ICSE biology std 10

1. Sense organs
Stimulus
Sensation
Receptors
-mechanoreceptors
- Chemo
- Photo
- Thermo
- extero

4. External Anatomy of the Eye

5. – Eyebrows
– Eyelashes
– Sebaceous gland- secrete sebum
– Lacrimal glands or tear glands-

6. Lacrimal Apparatus of the Eye

7. Lacrimal secretion:
lysozyme(bactericidal)
-washes the eyeball
-moistens the eyeball
-lysozyme present in the tears
kills germs

9. three layers of the eyeball=
• Sclerotic layer
• The choroid
layer
• The retina

10. Sclerotic layer=
sclera and cornea
– Sclera is a white coat that covers entire eyeball except cornea
– Cornea is transparent coat through which the iris can be seen

11. Detail view of the anterior anatomy
of the eye

12. The choroid layer or ulva

13. Intrinsic Eye Muscles and
their response to light

14. The retina
The retina is a thin layer of tissue
that lines the back of the eye on the
inside. It is located near the optic
nerve. The purpose of the retina is
to receive light that the lens has
focused, convert the light into neural
signals, and send these signals on to
the brain for visual recognition.

17. Yellow spot Vs Blind spot
– Yellow spot consist of cones only due to which it appears
yellow and it is present at the center of the retina. Yellow
spot or macula lutea is a small elevation of the retina
present near the blind spot and it has very high
resolution. Blind spot is present posteriorly where optic
nerves leaves the eye. Blind spot have no rods and cones
so the part of the image falling at this region is not
perceived.

19. Accommodation of the Lens
for near vision
– Ciliary muscles contract
– Ciliary body pulls forward and inward
– Tension on suspensory ligaments of lens is decreased
– Lens becomes thicker (rounder) due to its elasticity
– Pupils constricts

20. Accommodation of the Lens
for far vision
– Ciliary muscles relaxes
– Ciliary body returns to its resting state, backward and
outward
– Tension on suspensory ligaments of lens is increased
– Lens becomes thinner (flatter) due to its elasticity
– Pupils dilate

21. Convergence or binocular vision

24. How are eyes adapted to bright
and dark?
– in dark –Rhodopsin(visual purple) formation in dark
– Pupil dilates
– in light-breakdown of rhodopsin

35. Abnormalities of
The Eye:
1. Myopic -
nearsighted
2. Hypermetropic -
Farsighted
3. Presbyopia -
age-related failure of
lens to accommodate
4. Astigmatism -
Distorted vision due to
irregular-shaped lens or
cornea
5. Color Blindness -
genetic defect that
causes dysfunction of
cones

37. The EAR –organ of hearing and
balance

42. cochlea

43. – https://www.britannica.com/science/inn
er-ear#ref196743
– Click on the link for animations and
details about mechanism of hearing

44. – Semicircular Canals
Your semicircular canals are three tiny, fluid-filled tubes in your inner ear that help
you keep your balance. When your head moves around, the liquid inside the
semicircular canals sloshes around and moves the tiny hairs that line each canal.
These hairs translate the movement of the liquid into nerve messages that are sent
to your brain. Your brain then can tell your body how to stay balanced. If you spin
around and then stop, the liquid inside your semicircular canals moves awhile
longer and the hairs continue to send the message that you are spinning even
though you're not. That's why you feel dizzy after carnival or amusement park
rides. Whoa!

45. cochlea

48. SKIN RECEPTORS