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AP Psychology
SENSATION
Chapter 4 (Bernstein), pages 106-149
Introducing
Your Senses
You have been told you have to give up one of your senses.
1. which one would you choose NOT to have?
2. Why would you choose this sense and not one of the others?
3. Describe the physiological processes/physical structures that
would be affected by your lack of this sense.
Introducing
Your Senses
1. VISUAL DOMINANCE: we are very reliant on our sense of vision and “give
priority” to information that comes through that sense. (e.g., the McGurk Effect,
The Rubber Hand Illusion)
2. INTERACTION OF TASTE AND SMELL: by giving up smell, you are also
giving up much of the flavor of food. In addition, you will no longer be able to
use smell to detect danger (e.g., smelling smoke).
3. INCREASED SENSITIVITY: if you lose one sense, the other senses do NOT
become more sensitive (e.g., you cannot develop more rods and cones). Rather
you do attend more to the other sensory cues and would notice things that you
might not otherwise.
Introducing
Your Senses
Physiological Processes/
Physical Structures
1. VISION--lack of rods or cones or damage to the cornea, lens, retina, the optic
nerve, the occipital lobe or thalamus
2. HEARING--damage to the tympanic membrane, the mealleus, incus, or
stapes (conduction deafness), the basilar membrane, the auditory nerve
(nerve deafness), or the temporal lobe or thalamus
3. SMELL--damage to olfactory neurons or the olfactory bulb
4. TASTE--damage to the taste buds or papillae and the thalamus
Introducing
Your Senses
Physiological Processes/
Physical Structures
5. TOUCH--difficulty surviving; wouldn’t be able to swallow or feel pain
(which is important!). There could be damage to the skin’s sensory neurons,
the spinal cord, and the thalamus
6. KINESTHESIA--damage to receptors in the muscles and joints that send
information to the spinal cord and the thalamus
7. VESTIBULAR--no sense of balance or the positions of one’s head in space;
could have damage to the vestibular sacs in the inner ear or cerebellum; if
problem exists with the vestibular-ocular reflexes produced by the eye
muscles, there could be damage to the vestibular sense
WHAT ARE OUR SENSES?
1. A SENSE is as system that translates information from outside the
nervous system into neural activity.
2. Messages from the senses...SENSATIONS
3. Sensation v. Perception (the process of giving meaning to sensation, Ch. 5)
• difficult to distinguish because interpretation of sensations begins
in sense organs and continues into the brain
WHAT ARE OUR SENSES?
4. Some General Info
•
stream of info from different senses can interact (e.g., ______________ )
•
experience can change the sensations we receive (e.g., ______________ )
•
“reality” differs from person to person (e.g., ______________ )
5. Our senses gather information about the world by detecting various
forms of ENERGY (e.g., light, heat, sound, physical pressure).
6. Humans depend primarily on VISION, HEARING, and the SKIN
SENSES.
SENSORY SYSTEMS
1.
The “Steps” in Sensation
ACCESSORY STRUCTURES modify/change environmental energy before “detected”
by the sensory system itself (ex. the outer ear is an accessory structure that collects sound).
2.
TRANSDUCTION converts environmental energy into neural activity (much like
translating English into another language).
•
SENSORY RECEPTORS specialized cells that detect energy forms
•
Sensory receptors respond best to changes in environmental energy
•
ADAPTATION is a process in which responsiveness to an unchanging stimulus decreases
over time.
3. Sensory nerves carry output from receptors to CNS (spinal cord and brain)
4. for all senses except smell, info goes first to thalamus which relays it to appropriate sensory
area of the cerebral cortex for complex processing
SENSORY SYSTEMS
•
The Problem of Coding
CODING is the translation of a stimulus’ physical properties into a
pattern of neural activity that specifically identifies those properties
• DOCTRINE OF SPECIFIC NERVE ENERGIES states that stimulation
of a particular sensory nerve provides codes for that one sense, no
matter how the stimulation takes place (ex. gently pressing eyeball
produces optic nerve activity and little spots of light)
• In other words... We
have sensory systems which allow us to take in
information from the outside world and make “sense” of it in our
inside world (the brain).
HEARING
SOUND is a repetitive fluctuation in the pressure of a medium, such as air.
Vibrations of an object produce the fluctuations in pressure that create sound.
A wave is a repetitive variation in pressure that spreads out in three dimensions.
