How do we Stay Balanced?

The Vestibular System

Vestibular System (Balance)

Vestibular System (Balance)

Vestibular System (Balance)

Vestibular System (Balance)

Head accelerates this way

Cupula getspushed

Fluid goes this way

Vestibular System (Balance)

Head accelerates this way

Cupula getspushed

Fluid goes this way

Vestibular System (Balance)

• movement of the cupula is detected by hair cells

• hair cells in the vestibular system are more sensitive than hair cells on the basilar membrane!

Vestibular, Visual, and Proprioceptive Systems Work Together

• Try standing on one foot with your eyes closed!

Fun Facts about The Vestibular System

• Seasickness arises when the vestibular system and the visual system send conflicting information

Fun Facts about The Vestibular System

• Seasickness arises when the vestibular system and the visual system send conflicting information

• People can be knocked down by moving walls!

Fun Facts about The Vestibular System

• Seasickness arises when the vestibular system and the visual system send conflicting information

• People can be knocked down by moving walls!

• Alcohol causes the spins by (among other things) changing the density of the fluid in the semicircular canals

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 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) - possibly a protein

receptor– there may also be a lipid (fat) receptor

Taste

• 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 specific 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: Androstenone, found in male pig saliva, causes a female pig to allow the male to mate with her

Fun Facts about Pheromones

• androstenone is also found in the sweat of human males!

• Does androstenone (or pheromones in general) affect humans?

• Design an (ethical) experiment…

Fun Facts about Pheromones

• Kirk-Smith & Booth (1980) sprayed some of the seats in a dentist’s waiting room with androstenone

• Compared to a control condition, more women used the androstenone seat

Fun Facts about Pheromones

• Fewer men used the androstenone seat !

Fun Facts about Pheromones

• 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

• It is unclear whether molecules such as androstenone even qualify as pheromones - they may be just like other odour molecules

Pheromones