Sense organs

2. PRESENTED BY
MR .ROMAN BAJRANG
BASIC BS.C NURSING 2ND YEAR
RELIANCE INSTITUTE OF NURSING

3. INTRODUCTION
SENSATION
AWARENESS
PERCEPTION
STIMULUS
RECEPTOR
CONDUCTION
TRANSLATION

7. INTRODUCTION

8. The special senses of hearing, sight, smell and taste have
specialized sensory receptors (nerve ending) outside the
brain.
These sensory receptors are found in the ears, eye, nose
and mouth.
The receptor receives a particular stimulus & initiates a
nerve impulse in the neuron, which carries the impulses
to the brain.
In the brain, the incoming nerve impulses undergo
complex processes of integration and coordination that
result in the perception of sensory information and
various responses inside and outside the body.
INTRODUCTION

9. INTRODUCTION
Perception
Receptor
Nerve
impulse
Integrati
on &
coordina
tion
Stimulus

12.  The Eyes are the organ of sight. these are used of perception of
light & it is situated in the deep, protective bony cavities, called
orbits or eye sockets of the skull.
 Shape: spherical, Diameter:2.5 cm
 The space between the eye & the bony orbits is occupied by the
adipose tissue, connective tissue, ligaments and muscles.
 The bony walls of the orbit and the adipose tissue help to protect
the eye from injury.
ANATOMY OF EYE

13. STRUCTURE OFTHE EYE
• The wall of the eyeball is composed of three layer of
tissue:
• The outer layer: sclera & cornea
• The middle layer: choroid, ciliary body & iris
• The inner layer: Retina

14. STRUCTURE OF THE EYESTRUCTURE OFTHE EYE

15. It is thick, superficial layer
consists of two regions: Anterior cornea
of the eyeball that
&
The outer most layer of sclera (white portion) 2/3rd part & it
is composed of a dense connective tissue.
The sclera maintains the shape of eye, protects its inner
parts & gives attachment to the eyemuscles.
The anterior 1/3 rd part of the outer coat is called cornea i.e
transparent. It is the first part of eye through which light
enters.
Cornea is nonvascular (no blood vessels) in nature. So it can
easily grafted.
STRUCTURE OFTHE EYE
The outer fibrous layer
posterior sclera.
Sclera & Cornea

16.  The cornea is convex (curved) and is involved in refracting
(bending) light rays that helps focus the light on the retina.
 At the junction of of cornea & sclera there is a small canal called
as Canal of schlemm, which permit the drainage of aqueous
humor.
 Cornea is covered & protected by a very thin membrane called
conjunctiva.
STRUCTURE OFTHE EYE
Sclera & Cornea

17. STRUCTURE OFTHE EYE
Middle layer (vascular coat)
It is the middle layer of the eye that is composed of
three regions: Choroid, Ciliary body and iris.
Choroid
 The middle Coat is called choroid. It is deep chocolate color.
 Choroid is highly pigmented layer & very rich bloodsupply.
 The pigment cell produce a melaninpigment.
 The melanin in the choroid is responsible for its dark brown
colour. Melanin absorbs stray light and darken the eyeball cavity,
which prevents internal reflection within the eyeball. As a result,
the image remains sharp andclear.

18.  It consist of ciliary muscles which gives attachment to
STRUCTURE OFTHE EYE
Ciliary body
suspensory ligament.
 The process of contraction and relaxation of the ciliary muscle
changes the tightness of suspensory ligaments, which alters the
shape of the lens and the permits the adaptation for near or far
vision (accommodation)
 Ciliary body also helps in the secretion of aqueous humour.
Iris
 Iris is the coloured portion of the eyeball that extends interiorly
from the ciliary body and is suspended between the cornea and
the lens. It consist of melanocyte & circular and radial smooth
muscle.
 The centre of iris is calledpupil

20.  The principal function of the iris is to regulate the amount of
light entering the eyeball by varying the diameter of pupil. this
variation of pupil is regulated by sympathetic and
STRUCTURE OFTHE EYE
Iris
parasympathetic nerve.
In bright light:
Parasympatheticfibres
Contractcircularmuscles
Constrictthe pupil
Less lightenters the eye
In dim light:
Sympatheticfibres
ContractRadialmuscles
Dilate thepupil
More light is allowedto enter

