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Questions and Answers
What structure of a neuron is primarily responsible for receiving impulses?
What structure of a neuron is primarily responsible for receiving impulses?
What is a key characteristic that distinguishes myelinated nerves from unmyelinated nerves?
What is a key characteristic that distinguishes myelinated nerves from unmyelinated nerves?
Which property of nerves allows them to respond to various stimuli?
Which property of nerves allows them to respond to various stimuli?
Which statement accurately represents the 'All or none law' in nerve physiology?
Which statement accurately represents the 'All or none law' in nerve physiology?
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What term describes the potential difference across the membranes of excitable tissues during rest?
What term describes the potential difference across the membranes of excitable tissues during rest?
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Which factor does NOT affect nerve impulse conduction?
Which factor does NOT affect nerve impulse conduction?
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Adaptation in nerve physiology refers to which of the following?
Adaptation in nerve physiology refers to which of the following?
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What is meant by 'potential difference' in the context of nerve physiology?
What is meant by 'potential difference' in the context of nerve physiology?
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What is the typical resting membrane potential (RMP) value for nerve fibers?
What is the typical resting membrane potential (RMP) value for nerve fibers?
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Which ion has a higher permeability across the membrane at rest?
Which ion has a higher permeability across the membrane at rest?
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Which of the following processes primarily contributes to maintaining the resting membrane potential?
Which of the following processes primarily contributes to maintaining the resting membrane potential?
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What is the effect of depolarization on membrane potential?
What is the effect of depolarization on membrane potential?
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During hyperpolarization, what happens to the membrane potential?
During hyperpolarization, what happens to the membrane potential?
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Which ion distribution is characteristic of a typical nerve cell at rest?
Which ion distribution is characteristic of a typical nerve cell at rest?
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What causes the inside of a nerve cell to be relatively negative compared to the outside at rest?
What causes the inside of a nerve cell to be relatively negative compared to the outside at rest?
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How does the Na+/K+-ATPase pump function in maintaining resting membrane potential?
How does the Na+/K+-ATPase pump function in maintaining resting membrane potential?
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What is the threshold stimulus in the context of action potentials?
What is the threshold stimulus in the context of action potentials?
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During depolarization, which ions primarily rush into the cell?
During depolarization, which ions primarily rush into the cell?
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What occurs during the repolarization phase of an action potential?
What occurs during the repolarization phase of an action potential?
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What is hyperpolarization in the context of action potential?
What is hyperpolarization in the context of action potential?
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Which of the following describes the absolute refractory period?
Which of the following describes the absolute refractory period?
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Which mechanism helps return the membrane potential to the resting state after action potential?
Which mechanism helps return the membrane potential to the resting state after action potential?
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In which phase does the membrane potential change dramatically from -70mV to +35mV?
In which phase does the membrane potential change dramatically from -70mV to +35mV?
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What effect does the delayed opening of voltage-gated potassium channels have during hyperpolarization?
What effect does the delayed opening of voltage-gated potassium channels have during hyperpolarization?
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What is one primary mechanism for the removal of acetylcholine from the synaptic space?
What is one primary mechanism for the removal of acetylcholine from the synaptic space?
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What characteristic of neuromuscular transmission is described as involving a 0.5 msec delay?
What characteristic of neuromuscular transmission is described as involving a 0.5 msec delay?
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What effect does calcium influx have on neuromuscular transmission?
What effect does calcium influx have on neuromuscular transmission?
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Which drug is specifically known to antagonize the action of acetylcholine at the neuromuscular junction?
Which drug is specifically known to antagonize the action of acetylcholine at the neuromuscular junction?
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How does myasthenia gravis primarily affect the neuromuscular junction?
How does myasthenia gravis primarily affect the neuromuscular junction?
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What is an irreversible outcome of organophosphate exposure?
What is an irreversible outcome of organophosphate exposure?
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What condition can result in paralysis of respiratory muscles in its severe form?
What condition can result in paralysis of respiratory muscles in its severe form?
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What does the depletion of acetylcholine vesicles result in during neuromuscular transmission?
What does the depletion of acetylcholine vesicles result in during neuromuscular transmission?
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What is the primary characteristic of local potentials in terms of their signaling function?
What is the primary characteristic of local potentials in terms of their signaling function?
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What happens to the magnitude of a local potential when a stronger stimulus is applied?
What happens to the magnitude of a local potential when a stronger stimulus is applied?
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Which type of conduction occurs in myelinated nerves?
Which type of conduction occurs in myelinated nerves?
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How are local potentials characterized in terms of spatial propagation?
How are local potentials characterized in terms of spatial propagation?
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What is the nature of the response of local potentials to repeated stimuli?
What is the nature of the response of local potentials to repeated stimuli?
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What describes the conduction speed in unmyelinated nerves compared to myelinated nerves?
What describes the conduction speed in unmyelinated nerves compared to myelinated nerves?
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What directly affects the duration of acetylcholine's action in the synaptic space?
What directly affects the duration of acetylcholine's action in the synaptic space?
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Which statement about non-voltage gated channels is true in relation to local potentials?
Which statement about non-voltage gated channels is true in relation to local potentials?
