Biology Communication

8/17/2019 Biology Communication

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The eye functions as a sense organ by detecting light stimuli and transforming it into nerve

impulses to be carried to the brain.

Part Structure Function

Con/unctiva Thin# mucous membrane that covers the

front of the eye

Protects the eye and "eeps it moist

ith mucus

Cornea Transparent front part of the eye 0ts curvature helps to refract light

passing through to the retina

Sclera Tough# hite outer coating of the eye Protects eye and maintains shape of

eyeball

Choroid 1ar"# middle layer inside the sclera

containing many blood vessels

Prevents light scattering

Retina 0nner layer of the eye# contains the

photoreceptors %rods and cones'# fovea

%highest concentration of cone cells and

therefore greatest visual activity' and

blind spot %area here optic nerve /oins

the eye# has no receptors'

Changes light into nerve impulses

0ris pigmented tissue that contains to sets

of muscles to ad/ust the opening of the

pupil

Controls the si2e of the pupil and thus#

the amount of light that passes into

the eye

3ens transparent# elastic disc that is able to

change shape# varying from a rounder to

a flatter structure

Refracts light# focussing it on retina

4ueous humor atery li4uid found beteen the

cornea and the lens

Refracts light# and gives the eyeball

shape

5itreous humor /elly-li"e substance that fills the area

around the retina

Refracts light# and gives the eyeball

shape

Ciliary body Connects the choroid ith the lens. 0t

contains the ciliary muscles and

suspensory ligaments that hold the lens

in position

d/ust the curvature of the lens for

near and far vision

6ptic nerve The nerve connecting the eye and the

brain! there are no photoreceptors here

it leaves the bac" of the retina %blind

spot'

Carries information from the eye to

the brain

Use available evidence to suggest reasons for the differences in range of electromagnetic

radiation detected by humans and other animals.

1ifferent animal species can detect different parts of the electromagnetic spectrum due to

their environment and ay of life.

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Animal Range Reasons

$uman 5isible spectrum ctive during the day7 colour vision necessary

to distinguish food and

$oneybee Most of the visible spectrum. Can also

detect into the ultraviolet range.

Some floers have ultraviolet mar"ings on

them hich bees use to find pollen

Pit 5iper Most of the visible spectrum. Can

detect avelengths in the infrared

range.

Relies on infrared to locate prey in dar"

burros

Identify the limited range of avelengths of the electromagnetic spectrum detected by

humans and compare this range ith those of other vertebrates and invertebrates

(lectromagnetic radiation is made up of a large group of radiation aves that all travel at the

same speed# but all of hich have different avelengths and fre4uencies.

Humans

5isible light %avelengths from 89+ to :;+ nanometres' is the small part of the

electromagnetic spectrum that can be seen by the na"ed human eye. The visible part of the

spectrum can be split into : colours < Red# 6range# =ello# >reen# ?lue# 0ndigo and 5iolet.

The human eye is unable to detect avelengths into the ultraviolet %less than 8@+ nm' and

infrared %more than :@+ nm' range.

n!ertebrates

Many insects# including honeybees# can detect the shorter avelengths of the ultraviolet

range of the spectrum. $oneybees hoever# are unable to detect some of the longer

avelengths in the red part of the spectrum. Therefore# they do not see a ider range of

colours than humans# rather a different range.

"ertebrates

Many bird and reptile species %including gec"os' are able to detect light ell into the

ultraviolet range of the spectrum

3. The clarity of the signal transferred can affect interretation of the

intended visual communication

Identify the conditions under hich refraction occursAhen light passes from one medium to another medium ith a different density# the speed

at hich the light is travelling changes# causing light rays to refract %bend'.

(.g. hen light travels from air into ater# the medium is denser causing light to travel

sloer# resulting in refraction of light.

Identify the cornea, aqueous humor, lens and vitreous humor as refractive media

There are four refractive media in the eye!

