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118 Cards in this Set

  • Front
  • Back

The Role of Receptors

-Mechanoreceptors, detect pressure (pain) through skin and vibration through the ears.

-Thermo receptors, detect temperature through the skin and hypothalamus.

-Chemoreceptors, detect chemicals through taste buds and hypothalamus.

-Electroreceptors detect electricity through skin.

-Photoreceptors detect light through the retina.

A body's response to stimulus

The relationship between stimulus, receptor, messenger, effector and response to a stimulus.

-A stimulus (cold temp.) is detected by receptors (thermo receptors), sending a message to the hypothalamus through sensory neurons.

-The hypothalamus generates a response to the stimulus and sends a message through motor neurons to the effectors (muscles).

-Muscles react and shiver or undergo vasoconstriction to counteract a change.

-When receptors detect a change back to normal temperatures, the effectors cease to react and homeostasis is restored.

Sense/ Human Example/ Nature Example(Part 1)

-Sight (Visual)/ Face expressions show emotions (anger)/ Female chimps have coloured rumps when they are ready to mate.

-Smell (olfactory)/ Certain smells trigger a change in behaviour during a female's menstrual cycle/ Mice release a pheromone and the males will mate if they smell a receptive female.

-Touch (tactile)/ Used in mating like handshakes/ Bees dance to communicate the location of food.

Sense/ Human Example/ Nature Example(Part 2)

Role of receptors

-Hearing (Auditory)/ Language is used extensively to convey information and communicate/ Crickets use sound as a warning to attract males.

-Taste/ Taste buds are used to communicate enjoyment or distaste/Monarch butterflies have a bitter taste to communicate they are poisonous.

The role of receptors is to detect a change in an organism's internal environment, sending a message to the hypothalamus via a sensory neuron to restore homeostasis.

Eye: Name of tissue/ Structure/ Function (Part 1)

-Conjunctiva/ Thin translucent mucous membrane covering the sclera and inner surface of the eyelid/ Produce tears to lubricate the eye that prevents friction and protects the cornea from damage.

-Cornea/ Transparent tissue/ Admits light and refracts it to the retina to form an image.

-Sclera/ The tough, white outer coating of the eye composed of collagen fibers/ Maintains the shape of the eye and protects the inner parts of the eye against mechanical damage.

-Chloroid/ A membrane lying between the retina and sclera containing blood vessels/ Supplies blood to the retina and absorbs and prevents light scattering.

Eye: Name of tissue/ Structure/ Function (Part 2)

-Retina/ Layer of photoreceptors/ Detects light and converts it into an electrical signal.

-Pupil/ Hole in the middle of the iris/ Allows a certain amount of light to enter, depending on the iris.

-Iris/ A coloured ring of muscles which dilate or constrict/ Protects the retina by controlling light entering the eye.

-Lens/ Transparent, biconvex structure, held in place by the ciliary body and suspensory ligaments/ Refracts light to allow a fine focusing of the image on the retina.

Eye: Name of tissue/ Structure/ Function (Part 3)

-Aqueous humor/ A water fluid between the cornea and iris/ Maintains the shape of the eye and nourishes, refracting light.

-Vitreous humor/ Thick transparent gel filling the inside of the eye/ Maintains the shape of the eye and refracts light.

-Ciliary body/ A ring of muscles containing suspensory ligaments/ Supports and alters lens shape, producing fluid for the aqueous humor.

-Optic nerve/ Bundle of nerve fibers connecting the eye and the brain/ Transmits impulses generated in the retina to the brain.

Wavelengths of the EM Spectrum

-Wavelength of a wave is the distance between 2 peaks.

-Frequency of a wave is how many times the wave repeats in a second (Hz).

-Objects are seen when light is emitted or reflected from an object to an organism's eyes, that contain cones, sensitive to colour and rods, sensitive to light intensity.

-These cells generate never impulses, sent via the optic nerve to the visual centres in the bran (occipital lobe) where information is then processed and interpreted.

-EM waves are seen through infra-red radiaton, visible light and UV (from longest to shortest), from 300nm-850nm. Arthropods (bees) have UV range, and IR is snakes, such as pit vipers whose pit organs are located on the head, sensitive to heat.

Animal/ (In)vertebrate/ Part of EM spectrum/ Wavelength (nm)/ Wavelength/ Frequency.

-Bees/ Invertebrates/ UV/ 300-700/ Shorter/ Higher.

-Humans/ Vertebrates/ Visible Light/ 380-780/ Medium/ Medium.

-Pit Vipers/ Vertebrates/ IR/ 480-850/ Longer/ Lower.

Practical: Investigation of a mammalian eye: Aim/ Safety

Aim: To investigate the structure and function of the mammalian eye through dissecting a bullock's eye.

Safety: Risk/ Precaution

Infection from a foreign substance, such as bacteria in the eye/ Wear gloves and wash afterwards.

Cutting yourself or others with the scalpel/ Keep the blade towards the ground when walking around the room and when cutting slice smoothly away from the body.

Practical: Investigation of a mammalian eye: Method

1) Examine the outside of the eye before cutting.

