Podcast
Questions and Answers
What occurs during the ascending limb of the spike potential?
What occurs during the ascending limb of the spike potential?
- The membrane remains at resting potential and does not respond to stimuli.
- Gates of voltage-activated Na+ channels are already closed.
- The membrane is partially repolarized allowing strong stimuli to reopen Na+ gates. (correct)
- Membrane is hyperpolarized and cannot initiate another action potential.
What best describes the early part of the descending limb of spike potential?
What best describes the early part of the descending limb of spike potential?
- The membrane is hyperpolarized, preventing action potential generation.
- Na+ gates are closed and a sufficient period of repolarization is required. (correct)
- Membrane potential is at its peak allowing for multiple action potentials.
- Gates of Na+ channels are fully opened and allow repeated impulses.
What limits the number of impulses that a nerve fiber can conduct?
What limits the number of impulses that a nerve fiber can conduct?
- The presence of continuous stimuli that trigger depolarization.
- The speed of neurotransmitter release at the synapse.
- The overall length of the nerve fiber.
- The inability of the Na+ channels to open immediately after an action potential. (correct)
Which of the following is NOT a cause of failure in nerve impulse propagation?
Which of the following is NOT a cause of failure in nerve impulse propagation?
After a second stimulus is applied during the late part of the descending limb, what is the expected outcome?
After a second stimulus is applied during the late part of the descending limb, what is the expected outcome?
During the late phase of the descending limb, how is the membrane state described?
During the late phase of the descending limb, how is the membrane state described?
What happens when a strong stimulus is applied during the ascending limb of the spike potential?
What happens when a strong stimulus is applied during the ascending limb of the spike potential?
How does severe cooling affect nerve excitability?
How does severe cooling affect nerve excitability?
Which type of nerve conducts action potentials at a faster speed?
Which type of nerve conducts action potentials at a faster speed?
What is the energy consumption difference between continuous and saltatory conduction?
What is the energy consumption difference between continuous and saltatory conduction?
What initiates the depolarization process in a nerve?
What initiates the depolarization process in a nerve?
In saltatory conduction, what does the local current flow cause?
In saltatory conduction, what does the local current flow cause?
What is the threshold level required for an action potential to occur?
What is the threshold level required for an action potential to occur?
What is a key significance of saltatory conduction?
What is a key significance of saltatory conduction?
Which mechanism is involved in continuous conduction?
Which mechanism is involved in continuous conduction?
What is the resting membrane potential typically in a polarized resting node?
What is the resting membrane potential typically in a polarized resting node?
What effect does an increase in the internal diameter of a nerve fiber have on conduction velocity?
What effect does an increase in the internal diameter of a nerve fiber have on conduction velocity?
Which type of nerve fibers are characterized by being thick and myelinated?
Which type of nerve fibers are characterized by being thick and myelinated?
What defines orthodromic conduction?
What defines orthodromic conduction?
Which characteristic of myelination most significantly affects conduction velocity?
Which characteristic of myelination most significantly affects conduction velocity?
What is the conduction speed range for Type B fibers?
What is the conduction speed range for Type B fibers?
Which type of nerve fibers are most sensitive to local anesthetics?
Which type of nerve fibers are most sensitive to local anesthetics?
What source of energy does a nerve fiber utilize to maintain resting membrane potential (RMP)?
What source of energy does a nerve fiber utilize to maintain resting membrane potential (RMP)?
What is the diameter range of Type C fibers?
What is the diameter range of Type C fibers?
What is one of the main effects of increased metabolic reactions during nerve impulses?
What is one of the main effects of increased metabolic reactions during nerve impulses?
What characterizes the absolute refractory period (ARP) in nerve fibers?
What characterizes the absolute refractory period (ARP) in nerve fibers?
In what phase is the excitability of nerve fibers considered supernormal?
In what phase is the excitability of nerve fibers considered supernormal?
What happens during the delayed heat phase of nerve impulse conduction?
What happens during the delayed heat phase of nerve impulse conduction?
During which phase are stronger stimuli needed to excite a nerve?
During which phase are stronger stimuli needed to excite a nerve?
What is the primary reason for the increase in heat production during nerve impulse activity?
What is the primary reason for the increase in heat production during nerve impulse activity?
