1. Humans, and other animals, are able to detect a range of stimuli from the external environment, some of which are useful for communication

§ identify the role of receptors in detecting stimuli

Role of receptor:

- Detect specific signal in the external and internal environment so a response can occur

- Vital in keeping the body functioning properly

- Example: without chemoreceptors in blood vessels that detect amounts of CO2, there would be no automatic exhale process of CO2 before it reaches toxics levels in the body.

Types of receptors:

Receptor Stimulus detected Location Mechanoreceptors - Pain

- Pressure - Gravity - Touch

- Skin - Ear

Photoreceptors - Light - Rods and cones on the retina in the eye

Chemoreceptors - Chemicals - Taste buds - Blood vessels - Hypothalamus

Thermoreceptors - Temperature - Skin - Hypothalamus

Electroreceptors - Electricity - Skin

§ Explain that the response to a stimulus involves: (Stimulus, receptor, messenger, effector and response)

Coordinating systems:

- Living organisms must establish communication mechanisms that enable a response to messages sent between them and a changing external environment

- Example: nervous and endocrine systems

- Features of coordinating systems:

- Begin with stimulus (light, sound or touch)

- Organs called receptors detect stimuli and message is sent to the spinal cord to the brain

- Central nervous system (CNS): messenger as it passes message to effector

- Effector (muscle) produces response

- Example: Looking at a bright light

- Light (stimulus) detected by cells in retina (receptor)

- Electrical message is sent via spinal cord to brain where too much light is received

- Brain sends message to muscles in eye (effector) to contract and make pupil smaller

- Response: amount of light coming into eye is reduced.

2. Visual communication involves the eye registering changes in the immediate environment

§ Describe the anatomy and function of the human eye, including the: (conjunctiva, cornea, sclera, choroid, retina, iris, lens, aqueous and vitreous humor, ciliary body, optic nerve) The human eye: - Structure allows light to enter and hit photosensitive cells - Cells change the light stimulus into an electrochemical signal that is interpreted and responded to by CNS Structure and function of the eye:

Name of tissue Structure Function Conjunctiva Transparent membrane that

covers sclera - Lubricates and nourishes eye - Infection of conjunctive causes

conjunctivitis Cornea Sensitive transparent dome-

shaped casement that covers the front of the eye

- Refracts light and allows it to be focused on the cells of retina

Sclera Tough outer coating of the eye made of fibrin connective tissue (white of the eye)

- Protects inner parts of eye - Helps keep shape

Choroid Layer of blood vessels in between the retina and sclera

- Provides nutrients to back of eye

Pupil Opening made by the iris - Allows light to pass through to retina

Retina • 0.5 mm thick lining the back of the eye.

• Composed of approx. 150 million light sensitive nerve cells (rods and cones)

• Rods: more numerous than cones and are highly sensitive to shades of black and white but not to colour.

• Cones: colour-receptive cells.

- Converts light stimuli into electromechanical message sent to brain for interpretation

Iris Colored part of the eye that opens and closes to determine how much light enters

- Controlled by iris, sphincter muscles that relax and contract depending on the light intensity in the environment

Lens Transparent biconvex disc behind iris

- Help focus light onto retina - Shape changes by ciliary

muscles that help focus light entering eye

Aqueous humor Transparent fluid with water consistency tat is found between the cornea and lens

- Keeps shape of eye - Provides nourishment to cells

in front of eye Vitreous humor Transparent gelatinous fluid that

is found between the lens and retina

- Provides support for the back of the eye so light transmission to retina is clear an free of obstruction

- Fluid is mostly water, contains some salts, glucose and white blood cells to help prevent infection in eye

Cillary body Produces aqueous humor - Contains ciliary muscles that control shape of lens

Optic nerve Group of nerve fibers the travel from retina to brain

- Transmit electrical message from retinal cells to brain for interpretation and response

How do you see? - Light reflecting from object within line of vision enters eye through pupil - Iris controls amount of light coming in through pupil - Cornea and lens focus light onto the retina, detected by light-sensitive receptors (image is inverted, due to

the way the light passes through the cornea and lens) - Receptors send electrochemical signal or message to brain where image is converted to right direction to

coordinate response

§ Identify the limited range of wavelengths of the electromagnetic spectrum detected by humans and compare this range with those of other vertebrates and invertebrates

The electromagnetic spectrum:

Electromagnetic spectrum (EM): describes different types of radiation

- Radiation travels in forms of waves (transverse waves)

