Human eye, function of human ear.

Function Of Human Eye And Ear

RECEPTOR

RECEPTOR:

   Receptors are the organs which receive the change taking place in our environment.

   There are many types of receptors in the human body which perform different functions. 

i) Photoreceptor e.g. eyes.

ii)Sono Receptor e.g. ears. 

iii)Chemical receptor e.g. tongue and nose.

iv) Mechanical receptor e.g. skin.

HUMAN EYE

 Photoreceptor(eye): 

     Eye is the organ of the photoreceptor. Eyes are the organs of sight that receive stimulus in the form of light. 

Location: 

     It is located in a bony socket called Orbit. 

Optic nerves:

     The nerves that arise from the eye and carry information about the image to the brain are called optic nerves. 

Internal structure of eye: 

     Eye consist of three layers; 

1) Sclerotic.

2) Choroid 

3) Retina 

1) Sclerotic: 

       It is the outermost white, tough, muscular layer which covers the eye from outside. 

2) Choroid: 

       It is the middle and vascular layer of the eye. It contains blood vessels which give nourishment to the eye. 

3) Retina: 

       It is the innermost and most sensitive layer of eye. This layer is composed of special types of neurons called rods and cones. Rods work in dim light and cones work in daylight. Image formation occurs on the retina.

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 Other types: 

a) Cornea     b) Iris      c) Pupil 

d) Lens.        e) Aqueous humor.     f) Vitreous humor 

 (a) Cornea: 

       it is the interior, transparent and bulging portion of the eye. It receives light rays from the outer environment. 

(b) Iris:

       It is the colored  part of the eye which gives a proper color to the eye. It controls the speed and intensity of light by contraction and relaxation. 

(c) Pupil: 

        It is an opening between the irises. It contains black pigment. 

(d) Lens:

        Human eyes have biconvex lenses present behind the iris. It is held by a suspensory ligament at the side. Lens focuses the light rays on the retina. 

(e) Aqueous humor: 

       The region between lens and cornea is filled by a liquid called aqueous humor. It maintains the shape of the eye and controls light intensity. 

(f) Vitreous humor:

         The space between lens and retina is filled by a jelly-like substance called vitreous humour. It is nutritive in function and also gives shape to the eye.

 SHORT AND LONG SIGHTEDNESS

 SHORT SIGHTEDNESS: 

         It is also called myopia. It is the type of eye disorder in which a person can see near objects but cannot see far objects clearly. 

CAUSES: 

         This disease is caused by the enlargement of the eyeball which focuses light rays in front of the retina.

 TREATMENT:

         This disease can be corrected by wearing spectacles having concave lenses. 

LONG SIGHTEDNESS: 

          It is also Called Hypermetropia It is a type of disease in which a person can see far objects but cannot see nearby objects clearly.

 CAUSES:

         This disease is caused by short eyeballs which focus light rays behind the retina.

 TREATMENT:

          It is treated by using spectacles having convex lenses.

FUNCTION OF EAR

 PHONORECEPTOR (EAR): 

         The receptor (sense organ) that receives stimulus in the form of sound waves from the outer environment is called phonoreceptor (ear). 

PARTS OF EAR: 

        There are three part of ear; 

1) External Ear 

2)Middle Ear 

3)Internal Ear 

1). EXTERNAL EAR: 

          The outermost layer of ear is called External ear. 

It is consist of;

 i) Ear Pinna 

ii)Auditory Canal

 i). EAR PINNA: 

          It is the outermost, delicate, flexible and cartilaginous flap of ear. It catches sound waves from the outer environment.

 ii). AUDITORY CANAL:

           It is about one inch long tube ended at the eardrum. It contains hairs and wax which trap dust particles and small insects entering to the inner ear. 

2). MIDDLE EAR: 

       The middle ear is called the middle ear. It contains eardrum and ossicles.  

EAR DRUM: 

       It is a membrane like structure in the middle ear. Vibration is produced in the ear drum with sound waves. 

 OSSICLES: 

        This is a chain of three small bones. These are the smallest bones of the body. These malleus(hammer shaped), Incus(anvil shaped), stapes(stirrup shaped). Ossicles receive vibration from eardrums. 

3). INNER EAR: 

        Internal ear consists of cochlea, vestibules, and three semicircular canals. 

COCHLEA: 

        Cochlea is the real hearing organ. It is spiral in shape. Auditory nerves arising from cochlea.

 VESTIBULES: 

        It maintains the balance of the body. The nerves arising from the vestibule are called vestibular nerves.

THREE SEMICIRCULAR CANAL: 

        These are three canals located at the right angle with each other. It gave sense about position and balance of the body. 

FUNCTION OF EAR 

       There are two main functions of the body.

 1) Hearing of sound 

2) Balance of the body 

(1) Hearing Of Sound:

        Sound waves collected by ear pinna. From ear pinna ear canal transmit the sound waves to the eardrum which start to vibrate. From the eardrum ossicles transmitted vibration to the inner ear. The sensory cells in the cochlea are stimulated and an impulse is sent to the brain through auditory nerves. Here the brain interprets the impulse as sound.

 (2) Balance Of Body: 

         Internal ear consists of three semicircular canals. When a person moves, the fluid also moves in the canals and stimulates the sensory hair cells in the canal. Thus an impulse is sent to the brain through vestibule nerves which makes us aware of the position and equilibrium of the body.