During which phase does the nerve cell experience partial recovery of excitability?
During which phase does the nerve cell experience partial recovery of excitability?
What generally follows the temporal rise of excitability in nerve fibers?
What generally follows the temporal rise of excitability in nerve fibers?
What is the maximum speed of action potential propagation in myelinated nerves?
What is the maximum speed of action potential propagation in myelinated nerves?
How does energy consumption differ between continuous and saltatory conduction?
How does energy consumption differ between continuous and saltatory conduction?
Which node plays a critical role in saltatory conduction after the depolarization of an adjacent node?
Which node plays a critical role in saltatory conduction after the depolarization of an adjacent node?
What is the lower threshold level required for action potential initiation?
What is the lower threshold level required for action potential initiation?
Which type of nerve conduction consumes more energy?
Which type of nerve conduction consumes more energy?
In saltatory conduction, what happens at the nearest node of Ranvier during stimulation?
In saltatory conduction, what happens at the nearest node of Ranvier during stimulation?
What mechanism occurs in continuous conduction at the site of stimulation?
What mechanism occurs in continuous conduction at the site of stimulation?
What occurs after a second stimulus is applied during the late part of the descending limb of the action potential?
What occurs after a second stimulus is applied during the late part of the descending limb of the action potential?
What is a characteristic of the early part of the descending limb of the action potential?
What is a characteristic of the early part of the descending limb of the action potential?
How does local anesthetic, such as lidocaine, affect nerve impulse propagation?
How does local anesthetic, such as lidocaine, affect nerve impulse propagation?
During the ascending limb of the spike potential, what happens to the Na+ channels?
During the ascending limb of the spike potential, what happens to the Na+ channels?
Which of the following accurately reflects the state of the membrane during the late part of the descending limb?
Which of the following accurately reflects the state of the membrane during the late part of the descending limb?
What is a significant result of a second stimulus applied during the ascending limb?
What is a significant result of a second stimulus applied during the ascending limb?
What defines the mechanism of excitability in relation to nerve impulses?
What defines the mechanism of excitability in relation to nerve impulses?
What can severely hinder the ability of a nerve to conduct impulses?
What can severely hinder the ability of a nerve to conduct impulses?
What effect does the thickness of the myelin sheath have on nerve conduction velocity?
What effect does the thickness of the myelin sheath have on nerve conduction velocity?
Which type of nerve fiber exhibits the highest conduction speed?
Which type of nerve fiber exhibits the highest conduction speed?
What is the diameter range for Type B nerve fibers?
What is the diameter range for Type B nerve fibers?
What defines antidromic conduction in the context of nerve signaling?
What defines antidromic conduction in the context of nerve signaling?
Which factor primarily decreases internal resistance in nerve fibers, thereby increasing conduction velocity?
Which factor primarily decreases internal resistance in nerve fibers, thereby increasing conduction velocity?
What is a significant characteristic of Type C fibers?
What is a significant characteristic of Type C fibers?
What happens to the conduction velocity as the internal diameter of nerve fibers decreases?
What happens to the conduction velocity as the internal diameter of nerve fibers decreases?
Which of the following factors does NOT affect the conduction speed of action potentials in nerve fibers?
Which of the following factors does NOT affect the conduction speed of action potentials in nerve fibers?
What occurs during the absolute refractory period (ARP) of nerve fibers?
What occurs during the absolute refractory period (ARP) of nerve fibers?
Which phase indicates that the excitability of nerve fibers is considered to be below normal?
Which phase indicates that the excitability of nerve fibers is considered to be below normal?
During which phase do nerve fibers require stronger than threshold stimuli to be excited?
During which phase do nerve fibers require stronger than threshold stimuli to be excited?
Which of the following best describes the increased metabolic reactions during nerve impulse conduction?
Which of the following best describes the increased metabolic reactions during nerve impulse conduction?
What is the significance of the temporal rise of excitability in nerve fibers?
What is the significance of the temporal rise of excitability in nerve fibers?
What primarily drives the increase in heat production during nerve impulse conduction?
What primarily drives the increase in heat production during nerve impulse conduction?
What characterizes the delayed heat phase of nerve conduction?