- Waves are able to travel in a vacuum and carry energy

Waves carry energy:

- Energy of the different EM waves have various intensities

- Higher the energy, higher the frequency of wave

- Frequency: measured in Hertz, cycles or wavelengths per second

- Low energy waves: radio or television waves (frequency between 106 -109 Hertz) OR wavelength of 1-1000nm

- High energy waves: gamma and x-rays (frequency of 1017 -1019 Hertz) R wavelength of 1- 0.1nm

- The more energy a wave has, the more damaging it can be to human body

Light energy:

- Light waves form part of EMS in mid range of 1015 Hertz or 400-700 nanometers

- Known as ‘visible spectrum’

- Compromised of all colors of the rainbow from violet to red

- Sun and stars emit much of their radiation in this section

- Human eye is sensitive to this part of spectrum

- Frequencies above or below visible light cannot be detected by human eye

How do other vertebrates detect EM waves?

- Some animals can detect parts of EMS beside visible light

- Birds (e.g. Zebra Finches or Poephila guttata) can see Ultra Violet spectrum (UV)

- Plumage has patterns and characteristics that reflect UV light

- Plumage characteristics are used by females to puck a mate and to identify individuals

- Prefer males with low levels of UV pulmage reflectance to those with high levels

- Fish (e.g. Salmon or Oncohynchus kisutch and Gold fish Carassius auratus) detect polarized UV light

- Polarized UV light increases contrast of prey and predators in water, making them easier to catch or avoid

- May help salmon navigate during migration

- Australian pythons have heat sensitive pit that enables detection of infrared radiation making it easier to detect prey

How do invertebrates detect EM waves?

- Honey bees (Apis mellifera) detect UV radiation reflected by flower petals to guide them to the nectar of the plant.

- Australian buprestid fire beetle( Merimna atrata) detects fires using infrared sensors on abdomen. Once fire is detected, they lay their eggs underneath the freshly burnt wood. This lets the larvae munch away at a ready food supply and be cocooned by the dead wood.

3. The clarity of the signal transferred can affect interpretation of the intended visual communication

§ identify the conditions under which refraction of light occurs

Refraction:

Refraction: bending of light when light waves hit media of different density

- degree to which light bends is determined by refractive index (n) of medium

Refractive index:

- lower refractive index of a medium, the lower its density and the faster light moves trough it

- Higher refractive index slows down light and bends towards the ‘normal’ (90 degree line to the boundary of two mediums)

- Lower refractive index speeds up light and bend away from the ‘normal’

- Light waves are only refracted in a medium if they approach it at an angle

- if light approaches a boundary at 90 degrees it will continue traveling in a straight line.

Examples of medium’s refractive index:

- air: 1.003

- glass: 1.517

- water: 1.333

§ identify the cornea, aqueous humor, lens and vitreous humor as refractive media

- tissues in cornea, aqueous humor lens and vitreous humor have different densities, therefore different refractive indices.

- at the interface between each tissue, light refracts at a different angle if it approaches at an angle

Refractive indices of substances associated with the eye:

- Light refraction at greatest point where light meets the interface between the eye and the cornea as it enters eye. à Difference between refractive index of two mediums are great.

- Cornea is convex lens to assist in focusing light ray on retina.

-

Fluid Refractive index (n)

Vacuum 1.000

Air 1.003

Water 1.333

Cornea 1.377

Fluid Refractive index (n)

Aqueous humor 1.336

Lens 1.421

Vitreous humor 1.337

- refractive index (n) of air is 1.003 and cornea’s is greater at 1.377.

- as light hits air/cornea interface it will refract as it travels fro the less dense air to the denser cornea.

- convex lens of cornea allows light waves to move towards each other

- at cornea/lens interface, light will refract again to a lesser degree than that at the air/cornea interface.

- lens will converge light beams towards one another

- light waves are then focused on retina.

§ identify accommodation as the focusing on objects at different distances, describe its achievement through the change in curvature of the lens and explain its importance

- light wave travelling through eye changes direction many times to meet retinal cell directly

- objects can be on different planes and distances from your eye

- light waves from different objects hit your eyes at different angles

- objects at a distance reflect light waves almost parallel to cornea

- light will travel through the cornea and the lens, where the light will be directed onto the retina’s fovea

Fovea: focal point

- a clear image is then seen

- When an object is brought close to the eye, light rays will converge behind the retina and produce a blurry image.

