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Introduction to sense organs - class-XII

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The function of iris in the eyes of frog is to

  1. Refract the light rays

  2. Alter the size of the pupil

  3. Move the nictitating membrane

  4. Move the lens forward and backward


Correct Option: B
Explanation:

Smooth muscle cells of the frog iris sphincter contain rhodopsin and contract in response to light. It is the colored part of the eye, which regulates the size of the pupil controlling the entry of light into the eye.

The iris of eye is 

  1. Photosensitive

  2. Chemoreceptor

  3. Both A and B

  4. All of the above


Correct Option: A
Explanation:

The colored part of the eye is called as the iris. It controls light levels inside the eye. The round opening in the center of the iris is called as the pupil. It is photosensitive in nature and is embedded with tiny muscles that dilate (widen) and constrict (narrow) the pupil size depending on the presence or absence of light.
Therefore, the correct answer is option A.

In the chemistry of vision in mammals, the photosensitive substance is called as

  1. Sclera

  2. Retinol

  3. Rhodopsin

  4. Melanin


Correct Option: C
Explanation:

Rhodopsin, also known as visual purple, is a light-sensitive receptor protein. It is a biological pigment in photoreceptor cells of the retina. 

Rhodopsin is the primary pigment found in rod photoreceptors. Rhodopsins belong to the G-protein-coupled receptor (GPCR) family. This protein is necessary for normal vision, particularly in low-light conditions. It allows night vision and is extremely sensitive to light. Exposed to a spectrum of light, the pigment immediately bleaches, and it takes about 30 minutes to regenerate fully, but most of the adaptation occurs within the first five or ten minutes in the dark. 

A 22 years student goes to his ophthalmologist. He has problem in reading books, because he is not able to contract his

  1. Suspensory ligament

  2. Pupil

  3. Iris

  4. Ciliary muscles


Correct Option: D
Explanation:

The ciliary muscle is located in the eye and surrounds the lens. It is smooth circular muscle, that relaxes or tightens the zonules to enable the lens to change shape for focusing. When it contracts, it pulls forward, moving to a frontal portion to relax the fibers, that hold the lens in place; this process also allows it to take on a more spherical shape to provide short range focus.

Where is the image of an object formed in human eye?

  1. Iris

  2. Pupil

  3. Retina

  4. Cornea


Correct Option: C
Explanation:

  • The retina is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs.
  • The optics of the eye create a focused two-dimensional image of the visual world on the retina, which translates that image into electrical neural impulses to the brain to create the visual perception.
  • The retina serving a function analogous to that of the film or image sensor in a camera. Hence, the retina  is the image of an object formed in the human eye.
So, the correct answer is 'retina'.

The part of eye responsible for its shape is

  1. Cornea

  2. Sclera

  3. Iris

  4. None of the above


Correct Option: B
Explanation:

The part of the eye responsible for its shape is sclera. It is the opaque, fibrous, tough and the protective outer layer of the eye.

So, the correct answer is 'Sclera'.

Which of the following is transparent in nature?

  1. Conjuctiva

  2. Cornea

  3. Iris

  4. Both A and B


Correct Option: D
Explanation:
A. Conjunctiva is a transparent membrane that lines the eyelids. It protects the delicate cornea.
B. Cornea is a transparent layer that forms the front of eyes. It is the anterior portion of sclera, a dense connective tissue which maintains the shape of eye and also protects it.
C. Iris is an opaque and pigmented structure in the eye. It controls the size of pupil and thus, regulates amount of light entering the eye.
Hence, conjunctiva and cornea are transparent. So, both options A and B are correct.
So, the correct answer is 'Both A and B'.

Anterior chamber of the eye is the space between

  1. Lens and iris

  2. Cornea and iris

  3. Lens and retina

  4. Cornea and lens


Correct Option: A
Explanation:

  • The anterior chamber of the eyeball is the part of the human eye with the chamber at right.
  • The anterior chamber is the aqueous humor-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium.
So, the correct option is 'lens and iris'.

Eye spot is seen in

  1. Chlamydomonas

  2. Ulothrix

  3. Spirogyra

  4. Polysiphonia


Correct Option: A

Which of the following is the clean window in the sclera in front of iris ?

  1. $Conjuctiva$

  2. $Pupil$

  3. $Cornea$

  4. $Choroid$


Correct Option: A

Umbraculum, a covering on pupil is present in

  1. Cat

  2. Dog

  3. Camel

  4. Anableps


Correct Option: C
Explanation:

Umbraculum is a modification of iris which serves to reduce the excessive glare in daytime. It is found in animals like camels. It is also known as corpus nigra.

So, the correct answer is optionC.

Suspensory ligaments are found in

  1. Brain

  2. Eye

  3. Ear

  4. Kidney


Correct Option: B
Explanation:

Many suspensory ligaments are attached radially around the lens that serve to pull the edges of lens edges toward the outer circle of the eyeball. They maintain the relatively flat shape of the lens under normal conditions of the eye.

Largest eyes are found in

  1. Deer

  2. Horse

  3. Monkey

  4. Gibbon


Correct Option: B
Explanation:

The horse has the largest eye of any land mammal. Its visual abilities are directly related to the animal's behavior and the fact that the horse is a flight animal.
Thus, the correct answer is option B.

Supporting cells of retina is

  1. Dieters cells

  2. Hensen's cells

  3. Muller cells

  4. Amacrine cells


Correct Option: C
Explanation:

Supporting cells of the retina is Muller cells also known as Muller glia. They are a type of retinal glial cells, first recognized and described by Heinrich Muller. They are found in the vertebrate retina, which serves as support cells for the neurons of the retina.

