1. Sight Hearing Taste Smell Touching
THE SENSES
Sight
Hearing
Taste
Smell
Touching

2. General Sense Organs widely distributed throughout the body
detect stimuli (pain, touch, temperature, pressure);
Ex.: free nerve endings, Meisners & Pacinian
corpuscles

3. types of stimuli include:
Special Sense Organs
large and complex grouping of specialized receptors (eye, ear, tongue, nose)
types of stimuli include:
Photoreceptors  light
Chemoreceptors  chemicals
Mechanoreceptors  movement

4. Converting a Stimulus into a Sensation
1. Detect stimulus.
2. Stimulus 
converted to a
nerve impulse.
3. Nerve
impulse 
perceived
as a sensation
in the CNS.

5. THE EYE (photoreceptors) http://www.youtube.com/watch?v=GMGSw3GDyJQ
CORNEA – transparent part of sclera that covers the Iris
tough outer coat;
the white of the eye
PUPIL – hole
in center of the Iris
IRIS – colored part
SCLERA

6. contains rods (night vision)
and cones (colorvision)
-pigmented layer
that prevents
scattering of light
-nourishes eye
Ciliary muscle – muscles that control the opening & closing of the eye

7. fluid in anterior of lens
fluid in posterior of lens

8. directs light rays to retinano
receptors

9. To view distant objects: ciliary muscle relaxes & lens flattens
To view near objects: ciliary muscle contracts & lens curves

10. Conjunctivitis – infection of conjunctiva
membrane that lubricates the eye
Conjunctivitis – infection of conjunctiva

11. Normal focusing: clear, upside down image on retina, brain rights the image automatically

12. Myopia (nearsightedness): eyeball is too long; lens focuses image in front of retina
Hyperopia (farsightedness): eyeball is too short; lens focuses image behind retina

13. Astigmatism: irregular curvature of lens / cornea; ripples or flat spots in image
Glaucoma: fluid build up
in the eye; damages optic
nerve & restricts blood
flow; can cause blindness

14. Colorblindness: color perception problem; 1) lacking green and/or red cones and/or blue cones or 2) absorbs an abnormal wavelength of color

15. THE EAR (mechanoreceptors)
or auricle - surrounds external auditory canal
Structure :
External ear
Middle ear
Inner ear
Function:
Hearing: sound vibrations
Equilibrium and balance: fluid movements
3 smallest bones in body
External Auditory
tympanic
membrane

16. Tympanic membrane
Normal
Swimmer’s ear (Otitis Media)

17. through the canal, strike the eardrum, and cause it to vibrate.
sound waves travel
through the canal, strike the
eardrum, and cause it to
vibrate.
(function)
- contains hairs that respond to ear fluid set in motion by sound waves
Eustachian Tube: connects middle
ear to the throat

18. TASTE (chemoreceptors)
Papillae – contain tastebuds
Taste buds – chemoreceptors for taste

19. “Primary” taste
sensations: Sweet 2. Sour 3. Bitter 4. Salty
5th Taste: UMAMI ??

20. chemicals (odors/tastes) must be dissolved in nasal mucus / saliva in order to be detected; sent as an impulse to be interpreted
olfactory receptors (detect odors) are extremely sensitive but easily fatigued
impulses are closely associated with areas of the brain important in memory / emotion
a cold that interferes with olfactory receptors will dull taste sensations

21. SMELL (chemoreceptors)

22. Concept Check #1 1. What are 3 types of receptors that your
special sense organs detect. State the organ that
detects each stimuli.
Photoreceptors – eye
Chemoreceptors–tongue/nose
Mechanoreceptors - ear
2. Explain how a stimulus turns into a sensation.
a) stimulus detected b) converted into an impulse
c) Perceived as a sensation in the CNS
3. Draw a picture of an eye and label the cornea, sclera, pupil, & iris.
4. What are the 2 layers behind the sclera?
Choroid – prevents scattering of light
Retina – contains rods & cones for night / day vision.

23. Concept Check #2
5. How does the lens change to view distant and near objects?
Distant – lens flattens Near – lens curves
6. What happens during normal focusing?
Clear, upside down image on retina – brain rights it automatically.
7. Name and describe any 3 diseases/disorders associated with the eye.
Myopia, hyperopia, colorblindness, glaucoma, astigmatism
8. Draw the ear and label the pinna (auricle), external auditory canal, ossicles, eustachian tube, and cochlea.

24. Concept Check #3 9. Why is the ear considered a mechanoreceptor?
Detects fluid movements set in motion by sound waves
10. What must happen 1st before odors and tastes can be interpreted as stimuli?
dissolved in mucus and/or saliva
11. Draw a picture of the tongue and label the location of the 4 different taste sensations.