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Questions and Answers
An EEG measures electrical activity on the scalp primarily generated by what type of brain cells?
An EEG measures electrical activity on the scalp primarily generated by what type of brain cells?
- Microglia
- Pyramidal neurons (correct)
- Astrocytes
- Glial cells
If an adult is awake, alert, and engaged in active mental activity, which type of brain wave would likely dominate their EEG?
If an adult is awake, alert, and engaged in active mental activity, which type of brain wave would likely dominate their EEG?
- Theta waves
- Delta waves
- Beta waves (correct)
- Alpha waves
Theta waves are normal in children and during sleep. In which other scenario would the presence of theta waves be least expected?
Theta waves are normal in children and during sleep. In which other scenario would the presence of theta waves be least expected?
- An adult in a coma
- A child daydreaming
- A sleeping child
- An awake adult (correct)
Delta waves are most prominent during which state of consciousness?
Delta waves are most prominent during which state of consciousness?
Which of the following is a primary application of EEG in the medical field?
Which of the following is a primary application of EEG in the medical field?
A subject is resting quietly with their eyes closed. According to the information provided, which type of brain wave is most likely to be dominant in their EEG?
A subject is resting quietly with their eyes closed. According to the information provided, which type of brain wave is most likely to be dominant in their EEG?
What is the most likely frequency range of brain waves observed in an adult who is deeply asleep?
What is the most likely frequency range of brain waves observed in an adult who is deeply asleep?
What primarily causes the origin of bioelectricity?
What primarily causes the origin of bioelectricity?
What is the method of EEG measurement?
What is the method of EEG measurement?
Which of the following cellular structures is most directly responsible for generating the voltages and currents that cause electrical events to occur?
Which of the following cellular structures is most directly responsible for generating the voltages and currents that cause electrical events to occur?
What is the primary mechanism by which membranes generate action potentials?
What is the primary mechanism by which membranes generate action potentials?
Which sequence correctly describes the change in membrane permeability during the generation of an action potential?
Which sequence correctly describes the change in membrane permeability during the generation of an action potential?
The cell membrane separates which two volumes?
The cell membrane separates which two volumes?
What specialized feature of the cell membrane allows for the creation of voltage differences?
What specialized feature of the cell membrane allows for the creation of voltage differences?
How do connexons contribute to bioelectrical phenomena?
How do connexons contribute to bioelectrical phenomena?
If a cell membrane suddenly became impermeable to both sodium and potassium ions, what immediate effect would this have on the cell's ability to generate action potentials?
If a cell membrane suddenly became impermeable to both sodium and potassium ions, what immediate effect would this have on the cell's ability to generate action potentials?
What is the primary mechanism by which current flows across the electrode-electrolyte interface in a perfectly polarizable electrode?
What is the primary mechanism by which current flows across the electrode-electrolyte interface in a perfectly polarizable electrode?
Which characteristic defines a perfectly non-polarizable electrode?
Which characteristic defines a perfectly non-polarizable electrode?
What is the cause of the half-cell potential that arises at the electrolyte-electrode interface?
What is the cause of the half-cell potential that arises at the electrolyte-electrode interface?
Which of the following is an example of a perfectly polarizable electrode?
Which of the following is an example of a perfectly polarizable electrode?
When two electrodes of the same metal are placed in a solution, what could cause a fluctuating potential difference between them?
When two electrodes of the same metal are placed in a solution, what could cause a fluctuating potential difference between them?
In bioelectric measurements, why is the choice of electrode polarization important?
In bioelectric measurements, why is the choice of electrode polarization important?
What implications do overpotentials have on electrochemical measurements using electrodes?
What implications do overpotentials have on electrochemical measurements using electrodes?
Given the provided formulas, how would you calculate 'I' if $VLA = 5$, and $VRA = 2$?
Given the provided formulas, how would you calculate 'I' if $VLA = 5$, and $VRA = 2$?
What is the most appropriate interpretation of I, II, and III?
