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Questions and Answers
What is the primary structural and functional unit of nerve tissue?
What is the primary structural and functional unit of nerve tissue?
- Dendrite
- Muscle fiber
- Myelin sheath
- Neuron (correct)
Which part of the neuron is primarily responsible for receiving signals?
Which part of the neuron is primarily responsible for receiving signals?
- Axon hillock
- Dendrite (correct)
- Soma
- Axon terminal
What is the resting potential of a cell typically measured as?
What is the resting potential of a cell typically measured as?
- Zero volts
- Negative value (correct)
- Positive value
- Constant voltage
What happens to sodium ions when a neuron is excited?
What happens to sodium ions when a neuron is excited?
What characteristic does a cell have when it is in its resting state?
What characteristic does a cell have when it is in its resting state?
What is the range of typical membrane potentials measured in various cells?
What is the range of typical membrane potentials measured in various cells?
Which ion is primarily responsible for making the outside of the cell more positive when they flow across the membrane?
Which ion is primarily responsible for making the outside of the cell more positive when they flow across the membrane?
What structure maintains the resting potential of the cell?
What structure maintains the resting potential of the cell?
Why are physiological variables represented by statistical distributions rather than deterministic values?
Why are physiological variables represented by statistical distributions rather than deterministic values?
What is a major consequence of the variability in physiological measurements?
What is a major consequence of the variability in physiological measurements?
What challenges does interaction among physiological systems pose?
What challenges does interaction among physiological systems pose?
What role does a transducer play in physiological measurements?
What role does a transducer play in physiological measurements?
How does knowledge of physiological interrelationships benefit measurement practices?
How does knowledge of physiological interrelationships benefit measurement practices?
Which statement regarding feedback loops in physiological systems is true?
Which statement regarding feedback loops in physiological systems is true?
What effect does the design of a transducer have on dynamic measurements?
What effect does the design of a transducer have on dynamic measurements?
Why is a complete understanding of physiological interactions critical for clinicians and engineers?
Why is a complete understanding of physiological interactions critical for clinicians and engineers?
What is the typical duration of an action potential in nerve and muscle cells?
What is the typical duration of an action potential in nerve and muscle cells?
What is the absolute refractory period in nerve cells approximately?
What is the absolute refractory period in nerve cells approximately?
Which law states that an action potential is always the same for any given cell?
Which law states that an action potential is always the same for any given cell?
How long does the action potential usually last in heart muscle cells?
How long does the action potential usually last in heart muscle cells?
What prevents an action potential from re-exciting the portion of the fiber immediately upstream?
What prevents an action potential from re-exciting the portion of the fiber immediately upstream?
What is defined as the net height of the action potential?
What is defined as the net height of the action potential?
What happens during the relative refractory period?
What happens during the relative refractory period?
What is the term for the rate at which an action potential is propagated down a fiber?
What is the term for the rate at which an action potential is propagated down a fiber?
What is the process called when a cell changes from its resting state to an action potential?
What is the process called when a cell changes from its resting state to an action potential?
What is the approximate membrane potential during an action potential?
What is the approximate membrane potential during an action potential?
Which ions are primarily responsible for depolarizing the cell?
Which ions are primarily responsible for depolarizing the cell?
What mechanism quickly restores the original resting potential of a cell after an action potential?
What mechanism quickly restores the original resting potential of a cell after an action potential?
Which statement best describes the balance of potassium ions during depolarization?
Which statement best describes the balance of potassium ions during depolarization?
What occurs immediately after the rush of sodium ions into a cell stops?
What occurs immediately after the rush of sodium ions into a cell stops?
What facilitates the sodium pump's operation according to common belief?
What facilitates the sodium pump's operation according to common belief?
What is the primary reason for a cell's slight positive potential during the resting state?
What is the primary reason for a cell's slight positive potential during the resting state?
What is the typical range of nerve conduction velocities in meters per second?
What is the typical range of nerve conduction velocities in meters per second?
Which type of fibers in the heart have the slowest conduction rate?
Which type of fibers in the heart have the slowest conduction rate?
What does an action potential represent in nerve fibers?
What does an action potential represent in nerve fibers?
What processes occur during an action potential?
What processes occur during an action potential?
What is the average conduction velocity of heart muscle?
What is the average conduction velocity of heart muscle?
What typically occurs as an action potential propagates through a nerve?
What typically occurs as an action potential propagates through a nerve?
What represents the speed of nerve conduction in relation to nerve fiber diameter?
What represents the speed of nerve conduction in relation to nerve fiber diameter?
What is a microelectrode typically used for?
What is a microelectrode typically used for?
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Study Notes
Physiological Variability and Measurements
- Physiological variables are inherently variable and should be modeled using statistical distributions rather than deterministic values.
- Measurements taken at different times under the same conditions can lead to different results due to natural variability.
- Variability is even more pronounced among different subjects, necessitating the use of statistical methods to analyze relationships among physiological variables.
- A better understanding of interrelationships within the body could improve the interpretation of physiological measurements and facilitate indirect measurement techniques.
Interaction Among Physiological Systems
- Major physiological systems are interconnected through numerous feedback loops, causing interactions within and between those systems.
- Stimulation of one part of a system may lead to unpredictable effects on other parts and other systems.
- Cause-and-effect relationships are often unclear due to these interactions and feedback mechanisms.
- Inactive organs can sometimes be compensated for by other organs taking over their functions.
Transducer Effects on Measurements
- Measurements can be significantly altered by the presence of transducers, especially in living systems.
- For instance, inserting a large flow transducer into a blood vessel can obstruct flow and change pressure-flow dynamics.
Neurons Structure and Function
- Neurons are the primary units of nerve tissue, comprising dendrites, axons, and synaptic terminals.
- They can vary in size from 4 μm to 130 μm.
- The neuron structure includes the soma (cell body), axon hillock, node of Ranvier, and myelin sheath.
Resting and Action Potentials
- Resting potential is achieved when there is an imbalance of sodium and potassium ions, typically measured at -60 to -100 mV in various cells.
- During depolarization, sodium ions rush into the cell, leading to a temporary positive internal charge (approximately +20 mV) called action potential.
- Action potential is an all-or-nothing response, remaining consistent regardless of stimulus intensity.
Ionic Movements and Refractory Periods
- Action potentials propagate via ionic currents following depolarization, allowing neighboring cells to become excited.
- The refractory period consists of two phases:
- Absolute refractory period (about 1 msec) where no new stimuli can elicit action potentials.
- Relative refractory period lasts several milliseconds, requiring stronger stimuli for eliciting another action potential.
Propagation of Action Potentials
- In nerve cells, action potentials propagate without re-exciting previously activated areas due to the refractory period.
- The rate of propagation, known as conduction velocity, varies by nerve fiber type and size, typically ranging from 20 to 140 m/sec in nerves.
- Heart muscle propagation is slower, averaging 0.2 to 0.4 m/sec, with special fibers transmitting signals even slower (0.03 to 0.05 m/sec).
Summary of Action Potentials
- Action potentials reflect rapid changes in membrane potential characterized by initial depolarization followed by repolarization.
- Action potentials, also referred to as impulses, are crucial for neural communication and muscle contraction.
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