3-D sound wave
HEARING
Physical Characteristics of Sound
Sound is represented graphically by waveforms (2-D) which have three characteristics:
•
AMPLITUDE or intensity is the difference in air pressure from baseline to peak
•
WAVELENGTH is the distance from one peak to the next
•
FREQUENCY is the number of complete waveforms, or cycles that pass by a given
point in space every second. One cycle per second is 1 hertz (Hz).
•
Frequency and wavelength are related; the longer the wavelength, the lower the
frequency (and vice versa)
•
Most sounds are mixtures of many frequencies and amplitudes, but a pure tone
consists of only one frequency and is represented by a sine wave
Fun Science: SOUND
AMPLITUDE or intensity is the difference in air pressure from baseline to peak
WAVELENGTH is the distance from one peak to the next
FREQUENCY is the number of complete waveforms, or cycles that pass by a
given point in space every second. One cycle per second is 1 hertz (Hz).
Frequency Response Tests
HEARING
Psychological Dimensions of Sound
Physical characteristics of sound waves produce the psychological dimensions of sound.
•
LOUDNESS determined by amplitude of the sound wave; waves with greater
amplitude produce sensations of louder sounds.
•
•
Loudness is described in units called decibels, dB. Zero dB is the minmal
detectable sound for normal hearing.
PITCH is how “low” or “high” a tone sounds. High frequency waves are senses
as high-pitched sounds.
•
•
Humans can hear sounds from about 20 Hz to 20,000 Hz.
TIMBRE is sound’s quality. Consists of complex wave patterns that enables you
to differentiate sounds.
IN REVIEW...
Which physical characteristic
determines PITCH?
Which determines LOUDNESS?
What creates the TIMBRE of a sound?
PARTS OF THE EAR
Outer Ear...
CHANNELS sound (pinna,
auditory canal, tympanic
membrane/eardrum)
Middle Ear...
AMPLIFIES sound (hammer/
malleus, anvil/incus, stirrup/
stapes)
Inner Ear...
TRANSDUCES sound (cochlea,
basilar membrane, hair cells/
cilia, auditory nerve)
An Introduction to Your Ear
Part 1
An Introduction to Your Ear
Part 2
PARTS OF THE EAR
Outer Ear...
CHANNELS sound (pinna,
auditory canal, tympanic
membrane/eardrum)
PARTS OF THE EAR
Middle Ear...
AMPLIFIES sound
(hammer/malleus,
anvil/incus, stirrup/stapes)
PARTS OF THE EAR
Inner Ear...
TRANSDUCES sound
(cochlea, basilar
membrane, hair cells/
cilia, auditory nerve)
Auditory Transduction
(6:44)
HEARING
Focusing the Sound: THE HUMAN EAR
YOUR TASK
Create an entertaining and informative SKIT in which your group...
...describes the roles of the cochlea, basilar membrane, hair cells, and auditory nerve in
the process of AUDITORY TRANSDUCTION. Include a description of the types of
deafness. (GROUPS 1a and 1b see pp. 113-115)
...describes how information is relayed to the primary auditory cortex and how the
cortex codes the frequency and location of sounds. (GROUPS 2a and 2b see pp. 115-116)
...describes the process of coding auditory information. Discuss the relationship
between PLACE THEORY and FREQUENCY-MATCHING THEORY (VOLLEY
THEORY) on frequency coding. (GROUPS 3a and 3b see pp. 116-118)
PLACE THEORY v. FREQUENCY-MATCHING THEORY
Place Theory
Frequency-Matching Theory
http://clas.mq.edu.au/perception/psychoacoustics/hearing_theory.html
TEST YOUR MAD SKILLS!