2) Cut away fat leaving the sclera and cornea intact using scissors/scalpel.

3) Use scalpel to make an incision in the cornea until the aqueous humor is released.

4) Slice through the sclera with the scalpel and scissors and remove the iris and vitreous humor.

5) Remove the lens from the ciliary body and observe its properties.

6) Note the retina and chloroid.

7) Dispose of waste materials, taking care with scalpel and scissors. Disinfect area and tools and wrap contents of the eye and place in a bin.

Animal/ (In)vertebrate/ Wavelength/function

-Honey bees (Api Mellifera)/ Invertebrate/ 300-700Nm/ Many flowers have UV patterns on their petals, which direct the pollinating insects to the nectar.

-Rattlesnake (Crotalus ssp.)/ Vertebrate/ 480- 850 Nm/ Can detect infrared radiation as they hunt at night or in burrows, thus can detect endotherms for food.

Both animals/ Comparison with human eye/ Why the animal developed that way

-The eye is not as clear as a human's, as it has UV/ IR detection to supplement its vision. Prevalent in the pit organs, sensitive to heat given off by other animals.

-These adaptations provide a selective advantage to these animals, allowing them to compete greatly for food through their increased capability to detect it and thus breed and pass these superior traits to their offspring.

The conditions under which refraction of light occurs

-The refraction of light occurs as light travels through one medium to another of different densities, which relatively slows it down or speeds it up. The bending of light is dependent on the density of material as more dense materials have a higher refractive index than less dense materials.

-Light bends towards the normal when travelling from an area of low to high density.

-Yet, if light enters at the normal it will not bend.

Refraction effects

-TAGAGA: to/from normal

_Towards is air to glass (low to high density)

_Away is glass to air (high to low density)

-The degree of refraction of light depends on 2 factors:
_The refractive index of the two materials light is passing between.

_The angle of incidence of incoming light rays entering the medium, the cornea is the converging lens.

Accommodation as the focusing on objects at different distances (Part 1)

-Mammalian eye works like a camera, producing an image on the retina that is inverted, conveyed by electrical signals along the optic nerve which the brain then interprets.

-To interpret the image it is focused, achieved primarily by the cornea (80%), then is fine focused and corrected by the lens.

-The focal length is the distance between centre of lens and the point where light rays converge (focal point).

Accommodation as the focusing on objects at different distances (Part 2)

-Focussing concentrates an image upon the fovea, whilst the whole image refracts onto the retina.

-The curvature and the focal length are inversely proportional_ as focal length increases, the lens curvature decreases.

-Greater curvature, refracts light to a greater extent, close objects are focused.

-Less curvature, refracts light to a lesser extent, distant objects are focused.

Accommodation as the focusing on objects at different distances (Part 3)

-Ciliary muscles are responsible for adjusting the shape of the lens.

_As an object further away is focused upon there is minimum accommodation, ciliary muscles relax, suspensory ligaments are taut and lens to be flat (less biconvex), whilst inverse for close objects.

-Accommodation is the focusing of objects at different distances, changing the curvature of the lens. Fine-tuning of focus is achieved by suspensory ligaments acting on the lens, allowing light rays from a single point to reach the focal point on the fovea of the retina after refraction.

How you see?

-Light reflecting from an object enters the eye through the pupil, where the iris controls the amount of light seen.

-Both the cornea and lens focus the light (an inverted image) upon the retina, to be detected by light sensitive receptors.

-These send electrochemical signals to the brain for the brain to convert the right way up and to co-ordinate responses.

Changes in refractive power of the lens from rest to maximum accomodation

-At rest, the lens is flatted as ciliary muscles relax, thus the suspensory ligaments are taut. As refractive power is low (longer focal length) objects far away can be seen.

-When accommodation occurs, ciliary muscles contract towards the lens, thus suspensory ligaments loosen, producing a rounder lens to view closer objects. Refractive power of lens increases (greater curvature/ shorter focal length) allowing closer objects to be seen.

-Minimum distance to produce a clear image is the "near point of vision", where the refractive power of the lens is measured in diopters, in adults being 59-63 diopters.

Myopia (You have dis nigga)

-Myopia is also known as short-sightedness, where there is trouble seeing objects far away.

-The condition where light rays are refracted too much, thus focal point is in front of the retina.

-Caused by the refractive media being too strong or the eyeball being too long.

Myopia pictures (p7)


-Hyperopia is also known as long-sightedness, where the person affected has difficulty seeing objects nearby.

-Condition where light rays are not refracted enough, thus the focal point is behind the retina.

-Caused by the refractive media being not strong enough or the eyeball being too short.

Hyperopia (p7 diagram)

Corrective lens/ Refractive (laser) eye surgery

There are two main ways of correcting vision:

-Corrective lenses, biconcave for myopia and biconvex for hyperopia.

