SENSORY PHYSIOLOGY
-
Campbell 7e reads:
C49
pg1045-1049, 1058-63, 1066-74 &
fig's 49.8 & 49.12
-
Campbell 8e reads: C50
pg1087-1091, 1099-1105, 1105-1112 &
fig's 50.9 &
50.12
Sensations & Perceptions
sensation - is an awareness of sensory stimuli in brain
perception - meaningful interpretation or conscious understanding of sensory data
Not unlike the signaling we have seen before...
sensory signaling*
signal transduction hypothesis
5 COMPONENTS of SENSORY PHYSIOLOGY
1. Sensory Receptors -
structures that detect changes in
external & internal environment
modified neurons or
epithelial cells that have evolved
to respond to stimuli (eye, ear, nose, muscles)
Classes
of Sensory Receptors
chemo-receptors: chemicals
sense solutes in solvents, taste, smell
osmo-receptors: of hypothalmus which monitors blood
osmotic pressure
photo-receptors: light -
eye, eyespots, infrared receptors of snakes, etc...
thermo-receptors: radiant (heat) energy
phono-receptors: sound waves
electro-receptors: detect electric currents... electric eels, etc..
noci-receptors: pain receptors... naked dendrites of skin (epidermis)
mechano-receptors: mechanical forces
- stretching alters membrane permeability
(1)
hair
cells
(deflection* = depolarization = AP's)
lateral line of fish*
( mechanoreceptor = neuromasts
detect water movement -
anim)
(2)
stretch receptors of muscles*
U. Indiana Muscle Stretch reflex animation
(3)
equilibrium receptor of inner ear
animation of Pacinian receptors
(4)
receptors of skin
(touch, pain, cold, heat)
2. Reception -
ability of receptor to absorb energy of a stimulus
3. Transduction - conversion of stimulus energy into
a
membrane potential*, i.e.,
a Receptor Potential... RP
(or generator potential... GP
--> fires an AP)...
sort of like an EPSP or IPSP...
a change in permeability of a
post-synaptic membrane*
often graded = proportional to strength of stimulus
may be amplified and/or may be summed
may be strong enough (reaches threshold) to
generate action potentials.
4. Transmission - receptor potentials transmitted via
AP's to CNS
5. Integration - processing of frequency of receptor potentials
sensory information* is coded as
FREQUENCY of AP's
Sensory Adaptation - an attenuation of the stimulus...
a decrease in responsiveness by receptors due to continual stimulation
a uniformly maintained stimulus of constant intensity is perceived
as progressively weaker with time,
[movie house odor]
while a variable intensity stimulus of shorter durations
is perceived
as a progressivley stronger odor over time
Graph of
subjective intensity vs. concentration of H2S
*
for an example
of sensory physiology to Muscle Physiology* 
|
Some common disorders of vision - correctable by eye glasses |
myopia
(near-sightedness) |
lens point of focus falls within the vitreous body,
so that when light reaches the retina it is out of focus |
hyperopia
(farsightedness) |
point of focus falls behind the retina (out of focus) |
|
astigmatism |
results from defects in the
curvature of the cornea, light rays
don't form a point of focus on the retina = bluriness |
|
night blindness |
Vit-A deficiency or lack of pigment chromophore... retinal |
|
color blindness |
lack of trichromatic pigments |
|
glaucoma
|
result of increased pressure of fluids in the eye,
produces defects in field of vision & can lead to vision loss |
 Key Concepts*
go to Muscle Physiology
EYE PARTS - a specialized sensory organ capable of light reception
|
lens |
focuses light on rod & cone cell of retina - cuboidal epithelia |
|
retina |
a layer of nerve tissue
& millions of light receptor cells (rods/cones) |
|
rod-cone cells |
modified neurons -transmits electrical signals of varying light intensity |
|
fovea |
near center of retina, where cone cells give max sharpness of vision |
|
optic nerve |
retinal cells record light images & transmit to optic
nerve, which exits eyeball behind optic disk (blind spot) to the visual centers of brain. |
|
sclera |
tough outer shell of eyeball, made of dense fibrous tissue |
|
cornea |
stratified squamous epithelia, main refractory part of eye,
lets light pass & aids in
focusing |
|
vitreous humour |
transparent jellylike material, helps eye keep its spheroid shape. |
|
aqueous humour |
anterior chamber, filled with a watery fluid |
|
iris & pupil
|
muscular curtain that opens/closes to regulate amount of
light entering eye through the pupil (opening of iris into eye) |
Some Optical Illusions
- subjective
interpretations visual information.
Proximity... Seen as three groups of two asterisks rather than simply six asterisks.
* * * * * *
Similarity... Seen as
columns of Xs and Os rather than
rows of alternating Xs and Os.
X O X O X O X O X O
X O X O X O X O X O
X O X O X O X O X O
X O X O X O X O X O
Good Continuation... Seen as
two lines crossing, rather than
two bent lines touching,
or just a collection of
asterisks.
* *
These have crucial significance
* *
for the layout of information
* *
on screens and printed documents.
*
* *
return
* *
* *
Closure / Good Form... Seen as two overlapping squares rather than one irregular grouping of asterisks.
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