• The cornea# hich causes the most refraction

• The a4ueous humor

• The lens# hich is able to refract light to a greater or lesser degree by altering its

shape to fine focus the image onto the retina

• The vitreous humor

!nalyse information from secondary sources to describe changes in the shape of the eye"s

lens hen focussing on near and far objects

Type of vision Eye Shape of lens Action of

muscles of

ciliary boy

Tension of

suspensory

ligament

Refractive

po!er

1istant vision t rest lattened Relaxed Taut 3o

&ear vision ull

accommodation

?ulging and

rounded

Contracted Relaxed $igh

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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

ccommodation is the focussing of ob/ects at different distances# brought about by changing

the convexity of the lens and# as a result# its refractive poer. This change in shape of the

lens results from the action of the ciliary muscles# hich in turn affect the tension of

suspensory ligaments.

or distance vision# light rays do not need to be refracted much as they travel parallel# so the

curvature of the lens must be relatively flat. The ciliary muscles relax. This holds thesuspensory ligaments taut# hich pulls the lens flat.

or near vision# light rays must be refracted more as they tend to diverge# so the curvature of

the lens must be increased. The ciliary muscles contract. This loosens the ligaments# hich

allos the lens to bulge outards and become rounder.

Aithout accommodation# the eye ould not be able to change focus from distant to close

ob/ects. This ill stop the image from falling on the retina.

#ompare the change in the refractive poer of the lens from rest to maximum

accommodation

The refractive poer of the lens changes from lo %in a flatter lens' hen at rest# to high %in

a rounder lens' at maximum accommodation.

Distinguish beteen myopia and hyperopia and outline ho technologies can be used tocorrect these conditions

?oth myopia and hyperopia are visual defects.

Myopia %short-sightedness' is hen the eye can focus correctly on near ob/ects# but hen a

distant ob/ect is vieed the focal length is too short# so the focussed image falls in front of

the retina. This is caused by the eyeball being too long for the focal length or the curvature of

the lens is too great.

Contrastingly# hyperopia %long-sightedness' is hen the eye can focus correctly on distant

ob/ects# but hen a close ob/ect is vieed the focal length is too long# so the focussed image

falls behind the retina. This is caused by the eyeball being too short for the focal length of

the curvature of the lens is not enough.

There are several technologies top correct these conditions!• Spectacles! frames that hold corrective lenses in front of the eye.

• Myopia can be corrected by earing spectacles that have concave lenses. These

cause light rays to diverge slightly before entering the eye# extending the focal

length.

• $yperopia can be corrected by earing spectacles that have convex lenses. These

cause light rays to refract slightly before entering the eye# shortening the focal

length.

• Contact lenses! these or" similarly to spectacles# except that a lens is orn directly

on the surface of the eye

• Refractive laser eye surgery < a laser is used to reshape the cornea so that light is

refracted at the correct angle# correcting myopia and hyperopia. flap of the outer

cornea is cut then a laser is used to destroy part of the cornea to give the correct

curvature.

Explain ho the production of to different images of a vie can result in depth

perception

1epth perception is the ability to /udge the distance beteen ob/ects. This re4uires to

sources of vision %binocular vision'. The to eyes allo an overlap beteen the fields of

vie. The brain interprets these different signals to calculate the distance beteen ob/ects.

$rocess 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

Cataracts#

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cataract is the clouding of the lens# hich obstructs the transmission of light through the

eye causing vision to become blurred. ormation of cataracts is a gradual process that may

occur ith age# disease or over exposure to sunlight and results in blindness if let untreated.

$echnology#

surgical operation can be performed to replace a cloudy lens ith an artificial intraocular

lens %063'. Most cataract surgery are performed ith the small incision no stitch’ techni4ue.

small vibrating probe is inserted into the lens# hich brea"s up the lens into small particles

that can be suctioned out. The artificial lens is then inserted into the space left in the existinglens capsule. &o stitches are needed.

%ocial mplications#

0n ealthy countries this operation is performed routinely. 0t is cheap and simple and can

restore sight to many people# alloing them to return to their normal life. $oever# many in

poorer countries cannot afford the cost and their lac" of sight may become life threatening.

This ine4uality is access is un/ust

The red $ollos oundation or"s to correct this ine4uality. 0t has factories that produces

063s cheaply and train local doctors to perform this operation.

