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Lab Equipment Required: Description: The aim of this laboratory exercise is to record resting potentials across the membranes of fast extensor muscle fibers in the tail of crayfish. Microelectrodes are glass capillary tubes which have been melted and then pulled to produce a very fine (<0.5 um diameter) tip at one end. The tip is placed through the membrane and is so fine that the membrane seals around the tip. The microelectrode filled with potassium chloride acts as a “saline bridge” between the inside of the cell and the recording equipment.
Goals
1. Students will dissect a crayfish tail to expose the fast extensor muscles. 2. Students will assemble the equipment to record membrane potentials. 3. Students will understand the Na+/K+ pump and how it works to keep membranes polarized for contraction. 4. Students will test the hypothesis that all fibers within a single muscle are the same and therefore have the same membrane potentials. 5. Students will also test the hypothesis that membrane potentials are dependent upon the concentration gradient of different ions. 6. Students will continue to be successful at using the LabScribe software to move cursors, analyze data, record data to the Journal, and add functions to the Analysis window.
Outcomes
Students who have successfully completed this exercise will: 1. be able to successfully expose the muscles of the crayfish tail and be able to distinguish between the different muscle types. 2. have a better understanding of microelectrode recording from muscle fibers and the equipment used to perform such recordings. 3. gain an understanding of the Na+/K+ pump and how it relates to membrane potentials. 4. record membrane potentials from the different crayfish tail muscles to test a hypothesis and reach a scientific conclusion. 5. test various saline solutions to determine if the concentration of K+ ions has any effect on muscle membrane potentials. 6. feel comfortable transferring data to the Journal and interpreting that data to answer questions about their recordings. 7. have used the functions available in the Analysis window to determine values necessary for this exercise.
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Lab Equipment Required: 
Description: In this laboratory you will record action potentials from the sciatic nerve of a frog. Each nerve contains hundreds of axons with different diameters, thresholds, and degrees of myelination. The large, myelinated axons with the fastest conduction velocities are known as Type A fibers, which are further subdivided into α, β, γ, and δ types. Type B fibers are also myelinated, but have smaller diameters and slower conduction velocities. Type C fibers are very small, unmyelinated axons. When a large stimulus is delivered to the nerve, many axons respond and the recorded potential is the summation of all the axons firing. This potential is known as the compound action potential (CAP).
Goals
1. Students will dissect a frog leg to extract the sciatic nerve. 2. Students will assemble the equipment needed to be able to stimulate the nerve and record compound action potentials from nerves. 3. Students will understand the different types of fibers that make up the large sciatic nerve. 4. Students will test different hypothesis with regard to nerve function: ◦ Compound action potential: observing the one or more populations of different fiber types. ◦ Stimulus-response/axon recruitment: observing how the nerve response changes with increased stimulus voltage. ◦ Conduction velocity: measuring the speed at which action potentials propagate down the axons. ◦ Effects of temperature: observing how cooling affects the nerve conduction velocity. ◦ Bidirectionality: determining whether axons conduct in both directions. ◦ Refractoriness: observing how stimulus frequency affects the amplitude of compound action potentials ◦ Strength-Duration: observing how the amplitude of a stimulus required to stimulate axons is related to the duration of the stimulus. 5. Students will continue to be successful at using the LabScribe software to move cursors, analyze data, record data to the Journal, and add functions to the Analysis window.
Outcomes
Students who have successfully completed this exercise will: 1. be able to successfully excise the sciatic nerve of a frog and be able to understand the different fiber types within the nerve. 2. have a better understanding of electrical stimulation of nerve fibers and the equipment used to perform such stimulation. 3. gain an understanding of compound action potentials and how they relate to nerve function. 4. record compound action potentials from the sciatic nerve to test a variety of hypotheses and reach scientific conclusions. 5. have used the functions available in the Analysis window to determine values necessary for this exercise. 6. feel comfortable transferring data to the Journal and interpreting that data to answer questions about their recordings.
Included with:
Lab Equipment Required: Description: The purpose of this experiment is to demonstrate some of the electrical properties of a muscle and its motor neurons. Nerve and muscle action potentials will be recorded from a frog nerve-muscle preparation. The conduction time and synaptic delay of the neuromuscular unit will be determined. The effect of stimulus frequency, as well as the effects of specific chemical agents upon the muscle and nerve and the neuromuscular junction, will also be measured.
