band 6

THE WORLD THROUGH OUR SENSES Sensory organs enable a living organism to detect and respond to changes in the environment The human senses, sensory organs and stimuli are listed;

SENSE
SENSORY ORGANS
STIMULI

TOUCH
SKIN
TOUCH, PRESSURE, PAIN, HEAT, COLD
SMELL
NOSE
CHEMICALS
HEARING
EARS
SOUND
TASTE
TONGUE
CHEMICALS
SIGHT
EYES
LIGHT
RESPONSE TO STIMULI When a sensory organ detects a stimulus, information in the form of nerve impulses, is sent to the brain
The brain interprets the information and a suitable response is produced by effectors
The pathway of nerve impulses from stimulus to response;

Effectors are parts of the body that carry out responses to stimuli. Examples of effectors are muscles and glands
LIMITATIONS OF SIGHT
-OPTICAL ILLUSION
An optical illusion occurs when the brain incorrectly interprets images
The image that seen is different from the actual object
In optical illusions, impulses going to the brain are disturbed. These disturbances may be caused by the object itself or by conditions surrounding the object
Both the arrows are of the same length. However, arrow A appears to be shorter

-BLIND SPOT
The blind spot is an area on the retina which cannot detect images because there are no light receptors there
The blind spot can only be detected in one eye at a time
To show the existence of the blind spot, hold a card marked with a circle and triangle about 5 cm apart on it. Close your left eye and look at the circle with the right eye when you slowly bring the card near your face. The triangle will disappear at a certain distance. This happens because the image of the triangle forms on the blind spot.
5 cm

STEREOSCOPIC AND MONOCULAR VISION
Compares stereoscopic and monocular vision;

ASPECT
STEREOSCOPIC VISION
MONOCULAR VISION
LOCATION OF EYES
BOTH EYES AT THE FRONT OF THE HEAD
EYES AT THE SIDES OF THE HEAD
SIZE OF VISUAL FIELD
SMALL

WIDE

ADVANTAGES
-THREE