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

imulse

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

The retina is a thin sheet of cells# made up of several layers of nerve cells. The last layer of

cells that the light reaches is photoreceptors# hich contain light sensitive pigments.

There are to types of photoreceptors- rods and cones- hose role it is to!

,. bsorb light energy

*. Convert it into electrochemical signals that the brain can interpret

8. Transmit this as a nerve impulse bac" along the neurone layers toards the optic

nerve# hich carries the signals to the brain

The to main neurone layers are the bipolar and ganglion cells# hose role it is to pass

electrochemical signals from the photoreceptors to the optic nerve.

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

the human eye

Feature Ro Cells Cone Cells

1istribution 1istributed across most of retina# but absent from

fovea

Mostly in the fovea

Structure Rod-shaped outer segment# stac"ed ith

membrane layers of visual pigment

6nly one pigment < rhodopsin

Cone-shaped outer segment#

stac"ed ith membrane layers of

visual pigment

Contain three different forms of the

pigment iodopsin

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unction (xtremely light-sensitive# so used for night vision

and to detect light and shado contrasts

1o not detect colour

Poorer visual acuity due to retinal convergence

Peripheral vision# including the detection of

movement

Re4uire bright light# so used for

daytime vision

Colour vision- each type of iodopsin

pigment is sensitive to one of the

three primary colours of light

5isual acuity due to no retinal

convergence and being densely

pac"ed in the fovea

%utline the role of rhodopsin

Rhodopsin is a light-sensitive pigment present in rods. 0t consists of a protein called opsin

and a retinal.

0ts main role is to absorb light. Ahen light stri"es rhodopsin# the retinal becomes activated

and excitation occurs# hereby the opsin splits from the retinal. This bleached’ state

produces an electrochemical signal that travels to the brain# via the optic nerve. Retinal and

opsin then recombine# so that the rhodopsin can be reused.

Identify that there are three types of cones, each containing a separate pigment sensitive

to either blue, red or green light.

$umans have three types of cone cells# each ith a separate type of the pigment iodopsin.(ach of these pigments is sensitive to a particular avelength of light! The short avelength

of blue light# the medium avelength of green light or the long avelength of red light.

3ight of a particular avelength may stimulate more than one cone.

Explain that colour blindness in humans results from the lac& of one or more of the colour'

sensitive pigments in the cones

ull colour vision in humans depends on all three colour-sensitive pigments being present in

the cone cells. mutation in the gene that codes for a cone pigment leads to the inability of

this pigment to function properly or a lac" of the pigment altogether. s a result# the person

is unable to perceive colour in the normal trichromatic manner and is said to be colour blind.

Red and green colour blindness is a recessive# sex-lin"ed disorder# as the genes coding for redand green pigments are located on the D chromosome. The genes that code for blue cones

are not sex-lin"ed.

$rocess 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

Animal "isual system "isual acuity #umber an type of

photoreceptors

Colour

"ision

$uman

%mammal'

Single-lens eye forming an

image

Strong Rhodopsin7 three

types of cone cells and

one types of rod cell

=es7

trichroma

tic vision

?ee %insect' Complex compound eye

consisting of many ommatidia.These are made up of a cornea

orm a clearer

image thanplanarians# but

Rhodopsin7 able to

detect motion veryaccurately

=es#

includingultraviole

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and a crystalline cone that can

refract light.

ble to detect light# movement

and form a clearer image than

planarians

blurred to human

eye

t

Planarian

%flatorm'

Pigment-lined cup eye ith no

lens

&o image formed- only detectspresence and direction of light

Poor Rhodopsin < far feer

photoreceptor cells

than mammals andinsects

&o

ll photoreceptor cells share one similarity! they all contain the same basic light-absorbing

pigment

$rocess 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

or a message to be successful the receiver must be able to interpret the intended message.

$ence# animals that use colour for communication are usually those that have colour vision.

Colour communication in humans

• Colour coding of electrical ires# indicating to electricians hich colours should be

connected

• Aearing blac" clothes for mourning

Mammals

?aboons use colour communication as part of their sexual behaviour. Male baboons have a

bright band on their faces hen they are se&ually mature. Primate retinas have three types

of cone cells for colour vision.

