A broadly acceptable definition of a
sense would be "a system that consists of
a sensory cell type that responds to a
specific kind of physical energy, and that
corresponds to a defined region within
the brain where the signals are received
School children are routinely taught that
there are five senses (sight, hearing,
smell, taste, touch). The special senses
are the first four of these, touch is
specifically excluded as a special sense.
Instead, the various aspects of touch
(pain, heat, pressure) are all categorized
as somatic senses.
Somatic sensation consists of the various sensory receptors that
trigger the experiences labeled as touch or pressure(hence
shape, softness, texture, vibration, etc.), temperature (warm or
cold), pain (including itch and tickle), and the sensations of
muscle movement and joint position (including posture,
movement, and facial expression).
Touch may simply be considered
one of five human senses; however,
when a person touches something
or somebody this gives rise to
various feelings or emotions.
During special tests, scientists observe
that different areas of the brain become
active when subject to different stimuli.
The above image is a visual
representation only, not actual brain test
imagery. The areas of the brain that ‘light
up’ when feeling pain and empathy are
shown in red and blue respectively.
Pain and Empathy
Humans can generally hear sounds with frequencies between 20 Hz and 20
kHz. Human hearing is able to discriminate small differences in loudness
(intensity) and pitch (frequency) over that large range of audible sound. The
ear is sensitive to a change in pressure equal to 1X10-10 atmospheres
"Computation Provides a Virtual Recording of Auditory Signaling", Public Library of Science Biology, January 2005, Volume 3, Issue 1, e26, graphic ref. DOI: 10.1371/journal.pbio.0030026.g001
Sound is a disturbance of mechanical energy that travels through matter as
a longitudinal wave. Sound is characterized by the properties of sound
waves, which are frequency, wavelength, period, amplitude, and speed.
primAry Auditory cortex
Neurons in the auditory cortex are organized according to the
frequency of sound to which they respond best. Neurons at one
end of the auditory cortex respond best to low frequencies;
neurons at the other respond best to high frequencies.
The auditory cortex
is the most highly
processing unit of
sound in the brain.
This cortex area
The visible part is called the pinna and functions to
collect and focus sound waves. Some humans can
move the pinna (with the auriculares muscles).
From the pinna the sound pressure
waves move into the ear canal, a
simple tube running to the middle
ear. This tube amplifies frequencies
in the range 3 kHz to 12 kHz.
The middle ear contains three ossicles, which
amplify vibration of the eardrum into pressure
waves in the fluid in the inner ear. The
eustachian tube joins the tympanic cavity with
the nasal cavity, allowing pressure to equalize
between the inner ear and throat.
Ordinarily, when sound waves in air strike
liquid, more than 99% of the energy is reflected
off the surface of the liquid. The middle ear
allows the impedance matching of sound
traveling in air and sound traveling in liquid,
overcoming the interface between them.
The movement of the ossicles may be stiffened by two
muscles, the stapedius and tensor tympani, which are
under the control of the facial nerve and trigeminal nerve,
respectively. These muscles contract in response to loud
sounds, thereby reducing the transmission of sound to the
The inner ear is the
bony labyrinth, a
system of passages
(1)the organ of
hearing, or cochlea
and the (2)
organ of balance
that consists of
canals and the
The vestibule is the region of the inner ear where the
semicircular canals converge, close to the cochlea (the
hearing organ). The vestibular system works with the
visual system to keep objects in focus when the head is
moving. The brain receives, interprets, and processes
the information from these systems that control our
The semicircular canals are three
half-circular, interconnected tubes
located inside each ear. Because the
angles between the canals are not
perpendicular, movements of the
head stimulate horizontal and
vertical canals simultaneously.
In brief: theIn brief: the cochleacochlea is filledis filled
with awith a watery liquidwatery liquid, which, which
moves in response to themoves in response to the
vibrationsvibrations coming from thecoming from the
middle ear. As the fluidmiddle ear. As the fluid
moves, thousands ofmoves, thousands of "hair"hair
cellscells" are set in motion, and" are set in motion, and
convert that motion toconvert that motion to
electrical signalselectrical signals that arethat are
communicated viacommunicated via
neurotransmitters to manyneurotransmitters to many
thousands of nerve cells.thousands of nerve cells.