-Refractive (laser) eye surgery, used to remodel the eye to obtain the correct amt of refraction, involving:

1. Sterilizing the eye with drops and clamp open eyelids.

2. An instrument called a keratome lifts a flap of corneal tissue.

3. Laser is used to alter the curvature of the cornea.

4. Corneal tissue is re-adjusted back onto the eye.

5. Eye is sterilized then bandaged for 14 hours.

The production of 2 different images resulting in depth perception

-Depth perception is the ability to accurately judge the distance of an object.

-The cerebral cortex in the brain superimposes the images, using slight differences, as they are placed cm apart, creating 3D vision.

-Known as steroscopic or binocular vision, allowing distance, depth, height and width to be calculated.

-View from both eyes must overlap the same seam, thus fish must move their heads to view an object with each eye, deducing its displacement from the object.

-Depth perception is achieved from size of object and parallax effect, when head is moved, distant objects move less compared to close ones.

Accommodation prac (Aim/ variables)

-Aim: To model the process of accommodation by passing light through biconvex lenses of different curvatures (different focal lengths).


_Independent : Curvature of the lens (focal length).

_Dependent: Distance between light globe and lens to focus an image.

_Controlled: Type/ strength of light source (12V globe), distance between lens and screen (0.62m),type of lens (biconvex, glass medium), to maintain the validity of the experiment.


1. Select the lens with the intermediate curvature (medium focal length).

2. Move the light bulb until a focused image of the filament is formed on the screen.

3. Measure the distance between the light globe and the lens.

4. Repeat steps 1-3 with different lens focal lengths.

Accommodation Diagram (p8)

Accommodation Results

Focal length (cm) / amount of curvature/ Distance from eye for focussed image (cm)/ Ciliary muscles/ Ligaments

-5/ more rounded/ 6/ taut/ relaxed.

-15/ intermediate/ 20/ intermediate/ intermediate.

-53/ more elongated/ 246/ relaxed/ taut.

Accommodation Discussion

-Distance between the lens and the screen = length of the aqueous humor(doesn’t change).

-The light globe is not a single source of light - hence, the point ofconvergence does not occur on the screen/retina .

-Screen represents the retina.

-Lens of different focal lengths represents changing focal lengths ofthe lens due to accommodation.

-Distance between globe and the lens represents the distance betweenthe external light source and the eye

Changes of the eye as the lens focuses on near objects.

-Ciliary muscles contract

-Suspensory ligaments relax

-Shape of lens is rounded

Put diagram (p9)

Changes of the eye as the lens focuses on near objects.

-Ciliary muscles relaxed

-Suspensory ligaments taut

-Shape of lens is elongated

-Put diagram (p9)


Acataract is an opacification (progressively more opaque) or clouding of thelens of the eye occurring as proteins aggregate (culminate) in the lens,scattering light and preventing it from reaching the retina (thus impairingvision). A failure to treat cataracts over time may lead to blindness.


Cataractsare removed through a process called phacoemulsification:

1. Local anesthetics numb the eye

2. Small incision to the edge of the cornea, where a probe is insertedinto the lens capsule3. The probe emits an ultrasound that breaks up the protein in the lens

4. These parts are then removed by suction, leaving behind the lenscapsule

5. An artificial intraocular lens is inserted and unfolds to replacethe natural lens

Why do cataracts occur?

-Thereis an aggregation of protein in the lens, making it clouding, preventing lightfrom passing into the retina.

-New lens cells form on theoutside forcing older cells to be compacted at the centre, resulting incataracts.

World Impact

-Abouthalf the people that are blind, are blind due to cataracts. Most live indeveloping countries and their blindness impacts society, as those affected areunable to hold employment and support their families.

-This technology allowsthe removal of cataracts to restore vision, allowing them to fulfill theirroles in society.

-However, there are disadvantages, such as the medical costsinvolved in training doctors to conduct the surgery, which Government mustfund. -Nevertheless, these are outweighed by the long-term advantage of havingfully functioning individuals who can contribute financially to society. E.g. The Fred Hollows Foundation

The production of an image

1.Theretina consists of a thin sheet of photoreceptor cells (rods and cones), modifiedneurons that are sensitive to light.

2. Photons that hit each photoreceptor resultin a breakdown of light sensitive pigments.

3. This arises from minute changes in the permeability of the cell membraneto sodium and potassium ions, thus a wave of excitation along the membranegenerates an electrochemical impulse to bipolar cells in the retina.

4. Thesestimulate the ganglion cells, which form the optic nerve and transmit messagesto the brain for interpretation and hence, photoreceptor convert light energyinto a nerve impulse.

Cones (Distribution/ Structure)

-7 million cones in the human eye largely concentrated around the fovea where most daylight is focused.

-Sparsely distributed, unlike rods, as cones have individual synaptic terminals where rods can share terminals.

-Elongated conical cells with an individual synaptic terminal (one to one) and an outer terminal containing discs.

-Contain a pigment (Photopsin) sensitive to high intensity light and extensive nerve connections to brain = a detailed image.

-Exist in RGB forms.

Cones (Function)/ Rods (Distribution)

-Sharp images not sensitive tolight but distinguish colour.

-NOT sharp during night time because no high intensitylight to stimulate them.Visual acuity dependenton cones per area, as more = more impulses to the brain and greater detailedimage.