The major function of the Müller cells is to maintain the stability of the retinal extracellular environment by regulation of K+ levels, uptake of neurotransmitters, removal of debris, storage of glycogen, electrical insulation of receptors and other neurons, and mechanical support of the neural retina. So, the correct answer is option C.

Pigmented layer in eye is called as

  1. Cornea

  2. Sclerotic

  3. Choroid

  4. All of the above


Correct Option: C
Explanation:

The retina makes up the inner layer and occupies only the posterior two-third of the eye. The retina consists of several layers of cells, including the rods and cones, the sensory cells, that respond to light. The tips of the rods and cones are embedded in a pigmented layer of cells on the back of the retina. The pigment helps prevent light from scattering in the back of the eye. 

Largest eyes amongst land animals is of

  1. Elephant

  2. Deer

  3. Ostrich

  4. Man


Correct Option: C
Explanation:

Ostriches have the biggest eyes of all land mammals. The ostrich needs large eyes for its terrestrial lifestyle sharing the savanna as it does with an alarming army of fearsome predators. It is a flightless bird with strong hindlimbs to run.

So, the correct answer is option C.

Meibomian gland are associated with 

  1. Eyes

  2. Ears

  3. Reproductive organ

  4. Skin


Correct Option: A
Explanation:

The meibomian glands (or tarsal glands) are a special kind of sebaceous gland at the rim of the eyelids inside the tarsal plate, responsible for the supply of meibum, an oily substance, that prevents evaporation of the eye's tear film. Meibum prevents tear spillage onto the cheek, trapping tears between the oiled edge and the eyeball, and makes the closed lids airtight. There are approximately 50 glands on the upper eyelids and 25 glands on the lower eyelids. Dysfunctional meibomian glands often cause dry eyes.

The black pigment in the eye, which reduces the internal reflection is located in

  1. Retina

  2. Iris

  3. Cornea

  4. Sclerotic


Correct Option: A
Explanation:

Retina is the light-sensitive tissue lining the back of our eye. It is the black pigment in the eye, which reduces the internal reflection. Thereby, it controls the impact of the bright light entering our eye. Function of retina is to receive light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition. Hence option A is correct.

Eye lashes are lubricated by

  1. Ceruminous gland

  2. Pituitary gland

  3. Lacrimal gland

  4. None of the above


Correct Option: C
Explanation:

The almond-shaped glands in the eyes present above each eyeball are called lacrimal glands. Thes glands are called tear gland because they secrete the fluid called tears. These glands have their openings between the eyelashes. Water, salts and bactericidal protein such as lysozyme are components of tear. The secretion of this glands is involved in the clearance of dust, grit and microorganisms in the cornea. They are also involved in the lubrication of eyes and eyelashes. Thus the correct answer is option C.

Glands of zeis is present in the

  1. Ear

  2. Nose

  3. Eyes

  4. Tongue


Correct Option: C
Explanation:

Glands of Zeis are modified sebaceous gland located on the margin of eyelids and produces oil into the follicles of eye lashes. 

So, the correct answer is option C.

Which of the following statements about rods and cones is true?

  1. Rods are responsible for photopic vision and cones are responsible for scotopic vision.

  2. Rods are responsible for scotopic vision and cones are responsible for photopic vision.

  3. Rods and cones both are responsible for photopic vision.

  4. Rods and cones are responsible for scotopic vision.


Correct Option: B
Explanation:

Rods and cones are photoreceptors in the human retina. Rods are responsible for vision at low light levels (scotopic vision). They do not mediate colour vision and have a low spatial acuity. Cones are active at higher light levels (photopic vision), are capable of colour vision and are responsible for high spatial acuity. So, the correct answer is 'Rods are responsible for scotopic vision and Cones are responsible for photopic vision'.

Iodopsin is a light sensitive (photosensitive) pigment and is present in the

  1. Rods

  2. Cones

  3. Neuroglia

  4. Bipolar cells


Correct Option: B
Explanation:

Rods and cones are used to process light, in a human eye, their number is estimated to be 5-7 million cones and 110-130 million rods. Cones have iodopsin and are found mainly in the central area of the retina (fovea), while rods containing rhodopsin are found in the peripheral retina. Cones sense colour and need more light than rods to work well. Cones are most helpful in the normal or bright light. There are 3 types of cones - red, green, and blue - to help you see different ranges of colour. Together, these cones sense combinations of light waves, that enable our eyes to see millions of colours. The light-sensitive photopigments are made of the protein opsin and the chromophore retinene. Bleaching of iodopsin in cones is similar to rhodopsin in rods, only rods contain a higher concentration of visual pigment than cones, so more light is needed to cause an action potential to be fired in cones ( a threshold for cones is higher than rods). In other words, rods are mainly used for dim light vision, cones for bright light vision.

Sensory neurons of retina of eye are

  1. Rods and cones

  2. Maculae and cristae

  3. Pacinian and Ruffini's corpuscles

  4. All of the above


Correct Option: A
Explanation:

Rods and cones are the photoreceptors present in retina of the eye. They have their own bipolar neurons and photo-sensitive pigments.

Match the following and choose the correct option.

