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Questions and Answers
What is the resting membrane potential (RMP) typically in mammalian neurons?
What is the resting membrane potential (RMP) typically in mammalian neurons?
What is the resting membrane potential (RMP) primarily a measure of?
What is the resting membrane potential (RMP) primarily a measure of?
Which ions are primarily moved by the Na+/K+ pump and in what ratio?
Which ions are primarily moved by the Na+/K+ pump and in what ratio?
What occurs during depolarization?
What occurs during depolarization?
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What is a characteristic feature of graded potentials (GP)?
What is a characteristic feature of graded potentials (GP)?
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Which statement best describes the ionic mechanisms of action potential?
Which statement best describes the ionic mechanisms of action potential?
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What type of electrical signal serves as a long-distance signaling mechanism in neurons?
What type of electrical signal serves as a long-distance signaling mechanism in neurons?
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What is the primary characteristic of the threshold potential?
What is the primary characteristic of the threshold potential?
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What is a key feature of synaptic transmission?
What is a key feature of synaptic transmission?
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Which type of potential can be either excitatory or inhibitory?
Which type of potential can be either excitatory or inhibitory?
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During which phase does the membrane potential become more negative than the resting state?
During which phase does the membrane potential become more negative than the resting state?
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What defines a reflex arc?
What defines a reflex arc?
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What primarily contributes to the negative charge inside the cell at resting membrane potential?
What primarily contributes to the negative charge inside the cell at resting membrane potential?
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What type of channel is always open and allows for the constant flow of ions?
What type of channel is always open and allows for the constant flow of ions?
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What defines the concentration gradient maintained by the Na+/K+ pump?
What defines the concentration gradient maintained by the Na+/K+ pump?
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Which of the following describes the overshoot phase of an action potential?
Which of the following describes the overshoot phase of an action potential?
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What is the principle of bulk electroneutrality in the context of RMP?
What is the principle of bulk electroneutrality in the context of RMP?
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What type of proteins in the cell membrane actively transport ions?
What type of proteins in the cell membrane actively transport ions?
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During repolarization, what primarily occurs?
During repolarization, what primarily occurs?
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Which characteristic is true regarding the movement of anions across the plasma membrane?
Which characteristic is true regarding the movement of anions across the plasma membrane?
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What best describes the membrane's action potential property?
What best describes the membrane's action potential property?
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Which condition correctly describes a graded potential?
Which condition correctly describes a graded potential?
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What is the function of gated ion channels in the plasma membrane?
What is the function of gated ion channels in the plasma membrane?
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What happens during the repolarization phase of an action potential?
What happens during the repolarization phase of an action potential?
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What occurs immediately after the threshold is reached during an action potential?
What occurs immediately after the threshold is reached during an action potential?
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During which phase of the action potential do Na+ channels have not yet returned to their resting state?
During which phase of the action potential do Na+ channels have not yet returned to their resting state?
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In what condition does the membrane become most permeable to K+ ions during the action potential?
In what condition does the membrane become most permeable to K+ ions during the action potential?
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What primarily causes repolarization during an action potential?
What primarily causes repolarization during an action potential?
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What describes the period during which no action potential can be generated regardless of stimulus strength?
What describes the period during which no action potential can be generated regardless of stimulus strength?
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What is the main advantage of myelination in nerve fibers?
What is the main advantage of myelination in nerve fibers?
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Which type of conduction occurs in myelinated fibers?
Which type of conduction occurs in myelinated fibers?
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At resting membrane potential, which ion channel is primarily closed, contributing to the negative charge?
At resting membrane potential, which ion channel is primarily closed, contributing to the negative charge?
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What is the role of the node of Ranvier in A-type fibers?
What is the role of the node of Ranvier in A-type fibers?
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What primarily causes the initial depolarization during an action potential?
What primarily causes the initial depolarization during an action potential?
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What is the typical resting membrane potential for neurons?
What is the typical resting membrane potential for neurons?
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Which statement correctly describes EPSP and IPSP?
Which statement correctly describes EPSP and IPSP?
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Which of the following structures does NOT contribute to the propagation of electrical signals along neurons?
Which of the following structures does NOT contribute to the propagation of electrical signals along neurons?
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What type of postsynaptic potential is generated by an influx of sodium ions?
What type of postsynaptic potential is generated by an influx of sodium ions?
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Which neurotransmitter deficiency is most commonly associated with Alzheimer's disease?
Which neurotransmitter deficiency is most commonly associated with Alzheimer's disease?
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What causes an inhibitory postsynaptic potential (IPSP)?
What causes an inhibitory postsynaptic potential (IPSP)?
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What impact does alpha-latrotoxin from the black widow spider have on neurotransmitter release?
What impact does alpha-latrotoxin from the black widow spider have on neurotransmitter release?
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What does an excitatory postsynaptic potential (EPSP) typically lead to in a postsynaptic neuron?
What does an excitatory postsynaptic potential (EPSP) typically lead to in a postsynaptic neuron?
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Which part of the neuron is primarily responsible for synthesizing neurotransmitters?
Which part of the neuron is primarily responsible for synthesizing neurotransmitters?
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Which neurological disorder is characterized by a deficiency of dopamine in the basal nuclei?
Which neurological disorder is characterized by a deficiency of dopamine in the basal nuclei?
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What defines a spinal reflex?
What defines a spinal reflex?