The "critical period" is a time
in the early stages of a
human’s life during which
critical language skills are
developed. If the organism
does not receive the
appropriate stimulus during
this "critical period", it may
be difficult, or even
impossible, to develop some
functions later in life.
Broca's area is the section of the human
brain (in the frontal lobe of the cortex)
that is involved in language processing,
Wernicke's area is on the auditory cortex
(part of the brain where the temporal lobe
and parietal lobe meet). Wernicke’s area is
where the specialized language skill areas
can be found for the majority of people and
is particularly known to be involved in the
understanding and comprehension of spoken
The visual cortex is the most massive system in
the human brain and is responsible for higher-
level processing of the visual image. It lies at
the rear of the brain (highlighted in the
image), above the cerebellum.
“To suppose that the eye, (with so
many parts all working together)…
could have been formed by natural
selection, seems, I freely confess,
The visual system interprets the
information from visible light
to build a representation of the
world surrounding the body.
The retina consists of a large number
of photoreceptor cells which contain
a particular protein molecule called
an opsin. In humans, there are two
types of opsins, rod opsins and cone
opsins. Either opsin absorbs a photon
(a particle of light) and transmits a
signal to the cell through a signal
In the retina about 130
absorb light and
roughly 1.2 million
information from the
retina to the brain.
The information about the image via the eye is transmitted to the brain along
the optic nerve. In humans, the optic nerve is connected directly to the brain.
Rods and cones differ in
function. Rods are found
primarily in the periphery
of the retina and are used
to see at low levels of light.
Cones are found primarily
in the center (or fovea) of
There are three types of cones
that differ in the wavelengths
of light they absorb; they are
usually called short or blue,
middle or green, and long or
red. Cones are used primarily
to distinguish color and other
features of the visual world at
normal levels of light.
farsightedness, is a
defect of vision in
which light produces
an image focus
behind the retina.
a refractive defect
of the eye in which
light produces an
image focus in front
of the retina.
View your own retinal blood vessels!
Try it yourself –Blind Spot
A O X
Instructions: Your face should be very
close to the screen. Cover right eye and
focus the left eye on the X. Now slowly
move away from the screen.
The O will disappear, while the A which
is further to the left is still visible.
(Observe that you do not see a hole.
Instead of the O you see a uniform grey
background. The "hole" is filled in by
your brain. Make sure there is not a
glare on the screen as it will obscure the
The olfactory system is the sensory system used for smell. The
accessory olfactory system senses pheromones. The olfactory
system is often spoken of along with the gustatory system as
the chemosensory senses because both transduce chemical
signals into perception.
The olfactory system must
accomplish several tasks:
*Create a representation of
*Determine the concentration
of the odor
*Distinguish a new odor from
*Pair the odor with a memory
of what the odor represents
Patrick J. Lynch, medical illustrator
Odorants are inhaled and then transduced into electrical signals which then travel
along the olfactory nerve into the olfactory bulb. Axons from the olfactory sensory
neurons converge in the olfactory bulb to form tangles called glomeruli. Inside the
glomulerus, the axons contact the dendrites of mitral cells. Mitral cells send their
axons to a number of brain areas, including the amygdala.
Olfaction and taste
Olfaction, taste, and trigeminal receptors together contribute
to flavor. The human tongue can only distinguish among seven
to eight distinct types of taste, while the nose can distinguish
among hundreds of substances, even in minute quantities.
Olfaction amplifies the sense of taste.
Odor information is easily stored
in long term memory and has
strong connections to emotional
memory. This is possibly due to
the olfactory system's close
anatomical ties to the
hippocampus and amygdala,
areas of the brain that have
long been known to be involved
The gustatory system is the sensory system that
uses taste buds (or lingual papillae) on the upper
surface of the tongue to provide information
about the taste of food being eaten.
There are at least four types
of taste "bud" (receptor) on
the tongue. The inabilty to
taste is called ageusia.
