Free Psychology for Dummies by Adam Cash Page A

cortex
(the part of the brain responsible for hearing)
for perceptual processing.

Touch
    The sense of touch includes sensing pressure, temperature, and pain. Specialized cells in the skin sense touch, which send a signal to the spinal chord and then on to the brain. In this case, transduction in touch is a physical or mechanical process; it’s much more straightforward than the chemical transduction in the eye for vision. When heat, cold, or weight stimulates touch receptors in the skin, this sends a neural signal toward the brain, much the same way that the hair cells of the inner ear operate. The pressure leads directly to a neural signal.
    Pain is a special case for the sense of touch because it would be hard to avoid harm and survive in this world without our sense of pain. How do I know fire can damage my flesh and possibly lead to death? Because it hurts when I touch it. Pain is an important signal that something is harming, damaging, or destroying the body.
    A-delta fibers
and
C fibers,
two specific nerve fibers located throughout our skin, signal pain to the brain. A-delta fibers carry sharp sensations and work rapidly, sending swift signals to the brain. C fibers send signals of chronic and dull pain and burning sensations.
     

     
    I’ve played sports most of my life, and one thing is for sure — pain tolerance is always an issue. “No pain, no gain!” I’d hear in practice every day. I’ve had to play through many an injury, and it really hurt! Some people seem to have a really high threshold for pain. The
gate-control theory of pain
states that pain signals must pass through a gate in the spinal cord that “decides” which signals will get through to the brain and which ones will not. If another sense is using the pain pathways, the pain signal may not reach the brain. Also, there might be competing signals coming from another body part toward the gate, thus inhibiting the pain signal from traveling up to the brain. If you’ve ever rubbed your thigh while your ankle aches, it seems to help. That’s because the rubbing signal (pressure) from the thigh is competing for access through the gate with the pain signal from the ankle. That’s amazing! I’m always blown away by the complexity of the human body.

Smell and taste
    Our sense of smell is called
olfaction.
Sometimes I can smell my neighbor’s barbecue on the weekend. I have that experience because little particles from the cooking food,
volatile
chemical particles,
have become airborne and traveled over to the smell receptors in my nose. Inside my nose are thousands of olfactory receptors that can sense tens of thousands of different odors.
    The molecules from the volatile chemicals cause a chemical change in the receptors in my nose, which sets the transduction process in motion. The chemical energy is then converted into neural energy by the receptor cells, and a signal is sent to the
olfactory bulb
in my brain where the signal is processed. The olfactory bulb also connects with the part of my brain that involves emotion. Some researchers think that this connection is why smells can activate emotional memories from time to time.
    There’s been a lot of talk about
pheromones
scents that animals send out as signals to other animals, during mating season, for example. Some companies have marketed pheromone products for humans, especially for those men out there desperate to find a date. Do humans really produce pheromones? The research jury is still out, but a few recent findings seem to suggest that we do. One thing is for sure though: Pheromones or no pheromones, the perfume and cologne industries seem to be on to something!
    Gustation
refers to our sense of taste. Taste is a chemical sense made possible by the chemical receptors on our tongues known as
taste buds.
All tastes are variations on four themes: sweet, sour, bitter, and salty. We have approximately 10,000 taste buds. The taste buds react to the molecules of the food, which again