Sensory system
It is an organ of the body which response to external stimuli by
conveying impulses through the sensory neuron to the appropriate places within
the sensory nervous system.
There are five sense organs in the human body. It includes,
• Skin
• Eye
• Ear
• Tongue
• Nose
The human skin is the outer covering of the body and is the
largest organ of the integumentary system. The main functions are protection,
regulation and sensation.
The eye is a sensory organ. It absorbs light rays from our
environment and transforms them in such a way that the information in the brain
can be processeced further.
·
The eye has many parts work together to produce clear vision.
·
The sclera or white part of the eye protects the eyeball.
·
The pupil or black dot at the center of the eye is a hole
through which light can enter the eye.
·
The iris or coloured part, surrounding the pupil. It
controls how much light enters the eye by changing the size of the pupil.
·
The cornea, a clear window at the front of the eye covers
the iris and pupil.
·
A clear lens, located behind the pupil, acts like a camera
lens by focusing light in to the retina at the back of the eye.
·
The retina is a light sensitive inner lining at the back of
the eye. Ten different layers of cells work together in the retina to detect
light and turn it into electrical impulses.
·
The retina has special cells called cones and rods
are located in the retina. These all are known as photoreceptors and help
absorb light.
·
Cones cone cells help us see colour and detail.
·
Rods rod cells allow us to see in poor lighting and give us our night
vision.
1.
Light reflects of the object we are looking at
2.
Light rays enter the eye through the cornea at the front of the
eye.
3.
The light passes through a watery fluid and enters the pupil to
reach the lens.
4.
The lens can change in thickness to bend the light, which will
focus it on to the retina at the back of the eye.
5.
On the way to the retina, light passes through a thick, clear
fluid called a vitreous humour. The vitreous humor fills the eyeball and helps
maintain its round shape.
6.
The light then reaches the back of the eyes and hits the retina.
The retina translates the light into electrical impulses which are then carried
to the brain by the optic nerve.
Finally, the visual cortex of the brain interprets these impulses at what we see.
The ear is the organ for hearing. It is divided into three parts.
·
Outer ear-pinna /auricle, auditory canal
·
Middle ear-ear drum, ossicles, Eustachian tube
·
Inner ear- cochlea, vestibule and semicircular canal.
Pinna: receives sound waves that travel the auditory canal or ear
canal.
The curved formation on the outside [the pinna] helps funnel sound
down the ear canal to the ear drum.
Acts as a funnel and leads to the ear drum. which protects the
eardrum from shock and intrusion by external objects.
·
It is a cone shaped piece of skin.
·
It is very sensitive, even the slightest pressure variation will
cause it to vibrate.
·
It is also separates the outer ear from the middle ear.
It transfer the energy of a sound wave by vibrating the three
bones found there.
Ossicles:- smallest bone of the body. Ear bones are malleus, incus
and stapes.
A tube that connects the middle ear to the back of the nose. It
equalizes the pressure between the middle ear and the air outside.
It has two main parts.
This is a spiral that is covered in a stiff membrane. It contains
thousands of hair cells attached to the end of the organ of the auditory nerve
called organ of corti. These tiny hairs bend because of the vibrations caused
by the sound waves.
The vibration from the hairs stimulated tiny nerve cells. The
nerve cells then send signals along the auditory nerve to the brain.
Any source of sound sends vibrations or sound waves in to the air.
These funnel through the ear opening, down the ear canal and strike eardrum
acquiring in to vibrate. The vibrations become nerve impulses and transported
to the brain, which interprets the impulses sound [music, voice, etc.]
Tongue is a muscular organ situated in the floor of the mouth. It
is associated with the function of taste, speech, mastication, degurtition.
·
Root
·
Tip
·
Body – it consists of two
·
Dorsum – oral part
·
Pharyngeal part
·
Posterior part
·
Inferior – inferior surface.
There are two groups of muscles of the tongue.
1. Four intrinsic - alter the shape of the
tongue and not attached to the bone.
2. Four paired extrinsic muscles- change the position
of the tongue and are anchored to the bone.
The tongue upper surface is covered by taste buds housed in
numerous lingual papillae. It is responsible for taste.
The organ of smell is located in the middle of the face. The
internal part of the nose lies above the roof of the mouth.
The nose consists of external nose and nasal cavity both are
divided by the septum into right and left.
·
Respiration
·
Olfaction
1.
Nose is the first part of the upper respiratory tract.
2.
Warming and moistening of the inhaled air.
3.
Filter the air by removing particulates.
Olfaction
It has olfactory receptor neuron and it is
responsible for sense of smell.
Speech
The
normal speech is produced with pressure from the lungs, this can be modified
using airflow through the nose in a process called nasalization.
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