'irds

The male satin bluebird use colour communication for courtship attraction. $e builds a

boer out of grass and tigs and then decorates it ith brightly coloured ob/ects such as

floers# favouring blue in particular. This bright courtship display is used to attract females.

The display of large colourful feathers by male peacoc"s is not only for mate attraction but is

also used as a (arning mechanism to defend territory and ard off rivals.

The retinas of birds have four types of cone cells.

nsects

Colouration of floers is used to attract agents of pollination# such as honeybees. Some

floers have ultraviolet mar"ings on them to attract honeybees# since they can detect E5

light.

". #ound is also a very imortant communication medium

for humans and other animalsExplain hy sound is a useful and versatile form of communication

•

?ends• Travels through all substances- solid# li4uid and gas

• variety of sounds can be produced by varying the pitch# loudness and tone

• Eseful both day and night

• The sender does not have to be visible to the receiver

• Can 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 created hen an ob/ect vibrates. This causes the molecules next to the ob/ect to

vibrate at the same fre4uency. 6ther molecules in contact pic" up the vibration and cause a

compression ave hich travels through a medium.

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$igh fre4uency sounds %high-pitch'

have a short avelength7 lo fre4uency

sounds %lo-pitch' have a long

avelength.

%utline the structure of the human

larynx and the associated structures

that assist the production of sound

The larynx %voice box' is positioned inthe throat# here the pharynx divides

into the trachea and the oesophagus. 0t

is a hollo box consisting of nine

cartilages# /oined by membranes and

ligaments# and houses the vocal chords.

8 main cartilages- thyroid# cricoid and arytenoid.

To produce sound# air from the lungs causes the vocal chords to vibrate# causing the glottis to

open and close rapidly. The vocal chords are muscular and can alter the pitch of the sound by

changing shape. The !egus ner!e’s function is to control the contraction and relaxation of the

vocal cord muscles. The shorter and tenser the vocal cords# the faster they vibrate and the

higher the pitch. Associated %tructures- The nasal cavity is responsible for the uni4ue voice produced by each

person. Sounds are shaped’ into voels and consonants by the muscles of the tongue# soft

palate# chee"s and lips.

(ather and process information from secondary sources to outline and compare some of

the structures used by animals other than humans to produce sound

Animal Soun prouction

Cric"etsF >rasshop Stridulation- Rub little pegs on their bac" legs against ridges on their foreings

Snapping shrimp Produce a loud sound by very rapidly expelling a ater bubble from their large

cla

ish - bream 0nsert a muscle into their sim bladder hich causes vibrations hen contracted.

6thers produce grunts and clic"s

$. %nimals that roduce vibrations also have organs to detect

vibrations%utline and compare the detection of vibrations by insects, fish and mammals

nsects! the tactile bristles on an insect’s cuticle and antennae respond to lo fre4uency

vibrations. Many insects possess more specialised structures. Crickets have a tympanum

%drum' on each leg. This is a fluid-less cavity hich vibrates hen struc" by sound aves and

the message is sent to the brain.

Fish# they have a lateral line# a pronounced pair of sensory organs# running the length of their

body. This contains receptors sensitive to pressure aves in the surrounding ater.

Some also have sensory organs called labyrinths %a series of tunnels in the inner ear'. Sound

vibrations cause the hair cells ithin these labyrinths to vibrate and the message is sent to

the brain.

Mammals# 0n "iller hales# sound is received by the loer /abone. This contains a fat-filled

cavity hich receives sounds aves and conducts it through the loer /a# middle ear# inner

ear and the auditory nerve to the ell-developed auditory corex of the brain.

%utline the range of frequencies detected by humans as sound and compare this range

ith ) other mammals, ith reasons for their differences.

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)cholocation- the process of transmitting soundaves and using the echoes that return after

hitting an ob/ect# to determine distance# direction# si2e# shape and speed of an ob/ect

$ammal Range of fre%uencies etecte as soun &'()

$uman *+-*+#+++ $2. The inflexibility of the basilar membrane limits the fre4uency range of human

hearing. 6ur effective three-dimensional vision has resulted in less reliance on the sense of

hearing

?ats *+++-,*+#+++ $2. ctive during the night so relies strongly on echolocation for navigation and

prey detection. The higher-fre4uency sound ave produces more detailed messages

1olphins ,;+ $2-,;+#+++$2. 5ery high sounds for precise echolocation. lso use lo-fre4uency sounds

to communicate over long distances

Describe the anatomy and function of the human ear.

