The body has several sensory systems that provide information about internal and external stimuli. The five traditional senses are sight, hearing, touch, taste, and smell. Vision involves light entering the eye and being processed by the retina and brain. Hearing detects sound waves that vibrate the eardrum and small bones of the middle ear. Touch receptors in the skin sense pressure, temperature, and pain. Taste buds on the tongue detect chemicals to distinguish different flavors. Smell receptors in the nose are stimulated by airborne molecules to perceive scents. Other senses include balance, hunger, thirst, and awareness of the body's position and internal sensations. Sensory information follows defined pathways from receptors to the brain for processing.

1. The body sense
Body sense is the ability to pay attention to
ourselves, to feel our sensations, emotions,
and movements, without the mediating
influence of judgmental thoughts.
Our senses constantly provide us with
information about our surroundings such as:
see, hear, and touch, taste and smell.
Our sense of equilibrium keeps us upright.
We also get information from our senses
about what is happening inside the body.
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2. Body sense are
1. Sensation of skin
2. Sensation of hearing
3. Sensation of taste
4. Sensation of smell
5. Sensation of vision
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3. SENSORY PATHWAY
The impulses involved in sensations follow very precise
pathways, which all have the following parts:
1.Receptors: detect changes (stimuli) and generate
impulses.
2. Sensory neurons: transmit impulses from receptors to
the central nervous system. These sensory neurons are
found in both spinal nerves and cranial
Nerves.
3. Sensory tracts: white matter in the spinal cord or
brain that transmits the impulses to a specific part
of the brain.
4. Sensory areas: most are in the cerebral cortex.
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4. CHARACTERISTICS OF SENSATIONS
1.Projection: the sensation seems to come from the area where
the receptors were stimulated.
2. Intensity: some sensations are felt more distinctly and to a
greater degree than are others. A weak stimulus such as dim light
will affect a small number of receptors, but a stronger stimulus,
such as bright sunlight, will stimulate many more receptors.
3. Contrast: simultaneous sensation on a current sensation,
which may then be exaggerated/greater or diminished/smaller. If
on a very hot day, you jump into a swimming pool, the water may
feel quite cold at first.
4. Adaptation: becoming unaware of a continuing stimulus. The
water in the swimming pool that seemed cold at first seems to
warm up after a few minutes.
5. After-image: the sensation remains in the consciousness even
after the stimulus has stopped. A familiar example is the bright
after-image seen after watching a flashbulb go off.
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5. CUTANEOUS SENSES ( touch)
The dermis of the skin and the subcutaneous
tissue contain receptors for the sensations of
touch, pressure, heat, cold, and pain.
Cutaneous Senses include touch and
everything else we feel through our skin:
temperature, pressure, vibration, and pain.
For example, when we run our fingers over a
rough surface, receptors in the skin of our
fingertips send information about the
surface’s texture to our brain.
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Epidermis: is the thin, outer layer of the skin
that is visible to the eye and works to provide
protection to the body. It is responsible for the
protection of the body.
Dermis: is the second and thickest layer of the
three major layers of skin, located between the
epidermis and subcutaneous tissues.
Hypodermis: is the innermost and thickest layer
of skin.
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8. Skin nerves
Meissner corpuscle: - stack of flattened disks in the
dermis just below epidermis; they respond to touch,
pressure, vibration.
Pacinian corpuscle: - onion-like capsule located deep in
the skin; they responsible for sensitivity to vibration and
pressure.
Nocieceptor: are sensory receptors that detect signals
from damaged tissue and chemical released from the
damaged tissues.
Thermoreceptors: are specialized nerve cells that are
able to detect differences in temperature, heat and cold.
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9. SENSE OF TASTE
The receptors for taste are found in taste buds, most
of which are in papillae on the tongue These
chemoreceptors detect chemicals in solution in the
mouth.
The chemicals are foods and the solvent (if the
mouth is very dry, taste is very indistinct).
There are five general types of taste receptors:
sweet, sour, salty, bitter, and savory.
The sense of taste is important because it makes
eating enjoyable.
Some medications may interfere with the sense of
taste, and this sense becomes less acute as we get
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10. Taste buds anatomy
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12. SENSE OF SMELL
the sense of smell is the process of creating the
perception of smell.
 It occurs when an odor binds to a receptor within
the nose, transmitting a signal through the
olfactory system.
