1. Chapter 3: Taste, Smell ,Touch and Pain
Johnny Kim
Archis R. Bhandarkar
Neuroscience Society

2. Sensation and Perception
The ability of a neural network to encode, perceive, and gather information of both external and internal environs
In today’s lecture we will be elaborating on two particular focus topics
Focus Topic: The Interrelated Senses of Taste and Smell
Focus Topic: The Somatic Sensory System- touch, proprioception, and pain

3. Part I: Taste and Smell

4. Taste and Smell The two senses act together to perceive flavor
Gustatory Neural Network
Alone taste distinguishes between 5 different tastes: sweet, salty, sour, bitter, and umami (savory)
Taste is detected with taste buds specialized cell structures embedded in the papillae of the tongue and palate
Impulses are conveyed by the facial nerve and sent to the thalamus for conscious perception of taste

5. Gustatory Neural Network (pictured)

6. Taste and Smell Olfactory Neural Network
Cilia, the hair-like extension of olfactory receptor cells, are stimulated by airborne odor molecules
Olfactory receptors cells are located in a small patch of mucous membrane lining the roof of the nose
Axons of these cells pass through small holes in the bone and enter either of two elongated olfactory bulbs

7. Olfactory Neural Network (pictured)

8. Part II: Touch and Pain

9. The Somatic Sensory System
Divided into certain distinguishable subsystems
Subsystem I: Relays information from cutaneous (in-skin) mechanoreceptors
Subsystem II: Specialized receptors in muscles, joints, and limbs that govern proprioception (interpretation of relative body position)
Subsystem III: Transmission of painful stimuli and sudden changes in temperature

10. Flow Chart of System
Sensory Transduction
Action Potentials Are Generated in Afferent Fibers
Dorsal Root Ganglia and Cranial Nerve Ganglia
Passes to Central Nervous System for appropriate decision making

11. Sensory Transduction
We always hear of electrical signals passing through the nervous system. But why? What mechanism converts sensory and chemical impulses to ELECTRICAL signals?
The Answer: Sensory Transduction. A stimulus alters the permeability of ion channels in afferent (of sens. receptor that conveys information to the CNS) nerve endings, resulting in depolarization and the production of a generator potential If the generator potential is large enough, it will be able to spark the appropriate action potential.

12. Afferent Fiber Variants
After sensory transduction, we pass through one of the afferent fiber variants in our “journey”
A Muscle Spindle
Function of Proprioception
13-20 micrometers in diameter m/s
Merkel, Meissner, Pacinian, and Ruffini Cells
Function of Touch m/s
Free Nerve Endings
Pain, temperature
Pain, temperature, itch

13. Afferent Fiber Variants Function
Merkel Cells: tips of epidermal sweat ridges
Sensing form and texture
Small Receptor Field
Meissner Cells: dermal papillae
Motion dection; grip control
Pacinian Cells: dermis and deeper skin tissue
Perception of distant events through vibration; tool use
Large Receptor Field
Ruffini Cells:
Motion direction

14. Final Relay Networks
Finally, this information is conveyed to either the dorsal root ganglia or cranial nerve ganglia and relayed to the CNS for appropriate decision making

15. Two Point Discrimination

16. Pain and the Somatic Sensory System
Nociceptors- sensory fibers that respond to pain stimuli. Nociceptors express molecules that are responsible for painful thermal, mechanical, or chemcial stimulation
Pain messages are transmitted to the spinal cord via small myelinated fibers (faster message arrival time- responding to a needle prick) and C fibers (slower message arrival time).
The ascending system- relays impulses from the spinal cord to the brain
The descending system- suppress the transmissions of the ascending system

17. Works Cited
Purves, Dale, George Augustine, David Fitzpatrick, William Hall, Anthony LaMantia, James Mcnamara, and Leonard White. Neuroscience.
Society for Neuroscience. Brain Facts.