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Chapter 4.4

PSY100H1 Chapter Notes - Chapter 4.4: Taste, Machismo, Nasal Congestion

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Michael Inzlicht

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Module 4.4 Touch and the Chemical Senses
- Would you ever describe your breakfast cereal as tasting pointy or round?
- Most of use can separately identify touch, taste, and smell, but some people cannot
- People with synesthesia experience blended perceptions
o People might hear colors or feel sounds
o Ex. A number may have a color associated with it
o Synesthesia can also involve blending taste and touch
The Sense of Touch
- Through touch we get info about texture, temperature, and pressure
- All these things are because of the actions of receptors under the skin, in the muscles, joints, and
- The receptors send info to the somatosensory cortex in the parietal lobes of the brain
o Somatosensory cortex: the neural region associated with your sense of touch
Sensitivity to touch varies across the body
- A simple method for testing sensitivity (acuity) is to use the two-point threshold test (Fig. 4.34, page
Regions with high acuity (e.g. fingertips) can detect the two separate, but closely spaced,
pressure points of the device
Less sensitive regions (e.g. lower back) will perceive the same stimuli as only one pressure point
- Research has shown that women have a little more refined (superior) sense of touch than men, precisely
because their fingers (and therefore their receptors) are smaller**
- The sensitivity of different parts of the body also influences how much space in the somatosensory
       ’ 
Places in the body that send a lot of sensory input to the brain (such as lips) have a larger
portion dedicated to them in the somatosensory cortex compared to ankles
- Touch is very sensitive to change
-       ’  ,       
o Haptics: the active, exploratory aspect of touch sensation and perception
Active touch involves feedback
o Haptics allow us not only to identify objects, but also avoid damaging and dropping them
o Fingers and hands coordinate their movements using a complementary body sense called
Kinesthesis: the sense of bodily motion and position
Receptors for kinesthesis reside in the muscles, joints, and tendons
These receptors transmit info about movement and the position of your muscles, limbs,
and joints to the brain
As you handle an object, your kinesthetic sense allows you to hold it with enough
resistance to avoid dropping it, and to keep your hands and fingers set in such a way as
to avoid letting it roll out of your hand
Feeling Pain
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- Nociception: the activity of nerve pathways that respond to uncomfortable stimulation
- Our skin, teeth, corneas, and internal organs contain nerve endings called nociceptors
o Nociceptors: receptors that initiate pain messages that travel to the CNS
They come in varieties that respond to different painful stimuli
(extreme heat or something
- Two types of nerve fibres transmit pain messages:
o 1) Fast fibres register sharp, immediate pain, such as the pain felt when your skin is cut
o 2) Slow Fibres register chronic, dull pain, such as the lingering feelings of bumping your knee
into a coffee table
- Both fast and slow fibres first send impulses to the spinal cord, the firing of neurons within the spinal
cord will influence how this pain is experienced
Pain varies from mild to severe
Pain also varies from acute (brief) to chronic
- How do we explain differences in pain experiences?
One theory of pain perception is the gate-control theory
o Gate-control theory: explains our experience of pain as an interaction between nerves that
transmit pain messages and those that inhibit these messages
o Based on this, cells in the spinal cord regulate how much pain signaling reaches the brain
            
o The spinal cord contains small nerve fibres that conduct pain messages and larger nerve fibres
that conduct other sensory signals (such as rubbing, pinching, and tickling)
o Stimulation of the small pain fibres results in experiencing pain, and larger fibres inhibit pain
o Basically, larger fibres close the gate that is opened by smaller fibres
According to gate-control theory, if you stub your bare toe, rubbing the area around the toes
may alleviate some of the pain, because the larger fibres carrying the message about touch
inhibit the firing of the smaller fibres carrying pain signals
- Input from both these fibres will be sent from the spinal cord to the brain
- In the brain, the sensory info will branch off to (at least) two different areas of the brain:
o The somatosensory cortex: registers the pain sensations occurring over the entire surface of the
o The anterior cingulate gyrus: influences our attentional and emotional responses to the pain
Located on the medial (middle) surface of the brain above the corpus callosum
- Pain is also an emotional response (feeling frustrated when you are hurt), mostly because the anterior
cingulate gyrus has a lot of connections with the limbic system
- But how do we feel when we see someone else in pain? OMG
Working the Scientific Literacy Model (Empathy and Pain)
-      ’ nsory experiences to influence those of another person?
- Step 1 (knowledge):
What do we know about empathy and pain?
o W’     
o If we see someone in pain, we experience negative emotions and sometimes even feel pain
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