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Questions and Answers
What is the membrane potential reached during the peak of an action potential?
What is the membrane potential reached during the peak of an action potential?
What primarily causes the rapid influx of Na+ during an action potential?
What primarily causes the rapid influx of Na+ during an action potential?
What happens to the membrane potential after K+ channels open at +30 mV?
What happens to the membrane potential after K+ channels open at +30 mV?
During the action potential, when do Na+ channels close?
During the action potential, when do Na+ channels close?
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What role does the Na+/K+ pump play in the action potential process?
What role does the Na+/K+ pump play in the action potential process?
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What initiates the opening of the voltage-gated Ca2+ channel?
What initiates the opening of the voltage-gated Ca2+ channel?
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Which of the following accurately describes the relationship between stimulus size and neurotransmitter release?
Which of the following accurately describes the relationship between stimulus size and neurotransmitter release?
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What happens if the threshold of -55 mV is not reached at the axon hillock?
What happens if the threshold of -55 mV is not reached at the axon hillock?
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What role does Ca2+ play once it enters the cell?
What role does Ca2+ play once it enters the cell?
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What type of receptors bind neurotransmitters on the post-synaptic cell?
What type of receptors bind neurotransmitters on the post-synaptic cell?
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How does the influx of Na+ affect the membrane potential?
How does the influx of Na+ affect the membrane potential?
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What occurs immediately following the arrival of an action potential at a nerve terminal?
What occurs immediately following the arrival of an action potential at a nerve terminal?
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What is the role of graded potentials in sensory cells?
What is the role of graded potentials in sensory cells?
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What effect does achieving the threshold of -55 mV have on action potentials?
What effect does achieving the threshold of -55 mV have on action potentials?
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What does the rapid influx of Ca2+ cause inside the cell?
What does the rapid influx of Ca2+ cause inside the cell?
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What is the primary function of sensory cell types in sensory systems?
What is the primary function of sensory cell types in sensory systems?
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How do graded potentials in sensory cells affect membrane potential?
How do graded potentials in sensory cells affect membrane potential?
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What is the main method by which neurotransmitters travel from pre-synaptic to post-synaptic cells?
What is the main method by which neurotransmitters travel from pre-synaptic to post-synaptic cells?
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What speed can action potentials travel in axons?
What speed can action potentials travel in axons?
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Which of the following is NOT a role of ion channels in nerve impulse transmission?
Which of the following is NOT a role of ion channels in nerve impulse transmission?
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What occurs in the cell body of a nerve cell in relation to sensory input?
What occurs in the cell body of a nerve cell in relation to sensory input?
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What role do muscle stretch receptors serve in the nervous system?
What role do muscle stretch receptors serve in the nervous system?
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Which statement accurately describes the flow of information in a synapse?
Which statement accurately describes the flow of information in a synapse?
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What is the primary consequence of ligand binding to the ligand-gated Na+ channel?
What is the primary consequence of ligand binding to the ligand-gated Na+ channel?
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What is generated as a result of the rapid Na+ influx into sensory cells?
What is generated as a result of the rapid Na+ influx into sensory cells?
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Which ion's movement primarily affects the membrane potential when the ligand-gated channel opens?
Which ion's movement primarily affects the membrane potential when the ligand-gated channel opens?
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What does an increase in membrane potential indicate after Na+ rushes into the cell?
What does an increase in membrane potential indicate after Na+ rushes into the cell?
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In what phase of activation do gated Na+ channels get stimulated?
In what phase of activation do gated Na+ channels get stimulated?
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What role does the ligand play in the function of the ligand-gated Na+ channel?
What role does the ligand play in the function of the ligand-gated Na+ channel?
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What type of potential is primarily associated with the activation of gated Na+ channels?
What type of potential is primarily associated with the activation of gated Na+ channels?
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Which of the following correctly describes the condition inside the cell before Na+ influx?
Which of the following correctly describes the condition inside the cell before Na+ influx?
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What happens to the intracellular Ca2+ levels during the activation of gated Na+ channels?
What happens to the intracellular Ca2+ levels during the activation of gated Na+ channels?
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When the ligand-gated Na+ channels open, how does this affect the overall ionic gradients?
When the ligand-gated Na+ channels open, how does this affect the overall ionic gradients?
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How does the resting membrane potential of a neuron typically behave?
