Neuro Notes

Introduction to the Senses: detect changes in the environment
• General vs. specialized/attuned (some animals are better)
– Human vision vs. taste/smell
– Humans are diurnal and nocturnal, helps senses
• A blind child was asked the following question: “What are the 7 wonders of the world?”
– To touch, taste, see, hear
– To feel, laugh, love
– Modalities/Senses: Vision, Taste, Smell, Hearing, Touch
Submodalities
• Information about these senses
• For vision, this includes light, color patterns, shading, motion, shapes
– The visual cortex allows us to see motions as continuous events (vs. split second)
– How difficult would it be to cross Park Ave. or Main St. if our brains could not integrate information?
• Taste/Gustation:
– Sweet, Sour, Salty, Bitter, Umami, Lipids
• Smell/Olfaction: >10,000 scents/odors
• Hearing:
– Pitch, Loudness
• Touch/Somatic sensation:
– Pressure, Position, Roughness, Vibration, Temperature, Itch, Pain
Sensory Receptors
• Detect physical or chemical phenomenon
• 3 types: Chemical (taste, smell, pain)
– Mechanical (hearing, vestibular, position, touch, pain)
– Electromagnetic (vision, orientation, migration, temperature, pain)
• Animal examples:
– Electric eels and cartilaginous fish detect electromagnetic energy
– Magnetic fields in migratory birds
– Temperature changes by snakes
Transduction-convert energy into ATP
• GPCR cascade
• Amplification
• Very Selective
• Receptor Potentials
- Similar to EPSPs
• - Non - propagating
- No Hodgkin Cycle
Receptor Potential
• Generation of AP
• AP travels to appropriate brain area, where perception occurs
– The latter steps are very similar to our discussion on electrical signals
Questions:
• Do the receptors work when you are asleep? Yes, stimuli enter dreams, can’t fall out of bed
• Can you tickle yourself? No, expect it
Perception
• Sensation- when sensory receptors detect signals/changes in the environment
– Sensations are subjective
• Perception- interpretation by brain
– Our brains are collecting so much sensory information, how can it focus?
– Commercial: if a tree falls in the forest, does anyone hear it?
For Chemical Senses
Threshold = minimum concentration for detection
• Olfaction: - peppermint is 0.02 mg/L
– methyl mercaptan is 10-5 mg/L
• Taste: glucose: 80,000 uM (micromolar)
– sour HCl, 190 uM, strychnine 1.6 uM
There are olfactory and tastant binding proteins (OBP, TBP) that help to transport substances through fluid
Taste cells have their own axons
Three nerves to tongue
Fig. 8.2
Can change over lifetime
Gustation
• The tongue epithelium is 1% taste receptors
• Papillae are bumps (taste buds) on tongue
– ~3,000
• Types: fungiform- front
– Foliate- sides
– Vallate- back
• Does the tongue have spatial coding?
• Submodalities detect ions or larger molecules
– umami, (MSG, an AA) lipids (cytoplasmic R?)
• Hotness- capsaicin in hot peppers
Tongue Nerve Pathway: Tongue  medulla (gustatory nucleus)  thalamus  gustatory cortex