Goals
1. Students will dissect a frog leg to extract the sciatic nerve and the muscles of the lower limb (either the gastrocnemius or tibialis anterior). 2. Students will assemble the equipment needed to be able to stimulate the nerve and muscles, and record compound action potentials from both. 3. Students will understand the correlation between nerve stimulus and muscle responses. 4. Students will test synaptic delay between nerve and muscle compound action potentials. 5. Students will test different drugs with regard to nerve and muscle function: ◦ eserine. ◦ curare. ◦ atropine. ◦ high acetylcholine concentration. ◦ nicotine. ◦ dantrolene. ◦ high magnesium concentration. ◦ high calcium concentration. 6. Students will continue to be successful at using the LabScribe software to move cursors, analyze data, record data to the Journal, and add functions to the Analysis window.
Outcomes
Students who have successfully completed this exercise will: 1. be able to successfully excise the sciatic nerve and muscles of a frog’s leg. 2. have a better understanding of electrical stimulation of nerve fibers and the equipment used to perform such stimulation. 3. gain an understanding of both nerve and muscle compound action potentials and how they relate to each other. 4. record compound action potentials from the sciatic nerve and lower limb muscles to test a variety of hypotheses and reach scientific conclusions. 5. have used the functions available in the Analysis window to determine values necessary for this exercise. 6. feel comfortable transferring data to the Journal and interpreting that data to answer questions about their recordings.
Included with:
Lab Equipment Required: Description: In this laboratory you will record action potentials from the ventral nerve cord of an annelid, the earthworm Lumbricus terrestris. The ventral nerve cord of some invertebrates is a structure analogous to the dorsal nerve cord of vertebrates. The ventral nerve cord of an earthworm contains three giant neurons. The cord has one medial giant neuron with a lateral giant neuron on either side of the medial neuron. Because of their size, the three giant neurons in the earthworm nerve cord can generate action potentials with conduction velocities that permit the worms to have a fast escape reflex. When a large stimulus is delivered to the nerve cord, the neurons respond and action potentials from the medial and lateral neurons are seen.
Goals
1. Students will anesthetize an earthworm. 2. Students will assemble the equipment needed to be able to stimulate the nerve and record compound action potentials from nerves. 3. Students will understand the different types of fibers that make up the nerve. 4. Students will test different hypothesis with regard to nerve function: ◦ Compound action potential: observing the one or more populations of different fiber types. ◦ Stimulus-response/axon recruitment: observing how the nerve response changes with increased stimulus voltage. ◦ Conduction velocity: measuring the speed at which action potentials propagate down the axons. ◦ Effects of temperature: observing how cooling affects the nerve conduction velocity. ◦ Bidirectionality: determining whether axons conduct in both directions. ◦ Refractoriness: observing how stimulus frequency affects the amplitude of compound action potentials ◦ Strength-Duration: observing how the amplitude of a stimulus required to stimulate axons is related to the duration of the stimulus. 7. Students will continue to be successful at using the LabScribe software to move cursors, analyze data, record data to the Journal, and add functions to the Analysis window.
Outcomes
Students who have successfully completed this exercise will: 1. be able to successfully anesthetize an earthworm. 2. be able to understand the different fiber types within the nerve and record CAPs from that nerve. 3. have a better understanding of electrical stimulation of nerve fibers and the equipment used to perform such stimulation. 4. gain an understanding of compound action potentials and how they relate to nerve function. 5. test a variety of hypotheses and reach scientific conclusions. 6. have used the functions available in the Analysis window to determine values necessary for this exercise. 7. feel comfortable transferring data to the Journal and interpreting that data to answer questions about their recordings.
