Download Detection of Environmental Conditions in Mammals

Detection of Environmental
Conditions in Mammals
Irritability
• The ability to respond to stimuli
• The
Stimuli
Receptors
Nerve
effectors
brain
impulses
(external
then
generate
(muscles
generates
are
or nerve
sent
internal)
orto
nerve
impulses
glands)
theare
brain
impulses
detected
then
after
for being
by
receptorssuitable
stimulated
interpretation
carrying
produces
suitable
or senseresponses
responses
organs to the effectors
Eye
• Sense organ for receiving light
• Protected by the skull
Structures around the eye-ball
• Tear glands: secrete tears which
– wash away dust
– contain lyzozyme which kills bacteria
– moisten the eye surface
• Eyelids
– protect eye from damage
• Eyelashes
– protect the eye from large particles to enter it
Internal structure of the eye-ball
• Wall of eye-ball consists of 3 layers
1. Sclera
• maintain the shape
of the eye-ball
• protects the inner
structures
• provides anchorage
to eye muscles
Internal structure of the eye-ball
2. Choroid
• With many blood
vessels and pigment
• Pigment
Blood vessels
absorbs
supplies
extra
light
oxygen
to
and nutrients
prevent
reflection
to the
eyes,
of
light
and
inside
to the
remove which
eyeball
metabolic
may
wastes
blur
thefrom
image
them
Internal structure of the eye-ball
3. Retina
• Contains light
sensitive cells (photoreceptors) and nerves
• Rods for blackand-white vision
• Cones for colour
vision
Internal structure of the eye-ball
Yellow spot
• densely packed with
cones
• no rod is present
• gives the most
distinct image and the
greatest colour
discrimination
Internal structure of the eye-ball
Blind spot
• the point where the
nerve fibres leave the
eye-ball
• no photo-receptors
cannot detect any
image
Internal structure of the eye-ball
Cornea
• Continuous with sclera
• Protected by
conjunctiva
• To allow light to enter
• To refract light onto
the retina
Internal structure of the eye-ball
Pupil
• The opening which
allows light to enter the
eye-ball
Iris
• To control the size of
the pupil
Change in the pupil size
• Iris is made of circular muscles and radial
muscles –antagonistic pair
Increase in the pupil size
• At dim light : circular muscles relax; radial
muscles contract
• increase in size of pupil
Decrease in the pupil size
• At bright light : circular muscles contract;
radial muscles relax
• decrease in size of pupil
Internal structure of the eye-ball
Lens
• Transparent, elastic,
biconvex structure
• To focus light rays
on the retina by
changing its
convexity
Internal structure of the eye-ball
Suspensory ligaments
• Hold the lens in
position
Ciliary body
• Regulates the
curvature of the lens
by contraction and
relaxation of the
ciliary muscles
Accommodation
• The ability of the eye to focus objects at
varying distances onto the retina
• Light entering the eye is refracted
successively at the cornea, the aqueous
humour, the lens and the vitreous humour.
• The image is formed on the retina and the
retina sends signal along the optical nerve to
the brain, causing the sensation of sight.
• The image formed on the retina is inverted
but is interpreted as erect.
Focusing near object
Light from near object
Focusing on near objects
Lens become
Ciliary
Tension
muscles
of suspensory
more
contract
convex
ligaments
is
 decreased
Decrease in circumference
Focusing far away object
Light from far away object
Focusing on distant objects
Ciliary
Tension
muscles
of suspensory
relax
ligaments
Lens
become
less
convex
is
 increased
Increase in circumference
Accommodation
Object
Near
Distant
Ciliary
Muscle
Shape
Contract Thicker
Relax
Focal length
Shortened
Thinner Lengthened
Near Point and Far Point
• The average normal eye can focus objects
easily from about 25 cm, i.e., the near point,
to infinity, i.e. the far point.
• This range of distance of clear vision varies
from one person to another and decreases
with age.
Short sight
Light from distant object
• The eyeball is a bit too long.
• The lens lacks the ability to
accommodate for a distant object.
Correction of short sight
Light from distant object
Diverging lens
( Concave lens )
Long sight
Light from near object
• The eyeball is a bit too short.
• The lens lacks the ability to
accommodate for a near object.
Correction of long sight
Light from near object
Converging lens
( Convex lens )
Causes
Defect
Eye lens
Eye ball
Correction
Short sight
Too thick
Too long
Concave lens
Long sight
Too thin
Too short
Convex lens
Eye defects
• Short-sighted
– Image of a distant object formed in front of the
retina
– Lens too thick
– Eye-ball too long
– Correction: wear concave lens
Eye defects
• Long-sighted
–
–
–
–
Image of a near object formed behind the retina
Lens too thin
Eye-ball too short
Correction: wear conves lens
Eye defects
• Colour blindness
– Defect of one or more of the three types of cone
cells
– Unable to distinguish between colours
– Inherited
Class Practice
1. Which of the following statements about the lens is/are
correct ?
(1) The image formed on the retina is real.
(2) The pupil is smaller in bright light than in dim
light.
(3) When the object distance changes, the eye
focuses an object by chaning the focal length
of the eye lens.
Internal structure of the eye-ball
Anterior chamber
• Filled with aqueous
humour
– to refract light onto the
retina
– to maintain the shape
of the eye-ball
– to supply nutrients to
the conjunctiva, conera
and lens
Internal structure of the eye-ball
Posterior chamber
• Filled with vitreous
humour
– to refract light onto the
retina
– to maintain the shape
of the eye-ball
Internal structure of the eye-ball
Optic nerve
• To transmit nerve
impulses to the optic
centre in the cerebral
cortex of the brain for
interpretation
Basic Fact of EAR
• Ears are used to detect
SOUND in
environment.
