Download substance P

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audition
vision
olfaction
taste
smell
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some addtl senses
◦ vestibular
◦ organ
◦ muscular tension
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sensory transduction
◦ - conversion of physical energy from the
environment into changes in electrical potential
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sensory coding◦ Making sense of that input
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vision - light waves -
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taste – chemicals in fluid –
hearing – sound wavestouch- pressure, temperature changes,
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smell- chemical in air
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vision
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taste hearing -
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touch
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smell
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- rods and cones in
retina
- taste buds on tongue
- hair cells in inner ear
(cochlea)
- specialized receptors
under skin
- hair cells in olfactory
epithelium
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Receptors show adaptation
◦ most sensitive to changes rather than constant
stimulation
◦ why is this important?
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General pathway for most sensory
information:
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General pathway for most sensory
information:
◦ sensory neurons – sensory nerves
 spinal tracts –
 thalamus –
 primary cortex –
 higher association cortex
Certain sensory neurons have a
spontaneous firing rate.
For these cells any change in their firing
rate will convey important info (i.e. color
vision)
Different rhythms of firing also can convey
different information
* most highly developed sense in humans
optic nerve for one eye - 1,000,000 axons
auditory nerve contains about 30,000
axons
adaptability and plasticity of visual system
- make sense out of nonsense
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iris
◦ largely a muscle that expands and contracts pupil
in response to light
◦ phenotypically unique –
 iris scan
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sclera
◦ tough opaque tissue
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pupil
◦ often used to determine neurological function
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light waves along the visual spectrum
1.
2.
inverted image on retina
region important for transduction is at very
back of the eye
retina - structure of eye important for
transduction
- retina contains neurons, glial cells and two
types of photoreceptors
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responsible for transduction
numerous differences between rods and
cones
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rods
shaped like a rod
insensitive to color
work well under low
illumination
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cones
shaped like a cone
sensitive to color
work best in bright
light
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rods
shaped like a rod
insensitive to color
work well under low
illumination
20,000,000/eye
location: found around the
periphery of the retina
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cones
shaped like a cone
sensitive to color
work best in bright light
5,000,000/eye
location – found
around the fovea of
the retina
◦ responsible for
sharp images and
vision
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a low ratio of synaptic connections between
neurons ensures higher definition and
sharpness compared to a higher ratio
sharp, acute
vision
less sharp focused
visual input
sharp, acute
vision
less sharp focused
visual input
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rods
shaped like a rod
insensitive to color
work well under low
illumination
20,000,000/eye
location: found around the
periphery of the retina
requires extended time until
optimal function
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cones
shaped like a cone
sensitive to color
work best in bright light
5,000,000/eye
location – found around
the fovea of the retina
responsible for sharp
images and vision
works optimally very
quickly
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there are at least two levels of communication
within the neural cells of the eye
◦ rods and cones – bipolar cells – ganglion cells
(axons make up the optic nerve) to CNS
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there are at least two levels of communication
within the neural cells of the eye
◦ rods and cones – bipolar cells – ganglion cells
(axons make up the optic nerve) to CNS
◦ across a single layer (rods and cones communicate
with each other; bipolar cells communicate with
each other; etc)
optic nerve (ganglion cell axons) – make a
blind spot on each eye!
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component (trichromatic ) or YoungHelmholz
◦ occurs at level of cones
 3 different cones more sensitive to different
wavelengths (ie colors)
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trichromatic or Young-Helmholz
◦ occurs at level of cones
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explains major type of color blindness
◦ deficits in certain types of cones can explain major
type of color blindness
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At level of cones- GREAT!
◦ there are different cones that produce greater changes in
electrical potentials depending on the color (wave)
◦ abnormalities in cones can explain red/green color
blindness
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Very rare to see complete color blindness - only
usually seen with brain injury
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~ 7% of US males (10,000,000) compared to 0.4%
women - red/green
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X-linked phenomenon
X
X
b
X
Y
XX
XY
XX
b
b
X Y
What happens in hereditary
color deficiency?
 Red or green cone peak sensitivity is shifted.
 Red or green cones absent.
40
437 nm
B
533 nm
564 nm
G
R
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5% of
Males
437 nm
B
564 nm
G
R
(green shifted toward red)
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1% of Males (there is no green
curve)
437 nm
B
564 nm
R
(no green cones; only red and blue)
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1% of Males (there is no red
curve)
533 nm
437 nm
B
G
(no red cones; only green and blue)
44
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At level of cones- GREAT!
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negative afterimage –
◦ phenomenon that occurs as a result of overactivity
or inhibition of neurons (due to color stimulation)
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opponent process theory
◦ occurs at level of bipolar cells and higher
 black/white, red/green; yellow/blue; one color excites
bipolar cell; other color inhibits it
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says nothing about complexity as information
reaches occipital lobe –
says nothing about color constancy
◦ color constancy and the retinex theory- occurs at
the level of the cortex……
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prestriate – primary occipital cortex; multiple
layers of higher association cortex
Copyright © 2006 by Allyn and
Bacon
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Touch (mechanical stimuli)
Temperature (thermal stimuli)
Pain (nociceptive stimuli)
Specialized receptors respond to the various
stimuli
Copyright © 2006 by Allyn and
Bacon
Ruffini ending
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Merkel’s disks
Free nerve endings
Figure 7.15
Copyright © 2006 by Allyn and Bacon
Pacinian corpuscles
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a necessary sense
too little or too much – yikes!
No obvious cortical representation (although
there are regions that appear to be involved
in the emotional component)
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Substance P◦ Most pain is a result of substances released by
damaged tissues including substance P
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What else causes substance P release?
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Substance P is a large peptide and synthesis
can take time SO
Release of large amounts of substance P
results in a brief time (when more is being
synthesized) that is “pain-free”
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Substance P
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Endogenous opioids
◦ endorphins – endogenous morphine-like
substances
 may explain acupuncture, placebo effects
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Descending pain control – pain can be
suppressed by cognitive and emotional
factors
PAG – periaqueductal gray
Copyright © 2006 by Allyn and
Bacon
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3 discoveries made this possible
◦ Electrical stimulation of the PAG has analgesic
(pain-blocking) effects
◦ PAG and other brain areas have large amounts of
opiate receptors
◦ Existence of endogenous opiates (natural
analgesics) - endorphins
Copyright © 2006 by Allyn and
Bacon
MIDBRAIN
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Congenital insensitivity to pain
Extremely rare – less than 100 cases currently in the U.S.
Inability to thermoregulate (through skin) or feel pain
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types: cancers, debilitating arthritis, back
pain, undiagnosed, migraine
Approximately 80 million people in the
United States suffer
Chronic pain consumes approximately $70
billion per year
Chronic low back pain affects nearly 31 million Americans and
represents the most common cause of disability in persons less than
45 years of age
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drugs – morphine derivatives
◦ oxycontin
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ESB
periaqueductal gray
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drugs – morphine derivatives
◦ oxycontin
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ESB
periaqueductal gray
acupuncture
pain management
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types: cancers, debilitating arthritis, back
pain, undiagnosed
phantom limb
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drugs – antidepressants; antiseizure meds
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cutting dorsal roots
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anesthetizing stump