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Lab Equipment Required: Description: In this experiment, students will collect data that can be used to discover how animals (cockroaches) are able to interpret mechanosensory input. The specific neuronal principles that students will explore include:
• Phasic vs. tonic sensory responses
• Coding of stimulus intensity by frequency of action potentials
• Neuronal adaptation
• Temperature response
Goals
1. Students will explore the basic characteristics of the chordotonal organs. 2. Students will record their response to direction and intensity of leg movement, and determine if the responses are tonic or phasic. 3. Students will learn the basic characteristics of tibial spines on the cockroach leg. 4. Students will determine the effect of repeated stimulations on the frequency of action potentials. 5. Students will also determine the effect of cold and warm temperatures on the neuronal response of mechanoreceptors to mechanical stimulation. 6. Students will continue to be successful at using the LabScribe software to move cursors, analyze data, record data to the Journal, and add functions to the Analysis window.
Outcomes
Students who have successfully completed this exercise will: 1. understand the difference between tonic and phasic responses during flexion and extension. 2. determine whether flexion or extension causes a greater response in action potential frequency, number, or response duration. 3. determine if movement of the tibia spine in one direction or the other causes different responses in action potential frequency, number or duration. 4. understand adaptation of responses. 5. be able to explain how and why physiological processes are dependent on temperature in poikilotherms. 6. have used the functions available in the Analysis window to determine values necessary for this exercise. 7. feel comfortable transferring data to the Journal and interpreting that data to answer questions about their recordings.
Included with:
Lab Equipment Required: Description: In this experiment, students will collect data that can be used to discover how animals (cockroaches) are able to interpret mechanosensory input. The specific neuronal principles that students will explore include:
• Coding of stimulus intensity by frequency of action potentials
• Neuronal adaptation
• Spatial summation
Goals
1. Students will assemble the equipment needed to be able to stimulate the cercal sense organs. 2. Students will elicit a ventral nerve cord response to air puffs and become familiar the responses. 3. Students will explore the effects of stimulus intensity on the number and frequency of action potentials produced. 4. Students will determine the number of hairs needed to trigger an action potential in the ventral nerve cord. 5. Students will determine the effect of a continuous stimulus on the frequency of action potentials. 6. Students will look at the response to a single stimulus after fairly complete adaptation. 7. Students will continue to be successful at using the LabScribe software to move cursors, analyze data, record data to the Journal, and add functions to the Analysis window.
Outcomes
Students who have successfully completed this exercise will: 1. will be able to graph the response changes as a function of intensity. 2. understand whether the response is a change as a function of intensity. 3. be able to explain how the response differences would be important to the cockroach in its environment. 4. be able to determine the minimum number of hairs required to elicit a response. 5. understand the concept of adaptation and explain the importance to cockroach survival. 6. have used the functions available in the Analysis window to determine values necessary for this exercise. 7. feel comfortable transferring data to the Journal and interpreting that data to answer questions about their recordings.
Included with:
Lab Equipment Required: Description: Students will record responses from two different types of stretch receptors that are positioned next to the dorsal superficial extensor muscles in the tail of the crayfish. Each type of sensory organ responds to a different stimulus, generates impulses of a different amplitude and frequency, and adapts to prolonged stimuli at a different rate.
Goals
Outcomes
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Lab Equipment Required: Description: The purpose of this experiment is to demonstrate the effect that electrical activity (action potentials) in a presynaptic cell has on the electrical activity (synaptic potentials) in a postsynaptic cell.
In this experiment, the same technique used to record the resting membrane potentials of frog muscle fibers is used to record the synaptic potentials from crayfish muscle fibers. Synaptic potentials will be recorded using the a microelectrode and an intracellular electrometer.
At the same time, the same technique used to record compound action potentials from frog nerve is employed to record the action potentials of crayfish motor axons. These spontaneously generated action potentials will be recorded using a suction electrode and an extracellular amplifier.
Goals
Outcomes
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Lab Equipment Required: Description: Continuation of Crustacean NMJ-A
In this experiment, the same technique used to record the resting membrane potentials of frog muscle fibers is used to record the synaptic potentials from crayfish muscle fibers. Synaptic potentials will be recorded using the a microelectrode and an intracellular electrometer.
At the same time, the same technique used to record compound action potentials from frog nerve is employed to record the action potentials of crayfish motor axons. These spontaneously generated action potentials will be recorded using a suction electrode and an extracellular amplifier.
Goals
Outcomes
Included with:
Lab Equipment Required: Description: The purpose of this experiment is to record the extracellular action potentials of crayfish motor axons. These spontaneously generated action potentials will be recorded using a suction electrode.