-125 million rodsin the human eye largely concentrated around the periphery of the retina, notin the fovea.

-Linked in groups on theretina to synaptic terminals (many to one).

Rods (Structure/ Function)

-Elongated rod shaped cells with a synaptic terminal and an outer terminal containing discs.

-Similar to the basic structure of a nerve cell.

-Pigment is rhodopsin.

-Very sensitive to light.

-Responsible for night vision seeing as sensitive to different intensities of light hence when pupils dilate rods become more exposed.

-Unable to discriminate colour, thus lack detail

Cones (Diagram p11)

Rods (Diagram)

Role of Rhodopsin

1) Light enters eye and travels through the rod.

2) As light travels through rot, it hits light sensitive pigment calledrhodopsin that breaks down into its two components, Opsin and Retinal.

3) This excitation of the cell changes cell membrane permeability tosodium/ potassium ions, thus there is a movement of these ions.

4) This movement of ions generate an impulse (Action potential) betweenrod and bipolar cell, with this impulse being transmitted to the brain via theoptic nerve.

5) Rhodopsin is formed again using energy derived from ATP. This is the visual cycle.

Cone Type/ Colour/ Responds best to

-L/ Red/ Long wavelengths (625Nm)

-M/ Green/ Medium wavelengths (530 Nm)

-S/ Blue/ Short wavelengths (455Nm)


-Cones consist of three different kinds of opsin (L,M,S) bount to a molecule of retinal.

-Cone cells react when a particular wavelength of light hits them, and they send an impulse to the brain.

-Different cone cells that react are interpreted by the brain as different colours.

-The trichromatic theory of colour vision suggest that each photopsin is sensitive to a different range of wavelengths corresponsing to red green and blue.

Colour blindness

-Full colour vision in humans depends on all three colour sensitive pigments present in cone cells.

-Colour blindness refers to the inability to see certain colours, caused by the absence of one or more of the colour sensitive pigments in cone cells, or their disfunction, due to a mutation in the cone cell gene.

-Therefore, the cone fails to function properly, leading to a loss of ability to detect certain wavelengths of light.

-Red/Green colour blindness (Red or Green cones are not working or not produced) is sex linked, 10% of males and 1% of females.

Photoreceptor cells in mammals

-Humans: Photoreceptors are nerve cells on the retina, stimulated by light to convert the detected light into electrochemical signals. They are then transmitted to the brain and converted into an image by the cisual cortex. Rods to differentiate light intensity and cones to differentiate colour are used to produce an image.

Photoreceptor cells in Insects

-Unlikethe human eye, which is a single structure, the insect eye consists ofthousands of separate units called ommatidia. Each ommatidium only forms animage of part of an object.

-A transparent cornea and a crystalline cone refractlight rays otto the retinal cells. The crystalline cone is unable to change itsshape, yet the insect eye is more efficient at detecting slight movement over awide range as multiple ommatidia detect images from every direction.

-Light detected by visual receptors causesattached pigment cells to conduct phototransduction and convert light toelectrical signals.

Photoreceptor cells in flatworms

The flatworm has an eyecup with no lens. The image (if formed) isnot clear and not inverted – only providing information about light intensityand direction. Fewer photoreceptor cells and poor visual acuity, with no colourperception.

-Dogs: Singular structure eyes as they are mammals, yet they only have 2 types of cones (violet-blue and yellow-green), thus can percieve only a selected range of colours, diminishing their vision. Colour vision of dogs resembles red green colour blindness in humans.

Colour used for communication in animals (P1)

-Many animals use colour to communicate, where the effectiveness ofthis relies upon the animals that receive this information, and having thecolour vision to detect it (well developed in fish and reptiles but onlyprimates have colour vision in mammals).

-Colour is generated in feathers or skin that absorbs white light,yet reflects back specific wavelengths, thus these chemicals allow fordifferent various colour combinations.

Colour used for communication in animals (P2)

-Animals may use colour vision to signal their availability to mate(peacock), to hide from predators (cephalopod squid) or for abiotic factors(Namaqua chameleon turning a dark colour to absorb more heat).

-Humans have 10,000 cones/ mm^2 compared to some birds that haveup to 120,000. The ability to easily perceive colours is beneficial for birdswho feed in the daylight, e.g. hummingbirds can spot redflowers from over a kilometre away.

Colour for communication

Animal/ Mechanism/ Structure/ Benefits

Cephalopod squid/ Camoflague/ Dual layered Skin/ Aidtheir survival as they blend into their environment so that they remainunnoticed by their predators, or by their prey.

Peacock/ Sexual Dimorphism/ Brightly coloured plummage/ Demonstrates its general health to impress a peahen.Colour used to distinguish between potential mates.

Why is sound a versatile form of comms (P1)

-The social life, mating behavior and feeding patterns of animalsdepends on the ability of individuals to communicate with each other.

-For these reasons, it is versatile because:

_Animals can manipulate the nature of sounds produced depending onpitch and amplitude.

_Allows the interpretation of diverse tones, enhancing the way weverbally communicate and emotionally express ourselves.

