Nervous System and Neuron Development
173 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which of the following accurately describes the flow of visual information in the nervous system?

  • Photoreceptors → RGCs → LGN → V1 → Higher Cortical Areas (correct)
  • Photoreceptors → V1 → Thalamus → RGCs → Motor Cortex
  • Thalamus → V1 → LGN → RGCs → Photoreceptors
  • RGCs → Photoreceptors → Thalamus → V1 → Spinal Cord

During nervous system development, what is the primary role of cell migration?

  • Ensuring neurons reach appropriate locations for communication. (correct)
  • Initiating the process of cellular proliferation and differentiation.
  • Establishing connections between neurons and their synaptic partners.
  • Determining the type of neurotransmitter a neuron will produce.

Which cellular structure is the primary location for synapse formation on a neuron?

  • Axon terminal
  • Axon hillock
  • Dendritic spines (correct)
  • Cell body

What initiates the release of neurotransmitters into the synaptic cleft?

<p>Influx of calcium ions ($Ca^{2+}$) into the pre-synaptic terminal. (B)</p> Signup and view all the answers

A neuron that transmits signals to skeletal muscles would be classified as which type of neuron?

<p>Motor neuron (C)</p> Signup and view all the answers

Which component of the neuron is responsible for generating the action potential?

<p>Axon hillock (C)</p> Signup and view all the answers

Which of the following is NOT a primary event in the development of the nervous system?

<p>Gastrulation (A)</p> Signup and view all the answers

Which of the following structures is part of the central nervous system (CNS)?

<p>Spinal cord (B)</p> Signup and view all the answers

Which of the following neuron classifications is based on the number of neurites extending from the soma?

<p>Unipolar, Bipolar, Multipolar (A)</p> Signup and view all the answers

During embryonic development, which germ layer gives rise to the nervous system and skin?

<p>Ectoderm (D)</p> Signup and view all the answers

Neural crest cells are crucial for the development of which of the following structures?

<p>Peripheral nervous system (B)</p> Signup and view all the answers

What key process occurs during gastrulation?

<p>Development of the three germ layers (D)</p> Signup and view all the answers

Why are model organisms like Xenopus frogs valuable in developmental biology?

<p>They allow for transplantation experiments. (A)</p> Signup and view all the answers

Which of the following is the correct order of events in early neural development?

<p>Cleavage → Gastrulation → Neurulation (D)</p> Signup and view all the answers

What is the primary role of the 'organizer region' in embryonic development?

<p>To induce the formation of the neural plate (B)</p> Signup and view all the answers

Which of the following statements best describes the process of neural induction?

<p>The interaction between embryonic regions that influences cell fate. (C)</p> Signup and view all the answers

Why is folic acid supplementation important during pregnancy?

<p>It reduces the risk of neural tube defects. (D)</p> Signup and view all the answers

Which part of the developing neural tube becomes the brain?

<p>The anterior part (B)</p> Signup and view all the answers

In the context of neuronal classification, what is a key characteristic of glutamatergic neurons?

<p>They are excitatory. (D)</p> Signup and view all the answers

During cortical layer formation, where do neurons originate before migrating to their final position?

<p>The ventricular zone (A)</p> Signup and view all the answers

An experiment involves culturing dorsal ectoderm. Under normal conditions, what fate would these cells acquire?

<p>Epidermal fate (B)</p> Signup and view all the answers

Which of the following best describes the role of cell migration during neural development?

<p>Organizing neurons into appropriate brain structures and layers. (D)</p> Signup and view all the answers

What is the limitation of using Drosophila as a model organism in the study of nervous system development?

<p>Limited similarity to the human nervous system (D)</p> Signup and view all the answers

What is the consequence of inhibiting BMP signaling in dissociated ectodermal cells?

<p>Induction of neural cell fate. (A)</p> Signup and view all the answers

Which of the following statements accurately describes the role of BMP-4 in ectodermal cell fate determination?

<p>BMP-4 induces epidermal fate in dissociated ectodermal cells. (C)</p> Signup and view all the answers

Noggin, Chordin, and Follistatin contribute to neural induction by which mechanism?

<p>Interacting with BMPs, preventing them from binding to their receptors. (B)</p> Signup and view all the answers

What would be the most likely outcome of treating an early blastula embryo with UV radiation, based on the information provided?

<p>Ventralization of the embryo and blockage of neural system development. (C)</p> Signup and view all the answers

How does the organizer region contribute to neural fate determination?

<p>By inhibiting BMP signaling, allowing the default neural fate to proceed. (A)</p> Signup and view all the answers

Which of the following is the primary mechanism by which signals from the notochord induce the formation of the floor plate in the neural tube?

<p>Secretion of Sonic Hedgehog (SHH), forming a concentration gradient. (C)</p> Signup and view all the answers

What accounts for the difference in gene expression patterns of Hox genes along the posterior neural tube?

<p>Different responsiveness of Hox genes to varying gradients of retinoic acid. (D)</p> Signup and view all the answers

How does SHH signaling promote the transcription of target genes involved in ventral cell fate determination?

<p>By binding to and releasing PATCH, which then allows Gli to translocate into the nucleus. (B)</p> Signup and view all the answers

Based on the information, which of the following regions is most crucial for understanding the mechanisms regulating early neural differentiation in Drosophila?

<p>The proneural region of the ventral part, where cells have the potential to become neuroblasts. (B)</p> Signup and view all the answers

What is the predominant role of Dorsalin in the context of neural tube differentiation?

<p>Promotion of neural crest cell differentiation and inhibition of motor neuron differentiation. (C)</p> Signup and view all the answers

In the development of the nervous system, what is the role of retinoic acid (RA)?

<p>Along with FGF, it patterns more posterior regions of the nervous system. (B)</p> Signup and view all the answers

Why do neural tissues induced by Chordin, Noggin, and Follistatin typically give rise to the forebrain?

<p>They establish the most rostral structure (forebrain) of the developing nervous system. (D)</p> Signup and view all the answers

What is the consequence of implanting a notochord adjacent to the neural tube?

<p>Induction of floor plate formation in the neural tube. (C)</p> Signup and view all the answers

What role do Otx2 and Gbx2 play in brain patterning?

<p>They are non-Hox genes involved in brain patterning. (A)</p> Signup and view all the answers

Why would HoxD13 but not Hox11 be expressed in the posterior neural tube region?

<p>Hox11 is expressed in the most posterior part but also a more anterior part because it is more responsive to retinoic acid (RA), while HoxD13 is less responsive to RA. (B)</p> Signup and view all the answers

What is the immediate consequence of the binding of Delta to the Notch receptor?

<p>Cleavage of the Notch intracellular domain (NICD) by a protease. (B)</p> Signup and view all the answers

How does Notch signaling influence neural fate determination in cells?

<p>It inhibits the expression of bHLH family genes, preventing cells from becoming neural precursors. (B)</p> Signup and view all the answers

In the context of lateral inhibition during neuroblast formation, what cellular event triggers the amplification of Delta expression in a single cell?

<p>Random fluctuations that lead to one cell expressing more Delta. (B)</p> Signup and view all the answers

What is the consequence of a mutation that disrupts Notch signaling in Drosophila?