How the eye correctly focuses images on the fovea of retina:

- Eye is able to change angle at which light waves are bent by altering the shape of the lens therefore its focal length

- cornea cannot change its shape

- lens of cornea can change shape using ciliary muscles and ligaments that connect it to the sclera

- process of focusing light with differing distances onto the retina is called accommodation.

- ciliary muscles are able to relax and contract --> change shape of lens through this

- refractive power of lens is determined by shape

- short thick lens will refract more than a long thin lens and shorten the focal length

- light rays near objects need more refraction and a shorter focal length to be focused on the retina than distant objects

- if object is brought close to eye, ciliary muscles contract, shortening and thickening the lens causing the light rays to be focused on the retina.

§ compare the change in the refractive power of the lens from rest to maximum accommodation

- refractive power of lens is measured in diopters

- a diopter is equal to the reciprocal of the focal length measured in meters

- focal length (distance) from cornea to retina of a normal relaxed eye is about 1.7cm (0.017m) or 59 a diopter lens

- focal length must change for image to be focused clearly on the fovea of the retina when objects are close.

- For example: if an object is 1m away from the eye, it must have a focal length of 1.67cm or a power of 60 diopter to be seen clearly.

- Power of accommodation: variation in the accommodation power of the eye from rest to its maximum accommodation value in viewing nearby objects.

- Normal health young adult has accommodation range from 59 diopters while at rest and 63 diopters when viewing an object 25cm away à total accommodation of 4 diopters

- with age, eye lens becomes more rigid and looses flexibility and therefore its ability to change shape

- by 70yrs old total accommodation power is approx. 1.5 diopters compared to a baby that starts with a total accommodation of approx. 15 diopters.

§ distinguish between myopia and hyperopia and outline how technologies can be used to correct these conditions.

- ability of eye to focus on far and nearby objects is compromised by problems associated with tissues within the eye

- bulging cornea or inflexible lens affect refraction of light and its focusing in fovea

- two most common vision defects are associated with accommodation power of the eye’

- myopia: short sightedness

- hyperopia: long sightedness

Myopia:

- difficulty focusing on objects that are in distance

- one-third of population affected (esp. young people)

- caused by cornea that is more curved than normal

- light coming from the distant object is refracted more than necessary and the image falls short of the fovea causing it to be blurred

- Also caused by longer eyeball, thus image will fall short of fovea

Hyperopia:

- difficulty focusing on objects nearby

- affects one in four people

- occurs when eyeball is too short, the cornea is too flat or the lens cannot become round enough

- closer the object to eye, the stronger the refractive power to be in focus

- refractive power is insufficient, thus image from nearby object is focused behind the retina producing a blurry image

- can occur in children when eyeball is shorter than normal

- Can be corrected as eyeball elongates with normal growth

Treatment:

- most common treatment is use of corrective artificial lenses (glasses or contact lenses)

- correct refraction of the light that enters the eye

- Myopic conditions: light is overly refracted so use concave lens to diverge light before it enters the eye

- cornea and lens then converge image correctly onto retina

- Hyperopia: light does not refract enough to focus on the retina so convex lens is used to converge light rays before they reach the cornea

Corrective surgery:

- reflective surgery LASIK (laser in situ Keratomileusis) can correct some vision defects such as myopia and hyperopia

- Involves use of instrument called keratome to gently lift flap of corneal tissue and then laser is used to reshape the cornea à alter the way light is refracted onto lens

- Cornea reshaped by using tissue from underneath to flatten it or by taking microscopic section from the top of the cornea

- laser of UV light source is used

- Hyperopia: heat from laser is used to shrink collagen around edges of cornea to make the curvature steeper

- Other treatments: implantable contact lenses where lens is attached by surgeon to iris or in front of normal lens

- Advantage: cannot be felt

- easily removed if complication occurs

- Plastic inserts are also being used around the edges of the cornea to flatten it

§ explain how the production of two different images of a view can result in depth perception Depth perception: ability to accurately judge distance of an object

- human eyes are spaced apart, thus take in the same image at different angles

- you can see this by closing one eye and the switching to the other --> different view

- two images are directed towards the brain where it puts together two images as one and fills in missing information

- as a result, we see 3D

- called binocular or stereoscopic vision

Cataracts:

- appears as cloudiness in the lens of the eye that stops light from reaching the retina

- lens is encased in a capsule made of water and protein

- when cells of lens die, the protein can accumulate in the capsule resulting in cloud covering the lens

- occur in older people as a process of ageing

- can also be caused by diseases (e.g. diabetes), use of drug containing steroids, smoking, excessive salt and alcohol and exposure to UV light.

