Indera

SENSE ORGANS

Dr. Sulistyani

Tujuan Pembelajaran

1. Mengetahui definisi dan macam-macam reseptor beserta fungsinya.

2. Mengetahui anatomi struktur bola mata dan fungsinya.

3. Mengetahui mekanisme kerja (proses) melihat beserta komponen-komponen yang terlibat.

4. Mengetahui beberapa gangguan penglihatan (kelainan syaraf, buta warna dan kelainan refraksi).

5. Mengetahui anatomi, fungsi dan mekanisme kerja indera pembau, perasa dan peraba.

Reseptor

• Receptors ? – Akhiran saraf sensorik atau sekumpulan sel dengan

akhiran saraf sensorik yang berfungsi untuk mendeteksi serta mengubah stimulus dari lingkungan dan menstranlasikan menjadi potensial aksi yang dapat dihantarkan ke sistim saraf pusat (SSP).

• Receptor or generator potentials?– Membangkitkan potensial aksi.

Specificity/ law of Specific Nerve Energies

• Saraf sensorik hanya peka terhadap satu jenis rangsang/stimulus (suhu, penglihatan, pendengaran)

• Reseptor pada tiap-tiap organ mempunyai nilai ambang yang lebih rendah terhadap rangsangan khusus daripada rangsang secara umumnya.

• Bentuk energi dimana reseptor sangat peka terhadap rangsang/energi tertentu disebut adequate stimulus.

Adaptation of Sensory receptors

• phasic receptors (adaptasi cepat)– perception decreases even though the stimulus is still there

• tonic receptors (adaptasi lambat)– Receptors that produce a relatively constant rate of firing as

long as the stimulus is maintained are known as tonic receptors

• Only about 1% of the sensory information taken in by afferent fibers actually reaches the cerebral cortex and conscious awareness (pusat kesadaran).

Components of Sensation

1. Stimulation : perubahan dilingkungan yang dapat meningkatkan status energi sehingga cukup/adekuat untuk depolarisasi membran sel/menginisiasi potensial lokal.

2. Transduction : penghantaran stimulus dan mentranduksikan ke dalam bentuk impuls saraf. (convert it from one form, like light, to another energy form, the electrical nerve impulse) by way of what’s called a generator potential)

Components of Sensation

3. Conduction: penghantaran impuls sepanjang saraf ke SSP.

4. Translation : Pada susunan saraf, impuls yang ada ditransalasikan menjadi respons

Level of sensation

• Batang otak pengendalian tidak sadar (seperti perubahan rata-rata denyut jantung dan frekuensi pernafasan)

• Thalamus, crude identification of the type of sensations occurs (pain ,touch, hearing)

• Korteks cerebri dapat mengidentifikasi dan menunjukkan lokasi (persepsi) dari pengalaman sensorik yang pernah dialami (nyeri, pembauan, penglihatan)

Table 1-1 Principal sensory modalities

Sensory Modality Receptor Sense Organ

1.Vision

2.Hearing

3.Smell

4.Taste

5.Rotational Acceleration

Rods and cones

Hair cells

Olfactory neurons

Taste receptors cells

Hair cell

Eye

Ear (organcorti)

Olfactory mucous membrane

Taste bud

Ear ( semicircular canals

6. Linear accel

7. Touch-pressure

8. Warmth

9. Cold

10. Pain

11. Joint position

And movement

12. Muscle length

13. Muscle tension

Hair cells

Nerve endings

Nerve endings

Nerve endings

Naked nerve endings

Nerve endings

Nerve endings

Nerve endings

Ear (utricle&sac)

Various2

Various2

Various2

Various2

Muscle spindle

Golgi tendon organ

Classifications of sensory receptor

• General sensory or somatosensory receptor (touch, pressure, temperature, pain, and muscle sense).

• Complex sensory organs or special sense organs (taste, smell, sight, hearing, and equilibrium).

Classification of Receptors by complexity

• Simple receptor are associated with general senses ( like pain, temperature, touch, proprioception )

• Complex receptor are associated with the special senses (like vision,hearing), and have complex receptors in specific localized organs of the body (eye, ear)

Classification of receptors by Location

• Exteroceptors in the skin and special sense organs provide information about the external environment( touch, smell, vision )

• Interoceptors ( visceroceptors) are in vessels or viscera and provide info about the internal environment such as the monitoring of the composition of body fluids ( not at conscious level, except perhaps pain)

• Proprioceptors are in muscles, tendons, joints, and inner ear and provide information body position and movement.

Classification of receptors by type of stimulus detected

• Mechanoreceptors – Mendeteksi rangsang mekanik (tekanan, suara).

• Thermoreceptors – Mendeteksi perubahan suhu.

• Nosireceptors – Mendeteksi adanya kerusakan jaringan (nyeri).