   Column I     Column II
 A  Fovea  1  Provides opening for entry of light
 B  Iris  2  Maximum visual acuity
 C  Pupil  3  Transmits information to CNS
 D  Lens     4  Controls amount of light entering
 E  Optic nerve     5  Focuses light on the retina
  1. (A)- 4, (B)- 1, (C)- 5, (D)- 2, (E)- 3

  2. (A)- (5), (B)- (1), (C)- (4), (D)- (3), (E)- (2)

  3. (A)- (3), (B)- (1), (C)- (4), (D)- (5), (E)- (2)

  4. (A)- (1), (B)- (2), (C)- (3), (D)- (4), (E)- (5)

  5. (A)- (2), (B)- (4), (C)- (1), (D)- (5), (E)- (3)


Correct Option: E
Explanation:

The fovea centralis is the central portion of the human retina, that has the most acute vision and the best color perception. The cones have 3 types of specific photopigments - red, green and blue, or RGB. Most of the color sensitive cones are packed in the fovea centralis.
The colored part of the eye is called as the iris. It controls light levels inside the eye similar to the aperture on a camera. The round opening in the center of the iris is called as the pupil. The iris is embedded with tiny muscles, that dilate (widen) and constrict (narrow) the pupil size.
The lens, by changing shape, functions to change the focal distance of the eye, so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina, which is then transmitted to the brain by the optical nerve.

Acute vision is found in which of the following?

  1. Vulture

  2. Frog

  3. Shark

  4. Bat


Correct Option: A
Explanation:

Vultures are highly reliant on their sensory systems for the rapid detection and localization of carrion before other scavengers can exploit the resource. Vulture has acute vision. Retina has a comb like pectin in birds.

The human eye is sensitive only to light having wave length ranging from 

  1. 80 to 280 nanometres

  2. 380 to 760 nanometres

  3. 780 to 870 nanometres

  4. 880 to 980 nanometres


Correct Option: B
Explanation:

The human eye is sensitive to violet (400 nm) to red (700 nm ) light only that can generate photometric effect i.e. visual sensation on an eye. So, the correct answer is option B.

Retina is most sensitive at

  1. Optic disc

  2. Periphery

  3. Macula lutea

  4. Fovea centralis


Correct Option: D
Explanation:
A minute yellowish area containing the fovea centralis located near the center of the retina of the eye at which visual perception is most acute is called as yellow spot or macula lutea. When an eye is looking directly at an object, light rays from that object are focused on the macula lutea, a yellow oval spot at the center of the retina. It is the part of the retina, that is responsible for sharp, detailed central vision also called as visual acuity.
So, the correct answer is 'Fovea centralis'

If the circular ciliary muscles of the eye are unable to contract, the 

  1. Lens will become more convex

  2. Lens will be thin and stretched

  3. Vision will be lost completely

  4. Bright light will have no adverse effect on retina


Correct Option: B
Explanation:

Ciliary body and the attached suspensory ligament change the shape (flattened or round) of the lens through relaxation and contraction of ciliary muscles and thereby the focal length to focus on the distant and near object. Contraction of ciliary muscles releases the suspensory ligaments and allow the lens to become round (convex) while relaxation of these muscles makes the lens taut. Since ciliary muscles are involved in accommodation required for close vision, loss of their contraction would not cause loss of vision but would affect the close vision only. The amount of light entering retina is controlled by the iris. 

So, the correct answer is option B.

Choroid is

  1. Middle layer of ear

  2. Innermost layer of eye

  3. Innermost layer of ear

  4. Middle layer of eye


Correct Option: D
Explanation:

The choroid is a layer of eyeball. The eyeball has three coats namely sclera, choroid, and retina. The choroid is middle dark pigmented thin vascular layer of the eyeball and is characterized by the presence of many blood vessels. Retina forms the innermost layer of the eye. 

Which of the following have "ommatidia" as unit of eye?

  1. Pheretima

  2. Housefly

  3. Pila

  4. Sepia


Correct Option: B
Explanation:

Compound eyes are the characteristic feature of insects. The compound eye of insects consists of many ommatidia, each of which is a separate visual unit that portrays each object into several broken pieces. This type of vision is called as mosaic vision. Among the given options, housefly is an insect and has ommatidia as a unit of an eye. Pheretima (annelid) and pila and sepia (molluscs) do not have compound eyes. 

So, the correct answer is option B.

The black pigment in the eye, which reduces the internal reflection is located in

  1. Retina

  2. Iris

  3. Choroid

  4. Cornea


Correct Option: C
Explanation:

The choroid is the part of the vascular coat in eyes. It also contains blood vessels that provide nourishment to the eye. It is pigmented towards a rear of the eye and absorbs light. It is a dark brown in colour. It darkens the cavity of the eyeballs to prevent internal reflection of light that might blur the image.

Thus, the correct answer is C.  

Skin is thinnest over.

  1. Back of hand

  2. Forehead

  3. Eye lids

  4. Sole of feet


Correct Option: C

Caring, diagnosis and cure of eye diseases

  1. Orthopaedics

  2. Ophthalmology

  3. Pathology

  4. Andrology


Correct Option: B
Explanation:
  • The word ''Opthalmology'' comes from the Greek roots ''Ophthalmol'' means ''Eye'' and ''Logos'' means ''Study''. Hence Ophthalmology literally means the ''The science of eyes''. 
  • An Ophthalmologist is a specialist in medical and surgical eye problems.
  • Hence Ophthalmology is the study of Caring, diagnosis and cure of eye diseases.
  • So, the correct answer is 'Ophthalmology'.

Skin melanocytes.

  1. Occur in stratum corneum

  2. Develop in dermis

  3. Pass into epidermis

  4. Both B and C


Correct Option: A

In a similarity with photographic camera, retina acts as

  1. Shutter

  2. Lens

  3. Diaphragm

  4. Film


Correct Option: D
Explanation:
In a photographic camera, image is formed on the film. Similarly, in eye, image is formed on the retina which is the light sensitive surface in the eye. The light rays enter the eye through an aperture called pupil. The eye lens which is biconvex, focus the light rays on the retina and an image is formed. Both the camera and eye have the ability to regulate the amount of light for image formation.
So, the correct answer is 'Film'.