Treatment for cataract blindness:

- treated with eye surgery

- small incision made on edge of cornea and small prove is inserted into the lens capsule

- probe emits an ultrasound and breaks up inner clouded lens

- parts a removed by suction leaving behind lens capsule

- after natural lens is removed, a clear bionic lens (intraocular lens) is inserted.

- bionic lens acts as natural lens and focus the light on the retina to produce a clear image. - Cataract blindness is the leading cause of blindness in the developing world.

- WHO estimates 18.5 million people are affected by cataract blindness.

4. The light signal reaching the retina is transformed into an electrical impulse

§ Identify photoreceptor cells as those containing light sensitive pigments and explain that these cells convert light images into electrochemical signals that the brain can interpret

- photoreceptors allow light to be transmitted to the brain and interpreted as an image

- Found on retina at back of eye

- retina is a nerve cell simulated by light

- two types of photoreceptors in human eye:

• Rods: - contain light sensitive pigments that absorb light coming from an object

- Light absorption excites cell and sends electrochemical signal to the brain

- Enable night and peripheral vision

• Cones: allow animals to perceive colors

§ Describe the differences in distribution, structure and function of the photoreceptor cells in the human eye

Where are photoreceptor cells found? - approx. 120-125 million rod cells in human retina

- uniformly spread across retina except on the peripheral section à higher density of rod cells

- cones are less numerous that rods (6-7million)

- Located mostly on fovea of the retina (fovea does not contain rods)

What to photoreceptor cells look like?

- Name of cell is related to shape of the end

- Each cell contains segments that are heavily folded

- Folds contain photosensitive chemicals that are responsible for activation of nerve cell.

How do the photoreceptor cells function?

- Function is to absorb light reflected from objects into the eye and change message into an electrochemical form that can be sent to the brain along the optic nerve

Rods:

- highly sensitive to light but are not used to see colors

- Used for night vision à responsive to various light intensities

- Not helpful in seeing detail or clarity of image

Cones:

- Responsible for color vision during fay

- Used for tasks requiring detail and clarity of image (reading)

o Outline the role of rhodopsin in rods Rhodopsin: photosensitive pigment that absorbs light waves in rods OR VISUAL PURPLE

- Made from two proteins: scotopsin (belongs to opsin group)

- Have one photosensitive pigment

- Scotopsin is 11-csi-retinal --> derived from Vitamin A or B-carotene.

- Rhodopsin is highly sensitive to light of wavelength around 440-500nm

- Allows to see shades of grey, white and black

- Rhodopsin cannot be made by humans alone

- Crucial to have good source of B-carotene (carrots) to allow rod cells and vision to be optimal

- Lack of vitamin A can result in night blindness

Light  hits  rhidopsin  casing  chemical  change  (decompostion  starts)    

   rhodopsing  changes  into  

metarhodopsin  II  or  active  rhodopsin  

changes  charge  of  rod  cell  creating  electric  

current  

More  light,  more  active  rhodopsin  cell  and  more  electric  current  runs  

along  cell  

electric  message  sent  along  rod  cell  to  

ganglion  (connected  to  optic  nerve)  

optic  nerve  sends  message  to  visual  cortext  of  brain    

light  is  interpreted  and  transmitted  

o Identify that there are three types of cones, each containing a separate pigment sensitive to either blue, red or green light

- Have one of three different pigments (red, blue and green)

- Contain photopsin protein

- When combined, three pigments allow to see a wide range of colors in visible spectrum

o Explain that colour blindness in humans results from the lack of one or more of the colour-sensitive

pigments in the cones Color blindness: inability to see color

- Causes by absence of one or more of the colour sensitive pigments in cone cells

- Most common form of color blindness is red-green (difficult to differentiate between red and green or similar colors)

- Genetic disease affecting more males (10%) than females (1%)

5. Sound is also a very important communication medium for humans and other animals

§ Explain why sound is a useful and versatile form of communication

- Sound is a form of energy caused by a vibration - Vibration is known as oscillation - As objects vibrate, it produces a series of disturbances in the particles surrounding it - Disturbances are caused by changes in pressure in the particles of gas, liquid or solid the vibration is

traveling in - Sound travels faster in solid than liquid or liquid than gas - Unlike light waves, sound cannot travel in a vacuum - Energy created in oscillation travels three dimensionally from source of vibration: compression wave - Compression wave is also called longitudinal wave - Energy moves (compressions) not the wave itself - Sound waves are detected by a sensor (ear drum) that allows sound waves to be heard

