Experiment 1. Arrangement of Cutaneous Receptors. HYPOTHESIZE whether sensory re
ID: 3475541 • Letter: E
Question
Experiment 1. Arrangement of Cutaneous Receptors.
HYPOTHESIZE whether sensory receptors for different types of adequate stimuli are uniformly distributed on your skin.
Mark an area of 2 square centimeters on a hairless part of the palmar surface of the forearm. On this area draw a 10 by 10 grid.
During this experiment, the subject must either look away from the region or keep his/her eyes tightly closed.
Explore each area for pain with a sharp object (eg, paper clip). Use uniform pressure, but realize that we are only testing for a prick. Do not in any way attempt to cause serious harm to your partner (remember peer evaluations!!).
Explore the same areas with a warm (NOT HOT) temperature probe. Dry the tip before using it.
Repeat with a cold temperature probe taken from ice water after it has been dried.
Repeat with a flat toothpick/thin bristle for the sensation of touch/pressure. Again, use uniform pressure.
On the data sheet, draw a map of the touch, pain, warm, and cool temperature sensitive spots of the arm.
Experiment 2. Localization. CHOOSE EITHER A (Two-Point Discrimination for Touch) or B (Tactile Localization). You do not need to do both experiments!!
HYPOTHESIZE whether all regions of the body have similarly sized receptive fields.
Two-Point Discrimination
As for experiment 1, the subject cannot watch the experiment since we are testing for touch, not vision.
Using the points of the spring dividers, LIGHTLY TOUCH the surface of the skin—remember that we are exploring for touch, not pain! Randomly alternate between one point and two points of the dividers touching subject so they cannot anticipate what you are doing. Clean the tips with alcohol pads before beginning.
Determine the minimum distance in millimeters between the points that provide separate sensations of touch. Be sure to touch the skin with both points simultaneously.
Explore the following areas and record the minimum distance on the data sheet:
Lips Back of neck
Index finger tip Calf
Palm of hand Big Toe
Wrist (palmar surface) Back
Wrist (plantar surface)
Tactile Localization
Have the subject close his/her eyes.
With the point of a pencil or pen, make a slight indentation on the lips. Remove the pencil and have the subject (with eyes still closed) indicate the point of stimulation with another pencil. Measure the error distance in mm. Repeat for the same stimulus point. Is there improvement with repetition?
Record the localization error for the following additional areas:
Lips Back of neck
Index finger tip Calf
Palm of hand Big Toe
Wrist (palmar surface) Back
Wrist (plantar surface)
Experiment 3. Adaptation and Negative After-Image in Temperature Receptors.
HYPOTHESIZE whether the hands will perceive temperature correctly after adaptation to warm and cold water.
Fill one of the 1L beakers halfway with water at room temperature. Half fill a second beaker with water of about 40°C, and half fill a third beaker with ice water.
Place the left hand in cold water and the right hand in the warm water for about 2 minutes.
Quickly insert both hands into the room temperature water.
On the data sheet, record the sensations felt by each hand.
Experiment 4. The Effect of Increasing the Number of Receptors on Sensation.
HYPOTHESIZE whether temperature sensation changes as more temperature receptors (more fingers) are added to the water.
Fill a 1-L beaker halfway with water as hot as you can bear.
Place the finger of one hand into the water.
Gradually add the other fingers, one at a time and finally the entire hand.
Indicate on the data sheet the effect of increasing the number of receptors stimulated on the sensation perceived.
What are your hypotheses for the following cutaneous experiments? After performing the experiments, indicate whether your data support or reject your hypothesis.
Experiment 1
Experiment 2
Experiment 3
Experiment 4
Explanation / Answer
1) Hypothesis : Sensory receptors for different types of adequate stimuli are uniformly distributed on skin.
The results obtained from the experiment supports the hypothesis that sensory receptors for different types of adequate stimuli are uniformly distributed on skin.
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