Why is sound a versatile form of comms (P2)

-And useful because:

_It travels as waves through any medium, day or night, and around corners.

_The sender does not have to be visible to the receiver.

-The relationship between wavelength and frequency is important because low frequency sounds that have a long wavelength will travel greater distances through media like air or water and can be used for communication over long distances by animals such as whales.

How sound travels

-Sound is produced by a vibrating energy that causes surroundingmolecules to oscillate, forming a compressionwave (or longitudinal wave) in amedium.

Sound will travel through a medium in a series of compressions and rarefractions, retaining its initial frequency.

_Low/ High pitch = lower/ higher frequency = longer/shorter wavelength

-Amplitude is the loudness of a sound, measured in decibels (dB)· -Travels fastest and longest through solids, as opposed to liquidsand gases as the atoms are closer together and more dense, thus allowing it tojump atom to atom quicker.

Human larynx and structures that produce sound (P1)

-Thelarynx is a tubular structure below the tongue and soft palate comprised of acomplex system of muscle, cartilage and connective tissue; with vocal cordsstretched across.

-The framework of the larynx is composed of three unpaired andthree paired cartilages.

-Exhaled air passing across the vocal foldscauses them to vibrate and this makes the air above the folds vibrate, which wehear as sound.

Human larynx and structures that produce sound (P2)

-Voluntary muscles in the larynx, coupled withthe tongue and hard and soft palate, change the tension in the vocal ligamentsand so change the frequency of sounds produced.

-As tension in vocalchords increase, the frequency of the sound increases.

-Loudness is produced bythe energy with which air is expelled from the lungs.

-Nasal/Oralcavities are important with sound formation when a person is congested withmucus (sick).

Low Frequency Vocal Cords (Diagram, p14)

High Frequency Vocal Cords (Diagram)

Vocal chord structure (Diagram)

Associated structures in producing sound: Subglottal system/ Supralaryngeal airway

-Subglottal system consists of the lungs and its associated muscles, controlling the loudness of sound. Louder sounds are made by using more energy to expel air from the lungs to the larynx.

-Supralaryngeal Airway is the airway that produces speech. The palate determines the direction of airflow into the mouth or nasal cavity and the movement of lips, tongue and jaw to form different sounds.

Structures in the vocal tract (p15)

Relationship between wavelength, frequency and pitch prac: Aim/ Variables

-Aim: Toinvestigate the relationship between wavelength, frequency and pitch of a sound

-Independentvariable: different frequency-producing tuning fork

-Dependentvariable: frequency and wavelength

-Controlledvariable: silent environment

Relationship between wavelength, frequency and pitch prac: Method

1. Turn on data logger and navigate to microphone setting à increase accuracy (most preciseinstrument available)

2. Produce a constant sound from the tuning fork à increase validity (asopposed to whistling)

3. Collect a sample of the sound and study the graph on the data logger4. Collect the period of the sound by measuring the time differencebetween 4 peaks (as opposed to 2 adjacent peaks) and dividing by fourto obtain the average period to increasereliability (greater sample size)

5. Calculate frequency: f =1/T (T=period)

6. Calculate wavelength: λ =330/f

7. Repeat for reliability then redo 1-7 with different pitched tuning forks.

Relationship between wavelength, frequency and pitch prac: Discussion

-Relationship between frequency/pitch and wavelength is inverselyproportional, (v=wavelength x frequency) (V=330 for sound)

-A microphone has a tiny membrane similar to the eardrum detecting vibrations in this membrane and creating an electricalsignal that represents the vibrations.

-The wavelength of speech is very complex; it is made up ofmany different frequencies of sound, constantly changing in amplitude andduration. This is how the complex messages of language are communicated fromone human to another.

Structures used by animals to produce sound: Grasshopper/ Fish

Grasshoppers Stridulation involves rubbing one body part against another (acting as a rasp and scraper). A row of pegs along the inside of a grasshopper’s hind legs acts as the rasp. It rubs this leg surface against the thickened forewing, causing a vibration and thus a sound.

-Many fishes produce sound by the rapid contraction and expansion of the sonic muscles near the swim bladder, thus creating drumming sounds. These are typically less than 1000Hz. E.g. silver perch

Structures used by animals to produce sound: Birds/ Cicadas

-Similar structure to larynx called a syrinx,containing a membrane that vibrates as air passes. This is located in the respiratory system atthe junction of the two bronchi, thus birds can whistle longer as they have twosources of air, allowing them to breath from one and whistle with the other.E.g. Lyre bird.

-Many insects like cicadas have a membranecalled a tymbal that vibrates directly through muscles.

Animal/ Structure/ Vibration detected/ How it works/ Similarities/ Differences


-Fish (Carp)/ Lateral Line/ Pressure waves/ Mechanoreceptors with hair cells detect changes in water pressure causing an impulse to the brain/ Receptors detect vibrations and nerve fibres send the information to the brain/ Lateral Line provides fish with information about changes in direction/ speed of water movement.

