Transcript The Sensory system

The Sensory system
Lesson 1
• OB 28 recall five sense organs in the human (eyes, ears,
nose, skin, and tongue) and understand how these
enable humans to gather information from their
surroundings
Lesson 2
• OB 29 describe the role of the central nervous system
and the sensory and motor functions of nerves
Lesson 3
• OB 30 locate the main parts of the eye on a model or
diagram and describe the function of the cornea, iris,
lens, pupil, retina, optic nerve and ciliary muscle
The Sensory system
The Senses
• What are the senses?
• Why do we need our
senses?
• Helps us to avoid
danger
• Allows us to appreciate
nice objects
The Senses
Animals have 5 senses:
1. Sight
2. Hearing
3. Taste
4. Smell
5. Touch
The Senses
The senses respond to stimuli:
• Light: sense of sight
• Sound: sense of hearing
• Pressure and Heat: Senses of touch
• Chemical substances: Sense of taste and smell
Sense Organs
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Eye: Organ of sight
Ear: Organ of hearing
Skin: Organ of touch
Tongue: Organ of
taste
• Nose: Organ of smell
Sense Organs
• Eyes: Detect light
• Ears: Detect sound
• Skin: Detects
pressure + heat
• Tongue: Detects taste
• Nose: Detects smell
Nervous system
• System of
communication
• Two Parts:
– Central nervous system:
consists of the brain and
spinal cord
– Peripheral nervous
system:
consists of the nerves or
neurons
Brain
• Is the centre of our intelligence
• Contains 100 billion nerve cells
• Electrical signals or impulses pass through
these cells
• Gives us our ability to think, make decisions
• Protected by the skull
Spinal cord
• Is an extension of the brain
• Nerves branch off from it
• Most signals pass from the
senses and go through the
spinal cord
• Most signals that pass from Sensory
Neurons
the brain go through the
spinal cord
• Protected by the backbone
Motor
Neurons
Nerves
• Nerves cell = neuron
• Two types:
• Sensory neurons: carry
signals from the senses
to the CNS
• Motor neurons: carry
signals away from the
CNS to the muscles
The Eye
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Organ of sight
Detects light and distinguishes colour
Made up of three parts
Sclera
Choroid
Retina
The Eye
Sclera
Iris
Choroid
Pupil
Aqueous
humour
Retina
Cornea
Vitreous
humour
Lens
Sclera & Cornea
• The sclera is the outer coating – protects
the eye.
• The cornea is the transparent bump on
the front of the eye; it bends the light,
producing an image on the retina.
(The lens provides fine adjustment of the
focus to match the distance to the object.)
Choroid
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Darkly coloured
Front part – iris – coloured part of eye
Pupil – centre of the iris
Allows light to enter the eye
Function of the iris is to control the
amount of light that enters the eye
Retina
• Part of the eye that detects light
• Cells are light sensitive
• Optic nerve carries nerve impulses from the
eye to the brain
• Blind spot – has no light sensitive cells
• Lens – adjusts the focus (depending on the
distance to the object) to form a sharp image on
the retina.
• Ciliary muscles – change the shape of the lens
to change the point of focus
The Eye
Sclera
Iris
Choroid
Pupil
Aqueous
humour
Retina
Cornea
Vitreous
humour
Lens
Part of The Eye
Function
Cornea
Provides most of the focussing of
light.
Iris
Controls the amount of light that
enters the eye.
Pupil
The hole in the middle of the iris;
allows light to enter the eye
Retina
Detects light and produces nerve
impulses.
Provides fine focus of the image
on the retina
Lens
Ciliary muscle
Optic nerve
Changes the shape of the lens
Carries nerve signals from the eye
to the brain
The Eye
Sclera
Iris
Choroid
Pupil
Aqueous
humour
Retina
Cornea
Vitreous
humour
Lens