How does the resting membrane potential of a neuron typically behave?
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What characterizes the medium frequency of action potentials based on the given content?
What characterizes the medium frequency of action potentials based on the given content?
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Which of the following best describes action potentials?
Which of the following best describes action potentials?
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What is the effect of low-frequency action potentials on neurotransmitter action?
What is the effect of low-frequency action potentials on neurotransmitter action?
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What is one role of neuroglia in relation to action potentials?
What is one role of neuroglia in relation to action potentials?
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Which statement about synaptic transmission is true according to the content?
Which statement about synaptic transmission is true according to the content?
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What is the consequence of high-frequency action potentials in the context of neurotransmitter action?
What is the consequence of high-frequency action potentials in the context of neurotransmitter action?
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In terms of graded potentials, what is their primary role in the nerve cell body?
In terms of graded potentials, what is their primary role in the nerve cell body?
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What does the time taken for ion diffusion to achieve equilibrium indicate about nerve cells?
What does the time taken for ion diffusion to achieve equilibrium indicate about nerve cells?
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Why is the propagation of action potentials in one direction important?
Why is the propagation of action potentials in one direction important?
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Study Notes
Nervous System
- Sensory cells convert a stimulus into a neurotransmitter release
- The nervous system has three types of neurons: Sensory, Inter, and Motor neurons.
- Sensory cells generate graded potentials, which are small changes in membrane potential that only travel short distances.
- Sensory cells release neurotransmitters when activated.
Nerve Impulse Transmission
- In nerve impulse transmission, the role of ion channels is crucial. They facilitate rapid changes in membrane potential, allowing for quick information transfer.
- Graded potentials are generated in the cell body of nerve cells.
- Axons are responsible for transmitting nerve impulses over long distances, traveling at speeds up to 100 meters per second.
- Synapses are specialized junctions where nerve impulses are transmitted from one neuron to another. They allow for extremely quick information transfer, involving the release and diffusion of neurotransmitters.
- Neurotransmitters (NTs) are released from the presynaptic cell and bind to receptors on the postsynaptic cell, causing a change in membrane potential.
Action Potentials
- Action potentials are short, identical electrical changes that occur in individual parts of a neuron.
- The frequency of action potentials is determined by the intensity of the stimulus.
- Action potentials propagate rapidly along the axon due to the opening and closing of voltage-gated sodium (Na+) and potassium (K+) channels.
- The opening of voltage-gated Na+ channels causes a rapid influx of Na+ ions into the cell, leading to depolarization (a more positive membrane potential).
- As the membrane potential rises, voltage-gated K+ channels open, allowing K+ ions to flow out of the cell, leading to repolarization.
- The membrane potential then returns to its resting state, and the cycle repeats.
Nervous System: Overview
- The nervous system plays a crucial role in decision-making and controlling various bodily functions, including muscle function, the gastrointestinal tract (GIT), and other processes.
- The nervous system senses both external and internal environments.
Diffusion
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Diffusion is the movement of molecules from an area of high concentration to an area of low concentration.
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Diffusion times for ions to reach 99% equilibrium can vary significantly based on distance, with longer distances requiring much longer times. With this in mind, the nervous system is unable to rely solely on diffusion for long-distance signaling.### Action Potential
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Sodium ions (Na+) influx into the cell is rapid because the sodium gradient is large as well as the electrical gradient.
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Sodium channels close when the membrane potential reaches +30 mV
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Potassium channels open at +30 mV
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Potassium ions (K+) efflux out of the cell is rapid due to the potassium gradient and the electrical gradient
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The sodium-potassium pump resets the resting membrane potential to -70mV
Nerve Cells
- The action potential originates from the initial segment of the axon and propagates down the axon towards the terminals
- Action potentials propagate in one direction because of the refractory period
- Insulated axons allow action potentials to propagate faster than un-insulated axons
- Myelin sheaths are formed by neuroglia cells
- Specialized sensory cells respond to specific stimuli which are converted into action potentials.
Synaptic Transmission
- Synapses are junctions between neurons which allow communication using neurotransmitters
- Synapses regulate neuronal circuits
Local Anaesthetics & Neurotoxins
- Local anaesthetics block sodium channels and prevent the conduction of action potentials.
- Neurotoxins interfere with synaptic transmission, preventing neurotransmitter release or binding.
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