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BIO303: Neurobiology

Unit 7: Somatic Sensory System   We will now begin looking at global neural systems. We will begin with the somatic sensory system, which detects physical stimuli such as pressure, temperature, and pain. There are two subsystems within the larger somatic sensory system—one for pressure (mechanosensory) and the other for temperature (thermoception) and pain (nociception). Between these systems, we have a number of receptors that will inform us everything from temperature to muscle stretch. We know a great deal about how these systems work. For example, our use of menthol and capsaicin takes advantage of temperature sensation to enable the feeling of “cool” mints and “spicy” oils. Our somatic sensory is among the oldest and most primitive of nervous functions, existing even in the simplest of organisms.

Unit 7 Time Advisory
This unit will take you 12 hours to complete.

☐    Subunit 7.1: 4 hours

☐    Subunit 7.2: 4 hours

☐    Subunit 7.3: 4 hours

Unit7 Learning Outcomes
Upon successful completion of this unit, the student will be able to:
- compare and contrast the major types of sensory receptors and their functions; - explain how the mechanosensory pathway changes throughout the body, the function of dermatomes, and the homunculus; and - explain how pain is perceived in relation to the types of pain receptors and the sensory pathways involved in pain perception.

7.1 Sensory Receptors   - Reading: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” Link: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” (HTML and Adobe Flash)
 
Instructions: Read the first paragraph on “Cutaneous Receptors,” and then take the quiz included at the end of this webpage.
 
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7.1.1 Free Nerve Endings   - Reading: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” Link: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” (HTML and Adobe Flash)
 
Instructions: On the webpage linked above, scroll down and read the section on “Free Nerve Endings.” Then click the “next” link to page 5 and read “Free Nerve Endings.”
 
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7.1.2 Meissner’s and Pacinian Corpuscles   - Reading: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” Link: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” (HTML and Adobe Flash)
 
Instructions: Read the sections “Cutaneous Receptors,” “Meissner Corpuscles,” and “Pacinian Corpuscles.”
 
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7.1.3 Merkel’s Disks   - Reading: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” Link: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” (HTML and Adobe Flash)
 
Instructions: Scroll down and read sections titled “Hair follicle” and “Merkel Complex.”
 
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7.1.4 Ruffini’s Corpuscles   - Reading: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” Link: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” (HTML and Adobe Flash)
 
Instructions: Scroll down and read the section titled “Ruffini Corpuscles.”
 
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7.1.5 Muscle Spindles   - Reading: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” Link: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” (HTML and Adobe Flash)
 
Instructions: Read the section titled “Muscle Spindles.”
 
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7.1.6 Golgi Tendon Organs (GTO)   - Reading: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” Link: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” (HTML and Adobe Flash)
 
Instructions: Scroll down and read the section titled “Golgi Tendon Organs.”
 
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7.1.7 Joint Receptors   - Reading: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” Link: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 2: Somatosensory Systems” (HTML and Adobe Flash)
 
Instructions: Scroll down and read the section titled “Joint Receptors.”
 
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7.2 Mechanosensory Pathway   7.2.1 Threshold and Two-Point Discrimination   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: Differences in Mechanosensory Discrimination Across the Body Surface” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: Differences in Mechanosensory Discrimination Across the Body Surface” (HTML)
 
Instructions: Read the entire webpage.
 
Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

7.2.2 Proprioception   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: Mechanoreceptors Specialized for Proprioception” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: Mechanoreceptors Specialized for Proprioception” (HTML)
 
Instructions: Read the entire webpage. Proprioception is the ability to know where you are in space. To understand this concept, close your eyes and point to your nose with your right index finger. You managed to complete this task without looking at your hand through the “magic” of proprioception. There are several types of receptors that function together to provide your brain with proprioception information. You should be able to identify these types of receptors and the contributions that each makes.
 