21. Figure15.9
Pupil Dilation and Constriction

22.  It is the inner most layer, present just below the choroid.
 Retina is the light sensitive layer, containing specialized cells
rods & cones
 Rods & cones detects light & set impulse, these impulse are
transmitted to the brain through 2nd cranial nerve (optic nerve)
Structure of retina:
The retina is the light sensitive portion of theeye.
 From outside to inside:
(1) Pigment layer
(2) Photoreceptor cell layer
(3) Bipolar cell layer
(4) Ganglion cell layer
STRUCTURE OFTHE EYE
Inner layer: the retina

23. Structure of Retina

24. Photoreceptor cell layer
Photoreceptors are the specialized cell present in the
retina that process light ray convert them to nerve
impulses.
There are two types of photoreceptor: rods & cones.
Each retina has about 6 million cones & 120 million
rods.
 The outer segment of rods are cylindrical and rods
shaped, hence the name rods. The rods cell is only for
dim light vision. The photo pigment present in the rods
is rhodopsin.
Structure of Retina

25. Photoreceptor cell layer
 The cones cells are sensitive to bright light and produce
colour vision. The following three different types of cones
are present in theretina:
1. Blue cones, which are sensitive to bluelight.
2. Green cones, which are sensitive to greenlight.
3. Red cones, which are sensitive to redlight.
 The stimulation of various combination of the three
types of cones by light of different wavelengths results in
the perception of different colour.
 Lack of one or more types of cone cells cause colour
blindness

26. •Receptor cells: rods and cones, sensitive to light
•bipolar cells: carry signals from receptors to ganglion cells
•Ganglion cells: axons of ganglion cells form the optic nerve
Structure of Retina

27. Rod shaped
Very high in numbers
about 12o million in
each eye.
Contain Rhodopsin
Dim light
They do not detect
colour
 Conical structure
Smaller in numbers
about 6 million in each
eye.
Contain Idopsin
Bright light
They detect colour
vision
DIFFERENCE BETWEEN RODS & CONES

28. Trans-retinene +scotopsin + energy
In light: Rhodopsin trans-retinene+scotopsin+energy
In dark: trans-retinene+scotopsin+energy Rhodopsin
Function of retina
(Mechanismand chemistry of dim & bright light)
1. Dim light vision
• Rod contains a pigment called rhodopsin
• opsin (protein) + Retinene (Aldehyde) Rhodopsin
• Retinene occurs in 2 forms: cis-retinene & trans-retinene
• When the light strikes the rods the cis-retinene converts into
trans-retinene.
• Rhodopsin
• This reaction cause local electrical changes &gets
up an impulse which is transmitted to the optic nerve. impulse
Bleaching

29. Function of retina
(Mechanismand chemistry of dim& bright light)
1. Bright light vision
 The cones are sensitive to bright light and produce colour
vision.
 The pigment of cones is idopsin. It also consist of retinene &
opsin.
 The opsin of idopsin is calledPhotopsin.
 When light of high intensity strikes the similar changes occur
i.e. cis-retinene of idopsin splits into photopsin & transretinene.
Idopsin photopsin+ trans-retinene+energy
impulseTransmittedto optic nerve

30. According to trichromacy theory, cones are responsible for
colour vision.
The cones cells are sensitive to bright light and produce
colour vision.
The following three different types of cones are present in
the retina:
 Blue cones, which are sensitive to bluelight.
 Green cones, which are sensitive to greenlight.
 Red cones, which are sensitive to redlight.
 The stimulation of various combination of the three types
of cones by light of different wavelengths results in the
perception of different colour.
 Lack of one or more types of cone cells cause colour
blindness
Colour Vision

31. STRUCTURE OFTHE EYE
Yellow spot or macula lutea
 A Small area of the retina present at the centre of its posterior
part is called the macula lutea or yellow spot here, only cones are
present.
 This region produces the sharpest vision.
Optic disc or blind spot
 The optic nerve leave the eyeball by piercing the eye coat at the
back.
 The point on the retina from where the optic nerve leaves the eye
is called the optic disc or blind spot.
 It is referred to as blind spot because its lacks the photoreceptor
cells rods and cones, therefore we cannot see an image that
strikes the blind spot.

