THE SENSESSight

HearingTasteSmell

Touching

General Sense Organs• widely distributed throughout the body• detect stimuli (pain, touch, temperature,

pressure); • Ex.: free nerve endings, Meisners & Paciniancorpuscles

Special Sense Organs• large and complex grouping of specialized receptors

(eye, ear, tongue, nose)

• types of stimuli include:

Photoreceptors light

Chemoreceptors chemicals

Mechanoreceptors movement

Converting a Stimulus into a Sensation1. Detect stimulus.

2. Stimulus converted to a nerve impulse.

3. Nerve impulse perceived as a sensation in the CNS.

THE EYE (photoreceptors) http://www.youtube.com/watch?v=GMGSw3GDyJQ

http://www.youtube.com/watch?v=RE1MvRmWg7I

SCLERA

tough outer coat; the white of the

eye

CORNEA – transparent part of sclera that covers the Iris

PUPIL – hole in center of the Iris

IRIS – colored part http://www.youtube.com/watch?v=JunCyiGfreo

Ciliary muscle – muscles that control the opening & closing of the eye

-pigmented layer that prevents scattering of light-nourishes eye

contains rods (night vision) and cones (colorvision)

fluid in anterior of lens

fluid in posterior of lens

directs light rays to retina

no receptors

To view distant objects: ciliary muscle relaxes & lens flattens

To view near objects: ciliary muscle contracts & lens curves

Conjunctiva –membrane that lubricates the eye

Conjunctivitis – infection of conjunctiva

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

Myopia (nearsightedness): eyeball is too long; lens focuses image in front of retina

Hyperopia (farsightedness): eyeball is too short; lens focuses image behind retina

Astigmatism: irregular curvature of lens / cornea; ripples or flat spots in image

Glaucoma: fluid build upin the eye; damages opticnerve & restricts blood flow; can cause blindness

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

Structure :

1. External ear

2. Middle ear

3. Inner ear

Function: Hearing: sound vibrations Equilibrium and balance: fluid movements

THE EAR (mechanoreceptors)

External Auditory

or auricle - surrounds external auditory canal

3 smallest bones in body

tympanicmembrane

http://www.youtube.com/watch?v=0jyxhozq89g

Normal Swimmer’s ear (Otitis Media)

Tympanic membrane

sound waves travelthrough the canal, strike the eardrum, and cause it to vibrate.

Eustachian Tube: connects middle ear to the throat

- contains hairs that respond to ear fluid set in

motion by sound waves

http://www.blackwellpublishing.com/matthews/ear.html

http://www.youtube.com/watch?v=ahCbGjasm_E (function)

Papillae – contain tastebuds

Taste buds – chemoreceptors for taste

TASTE (chemoreceptors)http://www.youtube.com/watch?v=0hwOL91cjwM

http://www.bbc.co.uk/science/humanbody/body/factfiles/taste/taste_ani_f5.swf

“Primary” taste sensations:

1. Sweet2. Sour3. Bitter4. Salty

5th Taste: UMAMI ??

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

SMELL (chemoreceptors)http://education-portal.com/academy/lesson/the-sense-of-smell-olfactory-bulb-and-the-nose.html#lesson

Concept Check #11. What are 3 types of receptors that yourspecial sense organs detect. State the organ thatdetects each stimuli.Photoreceptors – eye Chemoreceptors–tongue/noseMechanoreceptors - 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.

Concept Check #25. How does the lens change to view distant and near

objects?Distant – lens flattens Near – lens curves6. 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.

Concept Check #39. 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.