What characterizes the delayed heat phase of nerve conduction?
What is indicated by the numerical values of the stimuli during the relative refractory period (RRP)?
What is indicated by the numerical values of the stimuli during the relative refractory period (RRP)?
What is the main difference in speed between continuous and saltatory conduction?
What is the main difference in speed between continuous and saltatory conduction?
In what way does saltatory conduction conserve energy compared to continuous conduction?
In what way does saltatory conduction conserve energy compared to continuous conduction?
What causes the initial heat production during the conduction of a nerve impulse?
What causes the initial heat production during the conduction of a nerve impulse?
Describe the role of the node of Ranvier in saltatory conduction.
Describe the role of the node of Ranvier in saltatory conduction.
Explain the difference in excitability during the absolute refractory period compared to the relative refractory period.
Explain the difference in excitability during the absolute refractory period compared to the relative refractory period.
What occurs at the site of stimulation during continuous conduction?
What occurs at the site of stimulation during continuous conduction?
How does the excitability of nerve fibers change during the supernormal phase?
How does the excitability of nerve fibers change during the supernormal phase?
What threshold must be reached for an action potential to be initiated in both types of conduction?
What threshold must be reached for an action potential to be initiated in both types of conduction?
What metabolic changes occur during nerve impulse transmission?
What metabolic changes occur during nerve impulse transmission?
Explain how potential difference is established during saltatory conduction.
Explain how potential difference is established during saltatory conduction.
What is the role of ATP reform during the delayed heat phase in nerve impulses?
What is the role of ATP reform during the delayed heat phase in nerve impulses?
What is the effect of myelination on conduction velocity?
What is the effect of myelination on conduction velocity?
Describe the consequence of weak stimuli during the subnormal phase of excitability.
Describe the consequence of weak stimuli during the subnormal phase of excitability.
What significant advantages does saltatory conduction provide to the nervous system?
What significant advantages does saltatory conduction provide to the nervous system?
Discuss the importance of local depolarization in the temporal rise of excitability.
Discuss the importance of local depolarization in the temporal rise of excitability.
What is the significance of a strong stimulus during the relative refractory period?
What is the significance of a strong stimulus during the relative refractory period?
Describe the effect of strong stimuli on Na+ channels during the ascending limb of the spike potential.
Describe the effect of strong stimuli on Na+ channels during the ascending limb of the spike potential.
What occurs in the nerve membrane during the early part of the descending limb of the action potential?
What occurs in the nerve membrane during the early part of the descending limb of the action potential?
Explain the significance of the negative afterpotential in nerve impulse conduction.
Explain the significance of the negative afterpotential in nerve impulse conduction.
What characterizes the absolute refractory period in terms of nerve excitability?
What characterizes the absolute refractory period in terms of nerve excitability?
Identify the relationship between local anesthetic drugs like lidocaine and nerve excitability.
Identify the relationship between local anesthetic drugs like lidocaine and nerve excitability.
How does hyperpolarization of the nerve membrane affect subsequent action potential generation?
How does hyperpolarization of the nerve membrane affect subsequent action potential generation?
Discuss the impact of thermal cooling on nerve impulse behavior.
Discuss the impact of thermal cooling on nerve impulse behavior.
What role does sufficient repolarization play in action potential conduction?
What role does sufficient repolarization play in action potential conduction?
How does the diameter of nerve fibers influence conduction velocity in action potentials?
How does the diameter of nerve fibers influence conduction velocity in action potentials?
What is the role of myelination in the conduction of action potentials?
What is the role of myelination in the conduction of action potentials?
Distinguish between orthodromic and antidromic conduction.
Distinguish between orthodromic and antidromic conduction.
How does the speed of conduction vary among Type A, B, and C fibers?
How does the speed of conduction vary among Type A, B, and C fibers?
What types of fibers are most sensitive to local anesthetics and why?
What types of fibers are most sensitive to local anesthetics and why?
What is the significance of the resting membrane potential (RMP) in nerve fibers?
What is the significance of the resting membrane potential (RMP) in nerve fibers?
Explain the influence of energy consumption in continuous versus saltatory conduction.
Explain the influence of energy consumption in continuous versus saltatory conduction.
What types of physical stressors influence the sensitivity of nerve fibers, particularly Type A?