What is the most appropriate interpretation of I, II, and III?
If VLA increases while VRA remains constant, what happens to the value of I?
If VLA increases while VRA remains constant, what happens to the value of I?
In cardiac electrophysiology, which vector relationship best explains the calculations of I, II, and III?
In cardiac electrophysiology, which vector relationship best explains the calculations of I, II, and III?
Suppose a patient has a condition that affects the electrical activity primarily in the left ventricle. Which of the ECG leads (I, II, or III) might show the most significant changes and why?
Suppose a patient has a condition that affects the electrical activity primarily in the left ventricle. Which of the ECG leads (I, II, or III) might show the most significant changes and why?
If a malfunction occurs in the equipment such that the VRA reading is erroneously zero, how would this affect the calculated values of I, II, and III?
If a malfunction occurs in the equipment such that the VRA reading is erroneously zero, how would this affect the calculated values of I, II, and III?
Consider a scenario where the measured voltage VLL is equal to VLA. What is the resulting value of III?
Consider a scenario where the measured voltage VLL is equal to VLA. What is the resulting value of III?
Assuming standard electrode placement, what physiological event does the change in voltage measured by these leads (I,II,III) primarily reflect?
Assuming standard electrode placement, what physiological event does the change in voltage measured by these leads (I,II,III) primarily reflect?
In the equivalent circuit model of a cell membrane, what circuit element primarily represents the cell membrane's ability to store charge?
In the equivalent circuit model of a cell membrane, what circuit element primarily represents the cell membrane's ability to store charge?
Which of the following best describes the primary function of ion channels in the context of the cell membrane's equivalent circuit?
Which of the following best describes the primary function of ion channels in the context of the cell membrane's equivalent circuit?
Ion pumps move ions against their electrochemical gradients. How are these pumps represented in relation to the equivalent circuit model of a cell membrane?
Ion pumps move ions against their electrochemical gradients. How are these pumps represented in relation to the equivalent circuit model of a cell membrane?
If a cell membrane suddenly becomes more permeable to sodium ions (Na+), how would this change be represented in the equivalent circuit model?
If a cell membrane suddenly becomes more permeable to sodium ions (Na+), how would this change be represented in the equivalent circuit model?
Considering a typical cell, what is the relative concentration of potassium ions (K+) inside the cell compared to its surroundings?
Considering a typical cell, what is the relative concentration of potassium ions (K+) inside the cell compared to its surroundings?
Which of the following is the correct relationship between conductance (G) and resistance (R)?
Which of the following is the correct relationship between conductance (G) and resistance (R)?
In the context of bioelectricity, what best describes the 'electrochemical gradient' that influences ion movement across cell membranes?
In the context of bioelectricity, what best describes the 'electrochemical gradient' that influences ion movement across cell membranes?
How would increasing the surface area of a cell membrane impact its overall capacitance, assuming all other factors remain constant?
How would increasing the surface area of a cell membrane impact its overall capacitance, assuming all other factors remain constant?
In an equivalent circuit model for a cell membrane, which component primarily accounts for the membrane's ability to store charge?
In an equivalent circuit model for a cell membrane, which component primarily accounts for the membrane's ability to store charge?
What is the fundamental principle underlying Donnan equilibrium?
What is the fundamental principle underlying Donnan equilibrium?
A cell membrane is permeable to $Na^+$ and $Cl^-$, but impermeable to protein $A^-$. At equilibrium, how will the concentration of $Na^+$ relate between the inside (i) and outside (o) of the cell?
A cell membrane is permeable to $Na^+$ and $Cl^-$, but impermeable to protein $A^-$. At equilibrium, how will the concentration of $Na^+$ relate between the inside (i) and outside (o) of the cell?
Which of the following biopotential measurements would typically exhibit the smallest amplitude?
Which of the following biopotential measurements would typically exhibit the smallest amplitude?
What is the primary purpose of the electrode-skin interface in biopotential measurements?