The receptors for smell (olfaction) are
chemoreceptors that detect vaporized chemicals
that have been sniffed into the upper nasal
cavities Just as there are specific taste receptors,
there are also specific scent receptors, and
research indicates that humans have several
hundred different receptors.
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When stimulated by vapor molecules,
olfactory receptors generate impulses carried
by the olfactory nerves (1st cranial) through
the ethmoid bone to the olfactory bulbs.
The pathway for these impulses ends in the
olfactory areas of the temporal lobes.
Vapors may stimulate many combinations of
receptors, and it has been estimated that the
human brain is capable of distinguishing
among 10,000 different scents.
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14. Olfactory anatomy
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olfactory bulb: is a neural structure of the vertebrate
forebrain involved in olfaction, the sense of smell.
cribriform plate: is a sieve-like structure between the
anterior cranial fossa and the nasal cavity. It is
supports the olfactory bulb.
olfactory nerve: is the first cranial nerve and conveys
special sensory information related to smell. It is the
shortest of the cranial nerves.
Nasal cavity: is a large, air-filled space above and
behind the nose in the middle of the face.
olfactory tract: connects the olfactory bulb to the
remainder of the cerebral cortex.
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16. HUNGER AND THIRST
Hunger and thirst may be called visceral
sensations, in that they are triggered by internal
changes.
Hunger is a sensation that seems to be far more
complex than was first thought.
The receptors for both senses are specialized
cells in the hypothalamus.
The receptors for thirst detect changes in the
body water content, that occurs when your body
needs water.
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The sensation of hunger is related to
contractions of the stomach muscles.
Hunger is a normal sensation that makes you
want to eat.
Your body tells your brain that your stomach is
empty. Hunger controlled by a part of your brain
called the hypothalamus.
Fullness is a feeling of being satisfied. Your
stomach tells your brain that it is full.
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18. Sensation of eyes
• The human eyeball(bulbus oculi) is
approximately globe shaped, with diameter of
about 24mm.
• Eyeball is made of two segments an anterior
part and posterior part.
• Orbital cavity is a bony cavity of the eyeball
that keeps eyes from external forces.
• eyelids: protect eyeball from foreign particles
and open and close voluntarily as well as by
reflex actions.
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19. THE EYE
The eye or the organ of sight is situated in the
orbital cavity of the skull.
Each eyeball is similar to a camera and which
produces images.
 It is well protected by bony walls of the orbit,
also contains:
 muscles of eyeball,
nerves,
blood vessels,
lacrimal gland
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20. Anatomy of the eyes
Human eye ball it looks like globe shaped, with a
diameter of about 24mm. Eye ball is made up of
two segments, an anterior part and posterior part.
Eyelids: protect eyeball from foreign particles
coming in contact with its surface and cut of the
light during sleep. Eyelids opens and closed
voluntarily. As well as reflex action.
Conjunctiva: is thin mucus membrane, which
covers the exposed part of the eye. provides
protection and lubrication of the eye by the
production of mucus and tears.
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Lacrimal gland: secrete the watery component of
tears and are located behind the outer part of each
upper lid. It function is production of tears which
moist and cleanse of eyes surface.
Tear contains lysozyme that kills bacteria.
Lacrimal gland
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22. Wall of the eye ball
Wall of the eye ball is composed of three layers:
1. Outer layer (tunica externa or tunica fibrosa)
 Sclera
 Cornea
2. Middle layer ( TUNICA MEDIA OR TUNICA VASCULOSA).
 Choroid
 Ciliary body
 Iris
3. Inner layer ( tunica interna, or retina). It is delicate light
sensitive membrane that forms the innermost layer of
eyeball.
 Pigmented layer
 Sensitive or neuron layer
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23. Anatomy of the eye
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SCLERA: forms the outermost layer of the eyeball It
provides protection to the delicate structure within
the eye.
CHOROID: is a thin pigmented membrane, dark
brown in color which is situated in between sclera
(externally) and retina (internally).
CORNEA: is the transparent convex anterior portion
of the outer layer of eyeball, which covers the iris
and pupil.
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CILIARY BODY: is the continuation of choroid
consisting of smooth muscle fibers, i.e., the ciliary-
muscle
IRIS: is the pigmented membrane surrounds the
pupil.