<p>Overproduction of neuroblasts at the expense of epidermal cells. (D)</p> Signup and view all the answers

In the Xenopus model, what is the effect of introducing a high level of Delta proteins to one side of the neural tube?

<p>It inhibits the formation of neurons on that side. (D)</p> Signup and view all the answers

How does Numb regulate Notch signaling?

<p>By binding to the cytoplasmic tail of Notch, inhibiting its signaling activity. (B)</p> Signup and view all the answers

During the division of the Sensory Organ Precursor (SOP) cell in Drosophila, what is the consequence of the asymmetric distribution of Numb?

<p>One daughter cell receives Numb, leading to low Notch signaling, while the other does not, resulting in asymmetric cell fates. (A)</p> Signup and view all the answers

What would be the result of removing Numb from the Sensory Organ Precursor (SOP) cell?

<p>All cells will adopt the IIA fate (socket cell and hair cell). (D)</p> Signup and view all the answers

What is the primary role of Radial Glial Cells (RGCs) during cortical development?

<p>To provide a scaffold for neuronal migration and give rise to neurons and glia. (B)</p> Signup and view all the answers

During cortical development, what determines whether a dividing RGC will produce two RGCs or one RGC and one neuron?

<p>The plane of cleavage during cell division. (B)</p> Signup and view all the answers

How does asymmetrical distribution of Par3 protein during RGC division influence cell fate?

<p>It causes increased Notch signaling, promoting maintenance of the RGC phenotype. (C)</p> Signup and view all the answers

Which of the following describes the role of lateral inhibition mediated by Delta-Notch signaling in neuroblast formation?

<p>Selecting a single cell within a cluster to become a neuroblast while preventing its neighbors from adopting the same fate. (A)</p> Signup and view all the answers

How does Notch signaling in vertebrates differ from that in Drosophila regarding the regulation of neural development?

<p>In vertebrates, Notch signaling operates entirely within the neural lineage, maintaining the balance between neural progenitor maintenance and differentiation. (D)</p> Signup and view all the answers

What process is directly affected by the level of Achaete-Scute proteins in a developing cell?

<p>The expression of Delta proteins. (B)</p> Signup and view all the answers

Which of the following correctly matches a process with its outcome in neural development?

<p>High Delta expression: Inhibits neurogenesis in neighboring cells (C)</p> Signup and view all the answers

What is the consequence of high Par3 protein levels in retinal ganglion cells (RGCs)?

<p>Maintenance of the RGC phenotype through increased Notch signaling. (D)</p> Signup and view all the answers

Neural crest cells in the peripheral nervous system (PNS) differentiate into neurons upon receiving which type of signal?

<p>Bone Morphogenetic Proteins (BMPs). (A)</p> Signup and view all the answers

What is the primary mode of migration for inhibitory neurons originating in the ganglionic eminence as they populate different regions of the cortex?

<p>Tangential migration along the surface of the cortex. (B)</p> Signup and view all the answers

Which of the following proteins, present in the extracellular matrix, regulates layer formation during neuronal migration?

<p>Reelin. (C)</p> Signup and view all the answers

In the context of cortical development, what does the 'inside-out' neurogenesis program refer to?

<p>Older neurons are located in the deepest layers of the cortex, while newer neurons migrate past them to form superficial layers. (D)</p> Signup and view all the answers

What is the primary function of Dab1 in the context of cortical development?

<p>Regulating the speed of neuronal migration and detachment from radial glia. (B)</p> Signup and view all the answers

Which of the following best describes tangential migration in neural development?

<p>Neurons migrating laterally across the brain, often over long distances. (D)</p> Signup and view all the answers

What is the significance of the 'connectome' in the context of axon guidance and neural development?

<p>It describes the comprehensive map of neural connections in the nervous system, crucial for specific wiring. (B)</p> Signup and view all the answers

What was the major contribution of Harrison's experiments involving dissociated neurons in tissue culture?

<p>Observation that individual neurons can extend axons and dendrites in isolation. (D)</p> Signup and view all the answers

In the topographic map of retinal ganglion cells (RGCs), where do axons from dorsal RGCs typically terminate?

<p>Ventral/lateral part. (C)</p> Signup and view all the answers

How does the chemoaffinity hypothesis explain the formation of specific synaptic connections?

<p>Matching of complementary molecules on pre- and postsynaptic neurons leads to appropriate synaptic connections. (C)</p> Signup and view all the answers

Which of the following is NOT a described type of tangential migration?

<p>Neurons migrating along established blood vessel pathways. (B)</p> Signup and view all the answers

In the context of radial migration, what role do BDNF and NT-4 play?

<p>They promote the motility of migrating neurons along radial glial cells. (B)</p> Signup and view all the answers

In the cerebral cortex layering process, what would be the most likely result of a mutation that disrupts the function of Cajal-Retzius cells?

<p>Inverted cortical layering due to abnormal neuronal positioning. (B)</p> Signup and view all the answers

A researcher is studying a mouse model with a mutation that affects the anterior-posterior axis of the superior colliculus. Which aspect of RGC axon guidance would be most directly affected?

<p>The topographic mapping of nasal and temporal RGC axons. (A)</p> Signup and view all the answers

Roger Sperry's experiment involving the rotation of a frog's eye demonstrated which key principle regarding neural development?

<p>Axons have the capacity to regenerate and reconnect to their original target locations, guided by specific cues. (B)</p> Signup and view all the answers

In the context of neural development, what is the primary role of the optic chiasm?

<p>To act as a decision point where axons from retinal ganglion cells either cross to the contralateral side or remain on the ipsilateral side of the brain. (B)</p> Signup and view all the answers

In the experiment involving the transplantation of a small piece of tissue from the optic tract area into a host, what key observation suggested the presence of molecular cues directing axonal growth?

<p>Axons consistently grew towards the original caudal region of the graft, regardless of its orientation. (B)</p> Signup and view all the answers

Which of the following is NOT a potential mechanism by which local cues in the neuroepithelium guide axonal growth?

<p>Electrical synapse formation. (A)</p> Signup and view all the answers

How do growth cones navigate towards their synaptic targets?

<p>By sensing concentration gradients of chemical cues in their environment. (D)</p> Signup and view all the answers

What is the role of cytochalasin B in the study of growth cone dynamics?

<p>It disassembles actin filaments, disrupting growth cone motility and guidance. (A)</p> Signup and view all the answers

How does ephrin A influence Rac and Cdc42 activity in fibroblasts?

<p>It inactivates both Rac and Cdc42. (D)</p> Signup and view all the answers

What is the MOST likely effect of semaphorin on Rac GTPase activity?

<p>Inactivation of Rac by stimulating GTP hydrolysis. (D)</p> Signup and view all the answers

Which of the following is NOT a type of guidance cue encountered by growth cones as they advance to their synaptic targets?

<p>Electrical fields. (A)</p> Signup and view all the answers

What is the function of integrins in the context of growth cone guidance?

<p>To serve as receptors for extracellular matrix (ECM) molecules, linking the ECM to the actin cytoskeleton. (B)</p> Signup and view all the answers

How does Slit signaling influence Rho family GTPases?

