INTRODUCTION TO SENSORY
RECEPTORS
Exercise 20
BI 232
INTRODUCTION AND TERMINOLOGY
There are many types of sense receptors in the
body.
 They are not uniformly distributed
 Punctate distribution is the pattern of uneven
distribution throughout the body
 There is no perception without environmental
input, which are listed by type, or modality.
 Examples of modalities are: light, heat, sound,
pressure, and specific chemicals
 Receptors are the receiving units and respond
to stimuli
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RECEPTOR TYPES
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Photoreceptors- detect light
(retina)
Thermoreceptors – detect
temperature (skin)
Proprioreceptors – detect
changes in tension (joints)
Pain (nociceptors) receptors
(free nerve endings in skin
stomach etc.)
Mechanoreceptors - perceive
mechanical stimuli (touch)
Baroreceptors – change in
pressure (BP)
Chemoreceptors – changes in
chemical environment (taste
and smell)
TOUCH RECEPTORS
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Light touch receptors
include Meissner’s
corpuscles and Merkel
discs.
Found in the upper
dermis.
Deep pressure receptors
are the Pacinian
(lamellated) corpuscles
found deep in dermis or
hypodermis.
Remember from 231?
Review slides
TWO-POINT DISCRIMINATION TEST
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Map relative density of receptors
Partner sits with eyes closed and
hand resting on counter with palm
up.
Use calipers to touch your lab
partner’s fingertip with both points
of the instrument and see if they
can determine between one and two
points.
Start with calipers close to closed
and repeat the process opening the
calipers a little with each touch.
Stop when partner feels both points.
Measure the distance.
Do this again on the forearm, palm,
and back of neck and compare the
results.
WARM AND COOL RECEPTORS
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Skin has receptors that are
sensitive to cool or warm
temperatures:
Take 2 probes; one from ice
bath and one from warm
water bath.
Lab partner closes his or
her eyes
Test the ability of your lab
partner to distinguish
between the cool and warm
probes by putting the
probes on forearm
Do this 5 times with each
and see which temperature
was more accurate
MAPPING TEMPERATURE RECEPTORS
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Mark off a square that is 2
cm on a side on the
anterior forearm of lab
partner
Use hot and cold water
baths again
Use pointed end of probe
and place in cold water.
Test areas in the square.
When partner perceives
cold mark with blue
marker (not just touch.
Do the same with warm
probe
MAPPING LIGHT-TOUCH RECEPTORS
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Draw 2 cm square on
lab partner’s forearm.
Use Von Frey hair to
map the number of
areas in the square that
your lab partner can
perceive.
Press only until the hair
bends a little to
simulate the touch
corpuscles.
Use black felt pen to
record results
Do this again on lateral
side of the arm
ADAPTATION TO TOUCH
Tonic receptors
constantly perceive
stimuli.
 Phasic receptors
adapt to a stimulus
 Crumple a small piece
of paper into a ball.
 Place ball of paper
into partner’s palm.
 Are light touch
receptors tonic or
phasic?
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LOCATING STIMULUS WITH
PROPRIOCEPTION
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Have partner close eyes.
Touch partner’s forearm
with a felt marker.
Have partner try to
locate the same spot
with a felt marker of
another color.
Test 5 locations on
various parts of
forearm.
Repeat each location
twice
Or use parts of body:
corner of eye, ear lobe
and chin
TEMPERATURE JUDGEMENT
Place one hand in cold
water and another in
warm water.
 After hands have
equilibrated, place
them both in the room
temperature water.
 Describe to your lab
partner what you feel
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REFERRED PAIN
Perception of pain in
one area of the body
when the pain is
actually somewhere
else.
 Place your elbow into
a dish of ice water and
leave it there for 2
painful minutes
 Describe the sensation
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THE END OF EXERCISE 20
Go onto Exercise 26:
Eye and Vision
 Make sure that you
understand the tests
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