VISION
LIGHT
• a form of energy known as electromagnetic radiation
• most invisible to the human eye
VISION
VISIBLE LIGHT
• electromagnetic radiation with a wavelength from approx. 400
nanometers (one-billionth of a meter) to about 750 nanometers
• does not need a medium to pass through (such as air or
water...or molasses)
• has properties of both waves and particles (light rays and light
waves both correct terminology)
• sensations of light dependent upon two physical dimensions:
• LIGHT INTENSITY how much energy the light contains;
determines brightness
• LIGHT WAVELENGTH
determines color you sense;
different wavelengths produce sensations of different
colors (ROYGBIV)
VISION
Focusing the Light:
THE HUMAN EYE
Bill Nye on the Eye
Anatomy and
Function of the Eye
VISION
How Vision Works
Converting Light into Images (VISUAL TRANSDUCTION)
PHOTORECEPTORS the specialized cells in the retina that convert light into
neural activity
PHOTOPIGMENTS chemicals in photoreceptors that respond to light
• light strikes photoreceptors
• photoreceptors break apart and chemical reaction begins
• cell’s membrane polarity changes and signal sent to the brain
• in dim conditions photoreceptors make extra photopigment to detect little light
• DARK ADAPTATION
the increasing ability to see in the dark over time
(after half hour, sensitivity increases 10,000 fold)
VISION
RODS & CONES
RODS and CONES the two types of photoreceptors
in the retina that differ in shape, composition, and
response to light
• Approx. 120 million rods and 6-7 million cones
• Cones provide the basis for color vision
• Cones use one of three varieties of iodosin
photopigments, each sensitive to different light
wavelengths
• Rods use the photopigment rhodopsin, making them
more sensitive to light than cones; rods cannot
discriminate color
• Most cones concentrated in fovea allowing detailed
vision, or ACUITY
• Variations in density of cones in the fovea account for
differences in visual acuity
• Rods are located in the periphery of the retina, not in the
fovea
• Rods are useful for dark vision
VISION
RODS & CONES
INTERACTIONS IN THE RETINA
• Rods and cones connect to bipolar
cells and then to ganglion cells.
• Axons of the the ganglion cells form
the optic nerve which extends out of
the eye and into the brain.
• When amounts of light reaching any
two photoreceptors differ, the
photoreceptor receiving more light
inhibits the output to the brain from
the photoreceptor receiving less light,
making it seem like there is less light
at that cell than there is.
VISION
RODS & CONES
INTERACTIONS IN THE RETINA
• LATERAL INHIBITION is made possible by
interneurons which make sideways connections
between photoreceptors and exaggerate the
amount of light reaching them. This
exaggeration allows clearer vision.
• Each ganglion cell can relay info to the brain
only about its own RECEPTIVE FIELD, the
part of the retina and the corresponding part of
the visual world to which that cell responds
• These receptive fields create complex combinations that give us optimum
detection of light variations such as edges and small spots of light or dark.
• By enhancing the sensation of important features, the retina gives us an
“improved” version of the visual world.
VISION
RODS & CONES
INTERACTIONS IN THE RETINA
• The OPTIC DISK is located where
the optic nerve leaves the eye.
• It contains no rods or cones and
creates a BLIND SPOT or void in the
visual field.
• This is unnoticed because the other
eye compensates for it.
Find your Blind Spot
VISION
VISUAL PATHWAYS &
REPRESENTATIONS
• Once the optic nerve leaves each
eyeball, the bundle of fibers
meet at the OPTIC CHIASM in
the brain. Here they cross to the
opposite side of the brain. The
fibers from the inside half of
each eye cross over. The outside
half of each eye do not.
• This brings all visual info from
the left half of the visual world
to the right hemisphere of the
brain and all visual info from the
right half of the visual world to
the left hemisphere of the brain.
VISION
VISUAL PATHWAYS & REPRESENTATIONS
• From the optic chiasm, info is sent
to the region of the thalamus
called the LATERAL
GENICULATE NUCLEUS (LGN)
where neurons then relay the
visual input to the PRIMARY
VISUAL CORTEX for complex
processing.
• FEATURE DETECTORS specialized
neurons in the LGN that respond to
different aspects of an image such as
size, shape, and angle
• PARALLEL PROCESSING refers to how the brain processes multiple sources
of info at once. It’s still debated as to where all this processing takes place and
may involve several regions of the brain, not just the visual cortex.
“The Island of the Colorblind”
from the BBC series
THE MIND TRAVELER
with Dr. Oliver Sacks
Click HERE to begin program.
VISION
SEEING COLOR
PERCEPTION OF COLOR
• How we perceive color depends on three characteristics of light waves:
SATURATION, and BRIGHTNESS.
HUE,
• HUE
refers to the color people psychologically experience. It is determined by
wavelength. Short wavelengths produce bluish colors. Long wavelength produce
reddish colors. Medium wavelengths produce orange, green, yellow colors.
• SATURATION refers to color purity.
Purity depends on the complexity of light
wave. (ex. red comprised of a single wave; pink comprised of a combination of red and
white light)
• BRIGHTNESS (or VALUE) refers to the intensity of the light wave as determined
by the amplitude, or height, of a wave (tall wave/great amplitude would be a very
bright color; low wave/low amplitude would be a dull color)
VISION
SEEING COLOR
COLOR MIXING
Colors are based on the dominant wavelength present.