Part Structure Function

Pinna leshy external organ consisting

of a flap of cartilage and s"in

Collects sound and directs into the ear canal.

Tympanic

membrane

%eardrum'

Thin membrane beteen the

external ear and the middle ear

5ibrates hen sound aves reach it7 transfers the

vibration to the malleus

(ar 6ssicles Three tiny bones located in the

middle ear7 malleus# 0ncus and

Stapes

Magnify and transfer vibrations from the tympanic

membrane to the oval indo on the cochlea.

6val Aindo lexible membrane beteen the

middle and inner ear

Transfers vibrations from the stapes to the fluid in

the cochlea.

Round Aindo lexible membrane beteen the

middle and the inner ear

?ulges outards %into the middle ear' to allo

displacement of fluid hen vibrations are

transferred to the cochlea.

Cochlea luid-filled spiral that contains

the 6rgan of Corti

1etects different fre4uencies of sound < high pitch

sounds are detected at the start of the cochlea

and lo potch sounds at the end of the spiral

6rgan of Corti Consists of hair cells and leads

from the cochlea to the brain

$air cells translate vibrations into electrochemical

signals.

uditory nerve Consists of the axons of the hair

cells and leads from the cochlea

to the brain.

Transfers the impulse from hair cells to the brain.

External*outer

ear! Pinna#

auditory canal and

tympanic

membrane.

$ile Ear+ (ar

6ssicles# 6val

indo# round

indo G

(ustachian tube

,nner ear+ cochlea#

organ of Corti#

auditory nerve.

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%utline the role of the Eustachian tube

The (ustachian tube helps to e4ualise air pressure on either side of the tympanic membrane

by bringing in air from the mouth.

6utline the path of a sound ave through the

external# middle and inner ear and identify the energy

transformations that occur.

II Ahen the sound aves reach the tympanic

membrane# sound energy is converted into mechanical energy by the

movement of the tympanic membrane. II

II This mechanical energy is transmitted through fluid

in the cochlea and bends cells in the organ of Corti. The

hair cells convert it into an electrochemical signal# hich is

then transmitted to the brain via the auditory nerve. II

Describe the relationship beteen the distribution of hair cells in the organ of #orti and

the detection of sounds of different frequencies.

The organ of Corti contains ,;#+++

hair receptor cells hich are distributed

along the basilar membrane.

1ifferent fre4uencies cause

movement of the basilar membrane

at different locations. ctivation of

the hair cells occurs at points of

vigorous vibration of the basilar

membrane.

$air cells nearest the start of the basilar membrane %base' are activated by the higher

fre4uency sounds# hile those further along the basilar membrane %apex' are activated by

loer-fre4uency sounds.

%utline the role of the sound shado cast by the head in the location of sound.

The head casts a sound shado that causes the ear furthest aay from the sound to receive

less intense sound than the other. $umans can use this to trace the location of the sound# by

turning their heads until the intensity of the sound is e4ual in both ears7 at this point people

should be loo"ing in the direction of the source of the sound.

Evaluate a hearing aid and cochlear implant in terms of: the position and type of energy

transfer occurring, conditions under hich the technology ill assist hearing, limitations of

each technology.

-evice Type of Energy

transfer

'earing conition Avantages .imitations

$earing

id

Sound to

electrical then

amplified sound

energy

1amage to tympanic

membrane or ossicles.

or people ith

ade4uate residual

hearing

Relatively cheap# no

surgery re4uired

Aill not restore to

normal hearing7

amplifies bac"ground

noise

Cochlear Sound to Profound deafness7 Provides hearing to Surgery is expensive

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implant electrical damage to hair cells in

cochlear

profoundly deaf

people7 restores

hearing after in/ury

ith potential post-

operative side effects

such as infection and

facial nerve damage.