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Study Notes
Neuronal Transmission & Reflexes
- Neuronal transmission involves the passing of signals between neurons.
- Reflexes are automatic responses to stimuli.
- Neuron types include sensory neurons, interneurons (or association neurons), and motor neurons.
- Sensory neurons transmit signals from sensory receptors to the central nervous system (CNS).
- Interneurons connect sensory and motor neurons within the CNS.
- Motor neurons transmit signals from the CNS to effectors (muscles and glands).
- Reflex arcs are the pathways followed by nerve impulses during reflexes.
Membrane Potentials
- Resting membrane potential (RMP) is a voltage difference across a cell membrane.
- RMP is typically -70 mV in animal nerve cells.
- Depolarization is a change that makes the membrane potential less negative.
- Repolarization occurs when the ion movement changes to return the potential to its resting level.
- Action potential (AP) is a rapid, large change in membrane potential.
Synaptic Transmission
- Neurotransmitters are chemical messengers released from neurons.
- Neurotransmitters can stimulate (excitatory) or inhibit (inhibitory) neurons.
- Ion channels on the postsynaptic cell are involved in transmitting the signal.
Properties of the Cell Plasma Membrane
- The plasma membrane is a thin, non-conducting bilayer of phospholipids.
- It has important proteins that help in ion transport.
- Ion channels are important in regulating ion movement across the plasma membrane. These channels can be leak channels (always open) or gated channels (open or close in response to stimuli).
Types of Gated Ion Channels
- Voltage-gated channels open in response to a change in voltage across a membrane.
- Ligand-gated channels open in response to a ligand binding to the channel protein.
- Mechanically-gated channels open in response to physical deformation of the membrane.
Ion Concentrations
- Ion concentrations differ inside and outside a nerve cell.
- Na+, K+, Ca2+, and Cl- are important ions in transmitting nerve impulses.
- These ions have differing concentrations inside and outside the cell.
Na+/K+ Pump (Na+/K+ ATPase)
- This transmembrane protein is important in establishing and maintaining the resting membrane potential.
- This pump moves three sodium ions outside and two potassium ions inside the cell, against their concentration gradients.
- The pump is an important part of electrochemical gradients.
Types of Electrical Neuronal Signals
- Graded potentials are local changes in the membrane potential and can be positive or negative.
- Action potentials are large, rapid changes in membrane potential that are "all-or-none."
Types of Graded Potentials
- Receptor potentials.
- Postsynaptic potentials.
Propagation of Electrical Signals
- Electrical signals can be propagated through neurons through passive and active current flow.
- Active current is the movement of ions through ion channels, while passive current is the movement of charge along a neuronal process.
Synaptic Integration
- Temporal summation is summing of postsynaptic potentials generated at the same synapse in rapid succession.
- Spatial summation is summing of postsynaptic potentials originating from different synapses.
Conduction of APs along Nerve Fibers
- Myelinated fibers conduct impulses more rapidly than unmyelinated fibers due to saltatory conduction.
- The nodes of Ranvier are gaps in the myelin sheath where action potentials are generated.
Ionic Basis of Action Potential
- Initial depolarization is caused by opening of some non-selective cation channels and influx of Na+.
- During the rising phase of the action potential, voltage-gated Na+ channels open quickly; voltage-gated K+ channels are still closed.
- During the falling phase, Na+ channels inactivate and voltage-gated K+ channels open, repolarizing the membrane.
- The undershoot (after-hyperpolarization) occurs when the membrane potential becomes more negative than the resting potential.
Depolarization (Na+ Influx) & Repolarization (K+ Efflux)
- Depolarization occurs when voltage-gated Na+ channels open and Na+ ions rush into the cell.
- Repolarization occurs when voltage-gated K+ channels open and K+ ions rush out of the cell, returning the membrane to its resting potential.
Chemical Messengers/Neurotransmitters
- Chemical messengers are released from neurons and act on receptors.
- They include amino acids, cholinergic esters, and monoamines.
Neuronal Communication at a Synapse
- Neurotransmitters are released into the synaptic cleft and bind to receptors.
- This creates post-synaptic potentials, which are graded potentials that can be excitatory or inhibitory.
Excitatory & Inhibitory Postsynaptic Potentials
- An influx of Na+ causes an EPSP; the influx of CI- or the efflux of K+ causes an IPSP.
Clinical Significance of Neurotransmitters
- Changes in neurotransmitter levels are associated with several neurological disorders.
- Parkinson's disease is associated with dopamine deficiency.
- Alzheimer's disease is associated with acetylcholine deficiency.
- Schizophrenia is associated with dopamine excess.
- Depression is associated with decreased release of serotonin or norepinephrine.
What is a Spinal Reflex?
- A spinal reflex is a rapid, involuntary response to a stimulus.
- The reflex arc is the pathway followed by nerve impulses during a reflex.
- The reflex arc involves five components: receptor, sensory neuron, integrating center, motor neuron, and effector.
Example: Withdrawal Reflex (Polysynaptic)
- The withdrawal reflex is a protective response to noxious stimuli.
- It involves the activation of nociceptors, a sensory neuron, and excitatory interneurons; a motor neuron is stimulated.
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Description
Test your knowledge on neuronal transmission and reflexes with this quiz. Explore key concepts such as neuron types, resting membrane potentials, and the mechanisms of reflex arcs. Assess your understanding of how signals are transmitted in the nervous system.
