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Questions and Answers
How can ion conductances across the nerve fiber membrane be altered experimentally?
How can ion conductances across the nerve fiber membrane be altered experimentally?
They can be the result of electrical current applied through electrodes.
What is the stimulus artifact and why is it significant in nerve conduction studies?
What is the stimulus artifact and why is it significant in nerve conduction studies?
The stimulus artifact is a short period of irregular deflection of the CRO baseline caused by current leakage, indicating the moment the stimulus is applied.
What is the relationship between the velocity of a nerve impulse and action potentials?
What is the relationship between the velocity of a nerve impulse and action potentials?
The velocity is directly related to the sum of all the action potentials occurring in the individual neurons of the whole nerve.
What else does the nerve conduction velocity reflect besides action potentials?
What else does the nerve conduction velocity reflect besides action potentials?
What does the latent period represent in nerve conduction studies?
What does the latent period represent in nerve conduction studies?
Which axon characteristic is most dependent on its diameter?
Which axon characteristic is most dependent on its diameter?
Define the firing level in the context of depolarization.
Define the firing level in the context of depolarization.
How does myelination influence nerve conduction velocity?
How does myelination influence nerve conduction velocity?
What are the components of the spike potential during depolarization?
What are the components of the spike potential during depolarization?
What occurs during the repolarization phase of the spike potential?
What occurs during the repolarization phase of the spike potential?
What is the firing level in nerves during depolarization?
What is the firing level in nerves during depolarization?
Describe the composition of the spike potential.
Describe the composition of the spike potential.
What distinguishes saltatory conduction from conduction in unmyelinated fibers?
What distinguishes saltatory conduction from conduction in unmyelinated fibers?
What is the significance of the nodes of Ranvier in myelinated nerve fibers?
What is the significance of the nodes of Ranvier in myelinated nerve fibers?
How is nerve conduction velocity calculated in the example provided?
How is nerve conduction velocity calculated in the example provided?
What electrodes are used to measure the conduction velocity of the median nerve?
What electrodes are used to measure the conduction velocity of the median nerve?
What are the two components of after potential?
What are the two components of after potential?
What happens immediately after a point in a nerve fiber becomes depolarized?
What happens immediately after a point in a nerve fiber becomes depolarized?
Define a nerve.
Define a nerve.
What classification exists for nerve fibers based on conduction velocity?
What classification exists for nerve fibers based on conduction velocity?
How can nerve conduction velocity be measured?
How can nerve conduction velocity be measured?
What is the unit of measurement for nerve conduction velocity?
What is the unit of measurement for nerve conduction velocity?
What instruments are used to study nerve conduction velocity?
What instruments are used to study nerve conduction velocity?
What does the stimulus artifact indicate in the results?
What does the stimulus artifact indicate in the results?
What is the latent period in nerve conduction testing?
What is the latent period in nerve conduction testing?
What causes the stimulus artifact?
What causes the stimulus artifact?
What determines the compound action potential in a nerve trunk?
What determines the compound action potential in a nerve trunk?
What are the three main waves analyzed in the compound action potential?
What are the three main waves analyzed in the compound action potential?
How is group $A$ of nerve fibers further subdivided?
How is group $A$ of nerve fibers further subdivided?
What is the relationship between the diameter of a nerve fiber and its conduction velocity?
What is the relationship between the diameter of a nerve fiber and its conduction velocity?
What condition may lead to decreased nerve conduction velocity (NCV)?
What condition may lead to decreased nerve conduction velocity (NCV)?
Which type of nerve fibers are myelinated somatic nerves classified under?
Which type of nerve fibers are myelinated somatic nerves classified under?
What is a common symptom of Guillain-Barré syndrome?
What is a common symptom of Guillain-Barré syndrome?
What happens during carpal tunnel syndrome?
What happens during carpal tunnel syndrome?
Which nerve fibers are considered unmyelinated?
Which nerve fibers are considered unmyelinated?