• Photoreceptors – Mendeteksi rangsang cahaya.

• Chemoreceptors – Mendeteksi rangsang kimia melalui pengecap, pembau,

atau dalam cairan tubuh (O2 terlarut dalam darah).

Pain Sensations

• Pain receptors – Terletak dibagian superfisial kulit, kapsul

sendi, periosteum dan sekitar dinding pembuluh darah.

• Nociceptors – Terdiri dari akhiran saraf yang terletak pada

setiap jaringan tubuh; they exhibit slight adaptation (if at all); excessive stimulation of any receptor type can elicit pain (like a tremendously loud noise, bright light, etc.).

Ada 3 kategori rangsangan untuk nocireseptor:

1. Sensitif terhadap suhu yang ekstrim

2. sensitif terhadap kerusakan mekanik

3. sensitif terhadap zat kimia (contoh: zat kimia yang dilepaskan oleh jaringan tubuh yang rusak).

Jenis serabut saraf untuk nocireseptor:

- Type A (myelinated)

- Type C fibers (unmyelinated)

• Ketika impuls nyeri hanya dihantarkan sampai formatio retikularis atau thalamus, maka nyeri lokalisasi nyeri tidak nyata.

• Klasifikasi nyeri (speed of onset, quality of sensation, and duration)– Acute:

• nyeri dirasakan cepat, tajam dan tidak dirasakan bagian dalam tubuh.

– Chronic: • Nyeri terasa lambat, meningkat secara perlahan dan

dapat terjadi pada suprfisial kulit maupun jaringan tubuh bagian dalam (organ).

Jenis nyeri yang dikenal lobus parietal korteks cerebri

• Somatic Pain– Originates in the skin, body wall or appendages (muscles, joints,

tendons).

– Localization is usually precise, impulse is sent along general somatic afferent fibers, up ascending tracts, through thalamus, to cerebral cortex

• Visceral pain Originates in viscera (internal organs of the ventral body cavity, like lungs,

GI tract, etc.)

More difficult to localize, carried to ascending tracts by general visceral afferent fibers, may be "referred" to a somatic region that enters the same level of the spinal cord.

• Impuls nyeri sering dapat dihambat melalui:– pain-reducing drugs (AINS)– surgery (rhizotomy - cutting a sensory

root).

Baroreceptors

• These are types of mechanoreceptors of the general senses that monitor changes in pressure.

• These are free nerve endings that branch within elastic tissues of distensible organs, like urinary bladder or blood vessel walls.

• Many of these are involved in reflex activities, such as in the urinary system, respiratory system (to dilate airways) and helping to control blood pressure. The input from these may travel to areas of the brainstem (like the medulla) where many visceral reflexes are integrated.

Chemoreceptor

• These respond to water-soluble and lipid-soluble substances dissolved in body fluids.

• These do not send information to the primary sensory cortex ( postcentral gyrus), so we are not consciously aware of these types of chemopreception.

• These have to do with the respiratory, urinary, and cardiovascular systems

Proprioceptors

• Proprioceptors are located in the muscles, tendons, joints, and the vestibular part of ear.

• These convey nerve impulse related to muscle tone, movement of body parts, and body position.

• The information is needed for awareness of the position of body parts with respect to one another and of the movement of body parts.

Indera Penglihatan

. Indera

Penglihatan

Struktur assesori

BolaMata dan otot

Fisiologi Penglihatan

InnervasiVaskularisasi

Anatomi dan fungsi

Bagian dan fungsi

FisiologiAdaptasi gelap terang

Berseta kelainannnya

Kelainan mata

Gangguan refraksiButa warna

Accessory Structures of the Eye

1. Eyebrows (Alis)• help channel sweat and shield from the sun

2. Eyelids or palpebrae • which shade eyes from light, help moisten and

protect eyes via blinking3. Eyelashes (bulu mata)

• protect from foreign objects4. Conjunctiva 5. Apparatus lacrimalis6. Extrinsic eye muscles (there are six per eye,

voluntary skeletal muscle

Accessory Structures of the Eye

A. TUNIKA FIBROSA

• This is the outer coat of the eyeball.

• It can be divided into two continuous regions: – the anterior cornea (clear)– the posterior sclera (white),

• At the junction of the sclera and cornea is the scleral venous sinus (canal of Schlemm).