What types of physical stressors influence the sensitivity of nerve fibers, particularly Type A?
How does the internal diameter of a nerve fiber influence conduction velocity?
How does the internal diameter of a nerve fiber influence conduction velocity?
What role does the myelin sheath play in action potential conduction?
What role does the myelin sheath play in action potential conduction?
Differentiate between orthodromic and antidromic conduction.
Differentiate between orthodromic and antidromic conduction.
What is the speed range for Type A nerve fibers?
What is the speed range for Type A nerve fibers?
What types of stimuli are Type C fibers most sensitive to?
What types of stimuli are Type C fibers most sensitive to?
Compare the speed of action potential conduction in continuous versus saltatory conduction.
Compare the speed of action potential conduction in continuous versus saltatory conduction.
Describe the energy source utilized by nerve fibers to maintain resting membrane potential (RMP).
Describe the energy source utilized by nerve fibers to maintain resting membrane potential (RMP).
What role does the node of Ranvier play in saltatory conduction?
What role does the node of Ranvier play in saltatory conduction?
How does the thickness of the myelin sheath relate to conduction velocity?
How does the thickness of the myelin sheath relate to conduction velocity?
Explain the energy consumption difference between continuous and saltatory conduction.
Explain the energy consumption difference between continuous and saltatory conduction.
What diameter range do Type B nerve fibers typically have?
What diameter range do Type B nerve fibers typically have?
Describe the mechanism by which an action potential is generated at a polarized resting node.
Describe the mechanism by which an action potential is generated at a polarized resting node.
What is the primary significance of saltatory conduction in nervous system function?
What is the primary significance of saltatory conduction in nervous system function?
Identify the resting membrane potential typically found at a polarized resting node.
Identify the resting membrane potential typically found at a polarized resting node.
How does the metabolic energy requirement of continuous conduction compare to that of saltatory conduction?
How does the metabolic energy requirement of continuous conduction compare to that of saltatory conduction?
What happens to the neuronal membrane potential after it reaches +35 mV during action potential propagation?
What happens to the neuronal membrane potential after it reaches +35 mV during action potential propagation?
What occurs in the membrane state during the early part of the descending limb after an action potential?
What occurs in the membrane state during the early part of the descending limb after an action potential?
How does a second stimulus affect the membrane during the late part of the descending limb?
How does a second stimulus affect the membrane during the late part of the descending limb?
What physiological mechanisms underlie the excitability of nerve fibers?
What physiological mechanisms underlie the excitability of nerve fibers?
What happens during the hyperpolarization phase of a nerve fiber's action potential?
What happens during the hyperpolarization phase of a nerve fiber's action potential?
Describe the impact of mechanical stimuli, such as deep pressure, on nerve excitability.
Describe the impact of mechanical stimuli, such as deep pressure, on nerve excitability.
What is the role of cooling in nerve impulse conduction?
What is the role of cooling in nerve impulse conduction?
What characterizes the condition of a nerve fiber during the absolute refractory period?
What characterizes the condition of a nerve fiber during the absolute refractory period?
How does the repolarization process affect the conduction capabilities of nerve fibers?
How does the repolarization process affect the conduction capabilities of nerve fibers?
What are the two phases of heat production associated with nerve impulse conduction?
What are the two phases of heat production associated with nerve impulse conduction?
Explain the absolute refractory period (ARP) in terms of nerve excitability.
Explain the absolute refractory period (ARP) in terms of nerve excitability.
What governs the excitability of nerve fibers during the relative refractory period (RRP)?
What governs the excitability of nerve fibers during the relative refractory period (RRP)?
Describe the significance of the supernormal phase of excitability.
Describe the significance of the supernormal phase of excitability.
What effect does increased metabolic activity have on CO2 production during nerve impulses?
What effect does increased metabolic activity have on CO2 production during nerve impulses?
Identify how glucose utilization is affected during nerve impulse conduction.
Identify how glucose utilization is affected during nerve impulse conduction.
What role does local response play during the temporal rise of excitability?
What role does local response play during the temporal rise of excitability?
How does the delayed heat phase relate to ATP reform during nerve impulse activity?
How does the delayed heat phase relate to ATP reform during nerve impulse activity?
