Value of Senses• There are 5 basic senses but most of us

take our senses for granted. Hellen Keller was a renowned author and lecturer who lost both her vision and hearing at the age of 1 year and 7 months. But she’s able to recognize her friend by a touch of their face. A house, by the smell of the house and the occupants. The story of Hellen Keller is often used as an inspiring example of how people can overcome sensory deficiencies in one or two areas by fully developing other senses.

• The average adult eyeball weights about one ounce.• The average time between eye blinks is 2.8 seconds.• The average human eyelash lives about 150 days.• The pupil of the eye expands as much as 45% when a person looks at

something pleasing.• The eyes can process 36,000 bits of information every hour.• You can’t sneeze with your eyes open, can you?

Eyes: Our doorway to the world

Sense of Sight / Vision• Bodily receptor:• Stimulus:• Sensitive cells:

• Eyes• Light waves• Rods and cones (located in retina)

Characteristics of color• Hue – name by which the color is identified.

• Saturation – purity or a mixed color. (ex)

• Brightness / intensity – the background of the color that affects the brightness

Parts

• The part of the brain that is responsible for vision is….

• Occipital lobe

Retina• Cones• 6.5 million in each eye• Contains chemical iodopsin

– sensitive to color in the presence of light• Fovea centralis – area with

high concentrations of cones. Area of clear detailed vision

• Rods• 100 millions in each eye.• Contains rhodopsin –

function is to see in the dark

Scotopia / dark adaptation• A gradual increase in visual sensitivity under condition of low

illumination.

• Example

Photopia / light adaptation• A gradual decrease in visual sensitivity under condition of high

illumination.

• Example

Visual Acuity• Size of the object/stimulus

• Proximity or distance

• Illumination

Visual After Image• When perception of the visual stimulus does not disappear

immediately upon removal of the stimulus.

• Positive after image – the color resembles the original color.• Negative after image - the color is opposite of the original.

After Images• Stare at the eye of the red parrot while you slowly count to 20, then

immediately look at one spot in the empty birdcage. The faint, ghostly image of a blue-green bird should appear in the cage.

Blind spot• End of optic nerve without rods and cones

Visual Problems

VISUAL PROBLEMS

• Vision is measured by the Snellen Eye Chart (devised by a Dutch Opthalmologist, Dr. Hermann Snellen in 1862)

• Perfect visual acuity is 20/20

• The Snellen fractions, 20/20, 20/30, etc., are measures of sharpness of sight. They relate to the ability to identify small letters with high contrast at a specified distance

Forms of Colorblindness• Approximately 10% of men and 1% of

women have some form of colorblindness• Dichromats

• People who are blind to either red-green or blue-yellow

• Monochromats• People who see no color at all, only shades

of light and dark

• Trichromats – people with normal color vision

VISUAL PROBLEMS

• Colors of the rainbow as viewed by a normal person

• Colors of the rainbow as viewed by a person who can not see the red color (protanopia)

VISUAL PROBLEMS• Colors of the rainbow as

viewed by a person who cannot see the green color (deuteranopia)

• Colors of the rainbow as viewed by a person who can not see the blue color (tritanopia)

VISUAL PROBLEMS

• Glaucoma - is another hereditary visual problem; increase in eye pressure caused by the fluids in the eye cause nerve damage that may ultimately lead to blindness in one or both eyes

• From 1978 – 1984, the US National Eye Institute conducted studies that actually proved Cannabis Sativa or Marijuana to effectively lower intraocular pressure when administered orally, intravenously or by smoking

VISUAL PROBLEMS• Myopia or near-sightedness is a visual problem when the eye has difficulty

focusing distant objects• Causes:

• Hyperopia or far-sightedness is a visual problem when the eyes has difficulty focusing near objects

Visual problems• Astigmatism – caused by uneven curvature of the lens.

Visual problems• Cataract – a clouding of the lens inside the eye which leads to

decrease in vision.

Visual problems• Strabismus – eyes are not aligned properly and point in different

direction.

• Night blindness – inability to see under low illumination.

• Presbyopia - oldsightedness

EARS: the sound we hear/ Audition

If a tree falls in the forest…• The question “If a tree falls in the forest and there is

no one around to hear it, does it still make a sound?” • No, it would make no sound. • Sound is a purely physiological sensation that requires

an ear (and the rest of the auditory system) to produce it.• Why deaf are mute and mute are also deaf?

Sense of Hearing / Audition• Bodily receptor:• Stimulus:• Sensitive cells:

• Ears• Sound waves• Hair cells• Located in organ of corti• Organ of corti is located in cochlea.• Cochlea is located in inner ear

Sense of hearing• Last sense to develop

• It is where the smallest bone and cartilage can be found.

Parts

• The part of the brain that s responsible for hearing is:

• Temporal lobe

Deafness• There are generally two types of deafness.

• Conduction deafness is an inability to hear, resulting from damage to the structures of the middle or inner ear.

• Nerve deafness (Sensorineural Deafness) is an inability to hear, linked to a deficit in the body’s ability to transmit impulses from the cochlea to the brain.

Hearing Disorders• Central deafness / Central processing hearing disorder (CPHD) – the

problem is within the part of the brain that interprets sound.