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The term "astrocyte" originates from Ancient Greek words meaning "star" and "cavity," reflecting its star-shaped morphology.
Answer: True
The term 'astrocyte' is derived from the Greek words 'astron' (star) and 'kutos' (cell or cavity), accurately describing their characteristic star-shaped morphology.
Astrocytes are classified as neurons within the central nervous system.
Answer: False
Astrocytes are classified as glial cells, a distinct category from neurons, within the central nervous system.
Glial fibrillary acidic protein (GFAP) is a protein commonly used to identify oligodendrocytes in histological analysis.
Answer: False
Glial fibrillary acidic protein (GFAP) is a protein characteristically used for the histological identification of astrocytes, not oligodendrocytes.
Astrocytes in the central nervous system originate from mature neurons.
Answer: False
Astrocytes in the central nervous system originate from progenitor cells within the neuroepithelium, not from mature neurons.
Sonic hedgehog (SHH), fibroblast growth factors (FGFs), WNTs, and bone morphogenetic proteins (BMPs) are signaling factors involved in specifying macroglial cell lineage.
Answer: True
Canonical signaling factors such as sonic hedgehog (SHH), fibroblast growth factors (FGFs), WNTs, and bone morphogenetic proteins (BMPs) are integral to specifying the lineage of macroglial cells.
What is the etymological origin of the term "astrocyte," and what does it describe?
Answer: "Astron" (star) and "kutos" (cavity/cell), describing their star-shaped appearance.
The term 'astrocyte' originates from the Greek words 'astron' (star) and 'kutos' (cell or cavity), reflecting their characteristic star-shaped morphology.
What is the primary classification of astrocytes within the central nervous system?
Answer: Glial cells
Astrocytes are primarily classified as a type of glial cell within the central nervous system.
What protein is commonly used for histological identification of astrocytes?
Answer: Glial fibrillary acidic protein (GFAP)
Glial fibrillary acidic protein (GFAP) is a commonly used protein marker for the histological identification of astrocytes.
From what progenitor cells do astrocytes in the CNS originate?
Answer: Neuroepithelial progenitor cells
Astrocytes in the central nervous system originate from progenitor cells found within the neuroepithelium of the developing CNS.
According to Raff et al.'s classification, what are the key markers for Type 2 astrocytes?
Answer: A2B5+, GFAP+, Ran2-
According to Raff et al.'s classification, Type 2 astrocytes are characterized by the markers A2B5+, GFAP+, and Ran2-.
Astrocytes are exclusively found in the peripheral nervous system.
Answer: False
Astrocytes are primarily located within the central nervous system, specifically the brain and spinal cord, not exclusively in the peripheral nervous system.
Astrocytes constitute between 60% and 80% of all glial cells in the brain.
Answer: False
Studies indicate that astrocytes constitute a significant portion of glial cells, typically ranging from 20% to 40%, rather than 60% to 80%.
Human astrocytes are smaller than rodent astrocytes and contact fewer synapses.
Answer: False
Contrary to the statement, human astrocytes are significantly larger than rodent astrocytes and establish contact with a substantially greater number of synapses.
In humans, a single astrocyte can interact with up to 2 million synapses simultaneously.
Answer: True
A single human astrocyte is capable of interacting with an extensive network, potentially up to 2 million synapses concurrently.
Fibrous astrocytes are predominantly found in the grey matter of the brain and spinal cord.
Answer: False
Fibrous astrocytes are predominantly found in the white matter of the brain and spinal cord, whereas protoplasmic astrocytes are found in grey matter.
Protoplasmic astrocytes, the most prevalent type, are characterized by short, highly branched tertiary processes and are found in grey matter.
Answer: True
Protoplasmic astrocytes, the most common type, are indeed characterized by short, highly branched tertiary processes and are predominantly located in the grey matter.
All three forms of astrocytes contribute to the formation of the pia-glial membrane when near the pia mater.
Answer: True
When located near the pia mater, all three principal forms of astrocytes extend processes that collectively contribute to the formation of the pia-glial membrane.
Where are astrocytes primarily located within the body?
Answer: The brain and spinal cord, forming the central nervous system.
Astrocytes are predominantly found within the brain and spinal cord, which constitute the central nervous system.