Animal/ Structure/ Vibration detected/ How it works/ Similarities/ Differences


Mammals (Humans)/ Sound waves/ Tympanic membrane between the outer and middle ears converting sound waves into mechanical vibrations. The inner ear has hair cells that generate an action potential, sent to the brain./ Receptors detect vibrations and nerve fibres send the information to the brain/ Ears provide information about changes in direction, pitch and amplitude of sounds. Has a cochlea and ear opens to the outside with a tympanic membrane that detects sound vibrations.

Animal/ Structure/ Vibration detected/ How it works/ Similarities/ Differences

Insect (Cricket)/ Tympanum/ Sound waves/ Tympanum is an internal air chamber enclosed by a tympanic membrane where sound waves cause the tympanic membrane to vibrate and attached nerve fibres are generated sending messages to the brain/Receptors detect vibrations and nerve fibres send the information to the brain/ Tympanum provides information about the changes in direction of sound and detects certain pitches. Doesn't have a cochlea and the tympanic membrane exposed to the air.

Structure/ Anatomy/ Function

Pinna, Tympanic membrane, Ossicles.

-Pinna (Outer)/ Folds of skin over cartilage/ Collects and channels sound to the ear canal, protecting inner parts of the ear.

-Tympanic Membrane (Outer)/ Sensitive membrane that is taut and cone-shaped/ Vibrates at the same frequency as sound that hits it and provides airtight protection between the ext/ middle ear.

-Ear ossicles (Middle)/ three small bones in the middle ear (Malleus, Incus, Stapes)/ Transfers vibrations from tympanic membrane to the oval window at a greater force.

Structure/ Anatomy/ Function

Oval Window, Round Window, Cochlea

-Oval Window (Middle)/ Small thin membrane situated between the middle and inner ear/ Receives vibrations from the tympanic membrane via the ossicles at a much greater force.

-Round Window (Middle)/ Situated just below the oval window/ Bulges in and out to allow for the displacement of fluid when vibrations are transferred to the cochlea.

-Cochlea (Inner)/ A long tube wound around itself filled with liquid/ Fluid in the cochlea transfers vibrations to the hair cells in the organ of corti.

Structure/ Anatomy/ Function

Organ of Corti, Auditory Nerve

Organ of Corti/ Situated inside the cochlea, contains receptorhair cells that are attached to nerves/Hairs are tuned to certain frequencies and whenwaves pass over hairs, electrical impulse is triggered.

Auditory nerve (Inner)/A bundle of nerve fibres bound together/ Send electrical impulses to the brain for interpretation

Example Answers

1) Structure

2) Location

3) Relate structure to function

-The auditory ossicles(malleus, incus, stapes) together form an acoustic connection between thetympanic membrane and the oval window. Being made of bone, the ossicles aregood transmitters of sound, which is essential to their function. The bones acttogether as a series of levers to reduce the amplitude (but increase the force)of the vibrations from the tympanic membrane being transferred to the ovalwindow.

The Eustachian Tube

-The role of the Eustachian tube is to equalize pressure between the outer and inner ear.

-This prevents the tympanic membrane from being forced out of position and drains the middle ear that can be a route for bacteria causing infection.

-Equalization is able to occur as the inner ear connects with outside air in the pharynx, thus when one yawns or swallows, tubes open up and air in outside equalizes with air in the inner ear.

The Path of Sound Waves P1

-Sound waves are funnelled by the pinna into the auditory canal, vibrating at the same frequency as incoming sound.

-The tympanic membrane converts the sound wave into mechanical vibration.

-Attached to the tympanic membrane the Malleus is the first ossicleto receive the sound and vibrates in the middle ear, transferring mechanicalenergy.

The Path of Sound Waves P2

The role of ossicles is to dampen high amplitude sounds and amplify low amplitude sounds, tended to as energy is transferred to the Incus and then Stapes that is connected to the oval window producing vibration in the round window, then to the cochlea fluid.

-Hair cells in Organ of Corti are stimulated and convert wave toelectrochemical energy. ·

-Neurones in the auditory nerve transfer nerve impulses to the brainfrom the electrochemical energy.·

-Auditory centre in the temporal lobe interprets the message as sound.

The Path of Sound Waves P3

Pinna --> auditory canal -->tympanic membrane --> ossicles --> oval window --> round window

--> cochlea -->organ of corti -->temporal lobe

--> auditory nerve

The Path of Sound Waves Diagram

Organ of Corti P1

· The organ of Corti has sensitive hair cells that pick up the vibrationsfrom the round window and convert them into electrical signals to be sent tothe brain. Theorgan of Corti has three main components:

1. Basilar membrane

a. Composed of transverse hair fibres of various lengths wherevibrations at the oval window are transmitted through the fluid of the cochlea.

b. Transverse fibres of the membrane vibrate at different partsdependent on frequency of sound (High frequency at base and low frequency atapex)

Organ of Corti P2

2. Stereocilia

a. As the basilar membrane vibrates, these hairs are pushed against thetectorial membrane. Tiplinks on the haircells amplify the forces of the sound and hence in turn send electrochemicalimpulses along the auditory nerve to the brain.

