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How We Taste
How We Taste
How We Taste
• The chemical senses of taste and smell respond to chemical molecules dissolved in liquid (taste) or that are found in the air (smell). The chemical senses serve two purposes: (1) identification of molecules safe to consume and (2) identification and rejection of molecules that are dangerous.
How We Taste
• Transduction for the chemical sense of gustation occurs when molecules mix with saliva. Taste receptor cells are mostly located within taste buds and are not visible to the human eye. Taste buds are clustered in small bumps, known as papillae that are along the surface of the tongue. There are also receptors for taste at the back of the throat and along the roof of the mouth.
How We Taste
• Five Basic Tastes:• Sweet• Sour• Bitter• Salty• Umami (most recent discovery; a flavor enhancer associate with glutamate; meaty or savory)
How We Taste
• Considerable variation exists between individual in terms of how sensitive they are to various tastes, and this sensitivity is mostly determined by genetics.
• Both humans and other animals prefer sweet and salty tastes to sour and bitter ones.
• Evolutionary psychologists believe that these preferences evolved to help humans and animal more easily identify nutritious foods and avoid that that are rotten or poisonous.
• Taste receptors regenerate every 1‐2 weeks but overall responsiveness to taste declines with age and activities such as smoking and drinking alcohol.
How We Smell
How We Smell
• Our sense of smell results from chemicals in the air (odorants) entering the nostrils and sweeping upward to dissolve in mucous membranes containing olfactory receptor cells. The specialized receptor cells for olfaction are hair cells, or cilia.
• Researchers have been unable to identify specific basic smells, as they have for taste. It appears there are at least 350 different types of olfactory receptor cells that allow for the detections of over 10,000 different odors.
How We Smell
• The axons of the olfactory receptors travel to the olfactory bulb, located below the frontal lobe. Unlike all the other sense, olfaction does NOT involve processing by the thalamus, but instead travels directly to the olfactory areas of the temporal lobe that pass the information to the limbic system. Contact with the limbic system structures, including the hippocampus and amygdala, create the strong emotional responses and memories associated with smell.
Sensory Phenomena
SENSORY INTERACTION• Involves one sense affecting another.
• The perception of flavor as the combination of smell and taste as well as temperature and texture
SYNESTHESIA• Stimulation of one sensory system generates unexplained sensations in another sensory system. Research shows ≈ 1 in 2,000 have regular experiences, and 1 in 300 have some
• Being able to hear colors and taste shapes
How We Touch
How We Touch
• Transduction for the sensation of touch occurs when specialized receptor cells located in the skin throughout the body respond to physical pressure, temperature, or chemicals.
• The sense of touch is perceived in the brain by contralateral organization (sensations on the left side are perceived by the somatosensory cortex in the right hemisphere and vice versa). Additionally, areas of the body that are more sensitive to touch are represented by greater surface area along the somatosensory cortex.
Pain
Although pain is an unpleasant experience, it is critical for survival because it generates a rapid response designed to reduce or prevent damage from occurring to tissues.
There are pain receptors located throughout the body which follow one of two main pathways to the brain.
• Fast Pathway or A‐delta fibers (myelinated nerves that carry sharp/acute pain messages)
• Slow Pathway or C‐fibers (unmyelinated nerves that carry dull pain messages that persist after the initial injury; the throbbing sensation of chronic pain)
The Gate‐Control Theory of Pain
•An explanation for how the perception of pain can be managed and controlled.
•Based on the idea that pain signals traveling to the brain via the spinal cord pass through a series of invisible doors or gates.
• These gates open to allow pain signals to travel to the brain or close to block pain signals.
The Gate‐Control Theory of Pain
• (1) To close the gates, additional sensory information traveling up the spinal cord prevent the passage of pain messages (like when you rub the area around the injury and the rubbing sensation reduces the transmission or pain signals.
• (2) To close the gates, the brain may send signals down the spinal cord, closing the gate and preventing additional pain messages from traveling to the brain. This can include distractions, emotions, visual input, and the release of endorphins all of which can impact how much or how little pain is perceived.
