The Sensory System · Sensory & Motor Neurons •Carry messages from sense organs to the brain...

The Sensory System

Ms Rochford

Third Year Science

In this topic

• What does sensory system do?

• Our senses

• Central nervous system

• Motor and sensory neurons

• Responding to a stimulus

• The eye

How do we know something is living? Characteristics of living things:

1. Nutrition 3. Excretion

4. Growth

2. Respiration

5. Reproduction 6. Movement

7. Response

What does the sensory system do?

Response: the ability of an organism to gather information and respond to it

We have 5 senses

Sense Sense Organ

Sight Eyes

Hearing Ears

Smell Nose

Touch Skin

Taste Tongue

Central Nervous System • Made of the brain and spinal cord

• Brain

– Contains millions of nerve cells

– Neurons = nerve cells

• Spinal cord

– Contains neurons that carry messages to and from the brain

• The body’s neurons run to and from the central nervous system

Sense organs & Central Nervous System

• Neurons carry messages using electrical impulses

• Travel from sense organs to the brain

• Brain makes sense of the signal and responds

• It sends a signal to a muscle or group of muscles.

Sensory & Motor Neurons

• Carry messages from sense organs to the brain or central nervous system

1. Sensory Neurons

• Carry messages away from the brain or central nervous system to a muscle.

• Cause us to respond

2. Motor Neurons

Stimulus activates sense organ

Sensory neurons carry message

Brain

Sends message using motor

neurons

Muscle (s)

The Eye

Parts of the Eye

• Coloured part of eye

• Controls amount of light entering the eye

• Contracts let light in, expands to keep light out

Iris

Pupil

• Black circle in the eye

• Allows light into the eye

Parts of the Eye

• Flexible structure behind the iris

• Changes shape, depending on where we look

• Focuses light on the retina

Lens

Retina

• Light sensitive layer at back of eye

• Absorbs light which lets us see

Parts of the Eye

• Carries messages from eye to brain

Optic nerve

Cornea

• Transparent section of eye covering

• Allows light to pass into the eye

Ciliary muscle

• Contracts or relaxes to control the lens