<p>It activates Rho, while inactivating Rac and Cdc42. (B)</p> Signup and view all the answers

In an experiment where cells are cultured on a surface coated with collagen and certain parts of the collagen are UV-irradiated to make them inactive, what would be expected if a neuron requires collagen for growth?

<p>The growth cone would avoid the UV-irradiated areas and prefer the active collagen surfaces. (B)</p> Signup and view all the answers

What is MOST likely to happen if all GEFs (Guanine Exchange Factors) are knocked out in neurons, and then Slit is applied?

<p>Rho family GTPases will remain in their GDP-bound inactive state. (B)</p> Signup and view all the answers

What is the role of laminins in retinal ganglion cell (RGC) axon guidance?

<p>To serve as a growth-promoting substrate, guiding RGC axons along the vitreal surface towards the entrance of the ONH. (C)</p> Signup and view all the answers

How does altering the ratio of intracellular cAMP to cGMP affect neuronal responses to guidance cues?

<p>It can switch the response from attractive to repulsive or vice versa. (C)</p> Signup and view all the answers

What is the functional significance of commissural neurons expressing homodimers of DCC, while trochlear neurons express heterodimers of DCC and UncA5?

<p>Commissural neurons are attracted to Netrin, while trochlear neurons are repulsed. (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic feature of cadherins?

<p>They lack an intracellular domain. (A)</p> Signup and view all the answers

Why is local translation within the growth cone essential for axon guidance?

<p>It provides a rapid and spatially restricted mechanism to regulate receptor abundance. (B)</p> Signup and view all the answers

Which of the following is a calcium-independent cell adhesion molecule belonging to the immunoglobulin superfamily?

<p>NCAM (neural cell adhesion molecule). (B)</p> Signup and view all the answers

How can cell aggregation assays be used to investigate the function of cell adhesion molecules (CAMs)?

<p>By observing the rate at which cells aggregate in the presence or absence of functional CAMs. (D)</p> Signup and view all the answers

How does inhibiting protein synthesis in the growth cone affect the attraction of neurons to Netrin?

<p>It blocks the attraction to Netrin. (B)</p> Signup and view all the answers

How do blocking antibodies provide insights into CAM function?

<p>By preventing CAMs from binding to their ligands, thus inhibiting their function. (D)</p> Signup and view all the answers

What role does the 3' UTR (untranslated region) of mRNA play in local translation within the growth cone?

<p>It contains zip code sequences that target the mRNA to the growth cone for local translation. (C)</p> Signup and view all the answers

How do metalloproteases affect a growth cone's response to Netrin, and what is the MOST likely outcome of inhibiting them?

<p>Metalloproteases reduce the response; inhibition enhances it. (A)</p> Signup and view all the answers

What is a key difference between the function of ECM molecules and cell adhesion molecules (CAMs) in neural development?

<p>ECM molecules are secreted into the extracellular space to influence neuronal behavior, while CAMs are typically membrane-bound and mediate direct cell-cell interactions. (D)</p> Signup and view all the answers

What happens when Robo (Roundabout) receptor is knocked out in neurons regarding midline crossing?

<p>Neurons fail to cross the midline and accumulate at the floor plate. (C)</p> Signup and view all the answers

How does Slit binding to Robo affect DCC signaling and the neuron's response to Netrin?

<p>It silences DCC signaling, reducing attraction to Netrin. (A)</p> Signup and view all the answers

What is the general role of programmed cell death (PCD) during nervous system development?

<p>To match the number of neurons with the size of the target they innervate. (B)</p> Signup and view all the answers

During mammalian hand development, how does programmed cell death contribute to the formation of individual fingers?

<p>It sculpts the fingers by removing cells between them. (B)</p> Signup and view all the answers

Cell death balances the number of neurons connecting to a target. How can this same mechanism allow animals of different sizes to develop?

<p>The amount of cell death can change with target size. (D)</p> Signup and view all the answers

How do Ephrin-A molecules contribute to the formation of a retinotopic map?

<p>By establishing a concentration gradient on the tectum, with higher concentrations in the posterior, influencing RGC axon targeting based on receptor levels. (C)</p> Signup and view all the answers

What distinguishes forward signaling from reverse signaling in the context of Eph/Ephrin interactions?

<p>Forward signaling involves activation of signaling pathways downstream of Ephs upon ligand binding while reverse signaling involves activation of signaling pathways downstream of Ephrins upon binding to their receptors. (B)</p> Signup and view all the answers

Why is the intracellular domain of Plexin receptors crucial for Semaphorin signaling?

<p>The intracellular domain is necessary for Plexins to interact with co-receptors like Nrp and transduce signals. (C)</p> Signup and view all the answers

How do Slit proteins contribute to axonal guidance at the optic chiasm?

<p>They ensure axons cross at the chiasm and prevent wandering axons by acting as repulsive cues. (D)</p> Signup and view all the answers

What role does Netrin play in guiding commissural axons during development?

<p>Netrin attracts commissural axons towards the floor plate, promoting midline crossing. (B)</p> Signup and view all the answers

How does Sema5A contribute to axon guidance within the developing optic nerve?

<p>Sema5A creates a repulsive barrier that confines RGC axons within the optic nerve. (B)</p> Signup and view all the answers

What might be the consequence of a loss-of-function mutation in the Robo receptor concerning midline crossing?

<p>Axons would be unable to respond to Slit, potentially causing them to cross the midline inappropriately or multiple times. (A)</p> Signup and view all the answers

Which of the following best describes the role of Rho GTPases in growth cone guidance?

<p>Rho GTPases regulate actin and microtubule dynamics within the growth cone, influencing its morphology and movement. (C)</p> Signup and view all the answers

How do GEFs (Guanine nucleotide Exchange Factors) influence Rho GTPase activity?

<p>GEFs activate Rho GTPases by facilitating the exchange of GDP for GTP. (B)</p> Signup and view all the answers

What is the function of GDIs (Guanine nucleotide Dissociation Inhibitors) concerning Rho GTPases?

<p>GDIs sequester inactive, GDP-bound Rho GTPases, preventing their activation. (C)</p> Signup and view all the answers

How does the expression gradient of Ephrin-B1 influence the medial-lateral targeting of ventral RGC axons?

<p>It acts attractively on ventral RGC axons, causing them to terminate in the medial part of the tectum. (B)</p> Signup and view all the answers

In the context of commissural axon guidance, what is the sequence of events that directs axons from the dorsal spinal cord to cross the floor plate?

<p>Repulsion from the dorsal spinal cord, attraction to Netrin, midline crossing. (C)</p> Signup and view all the answers

Ablation of Slit-1 and Slit-2 leads to:

<p>Axon pathfinding defects including ectopic chiasm formation and wandering axons. (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of Semaphorins?

<p>They are exclusively secreted molecules. (B)</p> Signup and view all the answers

In an experiment involving RGC axons and membranes from the anterior and posterior optic tectum, what would be the expected behavior of temporal RGC axons?

<p>They would grow selectively on anterior membranes, reflecting their in vivo preference. (D)</p> Signup and view all the answers

Which of the following cellular changes is NOT a characteristic feature observed during apoptosis?

<p>Uncontrolled cell lysis leading to inflammation in surrounding tissues. (B)</p> Signup and view all the answers

An experiment reveals that blocking mRNA and protein synthesis prevents cell death induced by trophic factor removal. What does this suggest about the nature of this cell death?

