4. BRIEF INTRODUCTION OF SENSES
• It helps to integrate or gather information from the outer world
• Learning and knowledge comes through senses
• Senses help the person through various learned experiences
5. SIGNIFICANCE OF NORMAL SENSES
• Person can enjoys life with normal senses
• People with normal senses grasp valid information than their counterparts
• Normal senses makes the person more efficient in collecting information
6. PEOPLE WITH IMPAIRMENT SENSES
• Difficulty in life when person has deficiency of one or more than one sense
• Remain gap to learn information
• Person feels inferior because he/she is not equal to others
7. SENSES
• We experience reality through our senses. A sense is a faculty by which outside
stimuli are perceived.
• Our senses are split into two different groups.
• Exteroceptors
• Interoceptors
9. INTEROCEPTORS
A sensory receptor which receives stimuli from within the body, especially from the gut
and other internal organs.
The interoceptors receive stimulation from the inside of our bodies. For instance,
blood pressure dropping, changes in the glucose and Ph levels.
11. NOCICEPTORS
• a sensory receptor for painful stimuli.
• Respond to heat, mechanical stress and chemicals associated with tissue damage.
12. THERMORECEPTORS
• Respond to changes in temperature in dermis, skeletal muscles, liver and
hypothalamus
• These are cold receptors and warm receptors
14. CHEMORECEPTORS
• Respond to small concentration changes of specific molecules
• Internal chemoreceptors monitor blood composition
• These are also important for homeostasis.
15. FIVE SENSES
• Touch
• Olfaction (sense of smell)
• Gustation (sense of taste)
• Hearing And Equilibrium
• Vision
17. • Other senses of the body are found in specific areas of the body, your sense of touch
can be found all over the body.
• Sense of touch originates in the bottom layer of the skin called the dermis.
• The dermis is filled with nerve endings that send information to your spinal cord,
which then sends messages to brain so you know what your body is coming in
contact with.
18. • About 20 different types of nerve endings that all send messages to your
brain.
• There are a variety of different receptors but the most common receptors
include; heat, cold, pain, and pressure receptors.
• Pain receptors are the most important, because they protect you by
letting your brain know that your body is hurt.
• Some parts of the body may be more sensitive than others because they
contain more nerve endings
19. The part of the human body that has the most nerve endings are the
finger tips. There are about 100 touch receptors in each of your finger tips
20. • Our sense of touch is controlled by a huge network of nerve endings and
touch receptors in the skin known as the somatosensory system. This
system is responsible for all the sensations we feel - cold, hot, smooth,
rough, pressure, pain, vibrations.
• Within the somatosensory system, there are four main types of
receptors:
• Mechanoreceptors,
• Thermo receptors,
• Pain receptors,
• Proprioceptors
21. Mechanoreceptors: These receptors perceive sensations such as pressure,
vibrations, and texture.. The most sensitive mechanoreceptors, Merkel's disks and
Meissner's corpuscles, are found in the very top layers of the dermis and epidermis
and are generally found in non-hairy skin such as the palms, lips, tongue, soles of
feet, fingertips, eyelids, and the face..
Pain receptors: There are over three million pain receptors throughout the body,
found in skin, muscles, bones, blood vessels, and some organs. They can detect pain
that is caused by mechanical stimuli (cut or scrape), thermal stimuli (burn), or
chemical stimuli (poison from an insect sting).
• Proprioceptors: Proprioceptors are found in tendons, muscles, and joint capsules.
This location in the body allows these special cells to detect changes in muscle
length and muscle tension. Without proprioceptors, we would not be able to do
fundamental things such as feeding or clothing ourselves.
22. Thermo receptors: As their name suggests, these receptors perceive sensations related to
the temperature of the skin. There are two basic categories of thermo receptors: hot and
cold receptors.
Cold receptors start to perceive cold sensations when the surface of the skin drops below
95 ° F. They are most stimulated when the surface of the skin is at 77 ° F and are no
longer stimulated when the surface of the skin drops below 41 ° F. This is why your feet
or hands start to go numb when they are submerged in icy water for a long period of
time.
Hot receptors start to perceive hot sensations when the surface of the skin rises above 86
° F and are most stimulated at 113 ° F. But beyond 113 ° F, pain receptors take over to
avoid damage being done to the skin and underlying tissues.
24. Olfaction (olfactics) is the sense smell (L.olere =smell + facere = to make), is
20,000 times more sensitive than the sense of taste.
Normal Adults can sense up to 10,000 different odors and children can smell
better than adults.
This sense is not very much perfect as several poisonous gases are not detected
by olfactory system (e.g. carbon monoxide).
SMELL
25. these receptors locate high in the roof of the nasal cavity, in specialized areas of
the nasal mucosa called the olfactory epithelium.
