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Lecture 19

PNB 2264 Lecture Notes - Lecture 19: Olive Oil, Suspensory Ligament, Electromagnetic Radiation

Physiology and Neurobiology
Course Code
PNB 2264

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Notes Day 19
Special Senses
Special Senses
- Essential to survival, competition
o Olfaction, taste, sight, and hearing
- Greater level of organization of sensory neurons and associated tissues
- Must rapidly process large amount of data
o Processed by a large percentage of the brain
o Energy cost (not easy or cheap)
- Wide range of sensations
- Detection of outside world, reality
o Hallucinogens
- Vision
o Detection of light
- Hearing, balance, movement
o Inner ear, movement of mechanoreceptors
- Smell and taste
o Nose and tongue, chemoreceptors
- Detection of external chemicals (volatile)
o Can dissolve in air
o Volatile
- Within olfactory epithelium
- Superior nasal cavity
o Protective
- The air we ingest is mixed in the sinus and exposes the epithelium to the volatile
Olfactory epithelium
- 10^7 sensory cells, bipolar neurons
o replaces every 30 days, unique to this sensory
- dendrite ends in cilia, covered with musuc, axon projects to olfactory bulb
- odorants enter nose
- bind to receptor (7-TMS-G protein coupled), cAMP
o depolarization
- approx. 200 odroants
- 200 genes for receptors, largets gene family primordial function
o extremely important
- 1 receptor per neuron, a distribution of sensitivity overlap
- 4000 different smells
o a signature odor dependent on which neurons are activated
o a particular chemical can activate more than one receptor
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- species-specific chemicals
o social status and reproductive readiness
o steroid-derivatives in urine
dogs and cats spraying territory
evidence in humans
babies detecting mother by smell but mostly by sound of
mother’s voice
women in dorms cycling at the same time
false no evidence humans detect pheromones
Information processing
- information to olfactory bulb
o physical map
o to detect a smell information must go to place that processes information as
- very low threshold
o very sensitive survival technique
- women are 6 times more sensitive to smells then men
Neuronal pathways
- olfactory bulb
o mitral or tufted cells
o 200 receptors each glomerulus (1800 total)
o convergence
sensitivity at loss of spatial info
o mitral or tufted cells, associated neuron
o information modification (emotional, memory)
- tongue taste buds
- papillae (4 kinds)
- 10,000 taste buds, varied thresholds
o 10^4 vs 10^7 for smell, smell is much more sensitive
- sensory neurons
o replaced every 10 days
o once again, correct linkages must be made
- salt sodium enter leak channels
o saliva has low salt, least sensitive
which is why you need to add so much salt to food
o cell depolarization
- H+, same way
o Leak channels, block potassium channels, opens sodium channels
More sensitive to acid than salt
o Cell depolarization
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