<p>The cell death involves an active process requiring gene expression and protein synthesis. (C)</p> Signup and view all the answers

What experimental observation supports the hypothesis that the size of a target tissue influences the survival of innervating motor neurons during development?

<p>Fewer remaining motor neurons when a developing limb bud is removed. (B)</p> Signup and view all the answers

The administration of curare, which blocks acetylcholine receptors, results in preventing the developmental death of motor neurons. How can we explain this?

<p>Curare blocks muscle activity, which prevents the downregulation of trophic factors, promoting motor neuron survival. (D)</p> Signup and view all the answers

Nerve Growth Factor (NGF) was discovered due to its effects on which type of cells in developing chick embryos?

<p>Spinal and dorsal root ganglia neurons. (D)</p> Signup and view all the answers

What observation regarding DRG (dorsal root ganglia) supports the role of sarcoma-secreted factors in promoting neuronal survival and neurite outgrowth?

<p>DRG neurons die when separated from sarcomas but exhibit neurite outgrowth when co-cultured. (B)</p> Signup and view all the answers

After NGF binds to the TrkA receptor, what is the immediate subsequent event that initiates intracellular signaling?

<p>Receptor dimerization and tyrosine phosphorylation. (D)</p> Signup and view all the answers

If a neuron expresses both TrkB and p75 receptors, which factor would determine whether NGF binding promotes cell survival or cell death?

<p>The relative expression levels of TrkB and p75 receptors. (B)</p> Signup and view all the answers

Which molecular event is directly triggered by the dimerization of Trk receptors after neurotrophin binding?

<p>Phosphorylation of tyrosine residues in the intracellular domain. (A)</p> Signup and view all the answers

What is a primary role of neurotrophic factors in the nervous system?

<p>Preventing cell death and promoting neuron survival. (A)</p> Signup and view all the answers

How does NGF primarily reach the neurons it affects?

<p>It is secreted by target cells and taken up by neurons. (A)</p> Signup and view all the answers

Which signaling pathway is activated by TrkA receptor phosphorylation following NGF binding?

<p>RAS/MEK/ERK pathway (D)</p> Signup and view all the answers

What is the functional consequence of the phosphorylation of tyrosine residues on the intracellular domain of Trk receptors?

<p>Activation of intracellular signal transduction pathways. (B)</p> Signup and view all the answers

Besides survival, which of the following is a well-established action of neurotrophins on neurons?

<p>Stimulation of axon and dendrite sprouting in adult neurons. (D)</p> Signup and view all the answers

Which of the following neurotrophins primarily supports neurons in the peripheral nervous system (PNS)?

<p>Nerve Growth Factor (NGF). (C)</p> Signup and view all the answers

What is the immediate consequence of Ced-4 activation in the apoptosis signal transduction pathway?

<p>Activation of the caspase Ced-3. (A)</p> Signup and view all the answers

How does NGF (Nerve Growth Factor) prevent apoptosis in neurons?

<p>By activating Bcl-2, which inhibits caspase activity. (C)</p> Signup and view all the answers

What is the primary function of the SH2 domain in signal transduction?

<p>To bind to phospho-tyrosines on other proteins. (C)</p> Signup and view all the answers

What effect would a mutation that inactivates the SH3 domains of Grb2 likely have on Ras activation?

<p>It would prevent Grb2 from binding to Sos, reducing Ras activation. (C)</p> Signup and view all the answers

What is the role of the signalosome in neurotrophin signaling?

<p>To transport the Trk receptor bound to neurotrophin to the cell body. (D)</p> Signup and view all the answers

How do steroid hormones typically regulate gene expression in neurons?

<p>By binding to cytoplasmic receptors that translocate to the nucleus and bind DNA. (A)</p> Signup and view all the answers

What structural feature allows steroid hormone receptors to bind to DNA?

<p>A zinc finger motif. (D)</p> Signup and view all the answers

In male canaries, how does testosterone influence the song learning centers (HVA and RA) during the mating season?

<p>It increases neuronal number and dendritic complexity. (A)</p> Signup and view all the answers

What critical role does myelination play in neural transmission?

<p>It speeds up the transmission of neural impulses. (C)</p> Signup and view all the answers

During what developmental period does myelination primarily occur in humans?

<p>Starting in the third trimester and continuing into adulthood. (C)</p> Signup and view all the answers

What accounts for the majority of brain size increase in a child's first four years of life?

<p>The process of myelination. (B)</p> Signup and view all the answers

How does the PLC pathway contribute to cell survival?

<p>By activating Akt, leading to cell survival. (C)</p> Signup and view all the answers

A researcher infects PC12 cells expressing TrkA with DNA encoding Raf kinase and MEK. What outcome would be expected in the absence of NGF?

<p>The cells will differentiate and exhibit neurite outgrowth. (D)</p> Signup and view all the answers

In an experiment where sensory neurons are plated in a central compartment connected to chambers B and C, what happens when NGF is removed from chamber B only?

<p>Neurites in chamber B regress, but cell survival and neurites in chamber C are unaffected. (A)</p> Signup and view all the answers

Besides target-derived neurotrophins, what other sources of trophic support can neurons receive?

<p>Autocrine secretion of trophic factors like FGF or trophic factors from non-target cells like astrocytes. (B)</p> Signup and view all the answers

Which of the following glial cells is primarily responsible for myelination in the peripheral nervous system (PNS)?

<p>Schwann cells (D)</p> Signup and view all the answers

What is a key difference between oligodendrocytes and Schwann cells in terms of their myelination capacity?

<p>Oligodendrocytes can myelinate multiple axon segments, while Schwann cells typically myelinate only one segment of a single axon. (B)</p> Signup and view all the answers

In the PNS, what determines whether a Schwann cell will myelinate an axon or become a non-myelinating Schwann cell?

<p>The diameter of the axon it ensheathes. (A)</p> Signup and view all the answers

Which transcription factor (TF) is crucial for directing neural crest cells towards a Schwann cell fate?

<p>Sox10 (D)</p> Signup and view all the answers

What is the primary role of Shh (Sonic hedgehog) in the development of oligodendrocytes?

<p>It regulates the expression of Olig1 and Olig2, which are essential for oligodendrocyte development. (C)</p> Signup and view all the answers

What happens to Schwann cells in the PNS when an axon is damaged?

<p>They revert to an immature state to support axon regrowth. (D)</p> Signup and view all the answers

What is the function of the major dense line in the myelin sheath?

<p>It is formed by the apposition of the cytoplasmic faces of the myelin membrane and stabilized mainly by MBP. (D)</p> Signup and view all the answers

Which protein primarily stabilizes the intraperiod line within the myelin sheath in the CNS?

<p>PLP (D)</p> Signup and view all the answers

P0 protein, found exclusively in the PNS, functions as a homophilic cell adhesion molecule. What is its primary role in myelin structure?

<p>Supporting both the major dense line and the intraperiod line. (B)</p> Signup and view all the answers

Why do mutations affecting myelin proteins often result in severe neurological symptoms such as tremors and convulsions?