33. Lens
 The lens is an elastic transparent body present just behind the iris within
the eyeball cavity.
 It is attached with suspensory ligament & ciliary body.
 The light rays enter the eyes are reflected by the lens that helps focus
them on the retina to clear vision.
Interior of the eyeball
 The lens divides the eye ball cavity into twochamber:
 The anterior aqueous chamber: it is filled with clear, watery fluid i.e
aqueous humor & it is drained into canal of schlemm. it is responsible
for supply nutrition, remove waste products & maintains pressure in the
eyes.
 The posterior vitreous chamber : it lie between the lens and the retina
and consists of a thick, transparent jellylike substance, the vitreous
humor.
 The vitreous humor is secreted by the retina during development of eye
(embryonic stage)
 It too helps maintain the intraocular pressure and the shape of eyeball.

35. Middle Vascular
layer: choroid,
ciliary body, iris
Inner
nervous
layer: retina
Outerlayer
(Scelera&
Cornea )
Lens
Senseorgan
Eye
OVERVIEW OF EYE
Refract bend
the light rays
Contain
Photoreceptor cells
rods and cones
Convert light rays into nerve
impulses and send them to
occipitallobe for perception

36. Visual areas of hemisphere where the real perceptionof
vision arises
Physiology of Vision
Eye work on the principle of camera. similar to camera eye containsa lens
(to focus light ray).
The optical elements of the eye (i.e. cornea and lens) focus the image of an
object on the light-sensitive film, thatis retina.
the image is processed by the photoreceptor cells of the retina that convert
the light rays into nerveimpulses.

37. Physiology of Vision
 Various process are involved in focusing the light rays
and producing a clear image on theretina.
These processes are as follow:
 Refraction or bending of lightray
Accommodation
Change in pupil size

38. 1.Refraction or bending of lightray
 When light rays travel from a medium of one density (such as
air) to a medium of different density (such as water), they
undergo refraction(bending)
 As the light rays reflected by the objects enter the eyes, they
pass through the conjunctiva, cornea, aqueous humor, lens &
vitreous humor.
 These parts are denser than air, refracting (bending) the light
rays passing through the eye to bring them to a focus on the
retina.

39. 1.Refraction or bending of lightray
1. Near object vision
 For the objects which are nearer refraction is greater (increased
refraction)
 For Near object vision Ciliary muscles contracts & pulls the
suspensory ligament which increases refractive power, convexity
and thickness of the lens.
 In this process lens bulges in forward direction
2. Distant object vision
 For distant object needs least refraction.
 For near object vision ciliary muscles relaxes which pull the
suspensory ligament & it finally makes the lens thinner. So
convexity of lensdecreased.
 Finally image is produced by lens on the retina & this image is
inverted & reversed. however the brain interpreted that the image
in the right way.

40. Physiology of Vision

42. 2.Accommodation
It is the process by which light rays from near or distant objects
are brought to focus on the retina with the help of ciliary muscles
and suspensory ligament is calledaccommodation.
Close vision
 Constriction of pupil: size of the pupil, changes according to
used. It reduces the width of beam of light entering to the eye. So
its passes through central curved part of the lens.
 Convergence:
 It is the process of movement of eyeballs thus the extrinsic
muscles of the eye helps in convergence.
The nearer the object greater will be the convergence.
If the convergence is not complete eyes which are focused on
different objects or on different point of the same objects. In this
case two images will be sent to brain ( diplopia).

43. for distant
Changing the power of lens:
 It is done by changing the thickness oflens.
 Lens is thicker for near vision and thinnest
vision.(More than 6 meters distance)
Close vision
Distant vision
 For objects more than 6 meters away from eyes requires no
adjustment & convergence of eye. Only changes the power of
lens.

