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action potential physiology
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Lecture Outline• From passive to active membrane
properties• The action potential• Effect of myelination• Refractory periods• NBME priming• Synapses
ChemicalElectrical
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Lecture Outline• From passive to active membrane
properties• The action potential• Effect of myelination• Refractory periods• NBME priming• Synapses
ChemicalElectrical
Inward Na+ or Ca2+ current
K+ current
Time course of voltage and conductance changes during the action potential of nerve.
Lecture Outline• From passive to active membrane
properties• The action potential• Effect of myelination• Refractory periods• NBME priming• Synapses
ChemicalElectrical
Putting it all together …
Summation
Lecture Outline• From passive to active membrane
properties• The action potential• Effect of myelination• Refractory periods• NBME priming• Synapses
ChemicalElectrical
NBME Tuning
• The electrochemical driving force acting on Ca2+ ions at resting membrane potential is relatively very positive. This implies that?
a) Vm at rest approaches ECa
b) ECa - Vm at rest is a relatively large positive quantityc) The electrochemical driving force acting on Ca2+ ions
under resting conditions favors an efflux of this iond) Ca2+ ions have a significant impact on the time course
of an action potentiale) A large inward current would result if the neuronal
membrane becomes permeable to Ca2+ ions
• The electrochemical driving force acting on Ca2+ ions at resting membrane potential is relatively very positive. This implies that?
a) Vm at rest approaches ECa
b) ECa - Vm at rest is a relatively large positive quantityc) The electrochemical driving force acting on Ca2+ ions
under resting conditions favors an efflux of this iond) Ca2+ ions have a significant impact on the time course
of an action potentiale) A large inward current would result if the neuronal
membrane becomes permeable to Ca2+ ions
• Which of the following characteristics of an axon is most dependent on its diameter?
a) The magnitude of its resting potentialb) The duration of its refractory periodc) The conduction velocity of its action potentiald) The overshoot of its action potentiale) The activity of its sodium-potassium pump
• Which of the following characteristics of an axon is most dependent on its diameter?
a) The magnitude of its resting potentialb) The duration of its refractory periodc) The conduction velocity of its action potentiald) The overshoot of its action potentiale) The activity of its sodium-potassium pump
• An 82-year-old woman is brought to the emergency room complaining of extreme thirst and generalized weakness. She has consumed a large amount of orange juice to quench her thirst. Laboratory analysis reveals a significant hyperkalemia. Which one of the following changes in nerve membranes will most likely be observed?
a) The membrane potential will become more negativeb) The sodium conductance will increasec) The potassium conductance will increased) The membrane will become more excitablee) The Na-K pump will become inactivated
• An 82-year-old woman is brought to the emergency room complaining of extreme thirst and generalized weakness. She has consumed a large amount of orange juice to quench her thirst. Laboratory analysis reveals a significant hyperkalemia. Which one of the following changes in nerve membranes will most likely be observed?
a) The membrane potential will become more negativeb) The sodium conductance will increasec) The potassium conductance will increased) The membrane will become more excitablee) The Na-K pump will become inactivated
• The diagram below illustrates the concentration of a substance in two chambers. If the concentration of the substance in chamber A doubles, the diffusion of the substance will change from 10 mg/h to?
a) 5 mg/hb) 10 mg/hc) 15 mg/hd) 20 mg/he) 30 mg/h
20 mg/L
CHAMBER A
10 mg/L
CHAMBER B
• The diagram below illustrates the concentration of a substance in two chambers. If the concentration of the substance in chamber A doubles, the diffusion of the substance will change from 10 mg/h to?
a) 5 mg/hb) 10 mg/hc) 15 mg/hd) 20 mg/he) 30 mg/h
20 mg/L
CHAMBER A
10 mg/L
CHAMBER B
• Several genetic defects of voltage-gated Na+ channels are known to result in extended bursts of channel openings along with abnormal prolongation of the action potential. These defects are sometimes observed in patients suffering from paramyotonia congenita, and are most probably a result of?
a) Alterations of the voltage-sensing component of the channelb) Conformational changes associated with the channel porec) Abnormal afterhyperpolarization (AHP) during the time
course of the action potentiald) Changes in the time course of the repolarization phase of the
action potentiale) Disruption of refractory properties
• Several genetic defects of voltage-gated Na+ channels are known to result in extended bursts of channel openings along with abnormal prolongation of the action potential. These defects are sometimes observed in patients suffering from paramyotonia congenita, and are most probably a result of?
a) Alterations of the voltage-sensing component of the channelb) Conformational changes associated with the channel porec) Abnormal afterhyperpolarization (AHP) during the time
course of the action potentiald) Changes in the time course of the repolarization phase of the
action potentiale) Disruption of refractory properties
• Several genetic defects of voltage-gated Na+ channels are known to result in extended bursts of channel openings along with abnormal prolongation of the action potential. These defects are sometimes observed in patients suffering from paramyotonia congenita, and are most probably a result of?
a) Alterations of the voltage-sensing component of the channelb) Conformational changes associated with the channel porec) Abnormal afterhyperpolarization (AHP) during the time
course of the action potentiald) Changes in the time course of the repolarization phase of the
action potentiale) Disruption of refractory properties
Lecture Outline• From passive to active membrane
properties• The action potential• Effect of myelination• Refractory periods• NBME priming• Synapses
ChemicalElectrical
Chemical Synapse
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