The Sensory System
Stimulus and Response
anything in surroundings causes us to take action = stimulus (plural stimuli)
action = response
e.g. car horn = stimulus jumping out of way = response
sense organs
eye - sight
ear - hearing
skin - touch
tongue - taste
nose smell
Central Nervous system
consists of brain and spinal cord
brain = complex structure with nerve cells (millions) nerve cell = neuron
spinal cord has nerves that take messages to brain and away
Sense Organs and the Central Nervous system
sense organs send messages, electrical impulses, to brain. this way we can gather information
brain receives messages, memorises it and decides response
brain sends message along other nerve to muscle, brain causes response to stimuli
Responding to a stimulus
when pouring tea, eyes see cup almost full, sends message to brain, brain sends message to arm to stop, response is teh stopping
Sensory and motor nerves
2 types of neurons = sensory and motor nerve cells
sensory carries messages to brain - central nervous system aware of stimuli
motor carry messages away - cause us to carry out responses
The Eye
Iris
coloured part at front of eye, expands or contracts to control amount of light let in
pupil
black circle in eye, allows light into the eye, expands and contracts with iris and is black because it doesn't let light out
Lens
changes shape depending on what we are looking at
focus' light on retina
retina
retina is light sensitive layer at the back of the eye, absorbs light and allows sight
optic nerve
carries messages from eye to brain
cornea
transparent membrane covering eye, allows light to pass into eye
Ciliary muscle
surrounds lens, contracts or relaxes to cause the lens to change shape