How colors are mixed determines which color people
perceive. (Watch the first 2 minutes of THIS for more!)
SUBTRACTIVE COLOR MIXING
• occurs by mixing different paint “colors” (pigments)
• like other physical objects, paints reflect certain
wavelengths and absorb all others
• combining all paint colors will result in black
ADDITIVE COLOR MIXING
• the effects of the wavelengths from each light are
added together
• mixing two lights of equal intensity results in a color
midpoint on a line between the two starting colors on
a color wheel
• combining all colored lights will result in white
One more time!
VISION
• the eye has three types of receptors, each
TRICHROMATIC THEORY
OF COLOR VISION
(Young-Helmholz Theory)
sensitive to a specific wavelength
• blue-sensitive cone
short wavelengths
• green-sensitive cone
• red-sensitive cone
medium wavelengths
long wavelengths
• colors other than blue, green, and red triggers
combination of cones which produces other
colors (ex. purple results from triggering blue and
red-sensitive cones at the same time)
• COLOR BLINDNESS can be explained by the
trichromatic theory
• people born with cones containing only two of
the three color-sensitive pigments can
discriminate fewer colors
Click HERE for an explanation from Apple!
...and then HERE for another really short
explanation of Trichromatic Theory.
VISION
OPPONENT-PROCESS
THEORY OF COLOR VISION
(Ewald Hering)
• the color-sensitive components of the eye are
grouped into three pairs: red-green, blueyellow, and black-white
• each element signals one color or the other but
never both
• this theory explains AFTERIMAGES when an
image is perceived even though the stimulus
has been removed (ex. staring at a yellow dot then
looking away and seeing a blue dot...the afterimage)
• according to Hering, different colors are
produced through combinations of the pairs
being activated at the same time (ex. purple
results from red and blue elements being “on” while
the green and yellow elements are “off”)
Click HERE for a brief explanation
of Opponent-Process Theory of
Color Vision.
VISION EXPERIMENTS
Neuroscience for Kids: VISION EXPERIMENTS
Neuroscience for Kids: COLOR VISION
OPPONENT-PROCESSING THEORY Demo
Colorblindness Test Links: 1, 2, 3, 4 (information only)
PROBLEMS WITH VISION
Ocular and Optic Nerve
Causes of Visual Impairment
Neurological Vision Loss
The top circle represents visual impairment. The area above
the top of the large circle-line represents ocular and optic
nerve conditions (60%-70% of the cases of visual impairment).
The area of intersection of the two circles represents CVI
(30%-40% of the cases of visual impairment). The largest
circle represents the processing of visual information.
PROBLEMS WITH VISION
Ocular and Optic Nerve Causes (see handout)
light not focused properly on retina
presbyopia, myopia, hyperopia, astigmatism
damage to retina
retinal detachment (link), retinal degeneration, diabetic retinopathy, macular degeneration
(link 1, link 2, link 3, link 4)
blurring of light upon entering the eye
corneal disease and injury (link 1, link 2, link 3), cataracts (link)
damage to the optic nerve
glaucoma (link 1 at 16:30, link 2)
PROBLEMS WITH VISION
Neurological Vision Loss (Cerebral/Cortical Vision Impairment)
as much as 40% of brain estimated to be involved in interpretation and translation of
visual images generated by the eyes
any disruption along processing pathway results in impaired vision
various causes
traumatic brain injury (sports, accidents, combat injuries, premature infants)
asphyxia/interruption of oxygen supply to the brain
development brain defects
infections of the central nervous system (such as encephalitis or meningitis)
FOR MORE INFORMATION:
CVI Overview 1,2,3,4
American Foundation for the Blind
CVI in Children
PROBLEMS WITH VISION
PREVALENCE OF VISION IMPAIRMENT
(fact sheet from the World Health Organization)
1 285 million people are visually impaired worldwide: 39 million are blind and 246 have
low vision.
2 About 90% of the world's visually impaired live in developing countries.
3 Globally, uncorrected refractive errors are the main cause of visual impairment;
cataracts remain the leading cause of blindness in middle- and low-income countries.
4 The number of people visually impaired from infectious diseases has greatly reduced
in the last 20 years.