A student has problem in reading as he is unable to contract his ______.

  1. Suspensory ligament

  2. Ciliary muscles

  3. Pupil

  4. Iris


Correct Option: B
Explanation:
A. Suspensory ligaments attach the eye lens with the ciliary body.
B. Ciliary muscles change the shape of eye lens to focus on nearby and distant objects.
C. Pupil is an aperture in eye through which light enters the eye.
D. Iris is pigmented and opaque structure of eye which controls the amount of light entering the eye by changing the size of pupil.
If a student has problem in reading, this means his eye lens is not able to focus on the alphabets and this is due to inability of the ciliary muscles to contract.
So, the correct answer is 'Ciliary muscles'.

Which is not a refractive medium of eye?

  1. Lens

  2. Vitreous humour

  3. Aqueous humour

  4. Pupil


Correct Option: D
Explanation:
A. Lens of eye is a crystalline structure in the eye ball which is held in place by ligaments that are attached to ciliary body. It is biconvex in nature and focus the light rays on the retina.
B. Aqueous humour is a transparent fluid present between cornea and lens.
C. Vitreous humour is a transparent gel present between lens and retina.
D. Pupil is the aperture of eye through rays enter the eye.
Refraction of light occurs when it enters a different medium and its speed gets changed. Pupil is not a refractive medium because it is an aperture or hole through which light is directly passing.
So, the correct answer is 'Pupil'.

Which part of lens in human eye is helpful in adjustment of focal length?

  1. Cornea

  2. Mucus

  3. Ciliary body

  4. Conjunctiva


Correct Option: C
Explanation:

The ciliary body is the structure in the eye that releases a transparent liquid (called the aqueous humour) within the eye. The ciliary body also contains the ciliary muscle, which changes the shape of the lens when your eyes focus on something. This process is called accommodation.

Which of the following statements is incorrect regarding lysozyme present in saliva ?

  1. It acts as an antibacterial agent.

  2. It prevents infections.

  3. It acts as an enzyme.

  4. All of these


Correct Option: A

Photosensitive compound in human eye is made up of

  1. Opsin and Retinal

  2. Opsin and Retinol

  3. Transducin and Retinene

  4. Guanosine and Retinol.


Correct Option: A
Explanation:

The photosensitive compound present in vision is called rhodopsin, also known as visual purple which consists of a large protein called opsin and retinal. Opsins are a group of light-sensitive proteins found in photoreceptor cells of the retina. Five classical groups of opsins are involved in vision, mediating the conversion of a photon of light into an electrochemical signal, the first step in the visual transduction cascade. Retinal allows certain microorganisms to convert light into metabolic energy. So, the correct answer is option A.

Which part of the eye is grafted in a needy patient from a donated eye?

  1. Conjunctiva

  2. Cornea

  3. Choroid

  4. Ciliary muscles


Correct Option: B
Explanation:

When eye is donated or transplanted only cornea part of the eye is transplanted to the needy person.

The cornea is a contact lens sized, clear piece of tissue in the front of the eye.
So the correct option is 'Cornea'

_________ is a decrease in the response to an ongoing stimulus.

  1. perception

  2. visual accommodation

  3. sensory adaptation

  4. both (b) and (c)


Correct Option: C
Explanation:

Neural adaptation or sensory adaptation is a change over time in the responsiveness of the sensory system to a constant stimulus. It is usually experienced as a change in the stimulus that is, the responsiveness to constant stimulus is decreased or stop

So, the correct option is 'Sensory adaptation'

Which of the following gives the correct path for light rays entering the human eye?

  1. Sclera, retina, choroid, lens, cornea

  2. Fovea centralis, pupil, aqueous humour, lens

  3. Cornea, pupil, lens, vitreous humour, retina

  4. Optic nerve, sclera, choroid, retina, humours


Correct Option: C
Explanation:

  1. The first thing light encounters when it enters the eye is the cornea, a protective clear covering over the pupil and iris. The cornea bends the light and begins to form an image.
  2. Light passes from the cornea to the pupil, the dark circle in the centre of the iris, which is the coloured portion of the eye. The pupil regulates the amount of light that will enter the inner eye based on environmental conditions: It dilates, growing bigger to receive more light under dim lighting conditions, and shrinks in response to bright light. This response is quicker in young individuals and tends to slow with increasing age.
  3. From the pupil, light waves travel to the lens of the eye. The lens is a clear, flexible structure that focuses an upside-down image onto the retina. It is flexible so that it can focus on images that are close or far away. Eye injuries, normal variations in the eye and age can distort the lens, making it difficult to focus on nearby or faraway objects -- you see the objects, but details are hazy. Late in life, the lens can also become clouded and form cataracts that make images seem hazy and dim.
  4. The lens focuses light and images on the retina, a layer of light-sensitive cells at the back of the eye. It is made up of two kinds of photoreceptor cells: cones and rods. The cones transmit colour and sharp images. The concentration of cones is low on the sides of the retina and increases as the cones approach the centre of the retina or the macula. The rods are more sensitive to light and are more numerous than cones; They let you see when lighting is dim, although what you see lacks colour and clear details.
  5. Once the retina senses the image, it sends impulses to the optic nerve at the back of the eye. The optic nerve then transmits them to special areas in the brain, which automatically flips the upside-down image so that it becomes upright again. Disease or injury can damage the optic nerve, resulting in varying degrees of blindness.