<p>Because myelin is crucial for proper nerve conduction, and its disruption leads to impaired neural signaling. (D)</p> Signup and view all the answers

What is the approximate lipid-to-protein ratio in myelin?

<p>70-85% lipid and 15-30% protein (B)</p> Signup and view all the answers

How do nodes of Ranvier contribute to rapid axonal conduction?

<p>By enabling saltatory conduction through high concentrations of voltage-gated ion channels. (A)</p> Signup and view all the answers

What characterizes the paranodal regions of myelinated axons?

<p>They are the junctions between myelin and the axon, containing axoglial adhesions. (B)</p> Signup and view all the answers

Why is CNS regeneration more challenging compared to PNS regeneration after injury?

<p>The CNS environment contains inhibitory factors and scar tissue that impede axonal regrowth, whereas the PNS has a more permissive environment. (C)</p> Signup and view all the answers

Following damage to CNS neurons, what role does scar tissue formation play in hindering axon regeneration?

<p>Scar tissue forms a physical barrier and releases inhibitory chemicals that prevent axon regeneration. (A)</p> Signup and view all the answers

Why does a peripheral nerve graft in the spinal cord promote regeneration of injured CNS cortical neurons?

<p>It supplies a favorable regenerative environment that overcomes inhibitory signals in the CNS. (C)</p> Signup and view all the answers

Which of the following is a primary mechanism by which myelin debris inhibits axon regeneration in the CNS?

<p>By signaling to growth cones to limit their ability to regrow. (A)</p> Signup and view all the answers

How does NOGO, a myelin inhibitor, impede axon regeneration?

<p>It functions as a repellent, causing axons to retract or avoid areas with myelin debris. (A)</p> Signup and view all the answers

What is the primary role of astrocytes in the formation of a glial scar after CNS injury?

<p>To wall off healthy tissue from unhealthy tissue, limiting the spread of damage. (A)</p> Signup and view all the answers

How does inhibiting RhoA or ROCK promote axon regeneration?

<p>By preventing the collapse of the growth cone, allowing axons to extend more readily. (D)</p> Signup and view all the answers

Why might the knockout of tumor suppressor genes like PTEN lead to enhanced axon regeneration?

<p>Because tumor suppressor genes normally inhibit axon growth, so removing them promotes growth. (C)</p> Signup and view all the answers

How can the inflammatory response, triggered by injecting saline solution into the eye after retinal injury, paradoxically promote axon regeneration?

<p>It induces the release of pro-survival and pro-regenerative factors by macrophages. (C)</p> Signup and view all the answers

What is a 'conditioning lesion' and how does it promote axon regeneration after spinal cord injury?

<p>It is a lesion in the PNS that activates a pro-regenerative gene program in the cell bodies of CNS neurons. (D)</p> Signup and view all the answers

What is a primary advantage of using C. elegans as a model organism to study intrinsic regulators of axon regeneration?

<p>Unlike mammalian systems, <em>C. elegans</em> exhibit robust axon regeneration due to simpler, less inhibitory, intrinsic mechanisms. (B)</p> Signup and view all the answers

What is the primary goal of cell replacement strategies involving stem cells in the treatment of spinal cord injury?

<p>To remyelinate demyelinated fibers, promote outgrowth on permissive substrates, or introduce new relay neurons. (D)</p> Signup and view all the answers

What is a key advantage of using induced pluripotent stem cells (iPSCs) derived from a patient's own skin fibroblasts in cell replacement therapies for spinal cord injury?

<p>There is a reduced risk of immune rejection because the cells are derived from the patient themselves. (B)</p> Signup and view all the answers

Following spinal cord injury, which cells have been shown to exhibit neurogenic potential upon reprogramming?

<p>NG2 glia (D)</p> Signup and view all the answers

What role does SOX2 play in the reprogramming of NG2 glia cells following spinal cord injury (SCI)?

<p>SOX2 is required cell-autonomously for the SCI-induced reprogramming of NG2 glia. (D)</p> Signup and view all the answers

After a spinal cord injury, an elevated level of SOX2 in NG2 glia cells is sufficient to trigger what?

<p>Functional neurogenesis and injury recovery. (D)</p> Signup and view all the answers

What is the overall result of reprogramming NG2 glia following a spinal cord injury?

<p>It rebuilds neural circuits and promotes injury recovery. (C)</p> Signup and view all the answers

Flashcards

CNS

Central Nervous System consisting of the brain and spinal cord.

PNS

Peripheral Nervous System that gathers information from the external environment.

Neurons

Cells designed for information processing with compartments for inputs and outputs.

Glial Cells

Supportive cells in the nervous system that assist neurons.

Signup and view all the flashcards

Synapse Anatomy

Structure where neurotransmitters are released, facilitating communication between neurons.

Signup and view all the flashcards

Cellular Migration

Process of neurons moving to their appropriate locations in the nervous system.

Signup and view all the flashcards

Function of Neurons

Neurons can be classified based on their function: sensory, motor, neuroendocrine, glandular.

Signup and view all the flashcards

Thalamus

Relay center of the brain that processes sensory information before sending it to V1.

Signup and view all the flashcards

Neuroblast

A precursor cell that differentiates into neurons.

Signup and view all the flashcards

Lateral Inhibition

A process where one neuroblast inhibits adjacent cells from also becoming neuroblasts.

Signup and view all the flashcards

Notch Signaling

A pathway that regulates cell fate decisions and inhibits neuroblast formation.

Signup and view all the flashcards

Delta-Notch Interaction

The binding of Delta to Notch that influences cell differentiation outcomes.

Signup and view all the flashcards

Achaete-Scute Proteins

Transcription factors that promote neural fate in developing cells.

Signup and view all the flashcards

Progenitor Cells (PCs)

Cells that can differentiate into various cell types, including neurons and glial cells.

Signup and view all the flashcards

Neurogenin

A pro-neuronal factor that induces neuronal differentiation.

Signup and view all the flashcards

Asymmetric Distribution of Numb

The uneven distribution of Numb protein that results in different cell fates after division.

Signup and view all the flashcards

Radial Glial Cells (RGCs)

Cells that provide a scaffold for neuron migration and can give rise to neurons and glia.

Signup and view all the flashcards

Venticular Zone

The region in the brain where neural progenitor cells reside and divide.

Signup and view all the flashcards

Gliogenesis

The process by which glial cells are produced from radial glial cells.

Signup and view all the flashcards

Cleavage Plane in Cell Division

The orientation of cell division that determines cell fate outcomes.

Signup and view all the flashcards

Oblique Divisions

Cell divisions that lead to asymmetric distribution of proteins affecting cell fate.

Signup and view all the flashcards

Neural Tube

The embryonic structure that develops into the central nervous system.

Signup and view all the flashcards

SOP (Sensory Organ Precursor)

A cell that gives rise to multiple cell types, such as sensory neurons and glial components.

Signup and view all the flashcards

Neuron Types

Different shapes and functions of neurons include Stellate, Pyramidal, Basket, Chandelier, and Amacrine.

Signup and view all the flashcards

Neuron Polarity

Describes the number of neurites extending from soma: Unipolar, Bipolar, Multipolar.

Signup and view all the flashcards

Glutaminergic

Neurons that use glutamate as a neurotransmitter, typically excitatory.