44. Physiology of Vision
Physiology of Vision

45. 3.Change in pupil size
Iris
Circular muscles contracted
Result constricted of pupil
 The size of pupil to controls the amount of light entering to the
eye.
 In a Bright light pupils areconstricted.
 In a dim light pupils aredilated.
Bright light Dim light
Iris
Radial muscles dilated
Result dilated of pupil

46. ACCESSORY ORGAN OF THE EYE
Eyebrows
• The eyebrows contain numerous hairs that project obliquely from
the surface of the skin. they protect the eyeballs from sweat, dust
and other foreign objects.
Eyelids
• The eyelids are two movable folds of tissue situated above and
below of each eye. on the free edges of the eyelids, there are short
curved hairs, the eyelashes.
• The eyelids & eyelashes shade the eyes during sleep, protect the
eyes from excessive light and foreign objects, and spread the
lubricating secretions over the eyeball.
• The space between the upper & lower eyelids that exposes the
eyeball is called the palpebral fissure.

48. • They are situated between the socket and eye ball at upper &
lateral part. The lacrimal glands secrete the lacrimal fluid
(tears) that is composed of water, mineral salts, some mucus
and lysozome. A protective bactericidal enzyme. They have
many function:
 To maintain moisture of cornea
 To maintain optical properties ofcornea
 Tear also wash away many irritants, the dust.
 It prevent eye from microbial infection as it contains lysozyme
enzyme.
 It acts as a disinfectant.
Lacrimal Gland

49. Meibomian or tarsal glands (Sebaceous gland)
 They are modified sebaceous glands which are present along
the edges of eyelids.
 They secrete oily substance which lubricates corneal surface.
Zeis gland
 They are also sebaceous glands. They are associated with the
follicles of eyelashes.
Diseases of eye
 Glaucoma
 Cataract
 Presbyopia etc

50. Visual pathway
 The nerve impulses(action potential) generated in the photoreceptors is
transmitted to the occipital lobe of cerebrum by a nervous pathway, called
the visual pathway or optic pathway
 The various step of visual pathway:
 The optic nerve is formed by the axon of ganglion cells. The excited
ganglion cells transmit the action potential to the optic nerve, which leaves
each eye through the optic disc or blind spot.
 After leaving the eye, the axon within the optic nerves pass through the
optic chiasma, a crossing point of the optic nerves present near the
pituitary gland.
 After passing through the optic chiasm, the axons become part of the optic
tract and enter the brain.
 The nerve fibres of the lateral geniculates bodies of the thalamus then pass
through the internal capsule and form the optic radiations that terminate in
the visual area of the cerebral cortex in the occipital lobe of the cerebrum.

51. • The visual area of cerebral cortex contains three
areas, each with its own function. They are as
follows:
a. Primary visual area: it is concerned with the
perception of visual impulses
b. Visual association area: it is concerned with the
interpretation of visual impulses
c. Occipital eye field: it is concerned with movement
of eyes:
Visual pathway

52. • Optic nerve optic chiasma
Lateral genuculate bodies of thalamus
Optic radiations
Visual area of the cerebral cortex
Visual pathway

53. Visual pathway

55.  The Ear is the organ of hearing. It is supplied by 8th cranial nerve.
 The sense of hearing is the ability to detect the mechanical
vibrations i.e. sound.
sense of hearing & equilibrium Ears are associated which
maintenance.
Structure of ear
The ear is divided into 3 parts:
1. External Ear
2. Middle ear
3. Internal ear
ANATOMY OF EAR

57. Sense organ
External ear Internal ear
Ear
Middle
ear
OVERVIEW OF EAR
Eustachian
tube
Bones:
Milieus, incus, stapes
Maintains air
pressure in earAuricle Eardrum
Auditory
canal
Collects &
sends sound
waves
Vibrates
when sound
waves strike
it
VestibuleCochlea
Semicircular
canal
Involved in
equilibrium
Involved in
equilibrium

58. The auricle (pinna):
It is broad expanded, outer most flap called pinna.
Pinna is a cartilaginous structure composed of fibro elastic
cartilage.
It helps to receive & direct sound waves.
External Auditory Canal
 It is about 2.5 cm long canal which is “S” shaped.
 Lined with cerumen glands.
 The inner and of this canal is covered which is a delicate and sound
sensitive tympanic membrane.
 The Walls of tympanic canal contains special glands called
ceruminous glands. These gland secrete earwax which help to
protect ear from dust particles.
1. External Ear

