Sense organs

Sense organs

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

2. INTRODUCTION SENSATION A W A R E N ESS PERCEPTION STIMULUS RECEPTOR C O NDU C T I ON TRANSLATION

3. I N T ROD U C T I O N

4. 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

5. INTRODUCTION P e r ce p t i o n R ecept o r Nerve i m pu l s e I nte g r a ti on & c oo rd i na tion Stimulus

6. 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

7. STRUCTURE OF THE EYE T h e w a l l o f t h e e y e b a l l i s c o m p o se d o f t h r e e l a y e r of tissue: The outer layer : sclera & cornea The middle layer : choroid, ciliary body & iris The inner layer : Retina

8. STRUCTURE OF THE EYE STRUCTURE OF THE EYE

9. I t i s t h i c k , s u p e r f i c i a l l a y e r consists of two regions: A n t er i o r c o r n e a o f t h e e y e b a l l t h a t & The outer most layer of sclera (white portion) 2/3 rd part & it is composed of a dense connective tissue. T h e s c l e r a m a i n t a i n s t h e s ha p e o f e y e , p r o t ec t s i t s i nn e r parts & gives attachment to the eye muscles. The anterior 1/3 rd part of the outer coat is called cornea i.e t r a n s pa r e n t . I t i s t h e f i rs t p a r t o f e y e t h r o u g h w h i c h li g h t enters. Cornea is nonvascular (no blood vessels) in nature. So it can easily grafted. STRUCTURE OF THE EYE The outer fibrous layer posterior sclera. Sclera & Cornea

10. T he c o r n e a i s c o n v e x ( c u r v e d) a n d i s i n v o l v e d i n r e f r ac t i ng (bending) light rays that helps focus the light on the retina. At the junction of of cornea & sclera there is a small canal called a s C a n al o f s c h l e m m , w h i c h p e r m i t t h e d r a i n a g e o f a q u e o us humor. Cornea is covered & protected by a very thin membrane called conjunctiva. STRUCTURE OF THE EYE Sclera & Cornea

11. STRUCTURE OF THE EYE Middle layer (vascular coat) I t i s t h e m i d d l e l a y e r o f t h e e y e t h a t i s co m p o s e d 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 blood supply. The pigment cell produce a melanin pigment. T he m e l a n i n i n t h e c h o r oid i s r e s p o n s ib l e f or i t s d a r k b r o w n colour. Melanin absorbs stray light and darken the eyeball cavity, which prevents internal reflection within the eyeball. As a result, the image remains sharp and clear.

12. I t c on s i s t o f c i l i a r y m u s c l e s w h i c h g iv e s a t t a c h m e n t to STRUCTURE OF THE 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 called pupil

13. T he p r i n c i p a l f u n c ti o n of t h e i r i s i s t o r e g u l a te t h e a m o u n t of light entering the eyeball by varying the diameter of pupil. this v a r i a ti on o f p u pil i s r e g u l a t e d b y s y m p a t h e t i c a n d STRUCTURE OF THE EYE Iris parasympathetic nerve. In bright light: Parasympathetic fibres Contract circular muscles Constrict the pupil Less light enters the eye In dim light: Sympathetic fibres Contract Radial muscles Dilate the pupil More light is allowed to enter

14. Figure 15.9 Pupil Dilation and Constriction

15. 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 2 nd cranial nerve (optic nerve) Structure of retina: The retina is the light sensitive portion of the eye. From outside to inside: Pigment layer Photoreceptor cell layer Bipolar cell layer Ganglion cell layer STRUCTURE OF THE EYE Inner layer: the retina

16. Structure of Retina

17. 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

18. 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 the retina: Blue cones , which are sensitive to blue light. Green cones , which are sensitive to green light. Red cones , which are sensitive to red light. 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

19. 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

20. 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

21. Trans-retinene +scotopsin + energy In light : Rhodopsin trans-retinene+scotopsin+energy I n d a r k : t r a n s - r e t i n e n e + s c oto p s i n + e n e r gy R h od o p s in Function of retina (Mechanism and 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 u p a n i m p u l s e w h i c h i s t r a n s m itt e d t o t h e opt i c n e r v e . i m p u l s e Bleaching

22. Function of retina (Mechanism and 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 called Photopsin. When light of high intensity strikes the similar changes occur i.e. cis-retinene of idopsin splits into photopsin & trans retinene. Idopsin photopsin+ trans-retinene+energy impulse Transmitted to optic nerve

23. 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 blue light. Green cones , which are sensitive to green light. Red cones , which are sensitive to red light. 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

24. STRUCTURE OF THE 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.

25. L ens 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 two chamber: 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.