What is the estimated proportion of astrocytes in the brain relative to other glial cells, according to some studies?
Answer: Between 20% and 40%
Studies suggest that astrocytes constitute between 20% and 40% of all glial cells in the brain, though this proportion can vary by region and methodology.
How do human astrocytes differ from rodent astrocytes?
Answer: Human astrocytes are larger and contact significantly more synapses.
Human astrocytes are considerably larger than their rodent counterparts and interact with a much greater number of synapses.
How many synapses can a single human astrocyte interact with simultaneously?
Answer: Up to 2 million
A single human astrocyte is capable of interacting with approximately 2 million synapses concurrently.
Where are fibrous astrocytes typically located?
Answer: White matter
Fibrous astrocytes are typically found in the white matter of the brain and spinal cord.
Which type of astrocyte is most prevalent and found in grey matter, characterized by short, highly branched processes?
Answer: Protoplasmic astrocytes
Protoplasmic astrocytes are the most prevalent type, characterized by short, highly branched processes, and are predominantly found in grey matter.
A primary function of astrocytes is to regulate cerebral blood flow.
Answer: True
Astrocytes play a crucial role in regulating cerebral blood flow as part of their diverse physiological functions within the central nervous system.
Astrocytes are the primary source of cholesterol in the central nervous system, transporting it via apolipoprotein E.
Answer: True
Astrocytes serve as the principal source of cholesterol within the central nervous system, facilitating its transport through apolipoprotein E.
Astrocytes buffer potassium ions primarily through potassium channels like Kir4.1 and the Na+/K+ ATPase pump.
Answer: True
Astrocytes effectively buffer extracellular potassium ions utilizing mechanisms such as potassium channels, including Kir4.1, and the Na+/K+ ATPase pump.
Astrocytes store glycogen and can perform gluconeogenesis, providing fuel to neurons.
Answer: True
Astrocytes serve as a metabolic support system by storing glycogen and performing gluconeogenesis, thereby providing essential fuel to neurons.
Astrocytes are not involved in detecting interstitial glucose levels within the brain.
Answer: False
Astrocytes are involved in detecting interstitial glucose levels within the brain and can respond to changes in glucose concentration.
The endfeet processes of astrocytes encircle endothelial cells and are crucial for maintaining the blood-brain barrier.
Answer: True
The endfeet processes of astrocytes encircle endothelial cells, playing a critical role in the maintenance and integrity of the blood-brain barrier.
Abnormal extracellular potassium accumulation, if unmanaged, can lead to neuronal hyperpolarization and reduced epileptic activity.
Answer: False
Unmanaged abnormal extracellular potassium accumulation leads to neuronal depolarization, increasing the likelihood of epileptic activity, not hyperpolarization.
Astrocytes are believed to promote myelination by secreting the cytokine leukemia inhibitory factor (LIF) in response to neuronal electrical impulses.
Answer: True
Astrocytes are thought to promote myelination by secreting the cytokine leukemia inhibitory factor (LIF) in response to neuronal electrical impulses.
Which of the following is NOT listed as a key function of astrocytes?
Answer: Synthesizing neurotransmitters like dopamine.
While astrocytes perform numerous functions, including nutrient provision, blood flow regulation, and ion balance, the synthesis of neurotransmitters like dopamine is not among their primary roles.
How do astrocytes contribute to cholesterol transport in the CNS?
Answer: They are the primary source of cholesterol, transporting it via apolipoprotein E.
Astrocytes are the primary source of cholesterol in the central nervous system, facilitating its transport to other cells via apolipoprotein E.
What is the primary mechanism by which astrocytes buffer extracellular potassium ions, significantly increasing their energy demand?
Answer: Through the Na+/K+ ATPase pump.
The Na+/K+ ATPase pump is a primary mechanism by which astrocytes buffer extracellular potassium ions, contributing to a significant increase in their energy demand.
How do astrocytes support neurons metabolically?
Answer: By storing glycogen and performing gluconeogenesis to provide glucose/lactate.
Astrocytes provide metabolic support to neurons by storing glycogen and performing gluconeogenesis, thereby supplying glucose and lactate.
What is the consequence of unmanaged extracellular potassium accumulation, according to the source?
Answer: Neuronal depolarization and epileptic activity.