5 80% of all visual impairment can be avoided or cured.
more information from WHO
VISION
SYNESTHESIA
• involves more unusual mixing of senses that improve
the experience of a sensation
• “feeling” color or sounds as touches; “tasting” shapes;
sensing colors when hearing certain sounds
• possibly from connections between neighboring
sensory areas of the brain
THE CHEMICAL SENSES:
SMELL &
TASTE
OLFACTION (click HERE before continuing)
• Olfaction (or Smell) detects chemicals that are airborne, or volatile
• accessory structures include nose, mouth, and upper part of throat
• odor molecules reach receptors through nose or through opening in the palate at
back of mouth
• olfactory receptors on dendrites of specialized neurons in the moist lining of the
nose (mucous membrane)
• odor molecules bind to receptors causing depolarization of dendrites’ membrane
and changes in firing rates of neurons
• a single odor molecule can cause a change in the membrane potential of an
olfactory neuron but normal odor detection requires about 50 molecules
THE CHEMICAL SENSES:
SMELL &
TASTE
OLFACTION
• each olfactory neuron lives only about 2 months and are repeatedly replaced
• humans have approx. 1,000 different olfactory receptors (1-2% of genes) allowing
us to discriminate tens of thousands of different odors
• IMPORTANCE TO RESEARCH
• understanding how olfactory neurons generate may someday be helpful in
treating brain damage
• how smells are coded in combinations of receptors may help researches
develop “electronic noses” that may have an application in national security
and medical diagnosis
SMELL THIS!
(olfactory review)
BACK
THE CHEMICAL SENSES:
SMELL &
TASTE
More on OLFACTION
• the only sense that bypasses the thalamus
• olfactory axons extend directly into the brain to the olfactory bulb and then sent to
various brain regions for further processing
• olfactory bulb’s connection to the amygdala may account for relationship between
smell and emotional experiences (losing the sense of smell sometimes indicates
brain diseases that disrupt memory and emotion)
• mechanism of olfaction similar across species but sensitivity varies greatly (humans
have approx. 9 million olfactory neurons; dogs have about 225 million)
• no agreement on basic smells
BUT WAIT! THERE’S MORE!
THE CHEMICAL SENSES:
SMELL &
TASTE
PHEROMONES
• Dogs and many other species have an accessory olfactory system that detects
these chemicals that when released by one animal and detected by another can
shape the second animal’s behavior and/or physiology
• in mammals, pheromones can be nonvolatile chemicals that animals lick and
pass into an olfactory organ called the vomeronasal organ
• role of pheromones in humans less clear
• the human vomeronasal organ is capable of responding to certain hormonal substances and can influence certain
hormonal secretions
• not everyone has a vomeronasal organ
• odorants that cannot be consciously detected have been shown to influence mood and can alter parts of the brain
that not directly involved in olfaction
• a possible human gene for pheromone receptors has been found
• pheromones capable of producing physiological changes in humans related to reproduction but no solid
evidence for a human (or even a primate) sexual attractant pheromone
• associations between certain odors and emotional experiences that enhance sexual attraction is LEARNED
• individual mammals, including humans, have distinct “odor type” determined by immune cells and other
inherited physiological factors
THE CHEMICAL SENSES:
SMELL &
TASTE
GUSTATION
• Gustation (or Taste) is the chemical sense system in the mouth
• receptors for taste are in taste buds grouped together as papillae in mouth and throat
• humans have about 10,000 taste buds (mostly on tongue, also on roof of mouth and back
of throat)
• human taste system detects only a few elementary sensations (sweet, sour, bitter, salty)
• research has identified two other tastes
• umami enhances other tastes and is produced by monosodium glutamate (MSG)
and certain other proteins
• astringent produced by tannins such as those found in teas
THE CHEMICAL SENSES:
SMELL &
TASTE
GUSTATION
• different tastes transduced into neural activity in different ways
• sweetness and bitterness signaled when chemicals fit into specific receptor sites
• sour and salty act through direct effects on the ion channels in membranes of
taste cells
• salty also enhances taste of food by suppressing bitterness
• “supertasters”--about 25% of population has thousands of taste buds whereas
“nontasters” have only hundreds
THE CHEMICAL SENSES:
SMELL &
TASTE
SMELL, TASTE, and FLAVOR
• smell and taste act as two components of one system...FLAVOR
• most of what makes food taste good comes from odors detected by the olfactory
system