Sound travels as particles alternate between compression and rarefaction along the path of wave

§ 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’

Wavelength: - Sound wave is a cycle of alternating compressions and rarefactions - By measuring cycles (distance between wave) you measure the wavelength - Symbol for wavelength is λ - Measurement of wavelength can start at any point on the wave and end at the exact same point in the next

cycle

Frequency: Frequency: number of times it vibrates per second - One complete vibration: period - Unit to measure frequency à Hertz (1 Hertz = 1 vibration/second) - Sound that vibrates at a high frequency is high pitched - Sound that vibrates at low frequency is low pitched - Sound waves do not change frequency when transmitted - Frequency of oscillations produced by the source of sound is the same as the oscillations of the

transmitted sound wave Pitch: - The pitch of a sound is changed by wavelength of frequency For example: - If wave length is shortened, the frequency wave increases and pitch increases - Alternatively, if wavelength is increased, the frequency decreases and the pitch sounds lower

Compression:  particles  in  air  squeeze  

together  

Rarefaction:  compression  expands  as  the  particles  move  further  apart    

Amplitude: - Amplitude (loudness): measured in decibels (dB) - Further the peak of the waves moves from the midpoint, the louder it is

§ Outline the structure of the human larynx and the associated structures that assist the production of sound

Sound is useful because:

Easily  produced  • sound  can  be  made  by  vibrating  an  object  

Has  a  wide  range    • Sound  can  be  produced  at  low  levels  or  high  levels  depending  on  which  animal  is  detecting  and  prducing  it    

Can  be  manipulated  easily  • animals  can  change  pitch  or  amplitutde  of  sound  to  communicte  different  messages  

Travels  easily  through  a  medium  • Sound  can  travel  at  night  and  during  the  day  and  around  objects.    • the  object  dosent  have  to  be  seen  to  hear  it  (useful  in  hunting  prey)  • can  travel  long  distances    

Easily  detected  by  a  structure  that  can  sense  vibrations    

Producing sound: - Muscles change the shape of vocal folds (vocal cords), thus air passing through is emitted with

different sounds - Vocal folds located in the larynx (voice box or Adam’s apple) - Larynx is located at top of trachea - (No Man Pops Like Tom) - Vocal tract stretches from vocal folds to lips including the pharynx, tongue, teeth and soft and hard

palate. - All structures in vocal tract are responsible for producing different sounds humans make

The Larynx - Larynx is a tubular organ made of cartilage à allows to surround and protect vocal folds - Held in place by ligaments and muscle - When pulled tight, vocal folds vibrate at high frequency/ less tension, low frequency - In high pitch à vocal fold open and close more frequently

6. Animals that produce vibrations also have organs to detect vibrations

§ Outline and compare the detection of vibrations by insects, fish and mammals

Detecting sound: - As long as an organism has a receptor to detect vibrations, it can ‘hear’

Comparison of sound detection in insect’s fish and mammals:

Insect Fish Mammal Medium transmitting sound

Air, solid- ground or leaves

Liquid- water Air or liquid

Structure sensing sound

Tympanic membranes, hair cells

Swim bladders and internal ears, lateral line systems of neuromasts

Cochlea

Sensory cells Mechanoreceptors Hair cells and neuromasts

Hair cells in organ of Corti

Organism Way of hearing

Mammal - Have similar methods of detecting sound - Ear has three main sections:

- External ear: collect vibration - Middle ear: transmit vibration to inner ear - Inner ear: contains cochlea- main hearing organ - Cochlea contains structure called organ of corti à has tiny hairs that

receive vibration and convert into electrical pulses to be sent to the brain via nerve cells

Fish - Sound travels faster in water than air à ears on inside rather than out

- Sound passes easily through body to two internal ears - Ears filled with fluid and lined with cilia - Cilia detect movement of fluid caused by vibrations transmitted Swim bladder: - Air filled with air and easily compressed - Bladder detects sound à sends signal to ear where hair cells detect it and send to brain for interpretation Neuromasts: - Detect movement - Have hair cells line inner ear and use it to detect sound Lateral line system: - Series of small canals near head and side of body - Contain neuromasts

