[PhysioEX Chapter 3 exercise 2] PEX-03-02

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Exercise 3: Neurophysiology of Nerve Impulses: Activity 2: Receptor Potential Lab Report
Pre-lab Quiz Results
You scored 100% by answering 4 out of 4 questions correctly.

1. Assuming that the resting potential of a sensory neuron is -70 mV, which of the following represents a depolarization?
   You correctly answered: c. a change to -60 mV
2. Which of the following is a sensory modality (type of sense)?
   You correctly answered: e. all of the above
3. Which of the following is a sensory stimulus?
   You correctly answered: d. all of the above
4. Which of the following is true of the response of a sensory neuron to the appropriate sensory stimulus?
   You correctly answered: c. both a and b

Experiment Results
Predict Question:
Predict Question 1: The adequate stimulus for a Pacinian corpuscle is pressure or vibration on the skin. Which of the
following modalities will induce the largest amplitude receptor potential in the Pacinian corpuscle
Your answer : c. moderate-intensity pressure
Predict Question 2: The adequate stimuli for olfactory receptors are chemicals, typically odorant molecules. Which of the
following modalities will induce the largest amplitude receptor potential in the olfactory receptor?
Your answer : a. moderate-intensity chemical
Stop & Think Questions:
Why didn't the Pacinian corpuscle respond to high-intensity light?
You correctly answered: b. Light-transducing proteins are not present in the Pacinian corpuscle.
Judging from these results, does light have a smell?
You correctly answered: b. no
Why did the free nerve ending respond to several different modalities?
You correctly answered: c. The sensory end of this nerve is less specialized.
Experiment Data:
Receptor Modality Intensity Resting
Potential (mv)
Peak Value of
Response (mv)
Amplitude of
Response (mv)
Pacinian corpuscle --- --- -70 -70 0
Pacinian corpuscle Pressure Low -70 -60 10
Pacinian corpuscle Pressure Moderate -70 -45 25
Pacinian corpuscle Pressure High -70 -30 40
Pacinian corpuscle Chemical Low -70 -70 0
Pacinian corpuscle Chemical Moderate -70 -70 0
Pacinian corpuscle Chemical High -70 -70 0
Pacinian corpuscle Heat Low -70 -70 0
Pacinian corpuscle Heat Moderate -70 -70 0
Pacinian corpuscle Heat High -70 -70 0
Pacinian corpuscle Light Low -70 -70 0
Pacinian corpuscle Light Moderate -70 -70 0
Pacinian corpuscle Light High -70 -70 0
Olfactory receptor --- --- -70 -70 0
Olfactory receptor Pressure Low -70 -70 0
Olfactory receptor Pressure Moderate -70 -70 0
Olfactory receptor Pressure High -70 -70 0
Olfactory receptor Chemical Low -70 -64 6
Olfactory receptor Chemical Moderate -70 -58 12
Olfactory receptor Chemical High -70 -45 25
Olfactory receptor Heat Low -70 -70 0
Olfactory receptor Heat Moderate -70 -70 0
Olfactory receptor Heat High -70 -70 0
Olfactory receptor Light Low -70 -70 0
Olfactory receptor Light Moderate -70 -70 0
Olfactory receptor Light High -70 -70 0
Free nerve ending --- --- -70 -70 0
Free nerve ending Pressure Low -70 -70 0
Free nerve ending Pressure Moderate -70 -70 0
Free nerve ending Pressure High -70 -65 5
Free nerve ending Chemical Low -70 -70 0
Free nerve ending Chemical Moderate -70 -70 0
Free nerve ending Chemical High -70 -70 0
Free nerve ending Heat Low -70 -60 10
Free nerve ending Heat Moderate -70 -40 30
Free nerve ending Heat High -70 -20 50
Free nerve ending Light Low -70 -70 0
Free nerve ending Light Moderate -70 -70 0
Free nerve ending Light High -70 -70 0

Post-lab Quiz Results
You scored 100% by answering 4 out of 4 questions correctly.

1. A very intense stimulus can sometimes stimulate sensory neurons that have evolved for a different modality. Thus, with
   a blow to the eye, one "sees stars." In this example the photoreceptors in the eye are responding to
   You correctly answered: c. intense pressure.
2. Olfactory receptor neurons respond to low concentrations of chemical odorants because there are membrane proteins in
   the receptor ending of this sensory neuron that
   You correctly answered: b. can bind and respond to the specific odorant.
3. The sequence of events starting with a sensory stimulus and ending with a change in membrane potential is called
   You correctly answered: c. sensory transduction.
4. Starting at a resting membrane potential of -70 mV, a change to which of the following represents the largest receptor
   potential?
   You correctly answered: d. a change to -50 mV

Review Sheet Results

1. Sensory neurons have a resting potential based on the efflux of potassium ions (as demonstrated in Activity 1). What
   passive channels are likely found in the membrane of the olfactory receptor, in the membrane of the Pacinian corpuscle,
   and in the membrane of the free nerve ending?
   Your answer:
   The efflux of potassium is key factor of resting potential. So there will be potassium channel.
2. What is meant by the term graded potential?
   Your answer:
   Graded potential is changes of membrane potential out of resting potential in a short duration. It can cause depolarizing.
3. Identify which of the stimulus modalities induced the largest amplitude receptor potential in the Pacinian corpuscle. How
   well did the results compare with your prediction?
   Your answer:
   The moderate-intensity pressure modality causes a receptor potential in the pacinian corpuscle as predicted.
4. Identify which of the stimulus modalities induced the largest amplitude receptor potential in the olfactory receptors. How
   well did the results compare with your prediction?
   Your answer:
   The moderate intensity chemical modality causes a receptor potential in the olfactory receptors.
5. The olfactory receptor also contains a membrane protein that recognizes isoamylacetate and, via several other
   molecules, transduces the odor stimulus into a receptor potential. Does the Pacinian corpuscle likely have this
   isoamylacetate receptor protein? Does the free nerve ending likely have this isoamylacetate receptor protein?
   Your answer:
   Free nerve ending and the Pacinian corpuscle do not contain the isoamylacetate receptor protein because they did not
   show response to the the odor stimulus.
6. What type of sensory neuron would likely respond to the green light?
   Your answer:
   Optic sensory neuron will respond to green light. This sensory neuron may have receptor protein that respond to light.