Sensation is the detection of stimuli by sensory receptors and the conversion into neural signals. Perception is the interpretation of these signals in the brain. The document discusses the different types of receptors - chemoreceptors, photoreceptors, mechanoreceptors, and thermoreceptors. It also examines the primary sensory cortices for each sense - visual, auditory, olfactory, gustatory, and somatosensory. Finally, it reviews various causes of sensory loss such as vision, hearing, smell, taste, and touch.

1. Sensation and Perception
By: SHJ

2. Sensation
 Detection of a stimulus on the receptor cells of a sensory
organ, leading to a series of biochemical and
neurological responses
 The first stage in the function of the senses
 Comes from the environment and gets transformed into
neural signals that get interpreted in the brain through a
process called Transduction
 Transduction is regarded as the bridge that connects
sensation and perception together

3. Perception
-The mental process that represents the awareness of the
real-world causes of a given stimulus
-Creates useful information of the surrounding environment
(1)

4. Different types of receptors
Chemoreceptors
Photoreceptors
Mechanoreceptors
Thermoreceptors

5. Chemoreceptors
Detects chemical stimuli and
converts the signals into electrical
action potentials
Distance chemoreceptors are
involved in receiving stimuli in the
olfactory system
Direct chemoreceptors can be found
in taste buds and aortic bodies that
measure oxygen concentrations (2)

6. Chemoreceptors

7. Photoreceptors
 Converts light signals into a membrane potential
 Three types of photoreceptors: cones, rods, and
ganglion cells
 Cones respond to colors of different wavelengths,
such as short (blue), medium (green), and long
(yellow/red)
 Rods respond to light intensity, such as vision
adjustment in response to a dark room (3)
 Ganglion cells can be found in the adrenal medulla,
but also in the retina as part of the sympathetic
response (4)

8. Photoreceptors

9. Photoreceptors

10. Mechanoreceptors
 In response to mechanical forces, such as pressure and
distortion
 Hair cells in the auditory and vestibular systems
 Majority of mechanoreceptors can be found on the skin
and can be grouped into four subcategories: Slowly
Adapting type 1, Slowly Adapting type 2, Rapidly
Adapting, and Pacinian Receptors
 Slowly Adapting type 1-responds to form and roughness
 Slowly Adapting type 2-responds to stretch
 Rapidly Adapting-responds when a person slips
 Pacinian Receptors-responds to high frequency vibration (5)

11. Mechanoreceptors and
thermoreceptors

12. Thermoreceptors
Responds to temperature variation
Exact mechanism is unclear but
recent mammal studies reveal two
possibilities (6)
Bulboid Corpuscle detects above
body temperature
Ruffini’s end organ detects below
body temperature

13. Sensory cortex
 Multiple area of the brain at which senses
are received for processing
 Each of the five senses contains a primary
and secondary cortex (7)
Vision-visual cortex
Hearing-auditory cortex
Smell-primary olfactory cortex
Taste-gustatory cortex
Touch-somatosensory cortex

14. Visual cortex
 Often referred to as the primary visual cortex (V1)
and can be found in the Brodman area 17, in the
occipital lobe of the brain (8)
 Primary relay station for visual input to one of two
pathways: Dorsal stream and Ventral stream
 Dorsal stream detects the location of the stimulus
and how it’s presented (ex: on the ground and
sitting with the tongue sticking out)
 Ventral stream detects what the stimulus is exactly
(ex: it’s a dog) (9)

15. Visual cortex

16. Auditory cortex
Cochlea corresponds to the temporal
lobe
Consists of anterior transverse
temporal area 41 and posterior
transverse temporal area 42, also
known as Brodmann areas 41 and
42
Both areas receive and process
sound signals from the auditory
receptors (10)

17. Primary (blue) and secondary
(red) auditory cortex

18. Primary olfactory cortex
 Located in the temporal lobe
 Peripheral and central mechanisms of
action are present
 Peripheral-olfactory receptor neurons
transmits a chemical signal along the
nerve to the olfactory bulb at the end
 Central-multiple nerve axons combine to
form a glomeruli at the olfactory bulb,
before being transferred to the primary
olfactory cortex

19. Olfactory and Gustatory cortex

20. Gustatory cortex
 Detects taste sensations
 Contains anterior insula, which is part of the insular lobe,
and the frontal operculum, which is part of the frontal lobe
 Just like the olfactory cortex, the gustatory cortex also
contains a peripheral and central mechanism
 Receptors are located on the tongue, soft palate, pharynx,
and esophagus. They receive the signals and transmit them
to the primary sensory axons, which are then sent over to
the nucleus of the solitary tract in the medulla, also known
as the gustatory nucleus of the solitary tract complex.
 The signal is then sent to the thalamus, followed by the
gustatory cortex and other parts of the neocortex (11)
 Receptor-primary sensory axons--gustatory nucleus of
solitary tract complex--thalamus---gustatory cortex

21. Somatosensory cortex
 Located in the parietal lobe
 Cortex can be divided into Brodmann
areas 1, 2, 3
 Brodmann 3 is the primary processing
center, receiving most of the input from
the thalamus and creating somatic
sensations through electrical stimulation.
 Areas 1 and 2 get most of their input from
area 3

22. Somatosensory cortex

23. Loss of Sensation
Either due to ineffective receptors,
nerve damage, or cerebral
impairment
Vision loss
Hearing loss
Anosmia
Ageusia
Somatosensory loss