So, the correct answer is 'Cornea, pupil, lens, vitreous humour retina'.

Match column I with column II and select the correct option from the codes given below.

Column I Column II
A. Cornea (i) Provides opening for light to enter
B. Iris (ii) Transducens blue, green and red light
C. Lens (iii) Controls the amount of light that enters
D. Optic nerves (iv) Alters the shape of lens
E. Pupil (v) Transmit information to the CNS
F. Ciliary muscles (vi) Focus light directly on retina
G. Fovea (vii) Bends light and protects inner eye


  1. A - (vii), B - (iii), C - (vi), D - (v), E - (i), F - (iv), G - (ii)

  2. A - (i), B - (ii), C - (iii), D - (iv), E - (v), F - (vi), G - (vii)

  3. A - (vii), B - (vi), C - (v), D - i(v), E - (iii), F - (ii), G - (i)

  4. A - (vii), B - (iv), C - (vi), D - (v), E - (i), F - (iii), G - (ii)


Correct Option: A

Rhodopsin is found in

  1. Rods only

  2. Whole of retina

  3. Cones only

  4. Ganglion cells


Correct Option: A
Explanation:

Rhodopsin is found in specialized light receptor cells called rods. These are light-sensitive tissue present in the retina. They provide vision in low light. Other light receptor cells in the retina, called cones, are responsible for vision in bright light.

Thus, the correct answer is 'rods only.'

The portion of the eye which is differently coloured in different people and gives characteristically coloured eyes is the

  1. Retina

  2. Cornea

  3. Sclera

  4. Iris


Correct Option: D
Explanation:

Retina is the innermost layers of the eyeball. The cornea is the transparent anterior window of the outer layer of the eyeball located within otherwise opaque sclera. Iris is the colored part of the eye that imparts characteristic color of eyes to different people. 

So, the correct answer is option D.

A comb-like vascular structure pectin, used for nourishment and focussing in the eyes of

  1. Amphibians

  2. Birds

  3. Mammals

  4. Reptiles


Correct Option: B
Explanation:

In the eye of the bird, a comb-like structure is present. It is called as pectin. It is soft and vascular. It is a rectangular plate. It projects into the vitreous humor from the blind spot. So, the correct answer is option B.

The entry of light in a photographic camera is controlled by the shutter and iris diaphragm, comparable structure in human eye are

  1. Cornea and iris

  2. Eyelids and iris

  3. Ciliary muscles and pupil

  4. Ciliary body and iris


Correct Option: B
Explanation:

Iris is the part of the eye, which acts like the diaphragm of a camera, dilating and constricting the pupil to allow more or less light into the eye. The iris works like a shutter in a camera. It has the ability to enlarge and shrink, depending on how much light is entering the eye.
The two eyelids act to protect the front of the eye and excessive light by their closure. The inner layer of the cornea is made up of transparent tissue, which allows light to pass. The pupil is the dark opening in the centre of the coloured iris, that controls how much light enters the eye. The ciliary body is a structure located behind the iris which produces aqueous fluid that fills the front part of the eye and thus maintains the eye pressure. It also allows focusing of the lens

Thus, the correct answer is the option (B).

Which animal have porphyropsin instead of pigment rhodopsin in rods? 

  1. Fish

  2. Birds

  3. Reptiles

  4. Mammals


Correct Option: A
Explanation:

In the rods of fresh water fishes, rhodopsin is replaced by the purple photolabile pigment porphyropsin. This participates in a retinal cycle identical in form with that of rhodopsin, but in which new carotenoids replace retinene and vitamin A.

The retina of the eye acts as a

  1. Lens of the camera

  2. Aperture of the camera

  3. Film of the camera

  4. Shutter of the camera


Correct Option: C
Explanation:

The back of the eye is lined by a layer called as the retina, which acts like the film inside a camera. The retina is a thin layer of nerve tissue, that contains photoreceptors. Photoreceptors convert light rays into electrical impulses, which are then sent through the optic nerve to the brain, where an image is perceived. As with a camera, if the film is bad in the eye (i.e., the retina is damaged or diseased), no matter how well the rest of the eye is functioning, a good picture is not possible.

Ora serrata is

  1. A serrated junction between the retina and ciliary body

  2. Oral cavity of protochoradates

  3. Gland present in oral cavity of frog

  4. Present in utriculus of ear


Correct Option: A
Explanation:

The ora Serrata is a toothlike junction between the peripheral retina and the pars plana and is composed of forward extensions of the retina and backward extensions of the ciliary body. So, the correct answer is option A.

The normal eye which can sufficiently refract light rays from an object 20 ft. (6 mt.) away to focus clear object on retina is called as

  1. Myopic

  2. Emmetropic

  3. Hypermetrophic

  4. No specific name


Correct Option: B
Explanation:

A myopic eyed person focuses the light rays from a distant object in front of the retina, it can not focus distant objects sharply on the retina. Emmetropic eyes are characterized by sharp focusing of parallel light rays from distant objects on the retina when the ciliary muscle is completely relaxed to make the person see all the distant objects clearly. Hypermetropic eyes can not sufficiently bend the parallel light rays from the distant object to focus it on the retina in time.

The visual unit of a compound eye of an insect is

  1. Ommatidium

  2. Rods

  3. Rhabdom

  4. Cones


Correct Option: A
Explanation:

The compound eyes of arthropods are composed of units called as ommatidia. An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells.

Which one of the following is the correct difference between rod cells and cone cells of our retina?