What is a common cause of sciatic nerve problems?
What is a common cause of sciatic nerve problems?
What is the definition of a nerve?
What is the definition of a nerve?
What is the significance of the stimulus artifact in a nerve conduction velocity test?
What is the significance of the stimulus artifact in a nerve conduction velocity test?
How can nerve conduction velocity be measured?
How can nerve conduction velocity be measured?
What units are used to measure nerve conduction velocity?
What units are used to measure nerve conduction velocity?
What equipment is used to record nerve impulses during the test?
What equipment is used to record nerve impulses during the test?
What does the latent period represent in nerve conduction studies?
What does the latent period represent in nerve conduction studies?
What are microelectrodes used for in nerve conduction tests?
What are microelectrodes used for in nerve conduction tests?
What is the classification of nerve fibers based on?
What is the classification of nerve fibers based on?
Study Notes
Experimental Physiology Overview
- Changes in ion conductance across nerve membranes can occur through applied electrical currents.
- Nerve conduction velocity (NCV) is directly influenced by action potentials from individual neurons and their ion conductance.
Axon Characteristics
- Conduction velocity of action potentials is most dependent on axon diameter; larger diameters yield faster transmission.
- Myelination increases conduction velocity, especially over longer distances between Nodes of Ranvier.
- Resting and action potentials relate to ion channel density and Na+/K+ pump activity, not diameter.
Experimental Procedure for Nerve Conduction
- Insert two microelectrodes (one inside, one outside) into a neuron's axon; connect to a cathode ray oscilloscope (CRO) for recording.
- Stimulate the nerve and observe electrical changes.
Key Observations
- Stimulus Artifact: Immediate irregular deflection on CRO, indicating stimulus application and caused by current leakage.
- Latent Period: Iso-potential phase before potential changes; indicates impulse conduction time and can be used to measure NCV.
Action Potential Phases
- Depolarization: Comprises a slow initial phase and a rapid firing phase, starting at -55 mV.
- Repolarization: Involves both slow and rapid phases.
- Spike Potential: Defined by rapid depolarization followed by rapid repolarization, with after-potentials resulting in hyperpolarization or depolarization.
Impulse Conduction Mechanisms
- Unmyelinated Fibers: Nerve impulses propagate as continuous waves of action potentials; repolarization follows depolarization in the same direction.
- Myelinated Fibers: Utilize saltatory conduction, where impulses jump between Nodes of Ranvier, accelerating transmission.
Measuring Nerve Conduction Velocity
- To assess median nerve conduction, electrodes are placed on corresponding muscle and bony landmarks for measurement.
- Calculate NCV using latency differences and physical distance between stimulation points.
Compound Action Potential
- Detected using multiple electrodes; consists of different fiber groups (A, B, C), categorized by diameter, myelination, and conduction rate.
- Larger diameters correspond to higher conduction velocities, with decreased amplitudes indicating potential neuronal degeneration.
Nerve Fiber Classification
- Ia: Muscle spindle, Aa fibers
- Ib: Golgi tendon organ, Aa fibers
- II: Muscle spindle and touch receptors, Aβ fibers
- III: Pain and cold receptors, Aδ fibers
- IV: Pain and temperature receptors, C fibers
Clinical Importance
- NCV tests help diagnose conditions like Guillain-Barré syndrome, carpal tunnel syndrome, herniated disks, and sciatic nerve issues.
- Decreased NCV is often indicative of nerve damage such as compression or demyelination conditions.
Summary of Nerve Conduction Tests
- Utilizes CRO, microelectrodes, and amplifiers to measure electrical impulses in nerves.
- Latent periods and changes in compound action potentials provide insights into nerve function and health.
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Description
Test your knowledge on the fundamentals of experimental physiology with multiple choice questions. Explore concepts such as ion conductances, nerve impulse velocity, and their implications in nerve conduction. Perfect for first-year students aiming to solidify their understanding of physiological principles.