• ANOSMIA is inability to distinguish smells and also interrupts ability to determine
flavor even when the gustation system is in working order
• olfactory and gustatory pathways converge in the ORBITOFRONTAL CORTEX
where neurons also respond to the sight and texture of food
• responses of neurons in this “flavor cortex” also influenced by hunger and satiety
(fullness)
THE CHEMICAL SENSES:
SMELL &
TASTE
SMELL, TASTE, and FLAVOR
• tastes and odor prompt strong emotional responses
• reactions to bitter and sweet flavors appear to be inborn
• few other innate flavor preferences as most are LEARNED
• taste and flavor perception as well as motivation to consume certain flavors is affected
by nutritional needs (ex. desire for salty drink or food after exercise)
• flavor also affected by texture and temperature
Making Sense of Taste
THE SOMATIC SENSES
• also known as the body senses or somatosensory systems
• located throughout the body rather than in specific, localized organs
• include the following:
1.skin senses of touch, temperature, and pain
2.proprioception & kinesthesia--the sense that tells the brain where the parts of
the body are with respect to each other
3.vestibular system--tells the brain about the position and movement of the
head
THE SOMATIC SENSES
TOUCH AND TEMPERATURE
Stimulus and Receptors for Touch
• energy detected by the sense of touch is physical pressure on tissue (usually skin)
• skin covers approx. 2 yards of surface and weights more than 20 lbs
• hairs on skin bend and deform the skin just beneath them
• nerve endings in the skin act as receptors that transduce pressure into neural activity; are in,
or just below, the skin
• exact process of transduction in the skin is still unknown
• humans not just passive responders; touch is an active sense used to get specific information
• high density of touch receptors in fingertips
• some blind people can read 200 words of Braille per minute
THE SOMATIC SENSES
TOUCH AND TEMPERATURE
Adaptation of Touch Receptors
• constant input leads to adaptation resulting in reduced response to constant stimulation
• somatosensory system responds best to change in touch
• neurons fire rapidly when stimulus first sensed
• then most neurons slowly return to baseline while only a few fire giving a sense of a
constant stimulation
Coding and Representation of Touch Information
• sense of touch codes info about two aspects of an object in contact with the skin
• INTENSITY of stimulus (weight or heaviness) coded by both the firing rate of and
number of neurons stimulated
• LOCATION coded by the location of neurons responding to touch; input from left side
of body goes to right side of brain, and vice versa
THE SOMATIC SENSES
TOUCH AND TEMPERATURE
Temperature
• touch and temperature seem to be separate senses; difference not
always clear
• some sensory neurons of skin respond to change in temperature but
not to simple contact
• “warm fibers”
increase firing rate when temperature is
between 95-115 degrees F
• temperatures above 115 cause pain and
different fibers
• “cold fibers” respond to broad range of cool
temperatures
stimulate
THE SOMATIC SENSES
TOUCH AND TEMPERATURE
Temperature
• many fibers responding to temperature also respond to touch causing
sensations of temperature and touch/pressure to interact
• warm and cold objects can “feel” up to 250% heavier than bodytemperature objects
• touching an object made up of alternating warm and cold spots
gives sensation of intense heat
• people having frostbite feel burning sensation
THE SOMATIC SENSES
PAIN AS AN INFORMATION SENSE
• pain receptors are free nerve endings that extend from spinal cord
to skin and muscles (no dendrites)
• when stimulated, these sensory neurons cause the release of
various neurotransmitters including substance P, a neurotransmitter
that activates a “gate” in the spinal cord that either lets pain
impulses travel to the brain or blocks their progress (Gate-Control
Theory of Ronald Melzack and Patrick Wall)
• input from other skin senses (touch, temperature) may “take over”
pathways that pain impulses would have used (ex. rubbing area
around a wound; cold/hot pack on a injury)
THE SOMATIC SENSES
PAIN AS AN INFORMATION SENSE
• two types of nerve fibers carry pain signals to spinal cord where
they are sent to the thalamus and then relayed to somatosensory
cortex, frontal lobe, and limbic system (for emotional elements of
pain)
• A-delta fibers carry sharp pain and are myelinated to carry
inputs quickly
• C fibers carry chronic, dull aches and burning sensations
• each signals different brain areas
• different pain neurons cause release of different
neurotransmitters (allowing for the development of a variety
of new drugs for pain management)
THE SOMATIC SENSES
EMOTIONAL ASPECT OF PAIN
• all senses can have an emotional component, most of which are
