The Sense Organs Flashcards
Name the parts of EYES (not present inside the eye)
1] Orbits - the two deep sockets in the skull where eyes are present are called orbits.
2] Eyelids - The upper and lower eyelids protect the eyes. Each carries perfectly curved eyelashes.
3] Eyebrows - They prevent the rain drops or the trickling perspiration from getting into the eyes.
4] Tear glands - They are located at the upper sideward portion of the orbit.
In Structure of eyeball, Explain the 3 layers that make the wall of the eyeball.
1] SCLEROTIC LAYER is outermost layer made up of tough fibrous tissues and is white. It bulges out at the colored part of the eye. This part is called Cornea.
2] THE CHOROID LAYER - it is the layer which contains melanin and prevents light rays from scattering in the eye. The iris is also an extension of choroid which partially covers the lens leaving the pupil.
3] RETINA - it is the innermost layer. It contains cells called Rods and Cones. Rod cells contain pigment called rhodopsin(respond to dim light only).Cone cells contain pigment called iodopsin( respond to colour light only).
NOTE - there is a thin membrane covering the entire front part of the eye called Conjunctiva.
What is Yellow spot and Blind spot?
1] YELLOW SPOT
-It lies in the back of the eye almost at the center
-region of brightest vision
- Maximum number of sensory cells and particularly cones
2] BLIND SPOT
-No sensory cells
-point of no vision
What are Lens?
Lens is the transparent, flexible, biconvex, crystalline body located just behind the pupil.It contains transparent lens fibres. It is held in position by suspensory ligaments which attaches it to the ciliary muscles. Ciliary muscles are present at the junction of choroid and iris.
What are the 2 chambers of the eye?
1] Aqueous chamber is the front chamber between lens and the cornea. It’s filled with aqueous humour that
-it keeps the lens moist and protects it from physical shock
-it refracts light
2] Vitreous chamber is behind the lens and is filled with vitreous humour that
-helps in keeping the shape of the eyeball
-protects the retina and its nerve endings
Give all the regions of the Ear
The Ear is divided into 3 regions
1] Outer ear consisting of area from pinna to ear drum
2] middle ear consisting of ear ossicles and eustachian tube.
3] Inner ear consisting of cochlea, semicircular canals and the vestibule.
Give functions of Pinna, Auditory canal and Ear drum
PINNA - collects the sound waves and conducts them through the external canal.
AUDITORY CANAL - carries the sound waves
EAR DRUM - They set into vibrations when striked by sound waves.
Give functions for ear ossicles, eustachian tube
1] EAR OSSICLES
- Consists of 3 smaller bones called Malleus, Incus, Stapes
- in hearing, the ear drum sets into vibrations due to the sound waves and the sets the ear ossicles into vibration.
-Vibration of the Stapes is amplified due to the lever like action of the first two ossicles.
2] EUASTACHIAN TUBE
- Connects the cavity of the middle ear to the throat.
- It equalises the air pressure on either side of the ear drum allowing it to vibrate freely.
Give Functions of Cochlea
COCHLEA
- Spiral shaped, 2 and half turns, 3 parallel canals, median canal contains endolymph[fluid], and other 2 have perilymph.
- middle canal contains some sensory cells and an Organ of Corti
- while Hearing, vibrations in the fluid stimulate the the hair like processes of the sensory cells and the impulses are transmitted to the brain via auditory nerve.
Give functions of Semicircular canals
SEMICIRCULAR CANALS
- Consists of 3 canals arranged at right angles to each other.
- One end of each canal is widened to form ampulla which has sensory cells for dynamic balance.
Give functions of the Vestibule
VESTIBULE
- The short stem joining the bases of semicircular canals to the Cochlea shows two parts - a utriculus and a sacculus collectively called as vestibule.
- contains sensory cells for static equilibrium.