    Rod cells Cone cells
 a Visual acuity High Low 
 b Visual pigment Iodopsin Rhodopsin 
 c Overall function Vision in poor light  Colour vision and detailed vision in bright light
 d Distribution More concentrated in centre of retina Evenly distributed all over retina
  1. a

  2. b

  3. c

  4. d


Correct Option: C
Explanation:

The retina contains the cells, that respond to light. These specialized cells are called as photoreceptors. There are 2 types of photoreceptors in the retina: rods and cones. 

The rods are most sensitive to light and dark changes, shape and movement and contain only one type of light-sensitive pigment. 
Cones are most sensitive to one of three different colours (green, red or blue). Signals from the cones are sent to the brain, which then translates these messages into the perception of colour. Cones work only in bright light. 

If the source of the light in front of the eye suddenly becomes more bright 

  1. Pupil contracts

  2. Focus of lens changes

  3. Vitreous humour becomes liquid like

  4. Retinal blood supply is cut-off


Correct Option: A
Explanation:

In order to reduce the amount of light entering into the eye, pupils constrict, and this constriction helps to decrease the strong light, which can be harmful to cells in the retina. The retina is the innermost layer of the eye which contains photoreceptor cells, that are useful for the formation of the image and perceiving an object. Another advantage of constriction of the pupil is to improve the clarity of image by blocking some of the rays of light, which can optically cause distortion of the image. The size of the pupil is controlled by the action of the pupillary sphincter muscle and dilator muscle.

The pigment found in rods is 

  1. Rhodopsin

  2. Melanin

  3. Photosin

  4. Keratin


Correct Option: A
Explanation:

Rhodopsin is a light-sensitive receptor protein. It is a biological pigment in photoreceptor cells of the retina. It is the primary pigment found in rod photoreceptors. They are extremely sensitive to light, enabling vision in low-light conditions. 

So, the correct answer is option A.

Maximum refraction of light takes place at 

  1. Cornea

  2. Lens

  3. Iris

  4. Aqueous humour


Correct Option: A
Explanation:

Refraction is the phenomenon which makes image formation possible by the eye as well as by cameras and other systems of lenses. Most of that refraction in the eye takes place at the first surface since the transition from the air into the cornea is the largest change in index of refraction which the light experiences. About 80% of the refraction occurs in the cornea and about 20% in the inner crystalline lens.

Retina of the vertebrate eye consists of 

  1. Neurons and neuroglia

  2. Rods, cones, neurons and neuroglia

  3. Rods, cones and neuroglia

  4. Rods and cones


Correct Option: B
Explanation:

The retina is a layered structure with several layers of neurons interconnected by synapses. The only neurons that are directly sensitive to light are the photoreceptor cells. These are mainly of two types: the rods and cones. Rods function mainly in dim light and provide black-and-white vision, while cones support the daytime vision and the perception of colour. The third type of photoreceptor, the intrinsically photosensitive ganglion cell, is important for reflexive responses to bright daylight. Neural signals from the rods and cones undergo processing by other neurons of the retina. The output takes the form of action potentials in retinal ganglion cells, whose axons form the optic nerve. 

Lateral rectus muscle of the eye is served by which cranial nerve?

  1. Oculomotor

  2. Facial

  3. Abducens

  4. Spinal accessory


Correct Option: C
Explanation:

The abducens nerve innervates the lateral rectus eye muscle that turns the eye outward away from the midline. 

The oculomotor nerve serves the superior, inferior, and medial rectus muscles and inferior oblique muscles.
The facial nerve serves taste buds, facial muscles, and the associated glands. 
Spinal accessory nerves are not cranial nerves. These are the part of peripheral nervous system.
So, the correct answer is option C.

Photosensitive pigment is

  1. Similar in all eyes

  2. Different in all eyes

  3. Similar in all vertebrate eyes

  4. Red in all eyes


Correct Option: C
Explanation:

All photoreceptors share a common visual pigment: a mixture of a vitamin A-based chromophore (retinal) and a seven-transmembrane-helix apoprotein (opsin). Together, they form rhodopsin. The pigments belong to a special class of receptors called as G protein-coupled receptors, characterised by signaling through heterotrimeric G proteins. 

In vertebrates, the rhodopsin is thermally unstable, breaking down with light into the opsin and chromophore; rhodopsins are maintained by an enzymatic process. Invertebrate rhodopsins are stable, although renewal also must take place there.

In man, the nictitating membrane is 

  1. Absent

  2. Vestigial

  3. Non-functional

  4. Functional


Correct Option: B
Explanation:

The plica semilunaris in humans is a small fold of tissue on the inside corner of the eye. It is the vestigial remnant of the nictitating membrane, an organ that is fully functional in some other species of mammals.

Eye is most sensitive to 

  1. 20 $\mathring { A }$ light 

  2. 1000 $\mathring { A }$ light 

  3. 5000 $\mathring { A }$ light

  4. 7000 $\mathring { A }$ light


Correct Option: C
Explanation:

At extremely low intensities of stimuli, when only rods are stimulated, the retina shows a variable sensitivity to light according to its wavelength, being most sensitive at about 5000 angstroms, the absorption maximum of the rod visual pigment, rhodopsin. There is a characteristic shift in the maximum sensitivity from 5000 angstroms for scotopic (night) vision to 5550 angstroms for photopic (day) vision, called Purkinje shift.

For the synthesis of rhodopsin, which of the following food is needed?

  1. Mango

  2. Rice

  3. Carrot

  4. Tomatoes


Correct Option: C
Explanation:
Opsins are the light sensitive proteins of rods. Binding of opsin to retinal (a chromophore) makes rhodopsin which serves as the visual purple pigment of rod cells. Retinol is a form of vitamin A and carrots are a rich sources of vitamin A. So, the correct answer is option C.

