Upload
carmella-haynes
View
218
Download
0
Embed Size (px)
DESCRIPTION
Touch receptors send signals to the somatosensory cortex via long axons in the spinal cord Signals are sent to the opposite (contralateral) side of the brain
Citation preview
Sensory Systems:
• Touch, temperature, taste, smell
There
are
a variety
of touch receptors
• Touch receptors send signals to the somatosensory cortex via long axons in the spinal cord
• Signals are sent to the opposite (contralateral) side of the brain
• Wilder Penfield - Montreal Neurological Institue - 1940’s
• Found somatotopic map by stimulating brain during surgery
The
Homunculus
• Two-point discrimination threshold- How far apart do the points have to be to be perceived as two points?
Touch
Discri
mination
To Brain
Skin
Receptors
• Two-point discrimination threshold varies dramatically across the skin surface
• Where is it smallest? Where is it largest?
Touch
Discri
mination
• Two-point discrimination threshold varies dramatically across the skin surface• Where is it smallest? Where is it largest? • Best (smallest) threshold is on finger tips, tounge, and face• Worst (largest) threshold is on legs and back
Touch
Discri
mination
• Cortical representation correlates with two-point discrimination threshold
Touch
Discri
mination
• Two classes of thermoreceptors: warm and cold
Thermoception
Taste (Gustation)
Taste buds contain
chemical receptors
Taste
What are the various “tastes”?
• Multi-dimensional scaling reveals several “varieties” of tastes:
– sweet
– salt
– bitter
– sour
– umami (MSG) - protein receptor?
– fat receptor?
Taste
• What you “taste” depends critically on what you’ve recently been tasting– taste receptors adapt and reduce firing over time– for example: eating something salty reduces the perceived saltiness of subsequent foods
Taste is
Relative
• Olfactory bulb receives input from olfactory receptors which contact mucus in nasal cavity
Smell
• There are thousands of different receptors for different kinds of molecules
Smell
• Olfactory receptors use a “lock-and-key ” mechanism - only specif ic molecules will bind with a given receptor
Smell
Receptor
Odor Molecules
• Odor recognition is excellent in humans
• but odor identification (naming) is very poor
• Women tend to be (slightly) better than men at naming smells
Smell
• Smell is strongly influenced by “top-down” processes such as what you are expecting to smell
Smell
• Pheromones are not smells
• Pheromones are chemical signals sent from one animal to another
Pheromones
• Pheromones either induce a behavior in another animal or cause some physiological change
• Very common in insects...not so common in mammals...unclear role in humans
Pheromones
• For example: Alpha Androstenol, found in male pig saliva, causes a female pig to allow the male to mate with her
Fun
Facts
about
Pheremones
• Alpha androstenol is also found in the sweat of human males!
• Does alpha androstenol (or pheromones in general) affect humans?
• Design an (ethical) experiment…
Fun
Facts
about
Pheremones
• Kirk-Smith & Booth (1980) sprayed some of the seats in a dentist’s waiting room with alpha androstenol• Compared to a control condition, more women used the alpha androstenol seat
Fun
Facts
about
Pheremones
• Fewer men used the alpha androstenol seat !
Fun
Facts
about
Pheremones
• Other possible ways in which pheromones influence humans:
– synchronization of menstrual cycles
– mate selection - attraction to opposite major histocompatibility complex
Pheromones
• Pheromones do not control behavior!
• Human behavior is largely under top-down influences, but may be affected subtly by pheromones
Pheromones