Insects - Can detect sound in variety of ways and frequencies Moths, cicadas and grasshoppers: - Tympanic membrane on abdomen - Similar role to eardrum in human à sound energy is transferred into an electrical

impulse and sent to brain via nerves Mosquitos: - Have hair on antenna that detect vibration in air

Bees, ants and termites: - Mechanoreceptors on legs - Used to detect sound travelling through ground

§ Describe the anatomy and function of the human ear, including:

– Main role of ear is to convert incoming vibrations into electrochemical signals to be sent to brain

  Structure   Description   Function  

External Ear Pinna - Seen as ‘ear’ - Comprises folds of skin over

cartilage

- Collects sound and channels it to ear canal

- Helps determine direction of sound

- Protect inner part of ear

Ear canal - Tube leading from pinna to tympanic membrane

- Channels sound wave towards tympanic membrane

- Produces wax to protect and lubricate ear

Tympanic membrane

- Sensitive membrane (ear drum) - Situated between external and

middle ear

- Vibrates with same frequency as sound wave that hits it

- Provides airtight protection between external ear and middle ear

Middle Ear Ear ossicles - Three small bones in the middle of the ear: malleus (hammer), incus (anvil) and stapes (stirrup)

- Transfers vibrations from tympanic membrane across middle ear to oval window

- Acts as lever to reduce amplitude of vibration on tympanic membrane

- Amplifies force of vibrations to oval window

Oval Window - Small, thin membrane situated between middle and inner ear

- Receives the vibration from tympanic membrane via ossicles at greater force

Round Window - Situated below the oval window • Acts like a piston when bulges in and out

• Transfers vibration from oval window to fluid in the inner ear

Inner Ear Cochlea • Long tube wound around itself • Filled with liquid

- Fluid in cochlea transfers vibration to hairs in organ of corti

Organ of Corti - Situated inside cochlea - Contains receptor hair cells

attached to nerves

- Hairs are tuned to certain wave frequencies

- Wave passes over hairs --> electrical signal is triggered

Auditory nerve - Bundle of nerve fibers bound together

- Sends electrical signals to brain to be interpreted

  § Outline the role of the Eustachian tube

- In higher altitude, air becomes thinner thus decreases pressure

- Air does not put as much pressure on tympanic membrane --> moves outward to compensate

- Opposite occurs in descending altitude

- Slightest movement of tympanic membrane makes it difficult to hear and may cause pain

Role of Eustachian tube:

- Equalize pressure between outer and inner ear so tympanic membrane is not forces into a position it usually does not occupy

- Equalizes air pressure as it connects the inner ear with the outside air in the pharynx

- Usually canal of Eustachian tube is closed

- As you yawn, cough or swallow, it opens briefly allowing outside air to equalize with air in inner ear

- Inner ear can maintain same pressure as outer ear

- Tympanic membrane stays in usual position and ear can hear normally

§ Outline the path of a sound wave through the external, middle and inner ear and identify the energy transformations that occur

Path of a sound wave:

- As on table 8.6.2

External Ear - Sound energy in a sound wave hit side of head à pinna collects and channels vibrations down into ear canal

- Sound energy moves to end of ear canal hitting tympanic membrane à causing vibration

- Sound energy is converted into mechanical energy of moving tympanic membrane

- Tympanic membrane vibrates within same frequency as incoming sound wave

Middle Ear - Vibration transferred from tympanic membrane of external ear to oval window by series of small bones

- Bones are attached to each other but are not fixed in one position

- As they vibrate in time with the tympanic membrane --> act as a lever

- Reduce amplitude of loud sounds on the tympanic membrane (avoids damage to ear drums

- Increase force of vibrations on the oval window (to improve quality of low frequency vibrations)

- As oval window vibrates, it transfers vibration to the round window

Inner Ear - Round window pushes in and out acting as pressure release mechanism as it transfers vibration from oval window to fluid in cochlea

- In cochlea: hair cells of organ of Corti detect movement

- Hairs near centre of cochlea detect low frequency vibrations and hairs near outer spiral of cochlea detect high frequency vibrations

- Dendrites: end of nerve cells, touch ends of hair cells

- Vibrations that are transmitted being transmitted through the ear cause sensory hairs to move up and down à simulate nerve cells

- Mechanical energy is transformed to electrical energy

- Message is sent via auditory nerve to bran where it is interpreted.