Organ of Corti P3

3. Tectorial membrane a. Held in place on the side of the organ of corti above hair cells and when these stereocilia are vibrated by the Basilar membrane, they rub against the tectorial membrane that stimulates it.

Impulses are generated in nerve fibres that lead to the auditory cortex of the brain, hence sound is converted to electrical energy, to be interpreted by the brain.

Organ of Corti Diagram

Role of a Sound Shadow

-Humansand other mammals determine the direction of the source of sound using thesound shadow, a phenomenon where sound is absorbed/obstructed, reducing itsamplitude and speed in reaching a location.

-As the pinna is a thin flap of skinand cartilage, sound from the rear is softly modified, making it possible todistinguish its direction and source. -This is aided by the slight time andintensity difference in sound reaching each ear.

Organism/ Range (Hz)/ Reasons P1

Human/ 20-23000/ Communication between humans occurs between thisspectrum and do detect sounds from the external environment.

Bats/ 10,000-200,000/ High frequency sounds are used to determine thenature and location of objects using echolocation. Since bats are nocturnal and have pooreyesight, echolocation is used as a navigational tool.

Organism/ Range (Hz)/ Reasons P2

Elephants/ 15-11,000/ Infrasoundis less than 20 Hz.Elephantsproduce these waves in order to communicate with other elephants potentially kmaway. Lowerfrequencies can travel further as less energy is lost through the medium.

Hearing Aid: Description/ Position/ Energy transformation

-Electronicdevice that amplifies sound with a microphone, amplifier and earphonereceiver.

-Worn in a shell behind/inside the ear.

1) Detectssound and converts it into electrical signal.

2) Amplifies/strengthensthe signal.

3) Convertsamplified electrical energy back into sound energy of greater intensity thanoriginal sound

Sound --> electrical --> amplified sound

Hearing Aid: Conditions/ Advantages/ Limitations

People with sensorineural hearing loss but are not completely deaf.

Relatively cheap No surgery required.

Only works for people with adequate residual hearing. Not suitable for people with defective inner ear. May amplify background noises.

Cochlea Impant: Description/ Position/ Energy transformation

Device that bypasses damaged inner ear and electronically stimulates the auditory nerve. with a microphone, speech processor, transmitter, receiver and electrodes (inserted in cochlea)

Headset is worn externally and implant is surgically placed inside skull.

1) Detects sound vibration and sends to the speech microprocessor

2) Converts the sound into electrical signal and sends to transmitter

3) Transmits the signal to the receiver in the form of a radio wave

4) Transforms radio signals into electrical impulses

5) Collects electrical impulses and sends them to the brain via auditory nerve Sound à electrical à radio wave à electrical impulses

Cochlea Impant: Conditions/ Advantages/ Limitations

People who are profoundly deaf, but have functional auditory nerves

Provides hearing to profoundly deaf people Reduce financial burden on society Surgery needed to place implant in position.

Expensive/ongoing costs ($30,000+) The person must learn to interpret the sounds created by the implant as it only gives a useful auditory understanding rather than a complete restoration of hearing.

A nerve is a bundle of neuronal fibres

-A nerve cell is called a neurone

-A neuronal fibre is a series of neurons joined end-to-end, forming asingle pathway for signals to be carried.

-A nerve is a bundle of neuronal fibres, with associated bloodvessels and connective tissue

Types of neurones


Sensory neurons – perceive information from the internal and external environment and relay the message to the CNS.

-Motor neurons – conduct the coordinated response from the CNS to the effector cells. The effector cells will then respond to the stimulus that was detected by the sensory neuron.

Interneurons – communicate between sensory and motor neurons, and also between themselves.

Neuron Diagram

Structure/ Function of a neuron

-Dendrites, recieve the signal from the previous neuron

-Cell body, Largest part of the cell containing organelles, such as the nucleus, mitochondria and golgi body.

-Axon, Long projection that conducts the electrical signal away from the cell body.

Myelin sheath, Insulates the axon so the electrical signal can be transported quicker along the neuron.

-Axo terminals, line up next to dendrites of the next neuron,(neurons or target cells like muscle cells, where the signal leaves the neuron.

-Node of ranvier, some axons without myelin sheaths, therefore change in electrical conductivity in the node of ranvier.

Action potentials between neurons

-An action potential is an electrochemical signal that is conductedalong a nerve cell to relay a message.

-Electrical because they can be detected as changes in voltage.

Chemical because the movement of ions brings about the impulses.

-Neurons do not touch each other. When an impulse arrives at the endof a neuron (dendrites), there is a swelling called a synapse.

-The impulse triggers the release of a neurotransmitter that diffusesacross the synapse to the terminal of the next neuron.

-As it arrives, it activates receptors on the membrane of the newneuron and triggers a new impulse in this cell.

Resting potential

-During the resting potential, there is an overall negative chargeinside the neuron of -70mv, due to more anions than cations (Na+, K+)inside the cell membrane.

-The membrane is polarized. Na+ is unable tocross the membrane and enter the axon.