• Ears help to detect
movement & position.
• Ear is divided into
Outer Ear, Middle Ear
& Inner Ear.
Structure of EAR
• Outer Ear: EAR
PINNA, EAR CANAL
& EAR DRUM.
• Middle Ear: EAR
BONES
• Inner Ear:
EUSTACHIAN TUBE
& ADENOIDS.
Outer Ear
• It is the part which is visible
and is made of folds of skin and
cartilage.
• It leads into the ear canal,
which is about one inch long in
adults and is closed at the inner
end by the eardrum.
• The eardrum is a thin, fibrous,
circular membrane covered
with a thin layer of skin.
• It vibrates in response to
changes in the air pressure that
constitute sound.
• The eardrum separates the outer
ear from the middle ear.
Middle Ear
• It is a small cavity which
conducts sound to the inner ear
by means of three tiny, linked,
movable bones called
"ossicles."
• These are the smallest bones in
the human body and are named
for their shape.
• The hammer (malleus) joins the
inside of the eardrum.
• The incus joint with the
hammer and to the stapes.
• The base of the stapes fills the
oval window which leads to the
inner ear.
Inner Ear
• The inner ear is a very delicate
series of structures deep within
the bones of the skull.
• It consists of a maze of winding
passages, called the "labyrinth".
• The front (see cochlea) is a tube
resembling a snail's shell and is
concerned with hearing.
• The rear part is concerned with
balance.
Detection of SOUND
1.
2.
3.
4.
5.
Sound waves (air vibrations)
are collected by the OUTER
EAR.
Sound waves vibrate the EAR
DRUM.
Vibrations are amplified by
the EAR BONES.
Vibrations change the
pressure of the FLUID of the
INNER EAR.
Vibrations are transmitted to
signals to the brain via nerve
impulses.
Intensity Cues in Stereo
• When the volume of
two speakers are
equal, we will hear the
sound as come from
the centre.
Structure of the ear
• Three regions:
• Inner
Outer ear
Middle
ear
ear
Process of hearing
• Sound waves are collected by the ear pinna
Process of hearing
• Sound waves pass along the external
auditory canal to the ear drum
Process of hearing
• Ear
drum
converts
Sound
waves
makesound
the earwaves
druminto
to vibrate
mechanical vibrations
Process of hearing
• Ear bones
transmit and
amplify
vibrations
drum transmits
vibration
to the
ear
bones
Process of hearing
• Ear bones transmit vibration to the oval
windows
Process of hearing
• Oval window causes the perilymph in the
upper canal of the cochlea to vibrate
Process of hearing
• Perilymph transmits vibrations to the
endolymph in the middle canal
Process of hearing
• The sensory hair cells send
on theoff
bottom
nerve
membrane of the middle canal are stimulated
impulses
Process of hearing
• The auditory centre
nerve transmits
interpretsthe
theimpulses
nerve
to the auditory
impulses
and produce
centre of
thethe
sensation
cerebralofcortex
hearing
Process of hearing
• The
Round
vibrations
windowofbulges
perilymph
outwards
are transmitted
into the
to the round
middle
ear cavity
window
to release pressure
Equalizing the pressure on both
sides of the eardrum
• The middle ear is air-filled
– This
The ear
atmospheric
causes
drum
thecannot
ear
pressure
drum
vibrate
tomay
curve
properly
become
inwards
and
higher
or
or lower
outwards
causes
pain
than
and
thetemporarily
air pressuredeaf
in the middle ear
Equalizing the pressure on both
sides of the eardrum
• The pressure on both sides of the ear drum
can be equalized by the Eustachian tube
• It
Eustachian
is openedtube
onlyisduring
connected
swallowing
to the pharynx
or yawning
Detection of movement by the ear
• At
Thethesemi-circular
Above
base
the cochlea
of eachcanals
are
canal
three
is
areasemi-circular
perpendicular
swelling called
canals
to
ampulla
each
other
to detect head
movement
all planes
– They
are responsible
for detecting
headinmovement
Detection of movement by the ear
• Semi-circular
Gelatinous mass
canals
(cupula)
are filled
is found
withinside
endolymph
each
ampulla
Detection of movement by the ear
• The
Nerve
When
However,
endolymph
sensory
the
impulses
head
the
move,
endolymph
displaces
hair
are
generated
cells
theunder
the
semiin
circular
gelatinous
the
and
canals
gelatinous
transmitted
canals
will
mass
will move
move
inside
mass
along
isin
the
the in the
same direction
opposite
ampulla
stimulated
auditory
nerve
direction due to
inertia
Detection of movement by the ear
• Nerve impulses are generated and
transmitted along the auditory nerve to
• the cerebrum: aware of the direction of head
movement
• the cerebellum: leads to appropriate responses of
the muscles to maintain body balance
Nose - the olfactory organ
• For detection of smell
• By olfactory cells on the upper part of nasal
cavity
• Covered with mucus
– to dissolve chemicals in air which stimulate the
olfactory cells to produce nerve impulses to the
cerebrum
Tongue - the taste organ
• Detected by taste buds on the upper surface
of the tongue which are stimulated by
chemicals dissolved in saliva
• Different regions detect different tastes
• Flavour of food is
given by both the bitter
sense of taste and sour
odour of it
salty
sweet
The skin
• Contains many receptors for the sensation
of touch, cold, hot, pain and pressure
• The distribution of them are uneven
throughout the skin