What is the primary purpose of the electrode-skin interface in biopotential measurements?
Why is impedance matching an important consideration when acquiring biopotential signals at the electrode-skin interface?
Why is impedance matching an important consideration when acquiring biopotential signals at the electrode-skin interface?
Which of the following factors has the greatest influence on the magnitude of the biopotential signal recorded at the skin surface?
Which of the following factors has the greatest influence on the magnitude of the biopotential signal recorded at the skin surface?
Capacitive coupling at the electrode-skin interface is most effectively reduced by which of the following methods?
Capacitive coupling at the electrode-skin interface is most effectively reduced by which of the following methods?
Flashcards
Half-Cell Potential
Half-Cell Potential
Charge distribution at the interface between an electrolyte and an electrode due to ion-electron exchange.
Perfectly Polarizable Electrode
Perfectly Polarizable Electrode
An electrode where no actual charge crosses the electrode-electrolyte interface; it acts like a capacitor.
Platinum Electrode
Platinum Electrode
An example of a perfectly polarizable electrode.
Perfectly Non-Polarizable Electrode
Perfectly Non-Polarizable Electrode
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Ag/AgCl Electrode
Ag/AgCl Electrode
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Fluctuating Potential
Fluctuating Potential
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Conductance (G)
Conductance (G)
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Resistance (R)
Resistance (R)
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Capacitance (C)
Capacitance (C)
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Battery
Battery
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Cellular Ion Concentrations
Cellular Ion Concentrations
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Ion Channels
Ion Channels
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Ion Pumps
Ion Pumps
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Equivalent Circuit Model
Equivalent Circuit Model
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Cell Membrane Equivalent Circuit Model
Cell Membrane Equivalent Circuit Model
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Donnan Equilibrium
Donnan Equilibrium
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Space Charge Neutrality
Space Charge Neutrality
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Law of Conservation of Mass
Law of Conservation of Mass
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Donnan Equilibrium Problem (K+, Cl-, R+)
Donnan Equilibrium Problem (K+, Cl-, R+)
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Biopotential Measurements
Biopotential Measurements
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Typical Biopotential Range
Typical Biopotential Range
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Signal Acquisition Methods
Signal Acquisition Methods
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Einthoven's Lead I
Einthoven's Lead I
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Einthoven's Lead II
Einthoven's Lead II
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Einthoven's Lead III
Einthoven's Lead III
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Electrocardiogram (ECG)
Electrocardiogram (ECG)
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ECG Electrodes
ECG Electrodes
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Electrode Placement
Electrode Placement
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Cardiac Electrophysiology
Cardiac Electrophysiology
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Right Arm, Left Arm, Left Leg
Right Arm, Left Arm, Left Leg
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What is an EEG?
What is an EEG?
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EEG application?
EEG application?
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Alpha Waves State
Alpha Waves State
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Beta Waves occur when?
Beta Waves occur when?