Flashcards
Action Potential Propagation
Action Potential Propagation
The process of an action potential traveling along a nerve fiber.
Continuous Conduction
Continuous Conduction
Action potential propagation in unmyelinated nerve fibers.
Saltatory Conduction
Saltatory Conduction
Action potential propagation in myelinated nerve fibers.
Myelinated Nerve Fiber
Myelinated Nerve Fiber
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Unmyelinated Nerve Fiber
Unmyelinated Nerve Fiber
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Propagation Speed (Continuous)
Propagation Speed (Continuous)
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Propagation Speed (Saltatory)
Propagation Speed (Saltatory)
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Node of Ranvier
Node of Ranvier
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What affects action potential speed?
What affects action potential speed?
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Internal Diameter & Conduction Speed
Internal Diameter & Conduction Speed
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Myelination's Role
Myelination's Role
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Orthodromic Conduction
Orthodromic Conduction
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Antidromic Conduction
Antidromic Conduction
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Type A Fibers
Type A Fibers
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Type B Fibers
Type B Fibers
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Type C Fibers
Type C Fibers
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Metabolic Rate During Nerve Impulse
Metabolic Rate During Nerve Impulse
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Initial Heat of Nerve Impulse
Initial Heat of Nerve Impulse
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Delayed Heat of Nerve Impulse
Delayed Heat of Nerve Impulse
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What is the Refractory Period?
What is the Refractory Period?
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Absolute Refractory Period (ARP)
Absolute Refractory Period (ARP)
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Relative Refractory Period (RRP)
Relative Refractory Period (RRP)
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Supernormal Phase of Excitability
Supernormal Phase of Excitability
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Subnormal Phase of Excitability
Subnormal Phase of Excitability
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Ascending Limb of Spike Potential
Ascending Limb of Spike Potential
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Descending Limb of Spike Potential
Descending Limb of Spike Potential
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Second Stimulus During Ascending Limb
Second Stimulus During Ascending Limb
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Second Stimulus During Early Descending Limb
Second Stimulus During Early Descending Limb
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Significance of Refractory Period
Significance of Refractory Period
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Nerve Conduction Failure
Nerve Conduction Failure
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Thermal Causes of Conduction Failure
Thermal Causes of Conduction Failure
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Mechanical Causes of Conduction Failure
Mechanical Causes of Conduction Failure
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What is the difference between continuous and saltatory conduction?
What is the difference between continuous and saltatory conduction?
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What is a node of Ranvier?
What is a node of Ranvier?
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How does saltatory conduction conserve energy?
How does saltatory conduction conserve energy?
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Why is saltatory conduction faster?
Why is saltatory conduction faster?
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What is the role of the myelin sheath in nerve conduction?
What is the role of the myelin sheath in nerve conduction?
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What is the threshold level for an action potential?
What is the threshold level for an action potential?
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What is the refractory period in action potential?
What is the refractory period in action potential?
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What are the two types of refractory periods?
What are the two types of refractory periods?
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What affects nerve conduction speed?
What affects nerve conduction speed?
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Internal diameter's role
Internal diameter's role
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Myelination's effect
Myelination's effect
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Initial Heat
Initial Heat
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Delayed Heat
Delayed Heat
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Temporal Rise of Excitability
Temporal Rise of Excitability
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Ascending Limb: Sodium Channel Gates
Ascending Limb: Sodium Channel Gates
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Early Descending Limb: Sodium Channel Gates
Early Descending Limb: Sodium Channel Gates
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Why is a second stimulus weaker?
Why is a second stimulus weaker?
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What does refractory period limit?
What does refractory period limit?
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Conduction Failure: Thermal
Conduction Failure: Thermal
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Conduction Failure: Mechanical
Conduction Failure: Mechanical
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Local Anesthetics
Local Anesthetics
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Nerve Conduction Failure: Summary
Nerve Conduction Failure: Summary
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Myelination's effect on speed
Myelination's effect on speed
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Myelination's effect on energy
Myelination's effect on energy
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Local Current Flow
Local Current Flow
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Action potential & threshold
Action potential & threshold
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Refractory period
Refractory period
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Metabolism During Nerve Impulse
Metabolism During Nerve Impulse
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Conduction Phases
Conduction Phases
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What makes saltatory conduction fast?
