Sensation- awareness or mental process which is
aroused due to stimulation of a sense organ.
ACQUIRING SENSORY AWARENESS
1. Stimulation – anything which rouses a sense
organ to activity.
2 types of stimulus
1. physical energy
2. chemical form energy
Receptor Organ – highly specialized part of the
body and selecting sensitive to a definite
- doorway of the body responsible for all the
sensation we experience.
- “sense organ”
Presence of Receptor Cell
- the sense organ detect stimuli from the
environment and transmit information to the
appropriate areas of the brain.
Sense Receptor is stimulated by certain “stimulus”.
Stimulus must be transferred into a code of
electrochemical impulses which is travel to the
Transduction – process of converting physical
energy into activity in the nervous system which
takes place in the receptor.
QUESTION: When a stimulus is said to be detected?
ANSWER: Stimulus to be detected must be strong
enough and to produce sensation.
1. Absolute threshold – stimulus is in the inner limit or
does not go or reach beyond the threshold.
2. Subliminal threshold – stimuli are way above the
3. Terminal threshold – stimuli reach an increased
intensity it produces pain and individual
Sensory Adaptation :
1. Sense Receptor – ability to make adaptation to
changes/ adjust to a particular stimulus.
2. Sense Organ:
a. Distal senses – sensitive to stimuli coming
from a distance in the outside environment.
b. Proximal senses – bring information when we
come direct contact with the objects that
A. DISTAL SENSES
- utilize the physical characteristic of light.
EYE (receptor organ of Vision).
Light Waves ( stimuli for seeing)
waves of radiant energy coming from the sun.
Eye utilizes 2 basic properties of light:
1. brightness – intensity of light (the amount of radiant
energy coming from the sun.
2. color – wave length or frequency
Parts of the Eye:
1. Sclerotic coat (SCLERA) – hard and outer most
covering , it protects the eye.
2. Choroid coat – full of bloody tissues, gives
nourishment to the eye.
3. Retina – inner most covering of the eye.
Photosensitive plate of the eye. Regarded as the
true organ of vision.
RODS and CONS (receptors cells) embedded on
in the coat.
connects light energy to nerve impulse
Receptor cells of the eye:
RODS - slender nerve cells ( 100 million)
Function: used for twilight vision or low light intensity, enable one to make
colorless discrimination, sensitive to tiny amount of lights ( dim light ), color
blind (they see the world in black and white).
Cones – thicker / cone shape ; interprets color. ( 6 million)
Function: Daytime vision , enable one to discriminate brightness , hue or
See the color of the spectrum ( 3 types of cones)
3 dimension of colors
1. Hue - name of colors
red- longest wave length.
violet – shortest wave length.
blue , green , yellow – intermediate wave length.
2. Brightness – energy of the source of light
coloring range from bright to dim.
intensity of the stimulus.
3. Saturation – purity or richness of color.
highly saturated color – pure hues ( no tint of gray added)
low saturation – close to gray
note: Saturation of any color is reduced by mixing it with white.
Parts of the retina:
Fovea – in the central region, the point of
clearest and sharpest vision
Blind spot – are where all the nerve
fibers converge to form optic nerve which carries
impulse to the brain.
2 kinds of Blind spot
1. Dichromatic – 2 or 3 primary colors
2. Achromatic – no cones in the retina
1. pitch – highness or lowness of a sound.
2. loudness – intensity sound pursue that
activates the eardrum.
3. timbre – quality of musical tone.
Mechanism of the hearing
3 major parts:
1. outer / external serves to collect sound waves.
2. middle ear – transmit the sound waves.
3. inner ear – has sensitive receptors for hearing.
How do we hear?
Sound waves travel and collected by
Changes in air pressure
Middle ear Tiny bones hammer anvil
Stirrup ( to vibrate) 3 tiny bones conduct the
sound impulse inward to the
Hammer – eardrum- stirrup
Auditory portion of the
inner ear ( pressure
Changes , fluid
Hair cells (receptor
cells of organ of corti) Auditory nerve
II. Proximal Distance:
1. Olfaction – sense of smell
stimulus substance : gaseous substance( must
be dissolved in the air “ vaporous form.
Mechanism of Smell:
RECEPTOR – Olfactory receptor – long thread
like nerve tissue from
1. Anything that is sniffed must best dissolved in
2. Receptor cells detect the molecules dissolved
in the air that is sucked up in the nasal cavity.
3. Move up to the olfactory bulbs of the brain.
4. Physical Energy is transduced in the olfactory
epithelium to be able to reach the brain.
“ Tongue” organ for the sense of taste
Stimulus – chemicals – must transform into soluble
substance to penetrate into the taste cells.
Receptor – taste receptor
Papillae – tongue elevation
Taste buds – lie between the papillae ( taste receptor)
Pore – opening of the taste buds.
Mechanism of taste:
The food is transformed into soluble form .
Depolarized liquid substance can penetrate into
the taste cells:
Will incite the
Give rise to nerve