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Theta Waves State
Theta Waves State
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Delta Waves State
Delta Waves State
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Average Reference Signal
Average Reference Signal
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Electrical Stimulation of CNS
Electrical Stimulation of CNS
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Bioelectricity
Bioelectricity
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Cell Membrane
Cell Membrane
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Membrane Elements
Membrane Elements
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Action Potential
Action Potential
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Membrane Permeability
Membrane Permeability
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Resting State (Polarized)
Resting State (Polarized)
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Depolarization
Depolarization
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Repolarization
Repolarization
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Study Notes
- Bioelectricity originates from voltage differences between the inside and outside of cells
- Potentials arise from the cell membrane, which separates intracellular and extracellular volumes
- Membranes are the site of electrically active elements like pumps, channels, and connexons, which create voltages and currents for electrical events
Neuron Structure
- Neurons consist of dendrites, soma, axon, myelin sheath, and nerve endings for neurotransmission
Action Potentials
- Membranes generate action potentials by changing permeability to ions like sodium and potassium
- Permeability changes from resting to excited (polarized to depolarized) and back creates action potentials
- Action potential is characterized by depolarization, overshoot beyond 0 mV, and repolarization
- Some cells may hyperpolarize before returning to the resting potential
- Action potential initiation has a threshold behavior, where stimuli above a threshold initiate action potentials ("all or none")
- Threshold value varies depending on the stimulus, electrode location, tissue excitation, stimulus duration, and membrane
Electrical Circuit Elements
- Conductance (G)
- Resistance (R)
- Capacitance (C)
- Battery
- Most cells maintain a low internal sodium (Na+) and a high internal potassium (K+) concentration while external concentrations are reversed
Ion Channels
- Sodium and potassium channels allow ions to follow their electrochemical gradients
- Ion pumps move ions against their respective electrochemical gradients
- The cell membrane capacitance is represented by a capacitor (Cm)
- Ionic currents are combined into a nonlinear element, which regulates current/ion flow
Donnan Equilibrium
- Donnan Equilibrium in a defined space: [K+]o/[K+]i = [Cl-]i/[Cl-]0
- Space Charge Neutrality: Sum of all charges in a defined space is zero
- Law of Conservation of Mass
Biopotential Measurements
- Measurement of electric potentials at the body surface indicates physiological phenomena like neural or cardiac conduction (typically ranging between 1 µV and 100 mV)
- Signal acquisition at the Electrode – Skin Interface may occur via Impedance or Capacitance Coupling
- Charge distribution occurs due to ion-electron exchange at the interface
- This gives rise to half cell potential
Types of Electrodes
- Perfectly Polarizable Electrodes: No actual charge crosses the electrode-electrolyte interface when current is applied, and behaves like a capacitor
- Example Perfectly Polarizable Electrodes: Platinum Electrode (Noble metal)
- Perfectly Non-Polarizable Electrode: Current passes freely across the electrode-electrolyte interface, requiring no energy to make the transition, and sees no overpotentials
- Example Perfectly Non-Polarizable Electrode: Ag/AgCl electrode
Electrode Impedance
- The electrode-electrolyte interface has an impedance (Ze) which depends on the nature of the charge layer
- The Warburg model represents the electrode-electrolyte interface with Warburg resistance (Rw) and capacitance (Cw)
- Fields generated by activity in excitable tissues spread through the body's aqueous environment to the skin surface
- Electrodes placed on the skin can detect these potentials via an electrolyte like sweat or an electrolyte solution applied between the electrode and skin
Recording Biopotentials
- High skin impedance can cause poor biopotential signal detection
- Relative movement between the electrode and the skin produces an artifact called motion artifact
- Electrocardiogram (ECG) records the electrical activity of the heart on the body surface
- ECG waveform recordings involve differential measurements between two points on the body, traditionally referred to as leads (I, II, and III)
- Where, I = VLA- VRA, II = VLL - VRA, III = VLL-VLA , and RA = right arm, LA = left arm, LL = left leg
Cardiac Electrophysiology
- Cardiac Electrophysiology involves atrial depolarization, ventricular depolarization, and ventricular repolarization
Electroencephalography
- EEG records the brain's electrical activity on the head scalp surface, where pyramidal neurons act as electrical dipoles
- Applications of EEG include the diagnosis of Epileptic Seizures
Brain Waves
- Alpha Waves (8-13 Hz): Resting and relaxed adults with closed eyes
- Beta Waves (13-30 Hz): Alert and awake Adults
- Theta Waves (4-8 Hz): During sleep and in children; abnormal in awake adults
- Delta Waves (< 4 Hz): Normal in deep sleep & young babies
Electrical Stimulation of the Central Nervous System
- Electrical Stimulation of the Central Nervous System involves post-injury and conditioning techniques
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Description
Bioelectricity arises from voltage differences across cell membranes. Action potentials are generated by changes in membrane permeability to ions, leading to depolarization, overshoot, and repolarization. Stimuli above a threshold initiate action potentials in an 'all or none' manner.