59. Ceruminous glands:
 Cerumen (ear wax) contains lysozyme & immunoglobulin's so
prevents dust, insects & microbes from reaching the tympanic
membrane.
Tympanic membrane (Ear drum)
 It is a thin, silvery grey, delicate membrane that completelyseparates from
middle ear.
 The auricle allows the sound waves to enter the auditory canal, which directs
those waves towards the delicate membrane and causes the membrane to vibrate.
 It serves to convey sound waves to middle ear ossicles.
1. External Ear

61.  The external ear is followed by middle ear.
 The middle ear is an irregular-shaped, air filled cavity
enclosed in the temporal bone.
 It is separated from external ear by the eardrum and from the
internal ear by a thin bony partition that contains two small
membrane-covered openings: the oval window (fenestra
ovalis) and the round window (fenestrarotunda).
 The oval window is occluded by part of small bone called
stapes and the round window by a fine sheet of fibrous tissue.
 The middle ear are the three smallest bones in the body, the
auditory ossicles (ear bones), that extend from the tympanic
membrane to the oval window.
 These bones are present in a series and are connected to each
other by synovial joints.
2. Middle Ear

62.  The auditory ossicles are named according to their shapes: Malleus
( hammer shaped), incus (anvil shaped) and stapes (stirrup shaped).
 Malleus: the handle of malleus is attached to the internal surface of
the tympanic membrane and the head forms a movable joint with
the incus.
 Incus: the body of incus is joined to the malleus and the long
process to the stapes.
 Stapes: the head of stapes is joined to the incus and its foot plate
into the oval window.
The auditory ossicles transmit vibrations from the tympanic
membrane to the internal ear.
Eustachian tube/ auditory tube:
 The middle ear cavity is communicated with nasopharynx through
a tube called Eustachian tube.
 It help to maintain the pressure balance in theear.
 Most of the time this tube remains closed, it opens only during to
equalize the pressure & swallowing.
2. Middle Ear

63.  The internal ear is also called membranous labyrinth. It is submerged in a fluid
called perilymph.
 The membranous labyrinth containsanother fluid called endolymph.
 The composition of endolymph differs from rest of the lymph in the body as it
possess high concentration of k+ ions.
 Internal ear consistof
1. The vestibules (balancingorgan)
2. The cochlea (hearing organ)
3. Semicircular canals
3. Internal Ear

64. 1.Vestibule (vestibular apparatus)
 The part of inner ear other than cochlea is called as vestibular
apparatus.
 It is differentiate into twochambers
 Utriculus is upper widechamber
 Sacculus is lower smaller chamber
 These chamber are connected with each other by a duct called
endolymphatic duct.
3. Internal Ear

65. 2.Semicircular canals
Three semicircula canal are attached to utriculas. These are at right angle to
one another which are named as:
1. Anterior vertical canals
2. Posterior vertical canals
3. Horizontal canals
 The anterior and posterior canal arise from the same place & remain
associated with each other for a shortdistance.
 The place of origin of semicircular canals become swollen is known as
Ampulla.
 The utriculus, sacculus of semicircular canals which are filled with
viscous fluid called as endolmyph.
 Inner surface of utriculus & sacculus have patches of sensory hair cells
named asmaculae.
 Sensory hair cells which are associated with thousand of tiny particle of
caco3 called otolish (earstones)
3. Internal Ear

66. function (i.e
3.The cochlea (hearing organ)
 This part of internal ear is associatedwith auditory
hearing)
 Cochlae is a tube about 3.5 cm long, it is filled with endolymph.
 The canal of choclea is divided in to 3 chambers.
1. Scala vestibule (upper)-perilymph
2. Scala media (middle)-endolymph
3. Scala tympani (lower)-perilymph
 An important structure called organ of corti rests an basilar
membrane.
3. Internal Ear

67. Organ of corti
 The organ of corti lies the middle chamber of cochlea.
 It consists of 2 rods, outer &inner.
 Both rods run parallel to each other along the entire
length of cochlea & rest an basilar membrane.
 Outer rod- 3 rows of hair cells- no of hair cell 20000.
 Inner rod-one row of hair cells- 3500 cells.
 Bottom of each hair cell is associated with 8th cranial
nerve.
3. Internal Ear