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7.2.3 Dermatomes   - Reading: The University of Texas’s Neuroscience Online: Dr. Nachum Dafny’s “Ch 3: Anatomy of the Spinal Cord” Link: The University of Texas’s Neuroscience Online: Dr. Nachum Dafny’s “Ch 3: Anatomy of the Spinal Cord” (HTML and Adobe Flash)
 
Instructions: Scroll down and read the paragraph beginning “A dermatome is an area of skin…” and the associated Figure 3.5. 
 
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7.2.4 Dorsal Column-Medial Lemniscus (DCML) Pathway   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: The Major Afferent Pathway for Mechanosensory Information: The Dorsal Column-Medial Lemniscus System” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: The Major Afferent Pathway for Mechanosensory Information: The Dorsal Column-Medial Lemniscus System” (HTML)
 
Instructions: Read the entire webpage, click on the embedded hyperlinks, and explore all figures.
 
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7.2.5 Trigeminothalamic Pathway   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: The Trigeminal Portion of the Mechanosensory System” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: The Trigeminal Portion of the Mechanosensory System” (HTML)
 
Instructions: Read the entire webpage, click on any embedded links, and explore all figures. Both the DCML and trigeminothalamic pathways provide physical stimuli information to the brain. One covers the face, while the other covers the rest of the body. Be sure to know which one is which, and be able to trace a typical pathway of each in the body!
 
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7.2.6 Somatic Sensory Cortices and Homunculus   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: The Somatic Sensory Cortex” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: The Somatic Sensory Cortex” (HTML)
 
Instructions: Read the entire webpage, click on any embedded links, and explore all figures.
 
Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

7.3 Temperature and Pain   7.3.1 Nociceptor Types   - Reading: The University of Texas’s Neuroscience Online: Dr. Nachum Dafny’s “Ch 6: Pain Principles” Link: The University of Texas’s Neuroscience Online: Dr. Nachum Dafny’s “Ch 6: Pain Principles” (HTML and Adobe Flash)

 Instructions: Read the introduction, section 6.1 “Pain receptors”,
and section 6.6 “Nociceptor Neurons in the Spinal Cord
(Nocineurons).”  

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displayed on the webpage above.

7.3.2 Heat and Cold Perception   - Reading: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 4: Somatosensory Pathways” Link: The University of Texas’s Neuroscience Online: Dr. Patrick Dougherty’s “Ch 4: Somatosensory Pathways” (HTML and Adobe Flash)
 
Instructions: Read the entire webpage.
 
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7.3.3 First and Second Pain   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 10: The Perception of Pain” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 10:  The Perception of Pain” (HTML)
 
Instructions: Read the entire webpage, click on any embedded links, and explore all figures.
 
Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

7.3.4 Referred Pain   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Box A – Referred Pain” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Box A – Referred Pain” (HTML)
 
Instructions: Read the entire webpage, and view the figures.
 
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7.3.5 Anterolateral System   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 10: Central Pain Pathways: The Spinothalamic Tract” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 10: Central Pain Pathways: The Spinothalamic Tract” (HTML)
 
Instructions: Read the entire webpage.
 
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7.3.6 Trigeminal Tract   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: The Trigeminal Portion of the Mechanosensory System” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 9: The Trigeminal Portion of the Mechanosensory System” (HTML)
 
Instructions: Read the entire webpage.
 
Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

7.3.7 Sensitization   - Reading: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 10: Hyperalgesia and Sensitization” Link: NCBI Bookshelf’s version of Sinauer Associates, Inc., Purves, Augustine, Fitzpatrick, et al., editors’ Neuroscience, 2nd Edition: “Ch 10: Hyperalgesia and Sensitization” (HTML)
 
Instructions: Read the entire webpage.
 
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  • Assessment: The Saylor Foundation’s “Unit 7 Quiz” Link: The Saylor Foundation’s “Unit 7 Quiz (PDF)
     
    Instructions: Complete the entire assessment. You can check your answers with The Saylor Foundation’s “Unit 7 Answer Key (PDF).