Somatic and Special Senses
Chapter 10
Introduction
• Sensory Receptors- detect
environmental changes and trigger nerve
impulses that travel on sensory pathways
into the CNS for processing and
interpretation
http://michaeldmann.net/pix_4b/gust_receptors.gif
2 large types of sensory receptors
• 1. Somatic senses: touch, pressure,
temperature, and pain
• 2. Special senses: smell, taste, hearing,
equilibrium, and vision
http://www.medicalook.com/systems_images/Somatic_senses.gif
Receptors and Sensations
• Receptors are distinct to a type of
environmental change
• This selective response distinguishes the
senses
• 5 kinds
1. Chemoreceptors
• Stimulated by changes in the chemical
concentration of substances
2. Pain Receptors
• Stimulated by tissue damage
https://courses.cit.cornell.edu/psych396/student2006/the_biology_of_pain/receptor2.jpg
3. Thermoreceptors
• Stimulated by changes in temperature
http://resource.rockyview.ab.ca/t4t/bio30/images/m1/b30_m1_022_l.jpg
4. Mechanoreceptors
• Stimulated by changes in pressure or
movement
http://bdml.stanford.edu/twiki/pub/Haptics/ProjectOverview/mechanoreceptors.jpg
5. Photoreceptors
• Stimulated by light energy
http://thebrain.mcgill.ca/flash/d/d_02/d_02_m/d_02_m_vis/d_02_m_vis_1a.jpg
Sensation
• Sensation-a feeling that occurs when the
brain interprets sensory impulses
• Impulse is read depending on what area of
the brain receives it
• One area may be sound and one area
may be touch
http://www.drugabuse.gov/sites/default/files/slide4.gif
Projection
• Projection-process where the cerebral
cortex causes a feeling to stem from a
source
• It allows a person to pinpoint the region of
stimulation (eyes & ears)
Sensory Adaptation
• Sensory adaptation-sensory receptors
stop sending signals when they are
repeatedly stimulated
• Can only be triggered if stimulus strength
changes again
• Think smell (phasic)
http://www.cyndan.com.au/Portals/0/Media/F/Farm%20Mate%20cow.jpg
Somatic Senses
• 1. Sensory Nerve Fibers
– Common in epithelial tissues
– Are associated with touch and pressure
http://www.exploringnature.org/graphics/anatomy/sensory%20organs.jpg
• 2. Meissner’s Corpuscles
– Small masses of connective tissue
– Located in hairless portions of the skin (lips,
fingertips, palms, soles, nipples, external
genitalia)
– Interpret light touch
http://www.exploringnature.org/graphics/anatomy/sensory%20organs.jpg
• 3. Parcinian Corpuslces
– Large structures of connective tissue
– Located in deep tissue layers like ligaments
and tendons
– Respond to heavy pressure
Temperature Senses
• 1. Warm Receptors - nerve endings that
respond to warmer temperatures
(sensitive above 77°, unresponsive above
113°F)
• 2. Cold Receptors - nerve endings that
respond to colder temperatures (sensitive
between 50°F and 68°F)
http://herkules.oulu.fi/isbn9514259882/html/graphic22.png
Sense of Pain
• These protect the body because tissue damage
stimulates them
• Usually unpleasant and signals the person to
remove the stimulation
• Pain is persistent and doesn’t go away
• Four types
1. Visceral Pain
• Occurs in visceral tissues such as heart,
lungs, intestine
http://wehelpwhathurts.homestead.com/visceral-somatic_referral_patterns_resize_smaller.jpg
2. Referred Pain
• Feels as though it is coming from a
different part (heart pain may be felt as
pain in arm or shoulder)
• Caused from Nerves passing through the
same area
http://www.merckmanuals.com/media/home/figures/NEU_referred_pain.gif
3. Acute Pain
• Originates from skin, usually stops when
stimulus stops (needle prick)
https://courses.cit.cornell.edu/psych396/student2006/the_biology_of_pain/receptor2.jpg
4. Chronic Pain
• Dull aching sensations
http://criticalscience.com/wp-content/uploads/2011/08/pain-map_alphachimp_com.jpg
Regulation of pain
• Pain is interpreted by the Cerebral Cortex
in the brain.
• Three types of neuropeptides that inhibit
pain: serotonin, enkephalins,
endorphins.
• Natural brain chemicals can be mimicked
by drugs such as morphine.
Morphine
http://recoverylife.com/resources/gallery_photo/morphine60.jpg
Special Senses
• Smell: olfactory organs
• Taste: taste buds
• Hearing equilibrium: Ears
• Sight: Eyes
http://www.exploringnature.org/graphics/anatomy/poster_special_senses_small.jpg
Sense of Smell
• The sense of smell is associated with
complex sensory structures in the upper
region of the nasal cavity
http://www.umm.edu/graphics/images/en/8689.jpg
Olfactory Receptors
• Chemoreceptors that are stimulated by
chemicals that are dissolved in liquid
• Aid in food selection because smell and
taste are closely related
http://www.yalescientific.org/wp-content/uploads/2011/05/fulllengths-olfaction-2.jpg
Olfactory Organs
• Contain the olfactory receptors which are
masses that cover the upper parts of the
nasal cavity
http://www.medicalook.com/systems_images/Olfactory_sense.gif
Olfactory Receptor Cells
• Bipolar neurons surrounded by epithelial cells
• Covered in cilia which have receptor proteins that the
odor chemicals bind to
http://openwetware.org/images/b/ba/Olfactory_System_2.jpg
Olfactory Bulbs
• Receive the nerve impulses from the
receptor cells (located in the brain)
http://lynlaukimdak.wikispaces.com/file/view/42.jpg/219698964/42.jpg
Olfactory Tracts
• Located inside the olfactory bulbs and
interpret the nerve impulses
Smell Video
http://www.medicalook.com/systems_images/Olfactory_sense.gif