&. #ignals from the eye and ear are transmitted as

electrochemical changes in the membranes of the oticand auditory nerves

Identify that a nerve is a bundle of neuronal fibres

nerve is a bundle of neuronal fibres. These neuronal

fibres are the units hich ma"e up the nervous system

and are called neurones. There are three types!

sensory# motor G connector. They transmit electrochemical signals.

neurone consists of a large cell body containing the nucleus and other cell organelles# ith

extensions on both ends called dendrites and a&ons. myelin sheath* made up of specialisedcells called %ch(ann cells# surrounds the axon# providing an insulating cover that 4uic"ens

the transmission of the nerve impulse. The myelin sheath has small gaps called the nodes of

+an!ier beteen the Schann cells. This is here ion channels that function the action

potential are concentrated.

&eurons are separated by a small gap called the synapse,

Identify neurones as nerve cells that are the transmitters of signals by electro'chemical

changes in their membranes.

&eurons are nerve cells that transmit nerve impulses by electro-chemical changes in theirmembranes.

Ho(

&eurons contain ions %charged particles'. They have cell membranes ith ion channels

selectively permeable to sodium %&aJ' Potassium %KJ' and chloride %Cl-'.

neuron is in its resting state %or resting potential' hen there is a difference in charges on

either side of its cell membrane. This resting state measures about -:+ m5 and the neuron is

said to be polarised .

Charges in the environment of a neurone can affect the permeability of the membrane toions %causes the ion channels to open' and therefore change the membrane’s potential.

Ahen a stimulus causes a positive shift in the membrane’s potential %e.g. from -:+m5 to

-B+m5' it is called a depolarisation. Ahen the depolarisation reaches about -;;m5 a neuron

ill fire an action potential. This is hen the flo of ions causes the neurone to generate a

ner!e impulse# hich is transmitted from neurone to neurone across synapses.

t the synapse# chemicals called neurotransmitters diffuse across the synapse to the

membrane of the next neurone. This initiates an electrical signal in the next neurone and the

process is repeated along the nerve.

Define the term *threshold" and explain hy not all stimuli generate an action potential.

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The threshold is the amount of positive change in membrane potential hich is re4uired

before an action potential is produced. Ahen the depolarisation reaches about -;;m5 a

neuron ill fire an action potential.

0f the neuron does not reach this critical threshold level# then no action potential ill fire.

lso# each action potential is a separate event. Therefore# a cell cannot produce another

action potential until the previous one is complete and the cell is bac" to its resting state.

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

and sound.

The cerebrum is the largest part of the brain

here all conscious activity occurs. The

cerebrum splits into * hemispheres# a left

hemisphere and a right hemisphere. (ach

hemisphere receives impulses from and exerts

control over the opposite side of the body. 6n the outer surface

of the cerebrum is the cerebral cortex# hich is only a fe mmthic"# here most of the activities of the cerebrum occur.

The hemispheres are split into ; lobes! 0P6T- frontal# insular# occipital# parietal# temporal.

"ision and colour recognition are controlled by the occipital lobes. 0mpulses

reach this lobe from the retina via the optic nerve.

%ound is processed in * areas of the temporal lobes! ?roca’s

area and Aernic"e’s area. ?roca’s area is involved in speech

production# specifically assessing the syntax of ords - the

ordering of and relationship beteen the ords and otherstructural elements in sentences. The information is then

transferred to Aernic"e’s area here the content of the

ord is interpreted. 0mpulses reach the ?roca’s area via the auditory nerve.

Explain, using specific examples, the importance of correct interpretation of sensory

signals by the brain for the coordination of animal behaviour.

The brain interprets the signals arriving from the sensory organs. 0f there is damage to a part

of the brain the signals ill not be interpreted correctly# affecting the coordination of

behaviour. or example!

• Prospagnosia- occurs after damage to the occipital lobes. This causes face

blindness- the inability to recognise faces• /ernic0e1s aphasia2 is prouce by lesions in the temporal an parietal

lobes an may be cause by a stro0e or by a iet eficient in thiamine3 This

causes an inability to unerstan the information in !ritten or spo0en

!ors3

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