It is known that
there are four taste
Salty, and Sour.
In humans, the sense of
taste is conveyed via
three of the twelve
cranial nerves. The
facial nerve (VII) carries
taste sensations from
the anterior two thirds
of the tongue, the
(IX) carries taste
sensations from the
posterior one third of
the tongue while a
branch of the vagus
nerve (X) carries some
taste sensations from
the back of the oral
Taste is a form of chemoreception which
occurs in specialized receptors in the mouth.
serotonin is thought to act as an intermediary
hormone which communicates with taste cells
within a taste bud, mediating the signals
being sent to the brain.
Each of the five senses
activates a separate area of
the cerebral cortex, the sheet
of neurons that makes up the
outer layer of the brain's
Scott T. Barrows- National
Summary (another example of WPP)
Verses about our special sensesVerses about our special senses!
Your eyes have seen all that
the LORD did in Egypt to
Pharaoh, to all his officials and
to all his land. 3
With your own
eyes you saw those great
trials, those miraculous signs
and great wonders. 4
this day the LORD has not
given you a mind that
understands or eyes that see
or ears that hear. Deuteronomy
"Now, my God, may your eyes be open
and your ears attentive to the prayers
offered in this place………
if my people, who are called by my
name, will humble themselves and pray
and seek my face and turn from their
wicked ways, then will I hear from
heaven and will forgive their sin and will
heal their land. 15
Now my eyes will be
open and my ears attentive to the
prayers offered in this place. 16
chosen and consecrated this temple so
that my Name may be there forever. My
eyes and my heart will always be there.
2 Chronicles 6- 7:16
For the eyes of the LORD range
throughout the earth to strengthen
those whose hearts are fully
committed to him.
2 Chronicles 16:8-10
Ears that hear and eyes that see—
the LORD has made them both.
Does he who implanted the ear not
hear? Does he who formed the
eye not see?
My ears had heard of you but now my eyes
have seen you.
However, as it is written: "No eye has
seen, no ear has heard, no mind has
conceived what God has prepared for
those who love him" —
1 Corinthians 2:8-10
Since ancient times no one has heard, no
ear has perceived, no eye has seen any
God besides you, who acts on behalf of
those who wait for him.
Look, he is coming with the
clouds, and every eye will
see him, even those who
pierced him; and all the
peoples of the earth will
mourn because of him. So
shall it be! Amen.
How, then, can they call on the one they
have not believed in? And how can they
believe in the one of whom they have not
heard? And how can they hear without
someone preaching to them? 15
can they preach unless they are sent? As it
is written, "How beautiful are the feet of
those who bring good news!“
Lived when (
Lived where Adult height Adult mass
H. habilis 2.2 – 1.6 Africa
33–55 kg (73–
660 many 1960/1964
H. erectus 2 – 0.03
1.8 m (5.9 ft) 60 kg (130 lb)
850 (early) –
H. rudolfensis 1.9 Kenya 1 skull 1972/1986
H. georgicus 1.8
600 few 1999/2002
H. ergaster 1.9 – 1.4 E. and S. Africa 1.9 m (6.2 ft) 700–850 many 1975
H. antecessor 1.2 – 0.8 Spain 1.75 m (5.7 ft) 90 kg (200 lb) 1000 2 sites 1997
H. cepranensis 0.9 – 0.8? Italy 1000 1 skull cap 1994/2003
0.6 – 0.25
1.8 m (5.9 ft) 60 kg (130 lb) 1100–1400 many 1908
0.35 – 0.03
1.6 m (5.2 ft)
55–70 kg (120–
150 lb) (heavily
1200–1700 many (1829)/1864
H. rhodesiensis 0.3 – 0.12 Zambia 1300 very few 1921
H. sapiens sapi
0.2 – present worldwide
1000–1850 still living —/1758
H. sapiens idalt
0.16 – 0.15 Ethiopia 1450 3 craniums 1997/2003
H. floresiensis 0.10 – 0.012 Indonesia 1.0 m (3.3 ft) 25 kg (55 lb) 400 7 individuals 2003/2004