Cornea

The cornea is well supplied with nerve endings, most of which are pain fibers (some people can never adjust to wearing contact lenses)

When the cornea is touched, reflex blinking and increased lacrimal fluid secretion

B. TUNIKA VASKULOSA

• This is middle layer of the eyeball:

• It’s highly vascular composed of 3 continuous portion

1. The Choroid

2. The ciliary body

3. The iris

Function

• Provides blood supply

• Produces a fluid called aqueous humor

• Regulates the shape of the lens

• Controls the amount of light entering the eye

1.The Choroid

is dark-coloured due to a high concentration of the pigment melanin in its cells. These pigmented layers prevent internal reflection of light rays because they absorbs light rays so that they are not reflected and scattered within the eyeball

the choroid contains many blood vessels. Blood supplies the posterior side of retina with nutrients and oxygen and removes waste

2. The ciliary body

• Made of ciliary processes and ciliary muscle.

• The ciliary processes are folds where epithelial cells secrete aqueous humor.

• The suspensory ligament or zonule extends from ciliary processes to the lens, this halo of fine fibers encircles and help hold the lens in its upright position in the eye

• The ciliary muscle is a smooth muscles that alters the shape of lens for far and near vision.

LENSA MATA

C. TUNIKA NERVOSA

RETINA

• The inner coat of the eye lines the posterior three-fourths of the eyeball and is the beginning of the visual pathway.

• The primary function of the retina is image formation.

• Its neural portion contains three zones of neurons : photoreceptor neurons, bipolar neurons, and ganglion neurons.

• There are no rods in the fovea, but they increase in density toward the periphery (that's why in the dark, you see things better "out of the corner of your eye", but you can't see them when you stare directly at them, try it!).

• The blind spot is the optic disc where the optic nerve exits the eye, so there are no photoreceptors in the retina at that location.

FISIOLOGI PENGLIHATAN

How light enters the eye• Cahaya cornea pupil the aqueous

humour the lens the vitreous humour retina.

• To operate well in conditions of different light intensity, the eye must control how much light reaches the retina. It does this by changing the diameter of the pupil. In bright light, the pupil constricts (gets smaller) to prevent dazzling and over stimulation of the retina. In dim light, the pupil dilates (gets wider), letting in more light.

Focusing light on the retina

• If you do not focus a camera correctly, the picture you take is blurred. Similarly, the eye must focus light to produce a high resolution image on the retina.

• The eye focuses an image by refracting, or bending light using the cornea and the lens, forming an inverted image.

• Because of its composition and its curvature, most of the refraction of light occurs in the cornea.

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The rhodopsin retinal visual cycle

Reformation of Rhodopsin

• All trans Retinal reconvert into 11 CIS Retinal

• This process is catalyzed by the enzym Retinal isomerase (in dark)

• 11 CIS retinal Recombines with the scotopsin Rhodopsin

Vitamin A

• Is present both in the cytoplasm of the rod and in the pigment layer of the Retina

• Vitamin A is normally available to form new Retinal when needed

• When there is excess retinal in the retina, the excess is converted back into Vitamin A ( Light Sensitive Pigment in the retina )

ADAPTASI GELAP TERANG

Dark Adaption (light dark)

• Light --- Bleaching Reaction -- Rhodopsin in Rods & Visual pigments in cones decrease --- if the person enters a darkened room sensitivity to light is low & vision is poor

• A gradual photoreceptor sensitivity increase -- dark adaptation

• Dark adaptation occurs more slowly because you have to regenerate rhodopsin that has been bleached out.

Light adaptation ( dark—light)

• If your eyes are exposed to bright light for a long period of time ---much of the light-sensitive pigment in the rods and cones is broken down --- the sensitivity of your eyes to light is much reduced. In this situation, your eyes are said to be light adapted

SEL BIPOLAR DI RETINA

NERVUS OPTIKUS KIRI

CHIASMA OPTIKUM KIRI ( SERABUT BAGIAN ASAL

BERSILANGAN)

TRAKTUS OPTIKUS KIRI

KORPUS GENIKULATUM LATERALEKOLLIKULUSSUPERIOR

NUKLEUS PRETEKTALIS(KANAN-KIRI)

KORTEKS VISUALIS (OPTIKUM)

PUSAT REFLEKS DI MEDULLA

OBLONGATA

NUKLEUS EDINGER-WESTPHAL

M. SPHINCTER PUPILLAE

REFLEKS KONJUNKTIVA :SENTUHAN NERVUS OPTIKUS MEDULLA OBLONGATA NERVUS FASCIALIS M.OBRIKULARIS OKULI

• A colour blind person can see clearly but can not distinguish certain colours.

• The problem is hereditary and is passed via the X chromosome. Women, who have two X chromosomes, can ‘use’ their good chromosome if they inherit an affected X chromosome, so they are not colour blind but they are carriers.

COLOUR BLIND

COLOUR BLIND

• This means that they have a 50% chance of having a colour blind son, and a 50% chance of having a daughter who is a carrier too.

• If a girl inherits one of the affected X chromosomes from her mother (a carrier) and an affected X chromosome from her father (colour blind) she will also be colour blind. However, this set of circumstances is rare and only 0.5% of women have the condition.

