The document discusses the human sensory system. It describes how sense organs like the eyes, ears, tongue and skin contain specialized receptors that convert stimuli like light, sound, temperature and chemicals into electrical signals to the brain, allowing us to experience sensations. It provides details on the main sensory receptors for touch, taste, smell, hearing and vision located in the skin, tongue, nose, ear and eye respectively. The eye, ear and skin sections explain the key structures involved in sensing through those organs like the retina, semicircular canals and encapsulated nerve endings.

1. Damnjanović Ivana
The Sensory System

2. Introduction
 Our “senses” continually provide us with
information about our surroundings.
 Sense organs are complex organs like
the eye or specialized receptors in areas
such as the nasal mucosa or tongue.

3. Introduction
 Conversion of a stimulus to a sensation:
Stimuli (light, sound, temperature, etc. are
changed into an electrical signal or nerve
impulse.

4. Cutaneous Sensations
 Receptors of the general sense organs
are found in almost every part of the
body.
Encapsulated nerve endings – located in the
dermis; touch and pressure.
Free nerve endings – mainly in the dermis of
the skin, mucosa, internal organs. They
sense pain or crude touch.

5. Encapsulated nerve endings

6. Sense of Touch
The nerve endings in your skin can tell you if
something is hot, cold, smooth or rough .
They can also feel if something is hurting you.
Your body has different types of nerve
endings that all send messages to your brain.

7. Sense of Taste
 Taste buds – chemical receptors that
generate nervous impulses resulting in
the sense of taste. There are about
10,000 microscopic taste buds located
on the papillae of the tongue.
 Gustatory cells

8. Sense of Taste
 Taste Sensations
Sweet, sour, bitter, salty
Other flavors results from a combination of
taste bud stimulations and olfactory receptor
stimulation.

9. Magnified
taste
bud
Papillae
Microscopic view of
taste buds (x100)
brain
foo
d
sensory cell

10. Sense of Smell
 Olfactory receptors – chemical receptors
responsible for the sense of smell are located in
the upper part of the nasal cavity.

11. The Ear
 Sense organ associated with hearing
and equilibrium and balance.
 3 main parts
External
Middle
Inner
Ear Brain

13. External Middle Inner

14. The Ear
 External ear
 Pinna
 External Auditory canal – a curving tube about one
inch long; extends into the temporal bone and end
at the tympanic membrane (eardrum)
 Middle ear
 Tympanic membrane
 3 tiny bones called ossicles (bones) transmit
sound waves.

15. External Auditory canal
tympanic membrane
3 tiny bones

16. The Ear
Inner Ear – contains mechanoreceptors
that are activated by vibration and
generate nerve impulses that result in
hearing and equilibrium.
-Cochlea is the auditory portion of the inner
ear
Vestibule – membranous sacs (utricle and
saccule) adjacent to the oval window and
between the semicircular canals. Contains
receptors for equilibrium.

17. semicircular
canals
cochlea

19. The Eye
 Contains receptors for vision and a
refracting system that focuses light rays
on the receptors in the retina.
 Eyelids – contain skeletal muscle that allow us to
close them and totally cover the exterior eyeball.
 Eyelashes – help to keep dust out of our eyes.
 Tears

23. The Eye
 Cranial Nerves
Optic – vision
Oculomotor – eye movment
 The eye contains 3 layers

25. The Eye
 Structure of the eyeball
Sclera – tough fibrous tissue.
○ Front surface is the “white” of our eyes and
the cornea. The cornea is transparent
○ Sclera is covered by the conjunctiva in the
front of the eyeball.

26. The Eye
 Structure of the eyeball
Choroid - contains a dark pigment to prevent
scattering of light that enters the eyeball.
Also contains blood vessels and 2
involuntary muscles.
○ Iris
○ Ciliary body (muscle)

28. The Eye
 Structure of the eyeball
Lens – composed of transparent, elastic
protein; no blood supply
Retina – contains microscopic receptor cells
called rods and cones
○ Rods
○ Cones
○ Fovea