26. Middle Vascular layer: choroid, ciliary body, iris Inner nervous layer: retina Outer layer (Scelera & Cornea ) L e n s Sense organ 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 occipital lobe for perception

27. Visual areas of hemisphere where the real perception of vision arises Physiology of Vision Eye work on the principle of camera. similar to camera eye contains a 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, that is retina. the image is processed by the photoreceptor cells of the retina that convert the light rays into nerve impulses.

28. Physiology of Vision Various process are involved in focusing the light rays and producing a clear image on the retina. These processes are as follow: Refraction or bending of light ray Accommodation Change in pupil size

29. 1.Refraction or bending of light ray 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.

30. 1.Refraction or bending of light ray 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 lens decreased. 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.

31. Physiology of Vision

32. 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 called accommodation. 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).

33. f or d i s t a n t Changing the power of lens: It is done by changing the thickness of lens. 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.

34. Physiology of Vision Physiology of Vision

35. 3.Change in pupil size I r i s 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 are constricted. In a dim light pupils are dilated. Bright light Dim light I r i s Radial muscles dilated Result dilated of pupil

36. 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.

37. 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 of cornea 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

38. 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

39. 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.

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

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

42. Visual pathway

43. The Ear is the organ of hearing. It is supplied by 8 th cranial nerve. The sense of hearing is the ability to detect the mechanical vibrations i.e. sound. sense of hearing & equilibrium E a r s a r e a ss o c i a t e d w h i c h maintenance. Structure of ear The ear is divided into 3 parts: External Ear Middle ear Internal ear ANATOMY OF EAR

44. Sense organ External ear Internal ear Ear M i dd l e ear OVERVIEW OF EAR E us ta c h i an tube Bones: Milieus, incus, stapes Maintains air pressure in ear A ur i c l e Ear drum A ud i t o ry canal Collects & sends sound waves Vibrates when sound waves strike it Vestibule C o ch l ea Semicircular canal Involved in e qu ili b ri u m Involved in e qu ili b ri u m

45. The auricle (pinna): It is broad expanded, outer most flap called pinna. P i n n a i s a ca r t il a g i n o u s s t r u c t u r e co m p o s e d o f f i b r o e l a s t i c 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

46. 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 completely separates 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

47. 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 (fenestra rotunda). 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

48. 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 the ear. Most of the time this tube remains closed, it opens only during to equalize the pressure & swallowing. 2. Middle Ear

49. The internal ear is also called membranous labyrinth. It is submerged in a fluid called perilymph. The membranous labyrinth contains another 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 consist of The vestibules (balancing organ) The cochlea (hearing organ) Semicircular canals 3. Internal Ear

50. 1.Vestibule (vestibular apparatus) The part of inner ear other than cochlea is called as vestibular apparatus. It is differentiate into two chambers Utriculus is upper wide chamber Sacculus is lower smaller chamber T h e s e c h a m b e r a r e c o n n ec t e d with ea c h o t h e r b y a d u c t ca ll e d endolymphatic duct. 3. Internal Ear

51. 2.Semicircular canals Three semicircula canal are attached to utriculas. These are at right angle to one another which are named as: Anterior vertical canals Posterior vertical canals Horizontal canals T h e a n te r i o r a n d p o s t e r i o r ca n a l a r i s e f r o m t h e s a m e p l a c e & r e m a i n associated with each other for a short distance. The place of origin of semicircular canals become swollen is known as Ampulla. T h e u t r i c u l u s , s ac c u l u s o f s e m i c i r c u l a r ca n a l s w h i c h a r e f i l l e d wi t h viscous fluid called as endolmyph. Inner surface of utriculus & sacculus have patches of sensory hair cells named as maculae. Sensory hair cells which are associated with thousand of tiny particle of caco3 called otolish (ear stones) 3. Internal Ear

52. function (i.e 3.The cochlea (hearing organ) This part of internal ear is associated with 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. Scala vestibule (upper)- perilymph Scala media (middle)- endolymph Scala tympani (lower)- perilymph A n i m po r t a n t s t r u c t u r e ca l l e d o r g a n o f c o r ti r e s t s a n b a s i l a r membrane. 3. Internal Ear

53. Organ of corti The organ of corti lies the middle chamber of cochlea. It consists of 2 rods, outer & inner. B o t h r o d s r u n p a r a ll e l t o e a c h o t h e r a l o n g t h e e n t i r e 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. B o t t o m o f e a c h h a i r ce l l i s a ss o c i a t e d w it h 8 th c r a n i a l nerve. 3. Internal Ear