The Senses

• Senses in Animals

• Survival– Used for survival to tell animals what is going

on around them

Sense organs

Ears, nose, tongue, skin, eyes

• Senses in Animals

• Planarian– Lives in ponds, rivers, and lakes– 2 sense organs

• Knobs– used for detecting water currents

• Eyespots– only able to tell light from dark

• Senses in Animals– Earthworms

-light detectors

-located just below the skin

- Cricket

Detects sound from the front of the leg

Antennas detect feeling

Uses a compound eye for seeing

• Senses in Animals– Snake

• Snakes eyes are similar to human eyes

• Snakes use their tongue to smell

– They shoot their tongue out and it catches air molecules

– They bring the air back into its mouth , where They bring the air back into its mouth , where the sense of smell organ is locatedthe sense of smell organ is located

Human Sense Organs

• The Eye– Path of light through the eye

• Sclera• Iris• Pupil• Cornea• Lens• Retina• Vitreous humor

• The eye– Light passes and bends first through the cornea– Then light passes through the pupil and the lens

• The light bends again in the lens towards each other

Light then passes through the vitreous humorThe vitreous humor is clear. The light finally reaches

the retina

• The retina is made up of rods and cones– Rods detect motion and light or dark– Cones detect color

• Cones are nerve cells that detect color

• There are three types of cones, each type detects only one color-----red, green, or blue

• All the other colors are cones acting together

• The optic nerve– Carries the message from the eye to the vision– Center of the brain

• 2 things happen at the vision center– The brain interprets the message

– The image is rotated right-side up

The Ear

• 3 parts

• Outer, Middle, Inner

• Outer Ear• The only part that is visible of the entire ear• The ear flap helps direct the sound waves into

the ear• Sound waves travel through the ear canal and

bump against the ear drum

• Middle Ear– The vibration of the sound waves cause

the anvil, hammer, and the stirrup to move

– The stirrup is also connected to a membrane that vibrates with the motion of the ear bones

• Inner ear– The cochlea contains nerve cells that are

connected to the auditory nerve• The auditory nerve takes the message to the

brain to be interpreted

• Semicircular Cells– Nothing to do with hearing

– Helps maintain balance

The Tongue

• The tongue contains taste buds that detect taste– They detect the chemical molecules in

food– 4 different types

• Sour• Salty• Sweet• bitter

The Nose

• Detects gas molecules in the air• Neurons line the top of the nasal chamber• There are 7 different types of nerve cells in

the nose that detect a different odor• The olfactory nerve takes messages to your

brain and the cerebrum interprets the message

The Skin

• 2 different layers for the skin– The epidermis –outside– The Dermis—inner part – 5 nerve cell types

• Pain• Pleasure• Touch• Heat• Cold

• Most nerve cells are found in the dermis

• But both the epidermis and the dermis share the pain cell

• From the skin, the nerve cells travel to the cerebrum to be interpreted– They are perceived as cold, hot pain, pleasure,

or touch