Podcast
Questions and Answers
What is an action potential?
What is an action potential?
- The process of a cell dividing
- A single electrical change in a cell
- The constant electrical state of a nerve cell
- A series of electrical changes that occur in the membrane potential of excitable cells (correct)
Action potentials only occur in muscle cells.
Action potentials only occur in muscle cells.
False (B)
Name the two main phases that occur during an action potential.
Name the two main phases that occur during an action potential.
Depolarization and repolarization
The initial phase of an action potential, where the inside of the cell becomes more positive, is called ______.
The initial phase of an action potential, where the inside of the cell becomes more positive, is called ______.
What characterizes the repolarization phase of an action potential?
What characterizes the repolarization phase of an action potential?
Resting potential is typically a positive value.
Resting potential is typically a positive value.
If a cell's resting membrane potential is -70 mV, what does this indicate about the cell's charge?
If a cell's resting membrane potential is -70 mV, what does this indicate about the cell's charge?
What happens to the charge inside and outside of a muscle cell during depolarization?
What happens to the charge inside and outside of a muscle cell during depolarization?
Repolarization is the process where the potential in muscle cells ______ to its resting state.
Repolarization is the process where the potential in muscle cells ______ to its resting state.
Which phase of the action potential occurs first?
Which phase of the action potential occurs first?
Repolarization is a slower and longer process compared to depolarization.
Repolarization is a slower and longer process compared to depolarization.
What is the approximate value of the resting potential in millivolts (mV)?
What is the approximate value of the resting potential in millivolts (mV)?
After repolarization the membrane potential briefly returns to its ______ potential.
After repolarization the membrane potential briefly returns to its ______ potential.
Match the phase of action potential with its correct description.
Match the phase of action potential with its correct description.
Why is it important for nerve and muscle cells to have a resting potential?
Why is it important for nerve and muscle cells to have a resting potential?
Depolarization always leads to an action potential.
Depolarization always leads to an action potential.
If a stimulus causes a nerve cell to become more negative than its resting potential, what is this called?
If a stimulus causes a nerve cell to become more negative than its resting potential, what is this called?
In what type of cell is action potential observed?
In what type of cell is action potential observed?
The resting membrane potential is ______ mV.
The resting membrane potential is ______ mV.
Match the term to its correct definition.
Match the term to its correct definition.
Flashcards
What is action potential?
What is action potential?
A series of electrical changes that occur in the membrane potential when a muscle or nerve is stimulated.
Depolarization
Depolarization
The initial phase of action potential where the inside of muscles or potential becomes positive and the outside becomes negative.
Repolarization
Repolarization
The second phase of action potential in which muscles reverse the resting membrane potential.
Resting Potential
Resting Potential
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Study Notes
- Vibrations are oscillations around an equilibrium point in mechanical or structural systems.
Negative Effects of Vibration
- Vibration can cause wear and energy loss in machines.
- Vibration leads to passenger discomfort and safety risks in vehicles.
- Vibration leads to catastrophic failure in structures.
Positive Effects of Vibration
- Vibration has uses in vibratory conveyors for material transport.
- Vibration has uses in vibratory compactors for concrete, soil, and grains.
- Vibration testing machines use vibration for material, component, and structure analysis.
- Vibration is essential in musical instruments and human speech.
Periodic Motion
- Periodic motion is motion that repeats at consistent time intervals.
Cycle
- A cycle represents the motion occurring during one interval in periodic motion.
Period (τ)
- Period (τ) is the duration required for one complete cycle of motion in a vibrating system.
Frequency (f)
- Frequency (f) is the number of cycles that occur per unit of time, and it is the inverse of the period (f = 1/τ).
Amplitude
- Amplitude is the maximum displacement from the equilibrium position during vibration.
Harmonic Motion
- Harmonic motion is the simplest form of periodic motion, described by: x = A sin(ωt)
- x represents displacement at time t.
- A represents the amplitude.
- ω is the angular frequency in rad/sec.
Underdamped System
- An underdamped system indicates oscillation with diminishing amplitude as time progress.
Critically Damped System
- A critically damped system achieves equilibrium quickly without oscillation
Overdamped System
- An overdamped system returns slowly to equilibrium without oscillating
Undamped Free Vibration
- Consider a mass m attached to a spring with stiffness k.
- When displaced and released, the mass oscillates at its natural frequency (ωn).
- Natural frequency is given by: ωn = √(k/m)
- The equation of motion: mẍ + kx = 0
- ẍ is the acceleration of the mass.
- The general solution: x(t) = A sin(ωn t) + B cos(ωn t)
- A and B depend on initial conditions.
Damped Free Vibration
- Consider mass m, spring stiffness k, and damper c.
- The equation of motion is: mẍ + cẋ + kx = 0
- ẋ is the velocity of the mass.
- Damping ratio (ζ) defines damping: ζ = c/cc = c/(2√(mk))
- cc is the critical damping coefficient.
Undamped Harmonically Excited Vibration
- The equation of motion is: mẍ + kx = F₀ sin(ωt)
- Assume a solution: x(t) = A sin(ωt)
- Substitute to find amplitude: A = F₀ / (k - mω²) = (F₀/k) / (1 - (ω/ωn)²)
- Where: ωn = √(k/m)
- Define static displacement: xst = F₀/k
- Resulting equation: A = xst / (1 - (ω/ωn)²)
- (1 / (1 - (ω/ωn)²)) is the magnification factor.
- Resonance occurs when ω = ωn, leading to infinite amplitude.
- Resonance makes system sensitive even to small forces.
Damped Harmonically Excited Vibration
- Equation of motion: mẍ + cẋ + kx = F₀ sin(ωt)
- Assume: x(t) = A sin(ωt - φ)
- Amplitude: A = xst / √((1 - r²)² + (2ζr)²)
- Where: r = ω/ωn
- Phase Angle: φ = tan⁻¹(2ζr / (1 - r²))
Vibration Isolation
- Vibration isolation reduces the transmitted vibration from a source to a receiver.
- Achieved with vibration isolators to reduce vibration transmission.
- Vibration isolators use flexible materials with high damping.
Transmissibility Ratio
- Tr = FT/F0
- FT: Force transmitted to foundation.
- F0: Excitation force.
- Transmissibility ratio measures vibration isolator effectiveness.
- A ratio of 1 indicates no isolation.
- A ratio of 0 shows perfect isolation.
- $T_r = \frac{\sqrt{1 + (2\zeta r)^2}}{\sqrt{(1 - r^2)^2 + (2\zeta r)^2}}$
- Where: r = ω/ωn
- Effective isolation occurs when r > √2.
- Damping reduces transmissibility at resonance, increases it at high frequencies.
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