Glia

Question 1

What is the primary function of glial cells?

a) To carry nerve impulses
b) To destroy neurons
c) To provide physical support and nutrients
d) To generate electrical impulses

Answer 1

c) To provide physical support and nutrients

Question 2

Which type of glial cell is responsible for myelination in the central nervous system?

a) Astrocytes
b) Microglia
c) Oligodendrocytes
d) Schwann cells

Answer 2

c) Oligodendrocytes

Question 3

From which germ layer are microglia derived?

a) Ectoderm
b) Mesoderm
c) Endoderm
d) Neuroectoderm

Answer 3

b) Mesoderm

Question 4

Who is credited with first naming glial cells?

a) Ramon y Cajal
b) Pio del Rio-Hortega
c) Rudolf Virchow
d) Rene Dutrochet

Answer 4

c) Rudolf Virchow

Question 5

Which function is NOT associated with astrocytes?

a) Regulating the blood-brain barrier
b) Myelinating axons in the peripheral nervous system
c) Modulating synaptic function
d) Supporting neuronal growth and migration

Answer 5

b) Myelinating axons in the peripheral nervous system

Question 6

Which of the following is a major role of microglia in the brain?

a) Insulating neurons
b) Providing physical support to neurons
c) Regulating immune responses
d) Synaptic pruning

Answer 6

c) Regulating immune responses

Question 7

Radial glia primarily function during which stage of development?

a) Adult brain
b) Early development
c) Aging brain
d) Postnatal development

Answer 7

b) Early development

Question 8

What marks the onset of vasculogenesis in the telencephalic wall?

a) 4 weeks of gestation
b) 6 weeks of gestation
c) 8 weeks of gestation
d) 10 weeks of gestation

Answer 8

b) 6 weeks of gestation

Question 9

Which factor is crucial for the identity acquisition of O2A progenitors?

a) GFAP
b) SHH
c) Notch
d) Both b and c
e) Both a and b

Answer 9

d) Both b and c

Question 10

Schwann cells are derived from which type of cells?

a) Neural crest cells
b) Neural tube cells
c) Radial glia
d) Ependymal cells

Answer 10

a) Neural crest cells

Question 11

Describe the primary developmental roles of glial cells in the brain.

Answer 11

Glial cells guide the migration of neurons during early development, produce molecules that influence the growth of axons and dendrites, and are involved in synaptic transmission by regulating neurotransmitter clearance and releasing factors that modulate synaptic function.

Question 12

What are the four main functions of glial cells?

Answer 12

The four main functions of glial cells are: providing physical support to neurons, supplying nutrients and oxygen to neurons, insulating neurons to facilitate synaptic communication, and destroying and removing cell debris and unwanted molecules.

Question 13

What contributions do astrocytes make to the aging brain and brain diseases?

Answer 13

In the aging brain, astrocytes regulate the blood-brain barrier and synaptic function. In brain diseases, they can become reactive, contributing to the pathophysiology of conditions such as Alzheimer’s disease, Multiple Sclerosis, and Stroke by modulating inflammation and neuronal support.

Question 14

What is the primary origin of microglial cells?

a) Neural crest cells
b) Bone marrow
c) EMPs
d) Neural tube cells

Answer 14

c) Yolk sac erythromyeloid progenitors (EMPs)

Question 15

Who first described microglial cells using Nissl staining?

a) Santiago Ramón y Cajal
b) Pío del Río Hortega
c) Franz Nissl
d) Victor Babeş

Answer 15

c) Franz Nissl

Question 16

Microglial cells in the brain parenchyma exhibit which type of morphology?

a) Amoeboid
b) Bipolar
c) Ramified
d) Stellate

Answer 16

c) Ramified

Question 17

Which transcription factors are highly enriched in microglia and involved in their development?

a) SALL1, SALL3, MEIS3, and MAFB
b) GFAP, SHH, and Notch
c) PU.1, C/EBPs, RUNX1, and IRF8
d) BDNF, NGF, and NT-3

Answer 17

a) SALL1, SALL3, MEIS3, and MAFB

Question 18

During what stage do microglial cells acquire their ramified shape?

