ICSE Biology - Chapter 10.2: Sense Organs

I hate this part of the chapter. I hope it dies, and I hope nobody finds these flashcards.

Parts of Outer Eye

1. Eyelids: blink to lubricate

2. Eyelashes: shield

3. Lacrimal/Tear glands: secrete lubricant - tears; tears have bactericidal enzyme (lysozyme); keep eyes clean

4. Eyebrow

5. Conjunctiva: thin membrane

Main Layers of Inner Eyeball

Sclera; Choroid; Retina

Sclera coats the entire eyeball except for __________.

The iris.

Circular window of the choroid is called _______.

Pupil

What is the iris?

Part of choroid surrounding the pupil. Contains radial and circular muscles to contract and dilate the pupil.

Light enters the eye through the ________.

Pupil

Path of light/image from outer eye towards brain?

Conjunctiva — Cornea — Aqueous Humor — Pupil — Lens — Vitreous Humor — Retina (image formed)

Short note on lens.

Transparent; biconvex; crystalline; help by suspensory ligaments; shape controlled by cilliary muscles

Cells present in retina?

Photoreceptors — rods (b&w); cones (color)

Pigment present in rod cells?

Pigment present in cone cells?

Rhodopsin.

Iodopsin.

What is the blind spot?

Area of the retina where no photoreceptors are present. No image is formed here. It is present in front of the optic nerve. [Area of no vision.]

Which area contains the highest number of cone cells?

Yellow spot / Macula / Fovea centralis

Area of best vision; highly sensitive; magnified image.

Working of eye, short note.

• Path of light.

• Lens bends rays and they fall on retina to make an image.

• Image is inverted and real.

• Light produces chemical change in photoreceptors.

• Impulses are carried through optic nerve.

• Erect image in brain.

_______________ is known as accommodation.

Adjustment of the lens for viewing objects at varying distances clearly.

How does accommodation occur?

Change in curvature of lens by cilliary body and suspensory ligaments.

How does eye perceive depth?

• Stereoscopic/binocular vision.

• Simultaneous focus of the eyes on one object.

• Pons transmits impulses to both sides for coordination.

Common eye defects?

1. Myopia

2. Hypermetropia

3. Glaucoma

4. Astigmatism

5. Presbyopia

6. Cataract

7. Color-Blindness

8. Squint

Myopia

Short-sightedness. Lengthening of lens or eyeball. Lens is too convex. Can be fixed by concave lens. (-)

Hypermetropia/Hyperopia

Long-sightedness. Shortening of eyeball or flattening of lens. Corrected with convex lens. (+)

Astigmatism

Uneven curvature of cornea or lens. Some parts of image out of focus. Corrected by cylindrical lens.

Glaucoma

Aqueous humor not absorbed by veinous capillaries of ciliary body. Excessive stretching of eyeballs.

Cataract

Protein fibres of lens degenerate. Lens becomes opaque. Surgery and highly convex lens.

Presbyopia

Basically, hyperopia with age.

Main divisions of ear

1. Outer ear

2. Middle ear

3. Inner ear

Parts of outer ear and functions

1. Ear pinna: carries sound vibrations

2. Auditory canal: leads to middle ear; contains wax secreting glands

3. Tympanic membrane/ear drum: amplifies sound vibrations;

Middle ear—parts and functions

1. Ear ossicles: in tympanic cavity; transmit vibrations to the inner ear. three—malleus, incus, stapes.

2. Tympanic cavity — Eustachian tube — to throat: maintains equal air pressure on each side of membrane

3. Oval window: connects stapes to cochlea

4. Round window: dampens vibrations

Inner ear

1. Cochlea

2. Semicircular canals

3. Vestibule

Cochlea

• Scala vestibule - Perilymph — Reissner’s membrane — Endolymph — Organ of Corti — Basilar Membrane — Scala tympani - Perilymph [top to bottom]

• Organ of corti contains receptor hair cells

Vestibule

• Utriculus and sacculus

• Connects canals to cochlea

• MAINTAINS STATIC EQUILIBRIUM

Semicircular canals

• arranged perpendicularly

• swell into ampullae at endings

• contain sensory cells and endolymph

• MAINTAIN DYNAMIC EQUILIBRIUM

Two main types of hearing loss

• Sensorineural hearing loss

• Conduction hearing loss