What makes saltatory conduction fast?
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What is the threshold level?
What is the threshold level?
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What are the types of refractory periods?
What are the types of refractory periods?
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Larger Diameter, Faster Speed?
Larger Diameter, Faster Speed?
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Myelin's Role
Myelin's Role
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Orthodromic vs. Antidromic
Orthodromic vs. Antidromic
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Type A nerve fiber
Type A nerve fiber
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Type B nerve fiber
Type B nerve fiber
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Type C nerve fiber
Type C nerve fiber
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Nerve Energy Use
Nerve Energy Use
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Nerve Metabolism During Action Potential
Nerve Metabolism During Action Potential
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Ascending Limb: What happens to Na+?
Ascending Limb: What happens to Na+?
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Early Descending Limb: What happens to Na+?
Early Descending Limb: What happens to Na+?
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What does the refractory period limit?
What does the refractory period limit?
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Metabolic Rate During Impulse
Metabolic Rate During Impulse
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Initial Heat of Impulse
Initial Heat of Impulse
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Delayed Heat of Impulse
Delayed Heat of Impulse
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Nerve Conduction Phases
Nerve Conduction Phases
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Study Notes
Propagation of Action Potentials
-
Action potentials can be propagated continuously or saltatorily
-
Continuous propagation: Unmyelinated axons. Slow (0.5-2 m/sec). More energy consumption. Stimulation depolarizes the membrane at the site, then the depolarized area stimulates the adjacent area, generating local current flows. This creates a domino effect, causing the polarized area to reach the threshold level (-55 mV) and generate an action potential sequentially along the axon.
-
Saltatory propagation: Myelinated axons. Fast (up to 120 m/sec). Lower energy consumption (1% of continuous). Stimulation depolarizes the membrane at the nodes of Ranvier. The depolarized node creates a local current that jumps to the next node, skipping the myelin-coated segments. This rapid jumping of the action potential allows for faster conduction.
Factors Affecting Conduction Speed
- Internal diameter of nerve fibers: Larger diameter fibers have lower internal resistance, leading to faster conduction.
- Degree of myelination: Greater myelination increases membrane resistance, speeding up action potential propagation.
Types of Nerve Fibers
- Type A fibers: Thick myelinated. Somatic motor and sensory nerves. High speed (10-120 m/sec). Sensitive to pressure, alpha, beta, delta, and gamma.
- Type B fibers: Thin myelinated. Autonomic preganglionic nerves. Moderate speed (3-15 m/sec). Sensitive to O2 lack and hypoxia.
- Type C fibers: Thin unmyelinated. Somatic sensory (slow pain) and autonomic postganglionic. Slowest speed (0.5-1 m/sec). Sensitive to local anesthetics
Changes in Nerve During Conduction
- Electrical changes: Spike potentials and after-potentials.
- Metabolic changes: Increased energy use (ATP), increased CO2 production, and glucose utilization. Increase in heat production during nerve impulse.
- Thermal changes: Heat production during impulse generation and propagation, initial and delayed heat phases.
Excitability Changes
- Temporal rise in excitability: Associated with local responses in nerve fibers, before reaching firing level.
- Absolute refractory period (ARP): Complete loss of excitability in nerve fibers.
- Relative refractory period (RRP): Partial recovery of excitability, but still below normal.
- Supernormal phase: Excitability is above normal.
- Subnormal phase: Excitability below normal
Nerve Block
- Definition: Failure of initiation and propagation of nerve impulses.
- Causes:
- Thermal: Severe cooling
- Mechanical: Deep pressure
- Chemical: Local anesthetics (e.g., lidocaine), membrane stabilizers (changes in Ca, Na, K concentrations).
Multiple Sclerosis (MS)
- Definition: Autoimmune disease attacking myelin.
- Cause: Inflammation and injury to myelin sheath, surrounding nerve fibers.
- Incidence: Women more than men, usually diagnosed 20-50 years old
- Clinical picture: Muscle weakness, fatigue, sensory issues, blurred vision, slurred speech, bladder dysfunction.
- Treatment: Steroids (suppress immune system), Decrease antibodies formation.
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