a) Prenatal development
b) First 2 weeks postnatal
c) First month postnatal
d) Adult brain

Answer 18

b) First 2 weeks postnatal

Question 19

Who is considered the “Father of Microglia”?

a) Franz Nissl
b) Santiago Ramón y Cajal
c) Pío del Río Hortega
d) Victor Babeş

Answer 19

c) Pío del Río Hortega

Question 20

What is the significance of the study by Hickey and Kimura (1988) regarding microglia?

a) Identified the amoeboid morphology of microglia
b) Showed that perivascular microglial cells are bone-marrow derived
c) Characterized microglial response to brain lesions
d) First described microglial cells

Answer 20

b) Showed that perivascular microglial cells are bone-marrow derived

Question 21

What factor is NOT fundamental in shaping microglial identity in the brain?

a) CSF1
b) IL34
c) TGFβ
d) BDNF

Answer 21

d) BDNF

Question 22

Which function is NOT associated with microglia?

a) Phagocytosis
b) Antigen presentation
c) Synaptic pruning
d) Myelination

Answer 22

d) Myelination

Question 23

Microglia proliferate at a rate of approximately:

a) 0.1%
b) 0.5%-2%
c) 3%-5%
d) 10%-15%

Answer 23

b) 0.5%-2%

Question 24

Describe the role of environmental factors in the development and maintenance of microglia.

Answer 24

Environmental factors such as CSF1, IL34, and TGFβ play fundamental roles in shaping, maintaining, and reinforcing the identity of microglia. These factors ensure that microglia develop properly and maintain their functions within the brain’s environment.

Question 25

What are the primary functions of microglia in the brain?

Answer 25

The primary functions of microglia include immune surveillance, phagocytosis of debris and apoptotic cells, synaptic pruning, modulation of neuroinflammation, and maintenance of homeostasis within the brain.

Question 26

Summarize the key historical milestones in the discovery and understanding of microglia.

Answer 26

Key milestones include the initial visualization by Franz Nissl using Nissl staining in 1880, descriptions by Nissl and Robertson, the term “microglia” coined by Pío del Río Hortega around 1920, his characterization of their response to brain lesions, and the 1988 study by Hickey and Kimura showing that perivascular microglia are bone-marrow derived.

Question 27

Discuss the developmental lineage of microglia and their functional diversity within the brain.

Answer 27

Microglia originate from yolk sac erythromyeloid progenitors (EMPs) during early embryogenesis. EMPs give rise to uncommitted precursors that colonize the brain directly, without passing through the liver, differentiating into microglial cells. Initially, amoeboid in shape, microglia acquire their characteristic ramified morphology within the first two weeks postnatally. This process is driven by master regulators such as PU.1, C/EBPs, RUNX1, and IRF8, with environmental factors like CSF1, IL34, and TGFβ playing crucial roles in maintaining their identity.

Microglia exhibit a high degree of functional and transcriptional diversity, tailored to their specific roles in different brain regions. They function as the brain’s primary immune cells, responsible for phagocytosing debris, modulating neuroinflammation, and maintaining homeostasis. Additionally, microglia are involved in synaptic pruning, crucial for brain development and plasticity. Throughout life, microglia maintain a balance of proliferation and apoptosis, ensuring a stable population. This dynamic turnover highlights their adaptability and essential role in both healthy and diseased states of the brain. Research continues to uncover the complexities of microglial biology, emphasizing their significance beyond traditional immune functions.

Question 28

What percentage of axon-dendritic synapses in the hippocampus are surrounded by astroglial membranes?

a) 40%
b) 50%
c) 60%
d) 70%

Answer 28

c) 60%

Question 29

What is the main role of astrocytes in the tripartite synapse?

a) Synaptic inhibition
b) Synaptic modulation
c) Synaptic destruction
d) Synaptic isolation

Answer 29

b) Synaptic modulation

Question 30

Which of the following is NOT a function of astrocytes?

a) Neurogenesis and gliogenesis
b) Synaptic modulation
c) Muscle contraction
d) Regulation of synaptogenesis

Answer 30

c) Muscle contraction

Question 31

Which receptor types are primarily targeted by glutamate in the tripartite synapse?

