Senses & Sensory Relationships

– All of our senses respond to stimuli in the environment/

– ________________________________________– ________________________________________

________________________________________– The role of sense receptors is to ______________

________________ and to provide the other parts of the body with information about these stimuli.

Sense organs(Fill out the following table)

Sense Organ Perception

Taste Tongue Salty, sweet, spicy, bitter

1. The Eye • The eye is the organ of sight.• Our eyes enable us to appreciate:

– __________________– __________________– _____________________– ____________________________________

• The eye is made up of a system of 4 _________ and 3 ___________ substances

Anatomy of the EyeMembranes: - 1 membrane covers the front part of the eye . __________________

- it is transparent- under the cornea are:

1) _________: the coloured

ring of the eye

2) __________: the central

portion of this ring (black dot)

Anatomy of the Eye- the other 3 membranes line the

posterior (back) of the eye

They are all different:

1. ________________________________________

- rigid, gives the eye its shape

2. ___________________________- provides nourishment for the eye

3. ___________________________ - active nervous membrane =

receiver of stimuli

Anatomy of the EyeTransparent Substances:

Found inside the eye

1. _________________

2. ________________________

- located between the cornea

and lens- a liquid made up of water

and minerals

3. _________________________

- located between the lens and the retina

- jelly like substance

What path does light take as it travels through the eye?

1) Light must pass through a number of transparent media before it reaches the nerve cells of the eye. Where are these located?

__________________

2) Label these different structures in the order that light passes through:

vitreous humour, lens, retina, cornea, aqueous humour

1st _____________

2nd _____________

3rd ______________

4th ______________

5th ______________.

The Path Light Takes in the Eye– Light passes through and is bent by the

cornea and then the lens. WHY? ________________________________________________________________________

– Images appear inverted(______________) on the retina• When looking at near-by objects = the lens curves

and thickens.• When looking at far object = the lens flattens.

– The reflex that causes the lens to change shape is called the _____________________

near-far sightedness

Flattened lens

thickened lens

ughTHE PROPERTY OF REFRACTION (BENDING IF LIGHT), we are able to focus an image at the back of our eye, in the Retina.

The image for which we see from the outside environment is actually upside down on our retina.The Brain flips it back so we can see right-side-up.

• Light rays enter the eye and focus on the retinal nerve cells (neurons)

• These retinal nerve cells then change the light waves that strike them into nerve impulses that are carried along the optic nerve to the visual center of the brain

• Optic nerve– Nerve tissue formed by the axons of the

retinal cells– Transmits nerve impulses form the retina to

the optical centre of the brain

• Examples of retinal nerve cells:– Rods = detect light and dark– Cones = detect colour

Visual pathway

Visual Sensory Mechanics1. Stimuli = Light

2. Receptor = Retina

3. Processor = Rods and Cones

4. Nerve Impulse = Action Potential from Axons

5. Conductor = Optic Nerve

6. Analyzer = Brain (Occipital Lobe)

• It is only when the center for vision in the brain (in the occipital lobe) is stimulated that a person has any visual sensation

• Therefore, it is not only the eyes alone that allow us to “see” but also the brain.

Lenses

• Convex lenses– Also called converging– Cause light to

converge on a focal point

– This is like the actual lens inside your eye

• Concave lenses– Also called diverging

lens– Cause light to diverge

from a focal point

Eye Disorders

• Hyperopia (far-sighted):• The image is focused behind the retina• Close objects are blurred

– Requires CONVEX lenses

• Myopia (near-sighted):• The image is focused in front of the retina• Distant objects are blurred

– Requires CONCAVE lenses

• Presbyopia :– loss of elasticity of the lens (usually in old age)

Long eyeball

Myopia

Short eyeball

Hyperopia

Common visual defects