Signup and view all the flashcards

GABAergic

Neurons that use GABA as a neurotransmitter, generally inhibitory.

Signup and view all the flashcards

Development Steps

Key processes in embryo development: Cellular proliferation, differentiation, migration, and communication.

Signup and view all the flashcards

Cellular Communication

Process by which cells interact and transport information to one another.

Signup and view all the flashcards

Neural Crest

Cells that migrate from the neural tube to form parts of the PNS, skull, and pigment cells.

Signup and view all the flashcards

Gastrulation

Process that leads to the formation of three germ layers: ectoderm, mesoderm, and endoderm.

Signup and view all the flashcards

Neurulation

Development of the neural tube from the neural plate, leading to the formation of the brain and spinal cord.

Signup and view all the flashcards

Neural Tube Defects

Conditions like spina bifida caused by improper closure of the neural tube.

Signup and view all the flashcards

Folic Acid

Vitamin that helps prevent neural tube defects by ensuring proper cell division.

Signup and view all the flashcards

Organizing Region

Specific embryo region that influences the development of the nervous system.

Signup and view all the flashcards

Neural Induction

The process by which one embryonic region influences the fate of another, often leading to neural tissue formation.

Signup and view all the flashcards

Model Organisms

Species like chicken, frog, and zebrafish used to study nervous system development.

Signup and view all the flashcards

Neural fate

The default developmental path of ectodermal cells to become neural cells.

Signup and view all the flashcards

BMP signaling

A pathway that inhibits neural fate and promotes epidermal cell formation.

Signup and view all the flashcards

Dissociated ectoderm

Ectodermal cells separated from each other, leading to neural development.

Signup and view all the flashcards

Neural inducers

Signals like Noggin, Chordin, and Follistatin that promote neural cell fate.

Signup and view all the flashcards

Noggin

A neural inducer that prevents ventralization of the embryo.

Signup and view all the flashcards

Chordin

A neural inducer that promotes dorsal structures and neural fate.

Signup and view all the flashcards

Follistatin

A neural inducer that helps form neural crest cells during gastrulation.

Signup and view all the flashcards

Ectodermal specificity

Cells that become epidermal when exposed to BMP signaling.

Signup and view all the flashcards

Dorsal-ventral axis

An axis established by signals such as Sonic Hedgehog for body plan orientation.

Signup and view all the flashcards

Sonic Hedgehog (SHH)

A signaling molecule that induces formation of the floor plate and motor neurons.

Signup and view all the flashcards

Gradient signaling

Different concentrations of SHH induce specific neural cell types.

Signup and view all the flashcards

Hox genes

Regulatory genes involved in patterning the spinal cord and hindbrain.

Signup and view all the flashcards

Retinoic acid

A signaling molecule that influences the expression of Hox genes.

Signup and view all the flashcards

Proneural region

Part of the Drosophila that contains cells capable of becoming neuroblasts.

Signup and view all the flashcards

Neuronal Differences

Neurons vary genetically and biochemically based on their positional context.

Signup and view all the flashcards

Critical Period

A developmental phase during which neural connections are particularly sensitive to environmental stimuli.

Signup and view all the flashcards

Retinal Ganglion Cells (RGCs)

Neurons in the retina that send visual information to the brain via the optic nerve.

Signup and view all the flashcards

Optic Chiasm

The structure where half of the optic nerve fibers cross to the opposite side of the brain.

Signup and view all the flashcards

Guidance Cues

Molecules that direct axonal growth toward target areas in the nervous system.

Signup and view all the flashcards

Ephrins and Netrins

Types of guidance molecules involved in the regulation of axon guidance.

Signup and view all the flashcards

Extracellular Matrix (ECM)

A network of proteins and sugars providing structural and biochemical support to cells.

Signup and view all the flashcards

Integrins

Receptors on the growth cone that facilitate adhesion to the extracellular matrix.

Signup and view all the flashcards

Cadherins

Calcium-dependent cell adhesion molecules important for neural connectivity.

Signup and view all the flashcards

Neural Cell Adhesion Molecule (NCAM)

A calcium-independent adhesion molecule that aids in neuron-neuron connections.

Signup and view all the flashcards

Growth Cone

The dynamic structure at the tip of a growing axon that senses environmental cues.

Signup and view all the flashcards

Chemotropic Factors

Chemical signals that influence the direction of axonal growth.

Signup and view all the flashcards

Cell-Cell Adhesion

Interactions between adjacent cells that help maintain tissue structure.

Signup and view all the flashcards

Axonal Regeneration

The ability of axons to repair and reconnect after injury.

Signup and view all the flashcards

Transplant Experiments

Studies where tissue pieces are moved to assess axonal growth direction and response.

Signup and view all the flashcards

Vertical Division

Cell division that produces two identical cells with the same Par3 protein levels, leading to Retinal Ganglion Cells (RGCs).

Signup and view all the flashcards

Par3 Protein

A protein that influences cellular behavior in RGCs; higher levels lead to maintaining RGC phenotype.

Signup and view all the flashcards

Neural Crest Cells

Multipotent cells that migrate from the neural tube to form various PNS structures.

Signup and view all the flashcards

BMP Signals

Molecules that guide multipotent neural crest cells in acquiring neuronal identity.

Signup and view all the flashcards

Tangential Migration

The process where neurons move across layers, often using other neurons or axons as guidance.

Signup and view all the flashcards

Radial Migration

Neuronal movement directed from the ventricular zone to various layers of the cortex.

Signup and view all the flashcards

Inside-out Neurogenesis

Process where older neurons are pushed towards the deeper layers of the cortex as new ones form above them.

Signup and view all the flashcards

Reelin Protein

An extracellular protein that aids in cortical layer formation and neuron migration.

Signup and view all the flashcards

Dab1

An intracellular adaptor protein whose mutation disrupts proper neuron migration and cortical development.

Signup and view all the flashcards

Chemoaffinity

The concept that chemical cues help guide neurons to their exact targets in the nervous system.

Signup and view all the flashcards

Topographic Mapping

The organization of neural connections based on spatial location, especially seen in the retina.

Signup and view all the flashcards

Lissencephaly

A disorder resulting from improper neuron migration, leading to a 'smooth brain' appearance.

Signup and view all the flashcards

Axon Guidance

The process by which neurons find their specific targets to form synaptic connections.

Signup and view all the flashcards

Tangential Migration Types

Three types include following other neurons, growing axons, or migrating individually.

Signup and view all the flashcards

Ephrins

Molecules that serve as repulsive guidance cues for axon growth.

Signup and view all the flashcards

Ephrin A5

Ephrin A that interacts with EphA receptors to establish a retinotopic map.

Signup and view all the flashcards

Retinotopic map

Mapping of visual information from the retina to the tectum based on spatial position.

Signup and view all the flashcards

Ephrin B

Ephrin that attracts axonal branches through forward signaling.

Signup and view all the flashcards

Forward signaling

Activation of signaling pathways downstream of Ephs upon ligand binding.

Signup and view all the flashcards

Reverse signaling

Activation of pathways downstream of Ephrins upon receptor binding.

Signup and view all the flashcards

Semaphorins

A class of repulsive guidance cues that can be membrane bound or secreted.