Unmanaged extracellular potassium accumulation leads to neuronal depolarization, which can result in epileptic activity.
What is the primary role of astrocytic endfeet processes in relation to the blood-brain barrier?
Answer: To encircle endothelial cells and maintain the barrier's integrity.
Astrocytic endfeet processes encircle endothelial cells, playing a primary role in maintaining the integrity of the blood-brain barrier.
How do astrocytes contribute to glucose sensing and its impact on physiological processes?
Answer: By detecting interstitial glucose levels and activating gastric emptying when glucose is low.
Astrocytes contribute to glucose sensing by detecting interstitial glucose levels, which can trigger physiological responses such as activating gastric emptying when glucose is low.
Since the mid-1990s, research has shown that astrocytes are capable of active signaling, including releasing transmitters like glutamate.
Answer: True
Research since the mid-1990s has demonstrated that astrocytes are capable of active signaling, including the release of transmitters such as glutamate.
Gliotransmitters are signaling molecules released by astrocytes, but their release is not dependent on calcium levels.
Answer: False
Gliotransmitters are indeed signaling molecules released by astrocytes; however, their release is dependent on intracellular calcium levels.
The tripartite synapse concept highlights the isolation of glial cells from synaptic function.
Answer: False
The tripartite synapse concept emphasizes the close functional relationship between neurons and glial cells, highlighting their integration into synaptic function, rather than their isolation.
In the hippocampus, astrocytes can suppress synaptic transmission by releasing ATP, which is converted to adenosine.
Answer: True
In regions like the hippocampus, astrocytes can modulate synaptic transmission by releasing ATP, which is subsequently converted to adenosine, a modulator of neuronal activity.
What significant capability of astrocytes has been revealed by research since the mid-1990s?
Answer: Their capacity for active signaling, including releasing gliotransmitters.
Research since the mid-1990s has revealed that astrocytes possess active signaling capabilities, including the release of gliotransmitters.
What are gliotransmitters?
Answer: Signaling molecules released by astrocytes in a calcium-dependent manner.
Gliotransmitters are signaling molecules released by astrocytes, with their release mechanism being dependent on intracellular calcium levels.
What is the concept of a "tripartite synapse"?
Answer: The functional relationship between a presynaptic neuron, a postsynaptic neuron, and a glial element.
The tripartite synapse concept describes the functional unit comprising a presynaptic terminal, a postsynaptic element, and a closely associated glial cell, highlighting glial involvement in synaptic transmission.
How do astrocytes modulate synaptic transmission in the hippocampus, for example?
Answer: By releasing ATP, which breaks down into adenosine to inhibit transmission.
In the hippocampus, astrocytes can suppress synaptic transmission by releasing ATP, which is metabolized into adenosine, thereby modulating neuronal signaling.
What is the primary characteristic of GluT-type astrocytes?
Answer: Expression of glutamate transporters like EAAT1.
GluT-type astrocytes are primarily characterized by their expression of glutamate transporters, such as EAAT1.
What is the primary characteristic of GluR-type astrocytes?
Answer: Response to synaptic glutamate via channel-mediated currents and IP3-dependent calcium transients.
GluR-type astrocytes are characterized by their response to synaptic glutamate via channel-mediated currents and IP3-dependent calcium transients.
Radial glial cells are primarily found in adulthood and play a role in neuron myelination.
Answer: False
Radial glial cells are primarily active during development, where they guide neuron migration; they are not typically found in adulthood and do not play a role in neuron myelination.
Astrocytes regulate neural stem cells by releasing signals like ephrin-A2 and ephrin-A3, which activate stem cells to differentiate.
Answer: False
Astrocytes regulate neural stem cells by releasing signals like ephrin-A2 and ephrin-A3, which maintain them in a dormant state; reducing these signals activates differentiation.
What is the primary role of radial glial cells during development?
Answer: Neuron migration
During development, radial glial cells primarily serve to guide the migration of newly formed neurons to their correct positions in the nervous system.
Which of the following is an exception to radial glia being primarily present during development?
Answer: Bergmann glia cells in the cerebellum
Bergmann glia cells in the cerebellum are an exception, as they persist into adulthood, unlike most radial glial cells which are primarily developmental.
How do astrocytes regulate neural stem cells?