24. Vision loss
 Usually caused by varying degrees of damage,
either resulting in total blindness or no adverse
effect at all
 Also can be caused by sensory failure
 Opacities in the eye media alters the image
despite normal photoreceptor cells (ex:
glaucoma, diabetic retinopathy, and macular
degeneration)
 Optic nerve damage on the afferent pathways
after transmission from those normal
photoreceptor cells

25. Hearing loss
Also can vary from minimal to total
hearing loss
Can be caused by damage
mechanoreceptors secondary to
prolonged noise
Cochlear and auditory nerve
damage can also occur as a result of
HIV and meningitis, respectively
(12)

26. Anosmia
A loss of smell, due to damage to
the olfactory receptor neurons
Often due to nasal polyps or upper
respiratory tract infections
Also due to olfactory nerve damage,
often from hypothyroidism or
physical trauma. (7)

27. Ageusia
 Taste loss can also vary widely.
 Damage to the lingual nerve, affecting signals from the
front two-thirds of the tongue
 Damage to the glossopharyngeal nerve (cranial nerve
9), affecting signals from the back third of the tongue
 Damage may be due to neurological disorders, such as
Bell’s palsy or multiple sclerosis
 Damage can also come from infectious diseases such as
meningoencephalopathy.
 Other causes include a vitamin B deficiency, acidic/spicy
foods, radiation, and/or tobacco use (13)

28. Somatosensory loss
 Insensitivity to touch stimuli and loss of
motor stimulation.
 Caused by damage to the spinal cord or
other major nerve fiber, which can lead to
a loss of both afferent and efferent signals
to varying areas of the body.
 Other types of somatosensory loss include
hereditary sensory and autonomic
neuropathy, which consists of ineffective
afferent neurons with fully functioning
efferent neurons; essentially, motor
movement without somatosensation (14)

29. References
 (1) Gazzaninga, M., Heatherton, T., Halpern, D. & Heine, S.
(2010). Psychological Science ( 3 ed.). New York: W.W. Norton
& Company, Inc. p. 188
 (2) Satir,P. & Christensen,S.T. (2008) Structure and function of
mammalian cilia. in Histochemistry and Cell Biology, Vol 129:6
 (3) “eye, human." Encyclopædia Britannica. Encyclopædia
Britannica Ultimate Reference Suite. Chicago: Encyclopædia
Britannica, 2010.
 (4) Foster, R. G.; Provencio, I.; Hudson, D.; Fiske, S.; Grip, W.;
Menaker, M. (1991). "Circadian photoreception in the retinally
degenerate mouse (rd/rd)". Journal of Comparative Physiology
A 169. doi:10.1007/BF00198171
 (5) Winter, R., Harrar, V., Gozdzik, M., & Harris, L. R. (2008).
The relative timing of active and passive touch. [Proceedings
Paper]. Brain Research, 1242, 54-58

30. References
 (6) Krantz, John. Experiencing Sensation and Perception.
Pearson Education, Limited, 2009. p. 12.3
 (7) Brynie, F.H. (2009). Brain Sense: The Science of the
Senses and How We Process the World Around Us. American
Management Association
 (8) McKeeff, T. J., & Tong, F. (2007). The timing of
perceptual decisions for ambiguous face stimuli in the
human ventral visual cortex. [Article]. Cerebral Cortex,
17(3), 669-678
 (9) Hickey, C., Chelazzi, L., & Theeuwes, J. (2010). Reward
Changes Salience in Human Vision via the Anterior
Cingulate. [Article]. Journal of Neuroscience, 30(33),
11096-11103
 (10) Purves, Dale et al. 2008. Neuroscience. Second
Edition. Sinauer Associates Inc. Sunderland, MA
 (11) ^ Purves, Dale et al. 2008. Neuroscience. Second
Edition. Sinauer Associates Inc. Sunderland, MA.

31. References
 (12) ^ Bizley, J. K., & Walker, K. M. M. (2010).
Sensitivity and Selectivity of Neurons in Auditory Cortex
to the Pitch,Timbre, and Location of Sounds. [Review].
Neuroscientist, 16(4), 453-469.
doi:10.1177/1073858410371009
 (13) ^ Macaluso, E. (2010). Orienting of spatial
attention and the interplay between the senses.
[Review]. Cortex, 46(3), 282-297.
doi:10.1016/j.cortex.2009.05.010
 (14) ^ Li, X. (1976). Acute Central Cord Syndrome
Injury Mechanisms and Stress Features. Spine, 35,
E955-E964
 Wikipedia article on sensation (psychology)

32. Photos
http://science.howstuffworks.com/life/human-biology/taste1.htm
http://people.eku.edu/ritchisong/301notes6.htm
http://www.webexhibits.org/causesofcolor/1G.html
http://www.bem.fi/book/28/28.htm
http://bdml.stanford.edu/twiki/bin/view/Haptics/VibrationOrForce.html
http://thebrain.mcgill.ca/flash/i/i_02/i_02_cr/i_02_cr_vis/i_02_cr_vis.h
tml
http://en.m.wikipedia.org/wiki/File:Auditory_Cortex_Frequency_Mappin
g.svg
http://scientopia.org/blogs/scicurious/2011/05/11/science-101-cranial-
nerve-i-the-olfactory-nerve/
http://droualb.faculty.mjc.edu/Course%20Materials/Physiology%20101
/Chapter%20Notes/Fall%202011/chapter_10%20Fall%202011.htm