About 2.5 sq cm columnar olfactory epithelium, which is a small patch of
pseudostratified is present in each nostril.
The olfactory epithelium is made up of three kinds of cells: receptor cells:
sustentacular cells & basal cells
These receptors have life span of 30 days, and are continuously replaced by
newly formed olfactory neurons to form new synaptic connections in the
olfactory bulb which locates right between the eyes.
These olfactory cells can easily damage as they are the only neuron exposed to
external world, so we lose about 1% of olfactory receptor cells each year.
STRUCTURE OF OLFACTORY RECEPTORS
26.
27. • The human have 25 million bipolar receptor (each of the receptor is covered by sustentacular cells).
• The receptor cell ends in bulbous olfactory vesicle, the olfactory (bowman’s) glands the fluid secrete
through sustentacular cell which covers the surface epithelium
• and have many tiny hair-like cilia protrude from the olfactory receptor cell's dendrite into the
mucus covering the surface of the olfactory epithelium..
• Each olfactory receptor cell expresses only one type of olfactory receptor, but many separate olfactory
receptor cells express olfactory receptors which bind the same set of odors.
• The axons of olfactory receptor cells which express the same olfactory receptor converge to form
glomeruli which is a spherical structure located in the olfactory bulb of the brain
where synapses form between the terminals of the olfactory nerve and the dendrites of mitral, peri
glomerular and tufted cells.
STRUCTURE OF OLFACTORY RECEPTORS
28.
29. • first processed in glomeruli then initially olfactory cortex involved in differentiating and determining
the intensity of the odor.
• to sense the substance must be volatile, water-soluble and lipid-soluble
• on cell membrane odor molecules have some kind of physical interaction with protein receptor which
produce the action potential in nerve fiber of olfactory bulb, according to this theory the discrimination
of odor results from the simultaneous but varying stimulation of receptor cells.
• Seven categories of odors: musky, camphoraceous, floral, pungent, pepper minty, ethereal, & putrid
(they can be in combination). The quality of our sense of smell varies as conditions change (e.g. in cold
& hunger)
HOW ODER ARE PERCEIVED
30. • In the temporal lobe of cerebral cortex there is a primary olfactory cortex where
is the axonal branches are projects through the mitral cell in the olfactory bulb.
NEURAL PATHWAYS FOR OLFACTION
32. THE SENSE OF TASTE
(TASTE BUDS)
• The receptors for taste (gustation) is classified as
Chemoreceptors because they respond to chemicals
in an aqueous solution.
• The word taste comes from Latin “taxare”, meaning
“to touch, estimate, or judge”.
33. LOCATION AND STRUCTURE OF TASTE
BUDS
• Taste buds, the sensory receptor organ for taste, located
primarily in the oral cavity.
• 10,000 or more are on the tongue; few are scattered on the soft
palate, inner surface of cheeks, pharynx, and epiglottis of the
larynx.
• Most taste buds are found in peglike projections of the tongue
mucosa called papillae, which give the tongue surface slightly
abrasive feel.
34. PAPILLAE
• The papillae are of three major types: Foliate, Fungiform,
and Circumvallate.
Fungiform Papillae (mushroom-shaped) are scattered over
the entire tongue surface, but are most abundant at its tip
and along its side.
Circumvallate Papillae (round-shaped) are the largest and
numerous papillae, 7-12 of these form an inverted V at the
back of the tongue.
In human adults, the latter two types house most of
the taste buds.
35.
36. BASIC TASTE SENSATIONS
• Taste sensations can all be grouped into one of four basic qualities:
Sweet, Sour, Salty, and Bitter.
Although there are no structural differences between the taste buds
in different areas of the tongue, the tip of the tongue is most
sensitive to sweet and salty substances, the sides to sour, and the
back of the tongue to bitter.
• The Sweet taste is elicit by many organic substances including
sugars, saccharin, alcohols, some amino acids.
• Sour taste is produced by acids, specifically their hydrogen ions
(H+) in solution.
• Table salt (sodium chloride) tastes the “saltiest”.
• The bitter taste is elicited by alkaloids (such as quinine, nicotine,
caffeine, morphine, aspirin).
38. PHYSIOLOGY OF TASTE
A chemical to be tasted, it must dissolve in saliva, diffuse into the
taste pore, and contact the gustatory hairs. Binding of the food
chemical to the gustatory cell membranes induces a depolarizing
potential and these cells do contain synaptic vesicles
(neurotransmitter) contents.
The higher the concentration of a chemical, the more intense its
perceived taste. However, different gustatory cells have different
thresholds for activation. The bitter receptors detects substance
present in a minute amounts. The sour receptors are less sensitive;
the sweet and salt receptors are least sensitive.