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Study Notes
Nerve Physiology
- Nerve physiology is the study of how nerves function.
Structure of the Neuron
- Neurons consist of three main parts:
- Soma: The main cell body.
- Axon: A single, long projection extending from the soma. It transmits nerve impulses away from the soma.
- Dendrites: Branching projections from the soma. They receive impulses and conduct them toward the cell body.
Types of Nerve Axons
- Axons can be myelinated or unmyelinated:
- Myelinated axons: The axon is wrapped with myelin, a protein-lipid complex. Myelin sheaths interrupt at the Nodes of Ranvier. This type of nerve conduction is Faster and More Economical in energy consumption.
- Unmyelinated axons: The axon lacks myelin sheaths, and conduction is Slower and requires High energy consumption.
Properties of Nerves
- Excitability: The nerve's ability to respond to various stimuli.
- A stimulus is any change in the internal or external environment that causes a reaction. (Chemical, Electrical, Mechanical, and Thermal).
- Conductivity: The nerve impulse's rapid transmission along the nerve fiber.
- All or None Law: A minimal stimulus (threshold) is needed to excite a nerve. This stimulus produces a maximal action potential.
- Adaptability: The nerve quickly adapts to the stimulating current.
- Fatigue Resistance: Nerves resist fatigue due to repeated stimulations.
Basic Principles of Electricity
- Potential Difference: The difference in charge between two points.
- Membrane Potential: The difference in charge on both sides of the nerve membrane.
- Resting Membrane Potential (RMP): The potential difference across excitable membranes (nerve/muscle) at rest. Nerve fibers: -70mV; Skeletal and cardiac muscle fibers: -90mV.
Distribution of Major Mobile Ions Across the Plasma Membrane
- Differences exist in the composition of extracellular and intracellular fluids.
- The inside of the cell membrane is relatively negative compared to the outside during rest.
Resting Membrane Potential (RMP)
- RMP is the potential difference between the inner and outer surfaces of excitable tissue membranes at rest.
- Nerve Fibers: ~-70 mV
- Skeletal and cardiac muscle fibers: ~-90 mV
Causes of Unequal Ion Distribution
- Selective membrane permeability: Potassium (K+) ions pass through the membrane more easily than Sodium (Na+) ions; this is vital to maintain the negative internal environment of the cell.
- Active transport via the Na+/K+ pump: This pump actively transports 3 Sodium ions out of the cell and 2 Potassium ions into the cell, contributing to the maintenance of the resting membrane potential.
Action Potentials
- Transient changes in membrane potential that occur in response to a threshold stimulus.
- Phases of Action Potential:
- Depolarization: The membrane potential becomes less negative, and eventually positive. This results from the opening of voltage-gated sodium channels and rapid influx of sodium ions.
- Repolarization: The membrane potential returns to a more negative value. This results from the closing of voltage-gated sodium channels and the opening of voltage-gated potassium channels, allowing potassium ions to move out of the cell.
- Hyperpolarization: The membrane potential temporarily becomes more negative than the resting membrane potential. This occurs as the potassium channels remain open for a brief time after the membrane reaches the resting potential.
- Return to RMP: The membrane potential eventually returns to its resting state as the potassium channels close and the Na+/K+ pump restores the ion concentration gradients.
Types of Membrane Potentials
- Polarized state (RMP): A state of rest where the inside of the membrane is relatively more negative than the outside.
- Depolarized state (depolarization): Reduction in membrane potential negativity, sometimes reversing the polarity and becoming positive.
- Hyperpolarized state (hyperpolarization): An increase in membrane potential negativity, where the inside of the membrane becomes more negative than the value of the RMP.
Excitability changes during Action Potential
- Absolute Refractory Period: A period of time where the nerve is unresponsive to stimulation. It corresponds to the ascending limb of the action potential and the initial portion of the descending limb.
- Relative Refractory Period: A period of time in which the nerve is excitable, with a stronger stimulus needed for excitation. This period of partial recovery corresponds to the remaining portion of the action potential's descending limb.
Local Potentials (Graded Potentials)
- Subthreshold stimulation of excitable nerve or muscle membrane that produce a graded response proportionate to the strength of the stimulus. These potentials decay with distance.
- Important in short-distance signaling. localized stimuli.
Nerve Conduction
- Initiates at the axon hillock and travels along the axon.
- Two types of conduction: point-to-point and saltatory.
- Saltatory conduction in myelinated axons is faster and more energy efficient.
Neuro-Muscular Transmission
- Neurotransmitter Release: Acetylcholine is released into the synaptic cleft.
- Destruction of Acetylcholine: Enzyme Acetylcholinesterase breaks it down, ending the stimulation.
Myasthenia Gravis
- Autoimmune neuromuscular junction disease.
- Antibodies block or destroy acetylcholine receptors, leading to muscle weakness and paralysis.
- Treatment involves medications to increase acetylcholine levels.
Drugs That Influence Neurotransmission
- Drugs that enhance or block neuromuscular transmission can affect the process.
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Description
Test your knowledge on nerve physiology concepts, including neuron structure, impulse conduction, and resting membrane potential. This quiz covers key characteristics and principles that define nerve function. Perfect for students studying biology or neuroscience!