a) AMPA receptors
b) Kainate receptors
c) NMDA receptors
d) All of the above

Answer 31

d) All of the above

Question 32

Astrocytes can release which of the following gliotransmitters?

a) GABA
b) ATP
c) Dopamine
d) Serotonin

Answer 32

b) ATP

Question 33

What is the function of ATP as a gliotransmitter?

a) Insertion of AMPA receptors
b) Suppression of synaptic transmission
c) Paracrine activity through calcium waves
d) All of the above

Answer 33

d) All of the above

Question 34

Which brain region’s astrocytes form tripartite synapses with axonal projections from the alveus?

a) Hippocampal stratum oriens
b) Cerebellum
c) Substantia nigra
d) Amygdala

Answer 34

a) Hippocampal stratum oriens

Question 35

What type of channels do astrocyte endfeet at the blood-brain barrier contain for water transport?

a) Sodium channels
b) Potassium channels
c) Aquaporin-4 channels
d) Calcium channels

Answer 35

c) Aquaporin-4 channels

Question 36

What is the main structural feature of the blood-brain barrier?

a) Astrocyte cell bodies
b) Tight junctions between endothelial cells
c) Synaptic vesicles
d) Microglial cells

Answer 36

b) Tight junctions between endothelial cells

Question 37

Which type of synaptic activity do astrocytes of the hippocampal stratum oriens NOT respond to?

a) Glutamatergic synaptic activity from the Schaffer collateral
b) Cholinergic synaptic activity from the alveus
c) Dopaminergic synaptic activity from the substantia nigra
d) All of the above

Answer 37

c) Dopaminergic synaptic activity from the substantia nigra (wrong)

Question 38

Explain the concept of the tripartite synapse.

Answer 38

The tripartite synapse is a model of synaptic interaction that includes not only the pre- and post-synaptic neurons but also the surrounding astrocytes. Astrocytes regulate neurotransmitter levels, influence synaptic activity through gliotransmitter release, and contribute to synaptic modulation and maintenance.

Question 39

What are the key roles of astrocytes in the formation and maintenance of the blood-brain barrier?

Answer 39

Astrocytes contribute to the blood-brain barrier by extending endfeet that enwrap blood vessels and interact with endothelial cells. They regulate the permeability of the barrier, facilitate the transport of nutrients and ions, and help maintain homeostasis in the brain’s microenvironment.

Question 40

Describe the role of astrocytes in response to brain injury.

Answer 40

Following brain injury, astrocytes become reactive and contribute to the formation of a glial scar. This scar helps to contain the injury and limit inflammation, but it can also inhibit axonal regeneration and repair, presenting a challenge for recovery.

Question 41

Discuss the various functions of astrocytes in the central nervous system, focusing on their role in synaptic modulation, blood-brain barrier maintenance, and response to injury.

Answer 41

Astrocytes are versatile glial cells in the central nervous system (CNS) that perform multiple essential functions. In terms of synaptic modulation, astrocytes participate in the tripartite synapse model, where they regulate neurotransmitter levels, such as glutamate and ATP, thus influencing synaptic activity and plasticity. They can release gliotransmitters in response to neuronal activity, modulating synaptic transmission and contributing to processes like synaptic strength adjustment and homeostasis.

In maintaining the blood-brain barrier (BBB), astrocytes extend their endfeet to envelop blood vessels and form tight junctions with endothelial cells. This relationship is crucial for maintaining the selective permeability of the BBB, allowing essential nutrients to enter the brain while keeping out harmful substances. Astrocytes also assist in the transport of ions and molecules, such as glucose through GLUT1 transporters, ensuring the brain’s metabolic needs are met.

In response to CNS injury, astrocytes undergo reactive gliosis, where they proliferate and form a glial scar. This scar serves as both a protective barrier to isolate the injury site and prevent the spread of inflammation, but it can also impede axonal growth and regeneration, posing a challenge for neural repair. The dual nature of the glial scar highlights the complex role of astrocytes in both protecting and potentially hindering CNS recovery. Overall, astrocytes are indispensable for neural function, protection, and repair, showcasing their multifaceted roles in the brain’s health and disease states.