How many oblique and rectus muscles are found to move the eye ball in various direction inside the eye orbit? 

  1. Two

  2. Four

  3. Six

  4. Eight


Correct Option: C
Explanation:

Six extraocular muscles facilitate eye movement. These muscles arise from the common tendinous ring in the orbit, the eye cavity and attach to the eyeball. The six muscles are the lateral, medial, inferior and superior rectus muscles and the inferior and superior oblique muscles. The muscles, when contracting, cause movement of the eyeball, by pulling the eyeball towards the muscle.

Lens and retina of vertebrate eye develop from 

  1. Mesoderm

  2. Ectoderm

  3. Endoderm

  4. Partly from ectoderm and partly from endoderm


Correct Option: B
Explanation:

Neuroectoderm gives rise to the following compartments of the eye: retina, epithelial lining of ciliary body and iris, optic nerves. Surface ectoderm produces the following parts: lens, corneal epithelium, skin of eyelid.

Harderian gland occurs in 

  1. Lizard

  2. Frog

  3. Birds

  4. All of the above


Correct Option: D
Explanation:

The harderian gland is a gland found within the eye's orbit, which occurs in tetrapods (reptiles, amphibians, birds and mammals) that possess a nictitating membrane. The gland can be compound tubular or compound tubuloalveolar, and the fluid it secretes (mucous, serous or lipid) varies between different groups of animals. In some animals it acts as an accessory to the lacrimal gland, secreting fluid that eases movement of the nictitating membrane. 

Pigmented connective tissue in rabbit occurs in 

  1. The eyelids

  2. The choroid of eye

  3. The adipose tissue of skin

  4. The choroid and iris of eye


Correct Option: D
Explanation:

Vascular tunic is the middle coat of the eyeball consisting of highly vascular and heavily pigmented connective tissue consisting of a posterior choroid layer and an anterior ciliary body and the iris. Choroid is the posterior portion of the vascular middle tunic of the eyeball, lined on the inside by a layer of darkly pigmented cells; it provides the main blood supply to the back of the eye and gives rise to the ciliary body and the iris anteriorly.

The nictitating membrane of rabbit is 

  1. Also called as third eye lid

  2. Situated in the inner corner of the eye

  3. Movable across the eye ball to clean it

  4. All of the above


Correct Option: D
Explanation:

Nictitating membrane is also called as the third eye of rabbit and is found in medial canthus (inner corner) of an eye. This is swept closed across the eye in the direction from beak to ear to protect the eye as well as to clean and lubricate it with the moisture of lachrymal gland. 

So, the correct answer is option C.

Pecten is a comb like structure found in the eyes of 

  1. Amphibians

  2. Reptiles

  3. Birds

  4. Mammals


Correct Option: C
Explanation:

The pecten or pecten oculi is a comb-like structure of blood vessels, belonging to the choroid in the eye of a bird. It is a non-sensory, pigmented structure that projects into the vitreous body from the point, where the optic nerve enters the eyeball. The pecten nourishes the retina and controls the pH of the vitreous body.

The part of rabbit's eye which acts like diaphragm of camera is 

  1. Pupil

  2. Iris

  3. Lens

  4. Cornea


Correct Option: B
Explanation:

Iris is the part of the eye, which is responsible for one's eye color. It acts like the diaphragm of a camera, dilating and constricting the pupil to allow more or less light into the eye.

So, the correct answer is option B.

Which of the following in rabbit's eyes is responsible for frictionless blinking?

  1. Lachrymal glands

  2. Meibomian gland

  3. Harderian gland

  4. All of the above


Correct Option: B
Explanation:

Meibomian gland are present in the inner surface of the eyelids. They secrete an oily substance which spreads over the cornea and prevents the cornea from drying. These glands prevent the friction between two eyelids. These glands are present in animals like rabbits. They help in frictionless movement and blinking of the eyelids. 

So, the correct answer is option B. 

In the eyes, the image formed on the retina is 

  1. Erect and real

  2. Erect and virtual

  3. Inverted and real

  4. Inverted and virtual


Correct Option: C
Explanation:

The retina is the thin light-sensitive membrane lining the inner eyeball towards the back of the eye. When the light goes into the eye it must pass through the lens (a biconvex lens), which inverts the image we are seeing. When we look at an image, light bounces it into our eye. As it enters our eye and passes through the lens the image gets inverted- reversed and flipped the other way- so that the image on our retina looks like an upside down object going from right to left instead of left to right. Once this image is set on the retina, cone cells distinguish the colour and detail, while rod cells distinguish movement and shades of grey. 

The retina is connected to a nerve called the optic nerve- the image gets sent from the optic nerve to the occipital lobe in the brain where the image gets flipped and inverted once again to the proper image of the object we first saw- and is finally interpreted.

Which of the following glands are found in majority of mammals associated with their eyes?

  1. Harderian and meibomian

  2. Lacrimal and sudorific

  3. Lacrimal and meibomian

  4. Harderian and lacrimal gland


Correct Option: C
Explanation:

The lacrimal gland lies within the orbit on the outer portion of the upper eye. The gland continually secretes tears, which moisten, lubricate, and protect the eye. Meibomian gland is a type of gland in the eyelids, that makes a lubricant called as sebum, which is discharged through tiny openings in the edges of the lids. It is responsible for the supply of meibum, an oily substance that prevents evaporation of the eye's tear film and frictionless blinking.