Taste receptors adapts rapidly with partial adaptation in 3-5
seconds and complete adaptation in 1-5 minutes.
39.
40. THE GUSTATORY PATHWAY
• Afferent fibers carrying taste information from the tongue are found
primarily in two cranial nerve pairs. A branch of the FACIAL Nerve
(VII), the chorda tympani, transmits impulses from taste receptors,
whereas the lingual branch of the GLOSSOPHARYNGEAL Nerve
(IX) services the posterior third.
• The afferent fibers synapse in the solitary nucleus of Medulla, from
there impulses are transmitted to Thalamus and ultimately to the
gustatory cortex in the parietal lobes.
• Fibers also project to the hypothalamus and limbic system structures,
regions that determine our appreciation of what we are tasting.
• An important role of taste is to trigger reflexes involved in digestion.
As taste impulses pass through solitary nucleus, they initiate reflexes
that increase secretion f saliva into the mouth and gastric juice into
the stomach.
41.
42. INFLUENCE OF OTHER SENSATION ON
TASTE
Taste depends heavily on the stimulation of olfactory receptors. Indeed, taste
is 80% smell. When olfactory receptors in nasal cavity are blocked by nasal
congestion, food is bland.
• Without smell, morning coffee would lack its richness and simply taste
bitter.
44. WHAT IS HEARING AND EQUILIBRIUM?
• Hearing ( audition) and equilibrium are considered in the same section because both
sensations are received in the same organ : the inner ear. The ear actually has two
functional units :
• (1) The auditory apparatus ( also called the acoustic apparatus ) concerned with
hearing, and
• (2) The vestibular apparatus concerned with posture and balance. The auditory
apparatus is innervated by the cochlear nerve, and the vestibular apparatus is
innervated by the vestibular nerve. The two nerves are collectively known as the
vestibulocochlear nerve (cranial nerve )
45. ANATOMY OF HEARING
• The auditory system is organised to detect several aspects of
sound,including pitch,loudness,and direction.
• The anatomical components of this system are the external ear, the
middle ear,and the inner ear.
• The external ear is composed of the auricle and external auditory
canal; the middle ear is made up of the tympanic membrane ( ear
drum), tympanic cavity,auditory,( eustachian ) tube, and the three
auditory ossicles ( ear bones ); the inner ear,or membranous
labyrinth,is composed of vestibule ( which contains the utricle and
saccule ),semicircular canals and ducts, and cochlea ( which contains
the spiral organ of corti ).
46.
47. PHYSIOLOGY OF HEARING
• Sound is the alternating compression and decompression of the medium through
which the sound is passing .
• Sound waves reach the spiral organ through a sequence of vibrations that start in
the external ear and tympanic membrane, and progress into the inner ear.
48. • The displacement of the hairs of the hair cells in the spiral organ generates
generator potentials and, subsequently nerve impulses in the cochlear nerve.
• Their influences are conveyed to the auditory area of the temporal lobe via the
auditory pathways.
49. • Specific parts of the inner ear help the body to cope with changes in position and
acceleration.
50. • The main receptors for equilibrium are the utricle, saccule, and semicircular ducts
in the inner ear.
• The equilibrium system also receives input from the eyes and from some
proprioceptors in the skin and joints.
51. • The purpose of the vestibular system is to signal changes in the motion of the head (
dynamic equilibrium )
• In the position of the head with respect to gravity ( static equilibrium, or posture ).
• Specialized receptor cells of the vestibular sense organs are hair cells, which are
arranged in clusters called hair bundles.
52. • Stereocilia and a kinocilium are present in each hair bundle .When hairs are bent in
the direction of the stereocilia, the hair cells convert a mechanical force into an
electrical signal that is conveyed to the brain via the vestibular nerve.
• When the head moves in a change of posture, calcium carbonate crystals ( otoconia )
in the inner ear respond to gravity, resulting in the bending of the hairs of hair cells.
53. • The bending stimulates nerve fibres to generate a generator potential and then an
action potential,which is transmitted to the brain.
• The brain signals appropriate muscles to contract,and body posture is adjusted to
follow the new head position.
• The utricles and saccules are organs of gravitation,responding to movements of the
head in a straight line: forward,backward,up,or down.
54. • In contrast, the crista ampullaris of the semicircular ducts responds to changes in
the direction of head movements, including turning, rotating, and bending.
• Hair cells in the crista project into a gelatinous flap called cupula. When the head
rotates , the endolymph in the semicircular canals lags behind, displacing the
cupula and the hairs projecting into it.
55. • The resulting action potentials are sent to the neural centers in the brain, which
signals certain muscles to respond appropriately to maintain the body’s equilibrium.
56. WHY DOES YOUR VOICE SOUND DIFFERENT
ON A TAPE RECORDING?