learned
• pain is more direct
• specific pathways carry an emotional component of the painful
stimulus to areas of the hindbrain and reticular formation (in the
limbic system) as well as other areas via the thalamus
• necessary for our survival by allowing us to pull or away or stop
doing something that could cause us injury
• cognition affects our emotional response to pain
• understanding the nature of pain makes it less aversive although
just as intense
• pain-reducing strategies such as distracting thoughts also affects
emotional responses to pain
THE SOMATIC SENSES
NATURAL ANALGESICS
• brain closes “gate” by sending signals back
down spinal cord resulting in analgesia, or
absence of pain sensation in place of normally
painful stimulus
• at least three chemicals released during stress
play a role in the brain’s ability to block pain
signals: serotonin, endorphins, and
endocannabinoids
THE SOMATIC SENSES
NATURAL ANALGESICS
• endorphins act as pain killers at many levels
• in spinal cord, block synapses of fibers carrying
pain signals
• also released by adrenal and pituitary glands as
pain-relieving hormones
• “range of use” includes reducing labor pains during
late pregnancy to allowing severely injured athletes
and soldiers to continue to perform with no
apparent pain
• once crisis has passed, release of another
neurotransmitter reactivates pain sensitivity
counteracting endorphins’ analgesic effects
THE SOMATIC SENSES
PROPRIOCEPTION & EQUILIBRIOCEPTION
The proprioceptive senses and the sense of balance
provide information about the position of the body and
what each part of the body is doing
THE SOMATIC SENSES
EQUILIBRIOCEPTION
Vestibular Sense
• often thought of as “sense of balance”
• tells brain about position of head in space and its
general movements
• two vestibular sacs and three semicircular canals in the inner ear are the
organs for this sense
• vestibular sacs filled with fluid and contain small crystals called otoliths
that rest on hair endings
• semicircular canals are fluid-filled and arc-shaped tubes with tiny hairs
extending into fluid
• as head moves, otoliths shift in sacs and fluid moves in the canals
stimulating hair endings
THE SOMATIC SENSES
EQUILIBRIOCEPTION
Vestibular Sense
• neurons activated and travel along vestibular
nerve with auditory nerve, signaling brain
about amount and direction of head movement
• vestibular system has neural connections to:
cerebellum (coordinate body movements),
autonomic nervous system (affect digestion),
eye muscles (fix eyes on a point in space if head
is moving...vestibular-ocular reflexes)
• dizziness occurs when fluids in the vestibular
system not level
The Vestibular System
The Organs of Balance
THE SOMATIC SENSES
PROPRIOCEPTION
Kinesthesia
• the sense that tells you where parts of your body are with
respect to each other
• guide all our movements because the brain, with practice, will
automatically make them simple and fluid
• primary source of kinesthetic information comes from special
receptors (proprioceptors) in joints and muscles
• transduced info goes to spinal cord to thalamus to cerebellum
and somatosensory cortex for smooth coordination of
movements
The Proprioceptive System
Enhancing proprioceptive quality & adaptation:
The following exercises and body systems have an effect on proprioceptive awareness.
• Movement for movement's sake in any variety of movement patterns and ranges of motion with different
tensions/loads (i.e., dancing, tai chi, yoga).
• Traditional cardio, strength and flexibility conditioning.
• Balance conditioning, eyes open and closed.
• Rotational movements (not just linear and lateral).
• Visual acuity: Use vision to adjust movements when recovering balance. Instead of focusing downward, look
ahead to realign the head and neck.
• Auditory system: The inner ear registers head and body movement like a built-in level. To function properly,
the head and neck must be situated over a balanced spine.
• Rhythm: Heart beat, breathing patterns and even walking are rhythmic by nature. Have clients strive to feel
rhythm during sports and as they work out.
• Stance: Movements should be initiated from an "athletic stance" (ankles, knees and hips slightly flexed) and
an upright posture. Stance is also referred to as the clients' "base of support," or the distance created
between their feet.
• Weight transfer: Bodies are especially sensitive to weight changes that take place with stance or postural
shifts. Clients will feel weight transfer from the feet upward.
• Constant motion: Have clients get a feel for constant, dynamic movements (versus static positions) as they
try the drills mentioned in this article.
FROM: FITNESS MANAGEMENT MAGAZINE--A PUBLICATION DIRECTED TO FITNESS/HEALTH/ATHLETIC CLUBS AND FACILITIES