§ Describe the relationship between the distribution of hair cells in the organ of Corti and the detection of sounds of different frequencies

- Humans hear sound within a frequency as low as 16 Hz and as high as 25 000 Hz

- Adults have smaller frequency detection range à loose ability to detect higher frequencies

- Most adults detect up to 20 000 Hz

- Animals can hear a variety of frequencies that exceed that of humans

- Lower frequency sounds travel (up to a few km) further than high pitched

- As sound waves travel through a medium à molecules o medium move back and forth

- As the propagate à waves give energy to the medium therefore lose energy themselves

- Loss of energy means sound can only propagate a limited distance

- Low frequency waves moves less molecules than a high frequency wave

- à Gives less energy to medium and thus travels further

- Although waves that lose energy have decreasing amplitude, wavelength and frequency remain the same

Elephants:

- Use low sound frequencies ‘infrasound’

- Used to communicate over long distance

Bats:

- Use high frequency sound ‘ultra sound’ to communicate in their physical environment

- Do not travel as far as infrasound; they are less prone to distortion

- Important: bats have poor eyesight and use echolocation to position their prey

- Sound waves into environment and detect echo of wave once it bounces back off objects

Frequency range of different animals:

§ Outline the role of the sound shadow cast by the head in the location of sound

Locating direction of sound using sound shadow:

- Sound waves reach both ears with equal intensity when sound is directly in front of behind

- Sound vibrations hit one ear with greater intensity than the other

- When sound vibration strikes the closest ear, the intensity is much stronger than vibration striking the second ear --> shadow

- Due to: head blocking some of intensity of sound that is refracted around the head

- Human ears cannot move ears around like rabbits to locate direction of sound

- Direction of sound is determined by comparing sound intensity between two ears

Animal Frequency range Hz

Humans 16- 25 000

Dogs 20 – 45 000

Cats 20 – 64 000

Mice 1000 – 95 000

Elephants 5 – 11 000

Bats 100 – 200 000

7. Signals from the eye and ear are transmitted as electro-chemical changes in the membranes of the optic and auditory nerves

- Identify that a nerve is a bundle of neuronal fibers

- Neurons are responsible for communicating messages from one part of the body to another --> coordinate bodily functions (e.g. catching a ball OR digesting a meal)

Structure of a neuron:

- Neuron: elongates cell with specific structures (see table below)

- Electrical impulses are passed from one neuron to another

- Do not make physical contact with each other

- Space between neurons is called synapse

- Electric impulse carries message along neuron --> once reached the end, it is converted to neurotransmitter

- Neurotransmitter travels across the synapse to next neuron

Structure of a neuron:

Structure Function

Dendrite - Receives the signal from the previous neuron

Cell body - The largest part of cell - Contains organelles (E.g. nucleus, Golgi body, endoplasmic reticulum and mitochondria)

Axon - Long projection that conducts electrical signals away from the cell body

Myelin Sheath - Insulates the axon so that the electrical signal can be transmitted quicker along neuron

Axon Terminal - Lines up next to dendrites of next neuron or target cell (e.g. muscle cells) where the signal leaves neuron

- Identify neurons as nerve cells that are the transmitters of signals by electro-chemical changes in their membranes

Structure of a nerve:

- Neurons are bundled together to form a single nerve

- Axons of nerve cells form the fiber that becomes a nerve

Type of neurons:

- Peripheral nervous system: sensory, motor and interneurons

- Central nervous system: brain and spinal cord

Sensory Neuron

- Perceive or sense information from the internal and external environment

- Relay message to CNS

- Example: photoreceptors in eye receive stimulus from the environment that light intensity has increased. Then send this information to the brain

Motor Neuron

- Conduct the message from CNS to effector cells

- Effector cells carry out response to the stimulus detected by original sensory neuron

- E.g. if message is sent by photoreceptors informs the brain there is too much light hitting the retina, the motor neuron sends message to muscles around the iris to constrict pupil so less light enters the eye

Interneuron - Also known as; association, connector, multipolar or relay neurons

- Found in CNS

- Communicate with other neurons rather than the rest of the body

- Example: they communicate between sensory neurons and motor neurons as well as between themselves

- Define the term ‘threshold’ and explain why not all stimuli generate an action potential

- Nerve cells have different electrical charges across cell membrane to generate an electric signal

- Voltage across the cell membrane created by the charge difference: membrane potential

- Cell not sending any message: ‘resting’ and is known as ‘resting potential’

- During resting period there is an overall negative charge inside the neuron: -70mV (millivolts)

