Sense Organs 10th ICSE: Flashcards
What is the Conjunctivita?
It is a thing membrane covering the front part of the eye
What is conjujunctivitis
The outermost layer of the eye turns red due to a viral infection
What is the colored part of the eye called?
Cornea.
It can be replaced with a healthy one from a donated eye if the cornea is defective.
What are receptors? Name their types
They are cells that perceive the sensation that we feel. > Mechanoreceptors: touch > Chemoreceptors: taste > Photoreceptors: light > Thermoreceptors: heat and cold > Phonoreceptors: sound
State the functions of tears
> Lubricating the surface of the eye
washing away dust and other particles
Helps in killing germs due to the enzyme ‘lysozyme’
Communicating emotions
State the concentric layers of the eyeballs
- Outer sclerotic : tough, white fibrous tissue, visible through conjunctivita
- Middle choroid : Richly supplied with blood vessels, contains melanin
The Iris is an extension of the choroid. - Inner Retina : This layer is sensitive to light.
It contains 2 types of cells -
> rods : sensitive to dim light and unresponsive to color, contains rhodopsin (visual purple)
> cones : sensitive to bright light and responsible for color vision
contains iodopsin (visual violet)
What does the word ‘PUPIL’ mean?
It is derived from the latin word ‘pupa’ meaning ‘doll’ referring to the smaller reflection of oneself in the eye
What is a ‘Lens’? Where is it located?
A transparent flexible biconvex crystalline body.
It is located just behind the pupil.
What is the ‘Aqueous Chamber’?
It is the front chamber between the lens and cornea.
It is filled with a clear watery liquid called ‘AQEOUS HUMOUR’
> Keeps the lens moist and protects it from physical shock
Refracts light
What is the ‘Vitreous Chamber’?
It is the larger cavity behind the lens
Filled with a transparent jelly-like, thicker fluid called ‘VITREOUS HUMOUR’
> Keeps the shape of the eyeball
Protects the retina and its nerve endings
What is ‘Dark Adaption’?
It is the improvement in vision when one moves from a brighter to a darker area. ( The regeneration of the visual purple or Rhodopsin
> Dilation of the pupil
What is ‘Light Adaption’?
It is when vision returns to normal when one moves from a darker to a brighter area. ( The visual purple of the rods is bleached
> Constriction of the pupil
What is the scientific term for short sightedness? State reasons
It is known as Myopia
Two possible reasons are:
- The eyeball is lengthened from front to back
- The lens is too curved
Corrected with a concave lens
What is the scientific term for long sightedness? State reasons
It is known as Hyperopia
Two possible reasons are:
- shortening of eyeball
- Lens is too flat
Corrected with a convex lens
What is astigmatism?
defect in which some parts of the object are seen in focus while others are blurred.
This is due to the uneven curvature of the cornea