In frog, the eyes are

  1. Myopic on land

  2. Hypermetropic in water

  3. Bulging

  4. All of the above


Correct Option: D
Explanation:

The large round lens of the frog gives the animal a large field of view. The frog is naturally nearsighted (myopic) to -6 diopters giving it a focus of approximately 6 inches. Frogs and toads can change their focus by moving the lens out towards the cornea. 

In frogs, the focus range is a few diopters and in toads, the focus range is 5 diopters giving the best myopia of -1 diopters. During this accommodation, the pupil also increases in size. The advantage of nearsightedness is that it blurs the background clutter making foreground object characterization much easier. 
Eyes that are better adapted for terrestrial vision and are emmetropic (i.e., in focus) in the air tend to be hypermetropic (i.e., far-sighted) underwater, while eyes better adapted for aquatic vision and are emmetropic in water will tend to be myopic (i.e., near-sighted) in air. If the retinal image is to remain sharp in both media, the eye must cope with large changes in external refractive indices. The bulging eyes of most frogs allow them to see in front, to the sides, and partially behind them.

In frog, eyelids are 

  1. Functional

  2. Non-functional

  3. Absent

  4. None of the above


Correct Option: A
Explanation:

Frogs use their regular set of eyelids to keep their eyes moist and clean. They have a bottom lid that stays still and an upper lid that blinks. Frogs also have a third eyelid that serves a different purpose. This one, called as the nictitating membrane, is a semitransparent lid that covers the eye completely, helping the frog see underwater and hide from predators. 

So, the correct answer is option A.

Guanine pigment is present in

  1. Tapetum lucidum

  2. Tapetum fibrosum

  3. Tapetum cellulosum

  4. All of the above


Correct Option: A
Explanation:

The tapetum lucidum is a layer of tissue in the eye of many vertebrates. Lying immediately behind the retina it reflects visible light back through the retina, increasing the light available to the photoreceptors. The tapetum lucidum contributes to the superior night vision of some animals. Many of these animals are nocturnal, especially carnivores that hunt their prey at night, while others are deep sea animals. Choroidal guanine tapetum is seen in Elasmobranchii (skates, rays, and sharks) and chimaeras. The tapetum is a palisade of cells containing stacks of flat hexagonal crystals of guanine.

The thin covering which lines the inside of the eyelids is called as

  1. Cornea

  2. Retina

  3. Conjunctiva

  4. Optic nerve


Correct Option: C
Explanation:

The conjunctiva is the thin film composed of non-keratinized stratified columnar epithelium and goblet cells that line the inside of the eyelids and covers the white of the eye called as the sclera. The conjunctiva lubricates the produces mucus and tears in small amounts to lubricate the eye and also prevents the entry of microbes into the eye.
Therefore, the correct answer is option C.

A person is wearing spectacles with concave lenses for correcting vision. While not using the glasses, the image of a distant object in his case will be formed

  1. On the blind spot

  2. Behind the retina

  3. In front of the retina

  4. On the yellow spot


Correct Option: C
Explanation:

The person wearing spectacles with concave lenses for correcting vision suffers from myopia (near sightedness). In such a person, the image of distant object will be formed in front of retina, if he is not using the glasses.

Which one of the following is not a refractive medium of the eye?

  1. Lens

  2. Vitreous humour

  3. Aqueous humour

  4. Pupil.


Correct Option: D
Explanation:

The structures of the eye that deflect light is called refractive medium. Light is actually refracted through four media in the eye. The first is the cornea (the clear layer on the outside of the eye), then the aqueous humour (liquid), then the lens (which can change shape slightly to allow objects near and far to focus), and then there is the vitreous humour (liquid filling most of the inside of the eye) all of which light needs to pass through before it reaches the retina. Light enters the eye through the pupil, and the iris regulates the amount of light by controlling the size of the pupil. Since, pupil only contacts and dilates, therefore, it is the one not a refractive medium of the eye. So, the correct answer is option D.

Layer of skin is _____________.  

  1. Dermis 

  2. Epidermis

  3.  Both A and B

  4. None of these


Correct Option: C
Explanation:

The skin is one of the largest organs in the body in surface area and weight. The skin consists of two layers: epidermis and dermis. Beneath the dermis lies the subcutaneous fatty tissue. The skin has three main functions: protection, regulation and sensation.

A change in a wart or mole on the skin is observed in

  1. Adenoma

  2. Carcinoma

  3. Lymphoma

  4. Melanoma


Correct Option: D
Explanation:

Melanoma, also known as malignant melanoma is a type of cancer that develops from the pigment-containing cells known as melanocytes. Melanomas typically occur in the skin, but may rarely occur in the mouth, intestines, or eye. Sometimes they develop from changes in wart or mole such as an increase in size, irregular edges, change in colour, itchiness, or skin breakdown.

So, the correct answer is 'Melanoma'.

Who was first to develop artificial skin by tissue culture

  1. Harrison

  2. Carrel

  3. Maximov

  4. Engene-Bell


Correct Option: D

Which of the following is not included in the ororiferous products of faces?

  1. Methyl indole

  2. skatole

  3. odoriferous

  4. Mercaptans


Correct Option: C
Explanation:
  • The odoriferous properties of human feces are due to the compounds Indoles, Skatole, and Mercaptans.
  • The yellow color of the feces is due to Stercobilin which is derived by breaking down Bile salts.
  • So, the correct option is 'Stercobilin'.

Unlike all the other senses ________ signals are not relayed through hypothalamus.

  1. Taste

  2. Smell

  3. Sound

  4. Vision


Correct Option: A

association areas are not associated with :-

  1. Intersensory association

  2. memory

  3. Emotion and sexual behaviour

  4. Communication


Correct Option: A
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