When you hear yourself speak, you are hearing some extra resonance produced by
the conduction of sound waves through the bones of your skull. Your voice as played
by a tape recorder is the way it sounds to a listener, who receives the sound waves
only through air conduction.
57. HOW CAN YOU TELL THE DIRECTION OF A
SOUND?
• Depending on the position of the head , sound reaches the closer ear about 1/1500 of
a second sooner than the other ear. Also, the sound is a little louder in the closer ear.
These differences are recognized and analyzed by the brain to tell you from what
direction a sound is coming.
59. THE STIMULUS (PSYCHOPHYSICS)
• our eyes detect the presence of light.
• For humans, light is a narrow band of the spectrum of electromagnetic
radiation.
• Electromagnetic radiation with a wavelength of between 380 and 760 nm
• The perceived color of light is determined by three
dimensions:
• Hue (the dominant wavelength)
• Saturation (relative purity of the light that is being perceived)
• brightness (color; intensity)
60. ANATOMY OF THE VISUAL SYSTEM
image must be focused on the retina, the inner lining of the eye. This image causes
changes in the electrical activity of millions of neurons in the retina, which results in
messages being sent through the optic nerves to the rest of the brain
62. STRUCTURE & FUNCTION
IRIS
The iris is the colored
part of the eye
adjust the size of the
pupil
PUPIL
The pupil is the black
circle in the center of the
eye,
monitor the amount of
light that comes into the
eye.
63. STRUCTURE & FUNCTION
• SCLERA
• whites of the eye
• supports eyeball
• provides attachment
for muscles
• LENS
• The lens exists behind
the pupil
• responsible for
allowing your eyes to
focus on small details
like words in a book
64. STRUCTURE & FUNCTION
• CORNEA
• primarily responsible for
focusing the light that
comes into our eyes.
• Vitreous body
Transparent,
colorless mass of
soft, gelatinous
material that fills
the center of the eye
behind the lens.
65. • Choroid
Blood vessel-rich tissue behind the retina
that is responsible for its nourishment.
• RETINA
• internal membrane
• contain light-receptive cells (rods
& cones)
• converts light to electrical signal
STRUCTURE & FUNCTION
Retina
66. STRUCTURE & FUNCTION
OPTIC NERVE
• Transmits electrical impulses from
retina to the brain
• Creates blind spot
• Brain takes inverted image and
flips it so we can see
67. PHOTORECEPTORS
BIPOLAR CELL
A bipolar neuron located in the middle layer of the retina, conveying information from
the photoreceptors to the ganglion cells.
GANGLION CELL
A neuron located in the retina that receives visual information from bipolar cells; its
axons give rise to the optic nerve.
68. STRUCTURE & FUNCTION
• RODS (bipolar cells)
• 120 million cells
• detect brightness
(black & white)
• for night vision
• CONES (bipolar cells)
• 6 million cells
• detect colour (RGB)
• GANGLION CELLS
• Detect movement and
patterns
69. CONNECTIONS BETWEEN
EYE AND BRAIN
1.Light rays enter the eyes by passing through the cornea, the aqueous, the pupil, the
lens, the vitreous, and then striking the light sensitive nerve cells (rods and cones) in the
retina.
2.Visual processing begins in the retina. Light energy produces chemical changes in the
retina's light sensitive cells. These cells, in turn, produce electrical activity.
3.Nerve fibers from these cells join at the back of the eye to form the optic nerve.
70. CONNECTIONS BETWEEN
EYE AND BRAIN
1.The optic nerve of each eye meets the other at the optic chiasm. Medial nerves of each
optic nerve cross, but lateral nerves stay on the same side. The overlap of nerve fibers
allows for depth perception.
2.Electrical impulses are communicated to the visual cortex of the brain by way of the
optic nerve.
3.The visual cortex makes sense of the electrical impulses, and either files the information
for future reference or sends a message to a motor area for action.
71.
72. PROBLEMS IN VISION
Nearsightedness (Myopia), and Farsightedness (Hyperopia)
Near and farsightedness are the result of varying- shaped eyeballs
that cause light
to focus in front of or behind the retina.
Light is
focused from
near and far
objects
exactly on
the retina
73.
74. LOOK AT THE CROSS FOR 10 SECONDS.
WHAT DO YOU SEE?
77. READING
What is wrong with
with this sentence?
Aoccdrnig to rscheearch at Cmabrigde
Uinervtisy, it deosn't mttaer in waht oredr the
ltteers in a wrod are, the olny iprmoetnt tihng is
taht the frist and lsat ltteer be at the rghit pclae.
The rset can be a toatl mses and you can sitll
raed it wouthit a porbelm. Tihs is bcuseae the
huamn mnid deos not raed ervey lteter by istlef,
but the wrod as a wlohe.
