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COORDINATION SYSTEM
THE SENSES
Ch.9/XI bil
Sensory system
• Sense organs or receptors are receptors, it functions to
receive information
• These organs are designed to receive stimuli which
make us aware of changes taking place in our
environment
• Receptor is an external stimulus receiver
• Senses, which have special receptor cells to identify
changes in the external environment, have function to
provide information ( heat, cold,pressure, touch etc)
• Stimulus from external environment is carried by the
somatic nerve.
Sensory system
• All the senses have highly specialized receptors enabling
them to respond to stimuli
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Chemoreceptors : chemical
Photoreceptors : light
Phonoreceptors : sound
Tangoreceptors : touch/pressure
• Exteroreceptors = detects stimuli originating outside the body
• Interoreceptors = detects stimuli originating inside the body
• Proprioreceptors = located within the body muscles, joints and
bones (kinestetic)
Sense of touch
• The sense organ for touching and pressure is
skin.
• The skin is richly supplied with nerve endings
and these enable it to act as a sense organ
• Stimulation of nerve endings in the skin
produces sensations related to temperature,
pain and touch which are important for
survival
Skin
• Type of receptors in skin
Merkel : touch corpuscle
Paccini : pressure
corpuscle
Ruffini : heat
(thermoreceptor)
Meissner : cold
corpuscle
Free nerve endings :
pain
Sense of taste
• The tongue is covered by projections called
papillae on the surface.
• The papillae contain taste receptors – taste
buds
• The taste receptor is a chemoreceptor
because it can be stimulated by various
chemical substances
• Sense of taste depends to the sense of smell
Tongue
• There are 4 main kinds of
tastes :
Bitter : on the back
Sweet : on the tip
Sour : on the side to tip
Salty : on the sides
Sense of hearing
• The sense of hearing is concerned with the
perception of sound
• The ear is the only organ of hearing and it is
also concerned with balance
• There is a close relationship between the
sense of hearing and speech
Ear structure
• Three parts of ear :
Outer ear (external)
o Auricle/Pinna/flap : receive and collect the sounds
o Auditory canal : is a canal, covered by hair, sebaceous
and ceruminous glands – secretes cerumen (ear wax)
Middle ear
o Tympanic membrane
o Ear bones (ossicles): responsible for the transmission
 Malleus (hammer)
 Incus ( anvil)
 Stapes (stirrup)
o Eustachian tube : connect middle ear and pharynx
Ear structure
Inner ear (internal)
o Oval window
o Semicircular canal : balance organ
• Sacculus
• Utriculus
• Ampula
o Cochlea : Sound receptor
Ear
• Middle ear
The inner ear
• Semicircular canal
• Cochlea
Anatomy of inner ear
• Within the cochlea,
there is a fluid called
perilymph and
endolymph
– Scala vestibuli
– Scala media
– Scala tymphani
Sound transmission
Sense of smell
• Smelling rods (olfactory rods) – bipolar cells –
are located on the surface of the nasal cavity
(upper part)
• The nose is both an organ of the respiratory
system and sensory system
• The odor dissolves in the layer of moist
mucous membrane covering the receptors in
the upper nasal cavity. The impulses are
transmitted to the brain for interpretation
The nose
Sense of sight
• This sense organs responsible for vision.
• Eye is the vision organ that composed of photoreceptor
cells that receive light (intensity and colour) – visual
receptors in the retina are highly sensitive to light
• Two different receptors
– Cone cells : for vision in bright day and colours
– Rod cells : for vision in low light /night
• Accomodation power =
ability to change lens shape and focal length that enables
the eye to receive clear images of objects
Eye structure
The eye
• External structure
The eye
• Internal structure
Photoreceptors
Physiology of vision
Light transmission
The senses
(summary)
Sense organ
receptors
Type of
receptors
Type of
stimulus
location
Sense of touch
Nerve endings
exteroreceptor
touch
skin
Sense of taste
Taste buds
exteroreceptor
chemical
tongue
Sense of smell
Olfactory cell
exteroreceptor
chemical
nose
Sense of
hearing
Organ of corti
exteroreceptor
sound
ear
Sense of sight
Rod and Cones
exteroreceptor
light
eye
Disorders and disturbances