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Questions and Answers
Which mechanism allows for the reincorporation of catecholamines into presynaptic vesicles?
Which mechanism allows for the reincorporation of catecholamines into presynaptic vesicles?
What type of synapse is formed between an axon and a dendrite?
What type of synapse is formed between an axon and a dendrite?
Which neurotransmitter is broken down into acetate and choline in the synaptic cleft?
Which neurotransmitter is broken down into acetate and choline in the synaptic cleft?
What is the distinction of an axoaxonic synapse?
What is the distinction of an axoaxonic synapse?
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What treatment approach involves inhibiting the breakdown of norepinephrine?
What treatment approach involves inhibiting the breakdown of norepinephrine?
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What component is not considered a morphotype of synapse?
What component is not considered a morphotype of synapse?
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Which part of the neuromuscular junction consists of presynaptic vesicles containing acetylcholine?
Which part of the neuromuscular junction consists of presynaptic vesicles containing acetylcholine?
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What process can occur to deactivated neurotransmitters besides recapture?
What process can occur to deactivated neurotransmitters besides recapture?
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Which structure in neurons is primarily responsible for signal conduction away from the cell body?
Which structure in neurons is primarily responsible for signal conduction away from the cell body?
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What role do neurofilaments, microfilaments, and microtubules serve in neurons?
What role do neurofilaments, microfilaments, and microtubules serve in neurons?
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Which of the following statements about the myelin sheath is correct?
Which of the following statements about the myelin sheath is correct?
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What is the significance of the axon hillock in neuronal function?
What is the significance of the axon hillock in neuronal function?
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Which neurons in the adult human body are known to regularly replace themselves?
Which neurons in the adult human body are known to regularly replace themselves?
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Which of the following is a characteristic feature of dendrites?
Which of the following is a characteristic feature of dendrites?
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What is the primary role of lysosomes within neurons?
What is the primary role of lysosomes within neurons?
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Which component of the neuron is involved in the formation of microtubules?
Which component of the neuron is involved in the formation of microtubules?
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What is the primary function of dendrites in nerve cells?
What is the primary function of dendrites in nerve cells?
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Which characteristic does NOT describe dendrites compared to axons?
Which characteristic does NOT describe dendrites compared to axons?
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What shape do dendritic spines typically resemble?
What shape do dendritic spines typically resemble?
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What type of neurons are classified as pseudounipolar neurons primarily responsible for?
What type of neurons are classified as pseudounipolar neurons primarily responsible for?
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Which component of the dendrites is responsible for the majority of postsynaptic receptors?
Which component of the dendrites is responsible for the majority of postsynaptic receptors?
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In terms of cytoplasmic composition, which feature is characteristic of dendrites?
In terms of cytoplasmic composition, which feature is characteristic of dendrites?
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Which structural feature differentiates dendrites from axons?
Which structural feature differentiates dendrites from axons?
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What is the main implication of having up to 200,000 synapses in a single dendritic tree?
What is the main implication of having up to 200,000 synapses in a single dendritic tree?
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What is the main effect of inhibitory synapses on the postsynaptic membrane potential?
What is the main effect of inhibitory synapses on the postsynaptic membrane potential?
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Which component of the synapse is responsible for releasing neurotransmitters into the synaptic cleft?
Which component of the synapse is responsible for releasing neurotransmitters into the synaptic cleft?
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How do neurotransmitters primarily influence the postsynaptic cell?
How do neurotransmitters primarily influence the postsynaptic cell?
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What initiates the fusion of synaptic vesicles with the presynaptic membrane?
What initiates the fusion of synaptic vesicles with the presynaptic membrane?
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Where are inhibitory synapses primarily located within a neuron?
Where are inhibitory synapses primarily located within a neuron?
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What happens to excess plasma membrane after the fusion of synaptic vesicles?
What happens to excess plasma membrane after the fusion of synaptic vesicles?
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What is the approximate width of the synaptic cleft?
What is the approximate width of the synaptic cleft?
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Which of the following describes the primary classification of neurotransmitters?
Which of the following describes the primary classification of neurotransmitters?
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Which support cell in the peripheral nervous system is responsible for the formation of myelin around nerve fibers?
Which support cell in the peripheral nervous system is responsible for the formation of myelin around nerve fibers?
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What type of synapse is characterized by communication directly between two neurons through gap junctions?
What type of synapse is characterized by communication directly between two neurons through gap junctions?
