Sense Organs Flashcards
Name the five types of receptors
- mechanoreceptors - touch
- Chemoreceptors - tongue, nose
- Photoreceptors - rods cones
- Thermoreceptors - skin
- Phono receptors - sound
How many muscles help in moving of eye?
Six muscles
What are the 6 parts of eyes?
- Orbits or sockets
- Eyelids
- Eyebrows
- Tear glands (lacrimal glands)
- Tear ducts
- Conjunctiva
State functions of tears
- Emotions
- Help in killing germs with lysozyme
- Wash away dust
- Lubricate surface of eye
What are the three layers of eyes?
- Sclera or sclerotic layer
- Middle choroid
- Inner retina
What is the dark black pigment in chorus layer?
Melanin. It prevents light rays from reflecting and scattering inside eye
What are the two types of sense cells present in retina?
Rods and cones
What do rod cells contain? What do cones contain?
Rods - rhodopsin or visual purple
Cones - iodopsin or visual violet
What is the other name of yellow spot?
Macula lutea. This contains maximum number of senosry cells. This is the region of brightest vision.
What is the blind spot?
The blind spot has no sensory cells. No point of vision.
What is the lens?
The lens is a transparent, flexible, biconvex ,crystalline body located just behind the pupil. It contains transparent lens fibers.
What are the two chambers of eye?
- Aqueous chamber - contains aqueous humour. Aqueous humour keeps lens moist, refracts light and protects against physical shock.
- Vitreous humour - contains vitreous humour. It helps in keeping shape of eyeball, protects retina and nerve endings
Name the common defects of the eye:
- Near or short sightedness (myopia)
Reasons: eye hall is lengthened from front to back or lens is too curved
Correction: concave lens - Far or long (hyperopia)
Reasons: shortening of eyeball or lens is too flat.
Correction: convex lens - Astigmatism - is a defect in which some parts of object are seen in focus while others are blurred. Arises due to uneven curvature of cornea. Corrected by cylindrical lenses.
- Presbyopia - condition affecting older ppl who cannon see near objects. Corrected by convex lens.
- Cataract - lens turns opaque. Corrected by surgically removing lense.
- Night blindness - due to non formation of visual purple of rods. Deficiency of Vitamin A.
- Colour blindness- cannot discriminate between red and green. Mostly occurs in males.
- Corneal opacities
- Squint : cross eye and wide eye. Surgery and exercise
What are two functions of ear?
- Hearing
- Body balance
State three divisions of ear:
- Outer ear- pinna, auditory canal, ear drum (tympanum)
- Middle ear - tiny bones : malleus(hammer), incus (anvil), stapes (stirrup), Eustachian tube.
- Inner ear of membranous labyrinth-
Cochlea, semicircular canals, vestibule.