Signup and view all the flashcards

Nrp receptors

Receptors on neurons that interact with semaphorins, allowing signal transduction.

Signup and view all the flashcards

Sema5A

A semaphorin that creates a repulsive barrier along the optic nerve.

Signup and view all the flashcards

Slit proteins

Proteins that mediate crossing decisions at the optic chiasm, mostly repulsive.

Signup and view all the flashcards

Commissural axons

Axons that cross the midline of the CNS to connect left and right sides.

Signup and view all the flashcards

Morphogens

Signals that assist in axon guidance decisions during development.

Signup and view all the flashcards

Rho GTPases

Proteins that cycle between active and inactive forms to regulate cytoskeleton arrangement.

Signup and view all the flashcards

GAP and GEF

Proteins that regulate the cycling of Rho GTPases for signaling control.

Signup and view all the flashcards

Fibroblast activation

Changing the activation state alters the cytoskeleton rearrangement in fibroblasts.

Signup and view all the flashcards

Netrins effect

Netrins attract Rac and Cdc42 but inhibit Rho signaling pathways.

Signup and view all the flashcards

Semaphorin function

Acts as a repulsive cue, turning off Rac by activating GAP.

Signup and view all the flashcards

Effect of Slit

Activates Rho while inactivating Rac and Cdc42 signaling pathways.

Signup and view all the flashcards

cAMP ratio

Influences the response of growth cones to axon guidance cues.

Signup and view all the flashcards

Receptor expression control

Different receptor types can lead to varying responses to the same cues in different neuron populations.

Signup and view all the flashcards

Local translation

Refers to the production of proteins at the growth cone independently of cell bodies.

Signup and view all the flashcards

Post-translational modification

Modifies protein function and can influence neuron responses to guidance cues.

Signup and view all the flashcards

Receptor silencing

The process where binding of Slit to Robo silences DCC signaling, affecting axon guidance.

Signup and view all the flashcards

Programmed cell death (PCD)

A controlled process of cell death important for developing tissues.

Signup and view all the flashcards

Apoptosis

An active process of cell suicide critical in development and tissue homeostasis.

Signup and view all the flashcards

GAP function

GTPase-activating proteins that convert active GTP-bound proteins to inactive GDP-bound forms.

Signup and view all the flashcards

Phospho-tyrosines

Attachment points for SH2 domain-containing proteins like Shc.

Signup and view all the flashcards

Cell death in development

Excess cells are eliminated to achieve proper tissue structure during growth.

Signup and view all the flashcards

SH2 domain

A region in proteins that binds to phospho-tyrosines.

Signup and view all the flashcards

Grb2 protein

An adaptor protein with SH2 and SH3 domains that connects signaling pathways.

Signup and view all the flashcards

Ras GTPase

A protein activated by Sos that promotes cell proliferation.

Signup and view all the flashcards

ERK pathway

A signaling cascade involving RAS, RAF, MEK, and ERK, crucial for cell growth.

Signup and view all the flashcards

Akt pathway

Promotes cell survival upon activation, inhibits apoptosis.

Signup and view all the flashcards

Caspases

Proteases activated during apoptosis that cleave cellular proteins and DNA.

Signup and view all the flashcards

BCL-2

A protein that inhibits apoptosis and promotes cell survival.

Signup and view all the flashcards

Neurotrophins

Factors that promote neuron survival and differentiation.

Signup and view all the flashcards

Steroid hormone receptors

Receptors that regulate gene expression upon hormone binding.

Signup and view all the flashcards

Myelination

The formation of a myelin sheath around axons to speed up neural transmission.

Signup and view all the flashcards

Zinc finger motif

A structural motif in steroid receptors that binds DNA.

Signup and view all the flashcards

Neurite outgrowth

The process of neuron extensions growing towards their targets.

Signup and view all the flashcards

Retrograde transport

Transport of signals from the axon terminal back to cell body.

Signup and view all the flashcards

Cellular differentiation

The process where a cell changes from one type to another, often more specialized.

Signup and view all the flashcards

Morphological features of apoptosis

Key changes include cell shrinkage, DNA fragmentation, and membrane blebbing.

Signup and view all the flashcards

Necrosis

Uncontrolled cell death due to injury, leading to inflammation and mess.

Signup and view all the flashcards

Trophic factor

Protein that supports the survival and growth of neurons.

Signup and view all the flashcards

Nerve Growth Factor (NGF)

The first identified neurotrophic factor essential for neuron survival.

Signup and view all the flashcards

Neurotrophin family

Group of proteins including NGF, BDNF, NT3, and NT4/5 that support neurons.

Signup and view all the flashcards

TrkA receptor

High-affinity receptor for NGF, mediating survival signals in neurons.

Signup and view all the flashcards

p75 receptor

Low-affinity receptor that modulates NGF signaling and can promote cell death.

Signup and view all the flashcards

Survival actions of neurotrophins

Promote neuron survival by preventing cell death.

Signup and view all the flashcards

Growth actions of neurotrophins

Stimulate elongation of axons and dendrites in neurons.

Signup and view all the flashcards

Signal transduction cascade

Process following receptor activation, leading to cellular responses like survival.

Signup and view all the flashcards

RAS/MEK/ERK pathway

Intracellular signaling pathway activated by NGF binding to trkA receptor.

Signup and view all the flashcards

Gene expression in apoptosis

Activation of genes and protein synthesis is necessary for apoptosis.

Signup and view all the flashcards

Phagocytosis in apoptosis

Process by which remaining cells remove apoptotic bodies.

Signup and view all the flashcards

Motor neuron development

Process influenced by target size, with excess neurons initially produced.

Signup and view all the flashcards

Myelination in CNS

CNS myelination occurs via oligodendrocytes, which can myelinate multiple axons.

Signup and view all the flashcards

Myelination in PNS

PNS myelination is done by Schwann cells, with a one-to-one relationship.

Signup and view all the flashcards

Schwann Cell Precursors

Derived from neural crest cells and can mature into myelinating or non-myelinating Schwann cells.

Signup and view all the flashcards

Oligodendrocyte Origins

Oligodendrocytes develop from ventral neural progenitor cells influenced by Olig1 and Olig2.

Signup and view all the flashcards

Nodes of Ranvier

Interruptions in myelin that facilitate fast transmission of action potentials.

Signup and view all the flashcards

Saltatory Conduction

Rapid transmission of action potentials along myelinated axons from node to node.

Signup and view all the flashcards

Unmyelinated Axons

Axons lacking myelin, such as C fibers, transmitting signals more slowly.

Signup and view all the flashcards

Major Dense Line

The structure formed by cytoplasmic membranes aligned in myelin's compact layer.

Signup and view all the flashcards

Demyelinating Diseases

Conditions where myelin wraps are reduced, affecting nerve function, like MS.

Signup and view all the flashcards

Myelin Lipid Composition

Myelin is comprised of 70-85% lipids, including cholesterol and phospholipids.

Signup and view all the flashcards

Axoglial Adhesions

Molecular interactions between axons and glial cells essential for axonal function.

Signup and view all the flashcards

CNS Regeneration

CNS neurons do not regenerate effectively after injury due to scar formation.

Signup and view all the flashcards

Neuronal Injury Response

Following axon injury, immune cells clear debris but can also cause secondary damage.