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Which type of glial cell in the central nervous system is primarily involved in the response to injury and repair?
Which type of glial cell in the central nervous system is primarily involved in the response to injury and repair?
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Which type of axonal transport involves transporting materials away from the cell body?
Which type of axonal transport involves transporting materials away from the cell body?
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What is the primary function of the synaptic cleft in a chemical synapse?
What is the primary function of the synaptic cleft in a chemical synapse?
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Which type of neuron includes both sensory and motor neurons that are involved in reflex actions?
Which type of neuron includes both sensory and motor neurons that are involved in reflex actions?
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Among the support cells of the peripheral nervous system, which cell type is responsible for providing structural support to neuronal cell bodies?
Among the support cells of the peripheral nervous system, which cell type is responsible for providing structural support to neuronal cell bodies?
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Which type of synapse is responsible for the modulation of synaptic transmission and can either enhance or inhibit neuronal signals?
Which type of synapse is responsible for the modulation of synaptic transmission and can either enhance or inhibit neuronal signals?
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Study Notes
Neurotransmitter Deactivation
- Released neurotransmitters are deactivated mainly through recapture and degradation.
- High-affinity reuptake allows up to 80% of catecholamines (e.g., dopamine, norepinephrine) to be recaptured into vesicles via endocytosis.
- Enzymes on the synaptic membrane break down remaining neurotransmitters; for instance, acetylcholine is converted into acetate and choline.
- Inhibiting norepinephrine breakdown or high-affinity reuptake is beneficial for depression treatment.
Morphotypes of Synapses
- Axodendritic synapses connect axons to dendrites.
- Axosomatic synapses link axons to neuron bodies (perikaryon).
- Axoaxonic synapses connect one axon to another axon.
- Motor end-plates are specialized synapses at neuromuscular junctions, containing presynaptic vesicles with acetylcholine.
- Type II inhibitory synapses hyperpolarize postsynaptic cells, reducing action potential likelihood.
Chemical Synapses
- Presynaptic knobs contain synaptic vesicles (40-60 nm), rich in neurotransmitters.
- Over 100 known neurotransmitters can induce depolarization or hyperpolarization, acting as either excitatory or inhibitory.
- The synaptic cleft is a narrow (~20 nm) gap between presynaptic and postsynaptic membranes.
- Action potential triggers calcium channel opening, facilitating neurotransmitter release into the synapse.
- Endocytosis removes excess plasma membrane after neurotransmitter release.
Dendrites
- Dendrites are numerous, short, tapered processes designed to convey signals toward the perikaryon.
- Dendritic trees can have up to 200,000 synapses, maximizing synaptic contact area.
- Dendritic spines, shaped like mushrooms, host most postsynaptic receptors.
- Dendrites lack myelin and contain ribosomes and rough endoplasmic reticulum but no Golgi apparatus.
Major Types of Neurons
- Neurons can be classified as pseudounipolar, bipolar, or multipolar based on shape and process number.
- Pseudounipolar neurons are primarily sensory, with one large process branching into peripheral and central processes that transmit sensory information to the central nervous system.
Axonal Transport
- Axonal transport occurs in two directions: anterograde (moving materials away from the cell body) and retrograde (moving materials toward the cell body).
- Anterograde transport includes both fast and slow transport mechanisms.
Neuron Structure
- Neurons feature distinct structures: one axon per cell, dendritic processes, and axon terminals.
- Axons vary in length (up to 1 meter), maintain a constant diameter, and lack Nissl bodies at the axon hillock.
- Myelinated axons enhance signal transmission speed, while myelin sheath formation abnormalities can lead to disorders.
Cytoskeleton of Neurons
- Neuronal cytoskeleton is well-developed, consisting of neurofilaments, microfilaments, and microtubules.
- Neurons generally lack centrioles, preventing cellular division, with limited neuroblast replacement in adults, notably in olfactory neurons.
Support Cells in Nervous System
- Peripheral nervous system support cells include Schwann cells (involved in myelination) and satellite cells.
- Central nervous system support cells encompass astrocytes (with multiple types), oligodendrocytes, microglial cells, and ependymal cells, each with distinct functions and clinical relevance.
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Description
Test your knowledge on the mechanisms of neurotransmitter deactivation, focusing on recapture and degradation. This quiz covers important neurotransmitters like catecholamines, including dopamine and norepinephrine, and their reuptake processes.