- Due to more negatively charged organic ions and fewer charged positively charged sodium ions (Na+) and potassium ions (K+) on inside of cell membrane compared to outside

- Sensory neuron may be stimulated by a variety of stimuli (e.g. pin prick, change in temperature or mild electric shock)

- If stimuli is intense --> causes sodium channels in cell membrane to open

- Due to difference in charges across cell membrane, positively charged Na+ ions rush into the cell to equalize membrane potential to 0mV

- If membrane potential is higher than -50mV it reaches threshold and an action potential is generated

- Split second later- momentum of Na+ ions cause inside of cell to become positively charged to about +30mV

- Due to too many Na+ ions rushing in at once causing membrane potential to rise, the sodium channels close and K+ ions rush out of cell

- K+ ions are propelled by high positive charge inside the cell

- As soon as membrane potential moves back beyond -30 mV, the potassium channels close

- This section of cell membrane is resorted to is resting state

- Change in charges at successive section along the axon (electric current) is a nerve impulse

- Action potential: if the stimuli is strong enough, the charge with be transmitted along the axon to the axon terminals

- In doing so --> becomes an electrical message

- If stimulus is not strong enough to change membrane potential above -50mV there will be no action potential

- Therefore, not all stimuli generate an action potential

- Action potential is always conducted at the same strength and speed

- Action potential itself does not travel but begins at each new section of the axon

- Identify those areas of the cerebrum involved in the perception and interpretation of light and sound

Sound and light perception in the brain:

- Brain coordinates the messages that are transmitted to it by sensory neurons

- Contains billions of neurons

- Largest and most complex mass of nervous tissue in the body

- Different part of the brain receive sensory stimuli via sensory neurons situated in different parts of the body

- Example: sight and sound stimuli are received in separate location in the cerebrum

- The cerebellum has coordinating function and processes bodily functions

- The medulla oblongata relays signals between the brain and the spinal cord

Structure and function of the brain

Major structure Composing structures Function

Cerebrum Frontal lobe - Relates to learning, thoughts, memory and speech

- Speech section is located in Broca’s area where sound is instigated

Parietal lobe - Processes speech in Wernicke’s area

Occipital lobe - Processes visual signals where sight and vision is perceived

Temporal lobe - Processes auditory information where hearing is perceived

Cerebellum - Coordinates sensory signals - Helps with balance and movement,

coordination and processing of language

Medulla oblongata - Relays signals between the brain and the spine

The cerebrum:

- Largest part of the brain

- Contains small grooves or folds rich in blood supply

- Dived in to many sections - ‘lobes’

- Areas that perceive and interpret light and visual images sent from retina are located in the occipital lobe at back of the brain

- Hearing is perceived in the temporal lobe

- Speech is interpreted in the parietal lobe in Wernicke’s area

- Speech is formed in Boca’s area in frontal lobe

- Explain, using specific examples, the importance of correct interpretation of sensory signals by the brain for the coordination of animal behaviour

- If the brain does not correctly interpret a signal, it is unable to make a coordinated response

- Brain contains neurons that a responsible for receiving stimuli from the environment and coordinating a response via motor neurons

- It is coordinated response to stimuli that involves more than perceiving a signal and responding to it

- As signals do not arrive at the brain on their own and need to be interpreted alongside other signals, their combination reflects the way you interpret them.

- Example: sound signals can be interpreted differently depending on accompanying visual stimulus

- Visual and auditory stimulus can complement each other to direct interpretation a certain way

- Activity of brain in relation to stimuli is studied through positron emission tomography (PET)

- PET notes where blood is flowing when a person is given a different stimuli

- Example: different sound produce different activity of the brain suggesting they’re interpreted differently

- Sound like music: blood flow to the right side of the brain is increased,

- Sound like speech: the left side of the brain receives more blood.

- Interpretation can be subjective

- Brain makes sense of incoming sensory signal due to memory of past experiences

- Some behaviors are innate while others are learnt

- Learned responses gained from interaction and experience within environments that enable appropriate interpretation of electrochemical signals

- example: People who have suffered from a stroke that has damaged part of their brain often have to relearn tasks as simple as brushing their teeth. This is because they have lost their previously learnt experiences and have to learn how to re-coordinate them.

Parkinson’s disease- neuron- degenerative disorder

- Caused by imbalance of chemical dopamine in the brain

- Imbalance prevent brain from coordinating sensory signals properly

- People with PD have difficulty in motor coordination --> leads to shaking and rigid movements

- Experience impaired balance causing them to fall