COLOUR BLIND

• About 8% of males have the problem (of which, to either red, green or blue light.

• Activation of different combinations of these three about three-quarters have a problem with green and one quarter have a problem with red).

• There are three types of colour sensitive cones in the retina which respond cones provides us with an appreciation of all of the colours of the rainbow.

COLOUR BLIND

• Loss of just one of these cones is enough to disrupt your colour vision

• loss of two turns a multicoloured world into one that's just black and white

REFRAKSI

Light rays are refracted when they pass from one medium into a medium of a different density.Except when they strike perpendicular to the interfaceThe degree of refraction depend on :1.Refractive index2.Curvature of the interface between two media

• Light pass through air at velocity=300.000 km/sec BUT SLOWER through transparent solid & liquids.

• The RI a transparent substance is the ratio of the velocity of light in air to the velocity in the substance.

• RI of air is set at 1.00, RI cornea :1.38, RI lens :1.40 , RI aqueous humor :1.33

THE EYE AS CAMERA•Photographic camera has a lens system, a variable aperture system (pupil), and film (retina)•The lens system of eye is composed of 4 refractive interfaces :1.The interface between air and the ant or surface of the cornea (1.00:1.38)2.The interface between the postor surface of the cornea and the aqueous humor (1.38:1.33)3. The interface between the aqueous humor and the antor surface of the lens (1.33:1.40)4.The interface between The posterior surface of the lens and the vitreous humor (1.44:1.34)

REDUCED EYE

This is simple calculation

-A single refractive surface is considered to exist with its central point 17 mm in front of the retina and to have a total refractive power 59 diopters when lens is accommodated for distant vision.

-Most of the refractive power of the eye provided by the anterior surface of cornea not by the crystallize lens.

• Total refractive power of the crystalline lens is only 20 diopters(1/3 total refractive power of the eye’s lens system) BUT the importance of the crystallize lens is that its curvature can be increased markedly to provide “accommodation”

• The refractive power of the crystalline lens can be increased from 20 diopters to 34 diopters (in young children).This is total accommodation =14D

ACCOMMODATION

• When a normal eye views an object, parallel rays of light are refracted to a focal point or the retina.

• If the degree of refraction remained constant, movement of the object closer to or farther from the eye would cause corresponding movement of the focal point so that the focus would either be behind or in front of the retina.

• The ability to the eyes to keep the image focused on the retina as the distance between the eyes and object varies called accommodation

VISUAL ACUITY

• The sharpness of an image depends on the resolving power of the visual system. That is, on the ability of the visual system to distinguish (resolve) two closely space dots.

• The better the resolving power of the system, the closer together. These dots can be and still be seen as separate.

• When the resolving power is exceeded the dots blur are perceived as single image.

ANOMALI REFRACTION

Emetropia a light ray from an object that strike a lens more than 20 ft (6M) you focus light from an object in the retina This produces clear vision

Abnormalities of refraction are due to: 1. improper shape of the eyeball 2. or to irregularities in the surface of

the lens or cornea

1. HIPERMETROPIAIf you are long-sighted you are said to

have hypermetropiaand you focus light behind the retina.

Again objects appear blurred. Long sightedness results from 1. a shortened eyeball 2. a lens that is too thin and is corrected using a converging or

convex lens.

2. MIOPIA

o If you are short-sighted, a condition technically known as myopia

o you focus light from an object in front of the retina This produces a blurred image.

o Short sightedness can result from : 1. an elongated eyeball 2. a thickened cornea or lens.o It is corrected by using a diverging

or concave lens

3. ASTIGMATISME

A more complicated visual defect is astigmatism.

In astigmatism, the surface of the cornea is irregular, the object appears blurred because some of the light rays are focused and others are not (this is similar to the distortion produced by a wavy pane of glass).

Astigmatism is corrected using a cylindrical lens that bends light rays in one plane only

PRESBIOPIA• A person grows older the lens grows larger & thicker and become less elastic (denaturation of lens protein)•The ability of the lens change shape progressively decreases from 14 diopters (young child) to less than 2 diopters (45-50) and 0 at age 70•The eye can no longer accommodate for both near and far vision•Older person must wear bifocal glasses with the upper segment normally focused for far seeing and the lower segment focus for near seeing.

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Feature Rod cells Cone cells

Shape Rod shaped outer segment

Cone shape outer segment

Connection

Many rods connect with one bipolar neuron

Only a single cone cell per bipolar

Visual acuity

Low High

Visual pigment

Rhodopsin (no colour vision)

Contain 3 types of iodopsin(red, blue, and green).

Frequency

120 million per retina (20 x more common than cones)

7 million per retina

Distribution

All over retina All over retina but much concentrated in the center particularly in the yellow spot or fovea centralis

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