RETINA: Retina is the inner most layer of the
eyeball. It is translates the light impulses into
electronic impulse which travels down the optic
pathways to the brain.
Fovea: is a tiny pit located in the retina that
provides the clearest vision.
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 optic nerve: is located in the back of the eye.
 The function of the optic nerve is to transfer
visual information from the retina to the
vision centers of the brain via electrical
impulses.
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Blind spot: a small area of the retina where the
optic nerve enters the eye; this type of blind
spot occurs normally in all eyes.
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Ciliary muscles: focusing muscles that change the shape of
the lens.
Suspensory ligaments: connectors that join ciliary muscle
to the lens.
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vitreous humour: is a clear, colourless fluid that fills
the space between the lens and the retina of the
eye. 99% of it consists of water and the rest is a
mixture of collagen, proteins, salts and sugars.
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30. Visual sense pathway
Visual process in series of actions that take place during
visual perception.
 the image of an object seen by the eyes comes cornea.
 Next comes the pupil, the opening that lets light enter the
eye and ultimately reach the retina.
The retina converts the image formed by the light rays into
nerve impulses.
 the energy in visual spectrum is converted into electrical
impulses by rods and cones of retina through some
chemical reactions.
 the impulses from rods and cones reach the cerebral
cortex through optic nerve and sensation of vision
produced in cerebral cortex.
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31. The visual pathway contain six
components:
1) Optic nerve
2) Optic chiasma
3) Optic tract
4) Lateral geniculate body
5) Optic radiation
6) Primary visual cortex
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5. Optic nerve (CN II):is a paired cranial nerve that
transmits visual information from the retina to the
brain.
6. Optic chiasm:it is medial fibers of each optic
nerve cross the midline and join the uncrossed
lateral fibers of opposite side to form the optic
tract.
7. Optic tracts: is formed by uncrossed fibers of
optic nerve, on the same side and crossed fibers of
optic nerve from opposite side.
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8. lateral geniculate body: Part of the thalamus,
that the majority of the fibers of optic tract
terminate, and forms subcortical center for visual
sensation.
9. Optic radiation: are axons from the neurons in
the lateral geniculate nucleus to the primary visual
cortex. It functions to transmit visual input coming
from the retina, the optic nerve, and the optic tract.
10. Primary visual cortex: The primary visual cortex
is the part of the neocortex that receives visual
input from the retina.
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35. Hearing sense
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36. Anatomy of the ear:
Ear consisting of three parties:
1. External ear
2. Middle ear
3. Internal ear
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1. External ear divided into three parties:
pinna: the pinna consists of fibrocartilaginous plate
covered by connective tissue and skin, that
characterized folded and ridged.
External auditory canal: it is starts from the concha
and extends inside as a slightly curved canal, with
length of about 55mm. It consists outer cartilaginous
part and inner bony part.
Tympanic membrane(eardrum): thin layer of tissue
in the human ear that receives sound vibrations from
the outer air and transmits them to the auditory
ossicles.
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39. 2. Middle ear
It is a small, narrowed irregular laterally compressed
chamber, situated within the temporal bone.
Middle ear contains the following parties:
1) Auditory ossicles
2) Auditory muscles
3) Eustachian tube.
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40. Auditory ossicles
Auditory ossicles are the three bones, which are
arranged in the form of a chain, extending
across the middle ear from the tympanic
membrane to oval window.
Their functions is transmitting vibrations from
eardrum to inner ear. Auditory ossicles bones
are: malleus, incus, stapes.
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41. a
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42. Auditory muscles:
There are two skeleton muscles attached to
ossicles, that are:
Tensor tympani: is a larger of the two muscles of
tympanic cavity.
Stapedius: is a smallest skeleton muscle in human
body with length just over 1mm.
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43. Auditory muscles
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44. Eustachian tube( auditory tube)
It is flattened canal extending from the anterior
wall of middle ear to nasopharynx. It is upper
part is surrounded by the bony wall and lower
part is surrounded by fibrocartilaginous plate. It
function is balanced pressure.
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45. Internal ear
Internal ear is membranous structure, enclosed by
a bony labyrinth in petrous part of temporal bone.
It consist of sense organs of hearing and
equilibrium. Sense organ of hearing is the cochlea,
and sense organ for equilibrium is the vestibular
apparatus.
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46. The end
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