The senses
are the receptor organs that have task to receive the simulation. Inside your
body there are receptors to receive the stimulation from outside part of the
body (exteroceptors), receptors to receive stimulation from the inside part of
the body (interoceptors), and receptors to receive the stimulation exist in the
muscles (proprioceptors). The stimulation from the outside part of the body
might be in the form of smell, touch, sound, light, and also temperature. While
the stimulation from the inside part of the body can be in the form of hungry
and thirsty feeling.
There are
five exteroceptors in your body, they are sense of touch, sense of taste, sense
of smell, sense of hearing, and sense of vision.
1)
Sense of Touch
The skin is the sense of touch.
Inside the skin there are sensory nerve endings as the receptors for touch,
temperature, pressure, and pain. The nerve endings consist of encapsulated
nerve (called corpuscles) and free nerve endings. The corpuscles nerve
classified into Meissner corpuscles (receptor for touch) and Pacinian
corpuslces (receptor for pressure). While the free nerve endings classified
into Ruffini endings (receptor for heat) and the Krausse end bulbs (receptor
for cold).
2)
Sense of Taste
The tongue surface covered by
thousands of small elevations called papillae. Near the base of each papilla
there are groups of taste receptors called taste buds. The sense of taste is
able to receive stimulation from soluble chemical substances. Taste buds can differentiate
four different tastes, they are sour, bitter, sweet, and salty tastes. The
taste buds of sweet taste located at the tip of the tongue, the taste buds of
salty taste located at the left and right front side of the tongue, the taste
buds of sour taste located at the left and right back side of the tongue, and
the taste buds of the bitter taste located at the back of the tongue.
There are three kinds of papillae in
a tongue, they are filiform papilla, circumvallate papilla, and fungiform
papilla. The filiform papilla is like a thread and it is a touching papilla. This papilla is spread
out over all of surface of the tongue. The circumvallate papilla is taste
papillae. It has a form of V and the total number is 7-9 near the back of the tongue.
The fungiform papilla also tastes papillae, it is located at the edge of the
tongue.
3)
Sense of Smell
The smelling receptors located at the
nasal mucous membrane. There receptors
are able to receive stimulus in the form of smells come from evaporating
chemical substances. On the tip of the smelling receptors, there are cilia of
smelling hair that is related to the olfactory nerve and it goes to the
smelling center that is the brain. Between the cells of smelling receptor there
are supporting cells.
The works
of sense of smell are related to the works of sense of taste. We can enjoy
certain foods because of there is a cooperation between the sense of smell and
taste. If someone has a cold, it means that he get disturbance in his sense of smell
that is why he does not get satisfaction of eating certain foods.
4)
Sense of Hearing
The sense of hearing has form
receptor cells of sound wave (phonoreceptor) and it is located at the ears. An
ear consist of three parts, they are outer ear, middle ear, and inner ear.
a.
Outer ear
The outer ear consist of the auricle (pinna) and the
auditory canal. The auricle functions as the catcher of sound waves that next
will be continued to the middle ear by the auditory canal.
b.
Middle ear
Inside the middle ear there is the
tympanic membrane (eardrum), the auditory ossicles, and the Eustachian tube.
The tympanic membrane is a membrane that functions to receive the acoustic
vibration or sound wave. The auditory ossicles consist of the hammer (malleus),
the stirrup (stapes), and the anvil (incus). All of the ossicles function to
continue the acoustic vibration received from the tympanic membrane into the
inner ear cavity. While the Eustachian tube is a connecting tube between the
middle ear and the nasopharynx. Its function is to keep the equilibrium of the
air pressure between the outer air and the air of inner ear.
c.
Inner ear
The inner ear cavity consist of tube called labyrinth. The labyrinth can be divided into
the bony labyrinth and the membranous labyrinth. The bony labyrinth arranged
from the vestibule, the semicircular canals, and the cochlea. The semicircular
canals consist of a hearing organ called organ of Corti. The organ of Corti has
phonoreceptor in the form of hair cells.
5)
Sense of Vision
The eyes are sense of vision. The
eyeball consist of three layers, they are the sclera, choroids, and retina. The
sclera is the outer layer of an eyeball and it has white color. On the front
side of the eyeball, on the sclera there is a transparent layer and it has
strong wall that called the cornea.
The choroid is the middle layer that
has a lot of blood vessel. In front of the choroid, exactly behind the cornea
there is the iris that controls how much light will enter the eye. There is a
hall on the middle part of the iris, and it is called the pupil. Because of the
light influence, the pupil can be broadening and also narrowing. Behind the
iris and the pupil there is the lens that is in biconvex form. The chamber
between the lens and the cornea contains a lot of transparent liquid called the
aqueous humour. While the chamber behind the lens (between the lens and the
retina) contains lot of transparent jelly-like material called the vitreous
humour.
The retina is the inside part which
is sensitive toward the light. Inside the retina there are the light receptors
and nerve fibers. On the retina there is the yellow spot (fovea), it is the
most sensible part in receiving light stimulus because it contains receptors
and optic nerves. Beside that, there is what so called the blind spot, that is
the retina part that does not contain receptors
and optic nerves so that it does not sensible toward light.
On the retina there are two kinds of
photoreceptors cell, they are rod cells and cone cells. The rod cells are
sensible toward the light with the low intensity, but it cannot differentiate
color. The rod cells contains rhodopsin pigments (derivative compound of
vitamin A and a protein) which will be hang loosely if it is touched by the
light and it is reformed on the rhodopsin forming condition which needs more or
less 20 seconds. Meanwhile, cone cells contain iodopsin pigment (derivative
compound of retinal and opsin). The cone cells are sensitive to high-intensity
color and light.
The process of seeing begins with the
entrance of light into the eyes and reaches the retina. Then consecutively the
light passing in through aqueous humour, the pupil, the lens, the vitreous
humour, and finally arrives at the photoreceptor cells. From the photoreceptor
cells, the impulse is led to the brain through the optic nerve and seeing
perception, eventually occurs.