Answer: By releasing signals like ephrin-A2 and ephrin-A3 to maintain dormancy.
Astrocytes regulate neural stem cells by releasing signals such as ephrin-A2 and ephrin-A3, which serve to maintain the stem cells in a dormant state.
What is the role of astrocytes in regulating neural stem cells by reducing the release of certain signals?
Answer: To activate stem cells to differentiate into neurons.
By reducing the release of specific signals, astrocytes can activate neural stem cells to differentiate into neurons.
The glial scar formed by astrocytes after injury is primarily viewed as a barrier that prevents axon regeneration.
Answer: False
While historically viewed as a barrier, recent research suggests the glial scar formed by astrocytes after injury is essential for stimulated axon growth through injured spinal cord tissue.
What is a characteristic of pilocytic astrocytomas?
Answer: Grade I, benign, and slow-growing
Pilocytic astrocytomas are characterized as Grade I tumors, which are benign and exhibit slow growth.
Glioblastoma is classified as which grade of astrocytoma?
Answer: Grade IV
Glioblastoma is classified as a Grade IV astrocytoma, representing the most malignant form.
What role do reactive astrocytes play in Alzheimer's disease pathology, according to a 2023 study?
Answer: They exacerbate the pathological effects of amyloid-beta on tau.
A 2023 study indicated that reactive astrocytes exacerbate the pathological effects of amyloid-beta on tau in Alzheimer's disease.
How do astrocytes contribute to the phenomenon of spinal sensitization in chronic pain?
Answer: By detecting neuronal activity and releasing transmitters that influence synaptic activity, amplifying pain signals.
Astrocytes contribute to spinal sensitization in chronic pain by detecting neuronal activity and releasing transmitters that modulate synaptic activity, thereby amplifying pain signals.
What is the suspected cause of damage to Gomori-positive astrocytes?
Answer: Oxidative stress
Oxidative stress is the suspected cause of damage to Gomori-positive astrocytes.
What experimental approach was used to attempt to repair CNS trauma by replacing glial cells, and what was a key positive outcome?
Answer: Injecting human glial precursor cells into the injured spinal cord, promoting recovery and axonal growth.
Injecting human glial precursor cells into the injured spinal cord promoted recovery and axonal growth, demonstrating a potential for CNS trauma repair.
What is the prevalence of glioblastoma among all brain tumors?
Answer: Approximately 50%
Glioblastoma accounts for approximately 50% of all primary brain tumors.
Which of the following is a condition associated with astrogliosis or astrocytopathy?
Answer: Multiple Sclerosis
Multiple Sclerosis is one of several conditions associated with astrogliosis or astrocytopathy.
Early research suggested astrocytes used significantly more energy than neurons for signaling in gray matter.
Answer: False
Early research underestimated astrocyte energy consumption; later studies suggest astrocytes may be as metabolically demanding as neurons on a gram-per-gram basis.
It is conjectured that astrocytes function as the "logical switch" of the nervous system, enabling or blocking stimulus propagation.
Answer: True
It is conjectured that astrocytes function as the 'logical switch' of the nervous system, capable of enabling or blocking stimulus propagation based on their state and stimulus intensity.
Astrocytes alone are sufficient to drive molecular oscillations in the suprachiasmatic nucleus (SCN) and control circadian behavior.
Answer: True
Astrocytes possess the capacity to independently drive molecular oscillations within the suprachiasmatic nucleus (SCN) and thereby control circadian behavior.
How has the understanding of energy allocation in the brain evolved regarding astrocytes?
Answer: Later research suggests astrocytes may be as metabolically expensive as neurons, gram-per-gram.
Evolving research indicates that astrocytes, gram-per-gram, may be as metabolically demanding as neurons, a significant revision from earlier assumptions.
What is the conjectured role of astrocytes in the nervous system?
Answer: The "logical switch"
Astrocytes are conjectured to function as the 'logical switch' of the nervous system, influencing the propagation of neural stimuli.
What is the conjectured role of glia, particularly astrocytes, as a "logical switch"?
Answer: To block or enable stimulus propagation based on membrane state and stimulus level.
The conjectured role of astrocytes as a 'logical switch' involves their ability to block or enable stimulus propagation based on their membrane state and the level of the stimulus.