How do we taste ,hear and see?

Sense organs 

Following four sense organ found in humans 

Eyes

• Eyes are the sense organ for vision. The have photoreceptor, which convert the energy of  light into action potentials of nerve fibres.
• As a located in the Bony cavity called orbit.
• Each is a hollow spherical organ often called eyeball.
• The wall of eyeBall have 3 concentric layer i,e.sclera ,choroid and retina .

     Sclera

• It is the outer layer made up of white fibrous tissue and having transparent cornea.
• Cornea remain covered by thin and transparent membrane called conjuctive.

      Choroid

• Crowd is a middle layer that contain many blood vessel.
• It from the ciliary body which inturn  forms iris.
• Attached to salary body, a lens is present which is held in place by ligaments.
• In front of lens pupil is found.
• A Transparent watery fluid called aqueous humour fills the space between the lens and cornea.

     Retina

• It is a innermost light sense to layer.
• It is made up of two type of cells that is photoreceptor rod and cone cells .
• Road contain a purple coloured photo sensitive pigment Rhodopsin (formed from vitamin A) and are sensitive in dim light and dark. Their function is UV light vision.
• Kaun se wallet colour photo sensitive pigment iodopsin And are sensitive to bright  light and colour perception. The day light vision and colour vision are functions  of light.
• The space between lens and retina is filled with vitreous humour.
• Colour blindness is caused due to deficiency of cones.
• Presbyopia is a visual defect common in older people. In this disease ciliary  muscles are weekend causing harding of lens.
• Myopia -(short sightness) images formed in front of retina. Corrected by  using concave lens.
• Hypermetropia -(far sightness) images is formed behind the retina. The person cannot see the nearby object clearly. The near point of eyes gets  shifted away from the normal position. It can be created by using convex lens.
• Many domestic animal and Shark do not poses colour vision.
• Manky nocturnal  animal like owls have many rod in retina and are able to see in darkness. Human eyes have sensitive only to visible range of the spectrum (380- 760 mm).
• Can see ultraviolet light.

Human ear 

Human ear can hear sound of 60- 80 decibel .ear  consist of 3 part external , middle and internal ear.

1. External ear - it consists of an earlobe aur pinna and an external auditory cannal.it collect and director sound waves into the external auditory canal.
2. Middle ear- middle year have three small bones, called year or auditory ossicles. These are hammer shaped malleus ,anvil-shaped incus and stirrup like shape.
3. Internal ear - it consist of bony live in and membraneous labelled. The bony labyrinthsnhas three Bony semicircular canal. a bony  cavity called vestibule and a coiled bony  tube called cochlea .it is filled with perilymph.

 Tongue 

• Taste but the organ for taste sensation.
• A taste  bud  has taste receptor cells ,which acts as  chemoreceptors. Human tongue possess 10,000 taste buds .
• The interior part of the tongue is most sensitive to sweet taste, back to the bitter  and side to salty and sour.
• The taste of chillies  is sensation of burning, pain on the pain receptor of the tongue of the tongue .

  Nose

• Receptors for smell occur in a modified form of pseudostratified epithelium covering a part of the nasal  mucosa. It is called olfactory  epithelium.
• The all factory receptor sense function as chemoreceptors. They are stimulated by specific chemical substances and produce impulse of smell.