How action potentials work P1

-The charge on a neurone can be reversed (depolarized) if sufficiently stimulated. A threshold level (the point where a nerve impulse will be generated)above -50mv is needed to produce an actionpotential. Below this point, there will be no action potential ‘all ornothing’ principle.

-This prevents us from being inundated with information from ourenvironment as only necessary information floods our minds.

-At the action potential, due to differences in charge across themembrane, Na+ ions will flood into the cell (depolarization) to equalize the membrane potential.

-This will continue until the neuron reaches approximately 30mv.

How action potentials work P2

-Sodium channels then close and the potassium channels open,allowing potassium ions to rapidly leave the cell, repolarizing the neuronback to -70mv.

-As the potassium channels remain open past -70mv, the cell is hyperpolarized, resulting in a refractory period, which preventssuccessive action potentials.

-During this period, Na+ moves back out, K+moves back in. Requires a sodium potassium pump as they move against theconcentration gradient, resetting charge across the membrane.

-Gradually, the membrane returns to its resting potential at -70mv.

Inside/ outside cell at rest

Inside/ outside cell at sodium channels opening

Inside/ outside cell at potassium channels opening

Graph of whole action potential

Parts of the brain P1

-Twohalves to the brain called cerebral hemispheres, where the cerebrum (thelargest part) is divided into 4 lobes:

-Frontal _Located behind the foreheadwhere higher order thinking occurs additionally to memory and in the leftfrontal lobe is Broca’s area, important for speech production (patients withtumours cannot talk). -Parietal _Top of the head at theback, important for interpreting sensory signals, sight and sound, processingspeech at the Wernicke’s area.

Parts of the brain P2

-Occipital_Back of the head, concernedwith vision (retains visual cortex) and other perceptions being the largest sensory area in the cortex.

Temporal_Side of the head,associated with sound and interpreting the impulses from the ears, being animportant region for hearing, like in the Wernicke’s area, responsible forspeech processing and language function (patients with tumours hear can makesounds but not understand language).

-Cerebellum_Coordinates sensory signals and helps with balance, movement, coordinationand processing language.

-Medullaoblongata_ Relays signal between the brain and spinal cord.

Brain Diagram

The correct interpretation of sensory signals by the brain P1

-Stimuli must be detected by sense organs (such as the ear and eye)and transmitted to the brain or spinal cord, before being interpreted and causinga response by an effector organ (such as the muscles).

-Correct interpretation of these signals is crucial, as it ensures anappropriate coordinated response to the given internal or external stimuli.

-It is the learned responses gained from interaction and experiencewithin your environments that enable you to appropriately interpretelectrochemical signals, such as the rush of auditory signals a deaf personreceives when have a cochlea implant inserted.

The correct interpretation of sensory signals by the brain P2

-The importance of this interpretation and coordination ishighlighted when an individual experiences:

-Diseases (Parkinson’s disease)

-Problems associated with sensory organs (cataracts, damage toeardrum)

-Damage to brain cells (injury, ageing)

-Use of chemicals and drugs (alcohol)

Example 1

Under the influence of alcohol, a person’s ability to react todifferent stimuli is affected. It will reduce one’s reaction times,coordination and the ability to feel physical injury. Other coordinationproblems caused by alcohol include slurred speech and blurred vision.

Example 2

Parkinson’s disease is caused by the degeneration of the nerve cells in the mid-brain, and leads to the corresponding loss of the neurotransmitters produced by these cells, and transmission of electrochemical signals. A person suffering from this disease will have difficulty in motor coordination, leading to shaking and rigidity of balance.

1st hand investigation into the structure of neurons and nerves


-Observeprepared slides of nerves and neurones under a microscope.

-Drawa diagram of the observations and include a title/ magnification.


-Lamp is hot when active, and may burn hands – do not touch whilstoperating

-Microscope will damage foot or fingers if dropped – use two handswhilst carrying with care

Diagram of an actual neuron/ nerve

Dissection into a sheep's brain: Brain

-Thebrain is a computer that communicates messages transmitted to it by sensoryneurons.

-Itcontains billions of neurons, being the largest and most complex mass ofnervous tissue in the body with different parts receiving and detectingdifferent sensory stimuli.

Dissection into a sheep's brain: Aim/ Apparatus

-To examine an appropriate mammalian brain and distinguish the cerebrum, cerebellum and medulla oblungata and locate the regions involved in speech, sight and sound perception.

-Sheep's brain, rubber gloves, dissecting board, scalpel, dissecting scissors, tweezers.

Dissection into a sheep's brain: Safety (Hazard/Risk)

-Infection rom a foreign substance/ Wear gloves and wash hands after, taking care with pins that have been stuck in the brain.

-Cutting yourself and others with a scalpel, Cut blade aways from the body and when walking around the room keep it in firmly in grip walking near nobody else.

Dissection into a sheep's brain: Method

1. Observe the appearance of the sheep's brain.

2. Cut the brain into hemispheres using the scalpel.

3. Examine the various internal structures, taking note of the cerebrum, cerebellum and medulla oblangata and structures associated with speech, sight and sound perception.

Dissection into a sheep's brain: Actual image with labels