ear provides information
about changes in direction and
pitch of sounds.
Has an externally exposed
cochlea and tympanic
membrane
Tympanum provides
information about changes in
direction of sounds and
certain pitch.
Does not have a cochlea.
Has an externally exposed
tympanic membrane
Receptors detect vibrations
Nerve fibres send info to the
brain
Lateral line allows for
information on changes in
direction and speed of water
movement
Bony fish does not have a
cochlea and has an internal
ear
Pinna (cartilage): Is external and produces earwax for the purpose of directing and collecting sound waves.
-
-
Tympanic membrane (membranous): The earwax allows it to be moist for flexibility, and the thin, solid and flexible
structure allows it to transmit sound
Ear ossicles (bone): consists of the hammer, anvil and stirrup which allow sound to be transmitted and amplified
Oval Window (membrane): Is a covering between the middle and inner ear to transmit sound and hold fluid in the
cochlea.
Round window (membrane): Is at the base end of the lower canal of the cochlea to control pressure and transmit sound
Cochlea (membrane): Is snail shaped with three canals filled with fluid which allows for transmission, and the middle
canal contains the organ of corti.
Organ of Corti (membrane): The organ of corti converts mechanical energy (kinetic) into electrochemical energy. It does
this by its hair cells being stimulated to certain frequencies and sends the message through the nerve fiber that it is
attached to.
Auditory nerve (tissue): It is a collection of nerve cells that leads from the cochlea to the sense organ. It transmits
energy to the brain.
6.2.3
The role of the Eustachian tube is to equalize pressure on either side of the tympanic membrane by taking in air through the
mouth.
6.2.4
Auditory canal
SOUND TO KINETIC
External
ear
Tympanic membrane (vibrations)
Hammer (vibrations)
Anvil (vibrations)
Middle
ear
Stirrup (vibrations)
Oval window (vibrations)
Upper canal (vibrations)
Middle canal (vibrations)
Inner ear
Organ of corti converts MECHANICAL TO ELECTROCHEMICAL ENERGY
Lower canal (vibrations)
Round window
6.2.5
In the basilar membrane are hairs of different lengths which vibrate at a different frequency. The hairs are aligned in the basilar
membrane from those stimulated at high frequencies, to those stimulated at low frequencies (shortest to longest) from the base
to the apex. This determines the pitch, although the volume is detected by the amplitude of the sound wave, which influences
the amount of bending of the hair cells and the amount of nerve impulses generated in the neurons. There are 15500 receptor
cells, where 90% of the nerve fibres service the much less numerous inner hair cells.
6.2.6
The obstruction or absorption of a sound wave by an object is called a sonic or sound shadow. As humans are binaural (two ears)
the head placed between it creates a sound shadow for the ear on the opposing side to the source. Because of this, sound is
received less than a split second apart, creating the perception of source location. This is used by visually impaired people.
6.3.2
Humans can detect frequencies from 20Hz-20000Hz, being most sensitive between roughly 2000-4000Hz which corresponds
with the pitch of speech.
The kangaroo is nocturnal and therefore relies heavily on sound. It detects a higher range of frequencies, roughly
between 0.03kHz to about 50kHz, which is used to detect their predators who communicate at low frequencies.
Dolphins have an even broader range. This is attributed towards the lower frequencies in water and the higher
frequencies when surfacing, the decrease in visual capabilities and for echolocation.
These variations are derived from evolutionary adaptive requirements.
6.3.3
Description
Positioning
Conditions
Energy transfer
HEARING AID
Artificial hearing device
Battery operated
Single component (microphone,
amplifier, earphone)
Amplifies vibrations for natural
stimulation
Uses normal auditory pathway
Detects less sound than cochlear
implant
Sits inside the pinna and ear canal
Ruptured tympanic membrane or damaged
ossicles
Sound waves are picked up by the
microphone, magnified by the amplifier and
channeled into the regular auditory pathway
Limitations
Background noise is a problem
Distance is limited to less than 3 metres
Does not assist for inner ear problems
Implications
Allows for improved hearing
Is quit easy to input
Normal life can occur
COCHLEAR IMPLANT
Artificial hearing device
Battery operated
3 components (implant receiver,
speech processor, headset)
Electrically stimulates nerves
Bypasses normal auditory pathway
Detects more sound than hearing aid
Receiver package and electron array are
implanted in inner ear
Headset and speech processor are worn
externally
Damaged hair cells in the cochlea
For def people
Sound waves are detected by the microphone,
converted into electrical code and then is
transferred into electrical impulses which
stimulate the cochlea nerves. Electrochemical
messages are sent to the brain
Requires potentially dangerous surgery
Visible
Expensive with ongoing costs
Needs to be adjusted for different situations
Distance is limited
Can allow for speech
Allows individuals to participate in hearing
dependant events
Is quite obstructive
7.2.1
A nerve is a bundle of Neuronal fibres
7.2.2
Neurones are nerve cells that consist of dendrites that lead to a cell body, then an axon which are surrounded by myelin sheath
(not in interneurones) and branch out into axon branches. They are transmitters of signals by electro-chemical changes in their
membranes
7.2.3
Threshold is the amount of positive change in electrochemical potential change that must occur to cause an action potential.
Stimuli cause a change in electrical charge through the axon. The greater the stimuli that is detected, the greater the change in
electrical charge. Potassium ions exist inside the axon, with little amounts outside with sodium ions. Because of this, there is a
greater positive charge outside the axon, leaving the electrochemical potential charge inside the axon at -70mV. When a stimuli
is detected, active transport uses ATP to allow the membrane to become permeable to sodium ions at the node of Ranvier. This
process is called depolarization, where there is a reversal in membrane potential, resulting in action potential. In order for a
stimulus to generate action potential, it must reach a change in electrochemical potential of 15mV.
7.2.4
The components of the cerebrum that are involved in the perception and interpretation of light and sound are the medulla
oblongata, the cerebellum the occipital lobe which contains the visual section of the cerebrum, and the temporal lobe which
contains the auditory section of the cerebrum
7.2.5
The correct interpretation of sensory signals by the brain for the coordination of animal behaviour is important generally to
facilitate behavioural responses in survival. An example is the migration patterns that rely on detecting changes in the
environment and recalling mental pictures or maps in the brain. Another example is detecting a visual signal of a predator and
being able to remove itself from the danger.
7.3.1
We observed slides to identify the structure of a neurone. They have a collection of dendrites that lead to a cell body which then
attaches to a very thin, long axon. These axons are surrounded by myelin sheath, except for the interneurones, and branch out
into axon branches.
7.3.2
We used a scalpel and therefore had several safety requirements when dissecting a brain. We looked at the ventral surface and
identified the cerebellum and medulla oblongata. We then identified the region at the back on the occipital lobe as the area that
detects visual signals, the temporal lobe in the middle which detected auditory signals, and the area at the front and back which
causes speech.
7.3.3
We looked images which showed action potential, where sodium ions were represented with black dots, and potassium ions
were represented with white dots. Sodium entered at the node of Ranvier.