Signup and view all the flashcards

Schwann Cell Signals

Factors like Notch and NRG1 drive Schwann cells' maturation and myelination.

Signup and view all the flashcards

C fibers Function

C fibers are unmyelinated nerves associated with slow pain signals.

Signup and view all the flashcards

Axon Regeneration in CNS

Axons in the Central Nervous System (CNS) show poor regeneration capabilities due to inhibitory environments.

Signup and view all the flashcards

PNS Environment for CNS Neurons

Providing a Peripheral Nervous System (PNS) environment can support the regeneration of CNS neurons.

Signup and view all the flashcards

Myelin Inhibitors

Myelin debris contains inhibitors like NOGO that prevent axon growth.

Signup and view all the flashcards

Effects of NOGO knockout

Knocking out NOGO allows axons to regenerate after spinal cord injuries.

Signup and view all the flashcards

Role of Scar Tissue

Scar tissue inhibits axon regeneration due to the presence of astrocytes and fibroblasts.

Signup and view all the flashcards

Microfluidics in Research

Microfluidics helps isolate individual cells to study gene expression at lesion sites.

Signup and view all the flashcards

RhoA Inhibition

Inhibiting RhoA allows for better regeneration in axons by preventing collapse.

Signup and view all the flashcards

PTEN and Axon Growth

Knockout of the PTEN tumor suppressor boosts intrinsic signaling and axon growth.

Signup and view all the flashcards

Immune Cells in Regeneration

Immune cells can aid regeneration but may also cause additional damage at injury sites.

Signup and view all the flashcards

Oncomodulin

Oncomodulin is an inflammatory factor that promotes optic nerve regeneration.

Signup and view all the flashcards

Conditioning Lesion

A prior injury (conditioning lesion) can activate pro-regenerative gene programs for axons.

Signup and view all the flashcards

iPSCs for Regeneration

Induced pluripotent stem cells (iPSCs) can differentiate into neurons to aid regeneration.

Signup and view all the flashcards

Role of NG2 Glia

NG2 glia can be reprogrammed for neurogenesis following spinal cord injury.

Signup and view all the flashcards

SOX2 in Neurogenesis

Elevated SOX2 levels induce neurogenesis from resident glia after injury.

Signup and view all the flashcards

Study Notes

Nervous System Development

  • Two Nervous Systems: Central (CNS) – brain and spinal cord; Peripheral (PNS) – gathers info from the environment via sensory and autonomic ganglia, sending it to the CNS.

Organization of the Nervous System

  • Light activates photoreceptors.
  • Photoreceptors send signals to retinal ganglion cells (RGCs).
  • RGCs send signals to the lateral geniculate nucleus (LGN) in the thalamus.
  • The thalamus projects to the primary visual cortex (V1) for processing.
  • Processing continues in higher cortical areas, including the prefrontal cortex and hippocampus.
  • Output to motor areas (motor cortex) then spinal cord, finally muscles.

Nervous System Development

  • Cell Fate Determination: Different embryonic regions form different cell types (e.g., nervous system vs. epithelium).
  • Cellular Proliferation: Cells divide to increase in number.
  • Cellular Differentiation: Different cell types (neurons and glial cells) mature from progenitor cells.
  • Cell Migration: Neurons move to their appropriate locations (e.g., formation of cortical layers, PNS development).
  • Cellular Communication: Cells communicate through signaling pathways to coordinate development. Axons grow, establish connections (synapses), refine synapses.

Cells of the Nervous System

  • Neurons: Specialized for information processing; input, integration, output. Contain cell body, dendrites, axon, axon hillock, and pre-synaptic terminal.
  • Glial Cells: Support neurons.

Synapse Anatomy

  • Synaptic vesicles contain neurotransmitters.
  • Action potential (AP) leads to calcium influx, neurotransmitter release.
  • Neurotransmitters bind to receptors on the postsynaptic terminal.
  • Neurotransmitters are removed or internalized.

Neuron Classification

  • Function: Sensory, motor, neuroendocrine, glandular, neuron-neuron.
  • Shape: Stellate, pyramidal, basket, chandelier, amacrine. Unipolar, bipolar, multipolar.
  • Transmitter: Glutaminergic (excitatory), GABAergic (inhibitory), cholinergic, serotonergic, peptidergic.
  • Intrinsic Properties: Bursting, quiet cells. Molecular markers (e.g., calcium-binding proteins).
  • Inputs and Targets: Varies depending on neuron type.

Early Development

  • Fertilization: Mitosis leads to a 2-cell embryo.
  • Cleavages & Blastula: Cells divide and form a hollow ball of cells.
  • Gastrulation: Three germ layers (ectoderm, mesoderm, endoderm) form.
  • Neurulation: Ectoderm thickens into a neural plate, folds to form a neural tube. Neural crest cells differentiate into PNS.
  • Neural Tube Defects: Folate supplementation reduces risk.

Brain and Spinal Cord Formation:

  • Neural tube constrictions create brain subdivisions.
  • Regional identities are established, and neurons migrate to form layered structures (cortex).

Neural Induction

  • Organizer Regions: A specific region of the embryo can induce the formation of the nervous system.
  • BMPs: Inhibit the development of neural tissue into overlying epidermal tissue (if no neural inducer).
  • Neural Inducers (Noggin, Chordin, Follistatin): Block BMP signaling, promoting neural fate.

Patterning the Rostral-Caudal Axis /Anterior-Posterior Patterning

  • Hox genes: determine the anterior-posterior pattern in the spinal cord and posterior hindbrain. Their expression is regulated by retinoic acid gradients.
  • Other genes (Otx2, Gbx2) regulate brain patterning in anterior regions.

Patterning the Dorsal-Ventral Axis

  • Sonic Hedgehog (SHH): Secreted from the notochord, creates a morphogen gradient that influences ventral cell differentiation.
  • BMPs (Bone Morphogenetic Proteins): Secreted from the roof plate, influence dorsal cell differentiation.
  • Dorsalin: Inhibits motor neuron differentiation and promotes neural crest.

Neural Precursor Cell Differentiation

  • Vertebrate System: Neural tube with progenitor cells that differentiate into neurons and glia.
  • Drosophila: Delta-Notch signaling regulates the number of neuroblasts via lateral inhibition.
  • Notch and Delta: These proteins are crucial for cell-fate specification in epidermis and the formation of a given number of neuroblasts.

Cortex Development

  • Neuroepithelial cells in the ventricular zone differentiate into radial glial cells (RGCs).
  • RGCs act as scaffolding and provide a pathway for neuron migration within the developing cortex.
  • Inside-out Neurogenesis: Neurons generated later migrate past earlier-generated neurons to form more superficial cortex layers.

Reelin

  • Reelin is an extracellular protein secreted by Cajal-Retzius cells.
  • It regulates neuron migration and cortical layering. Mutations cause lissencephaly.

Tangential Migration

  • Migratory routes for cortical interneurons.

Axon Guidance

  • Chemoaffinity Hypothesis The position of neurons are encoded by biochemical cues. Axons grow from the developing retina to specific regions of the brain based on distinct molecular markers on the neurons and the target pathway
  • Experiment with cut optic nerves: regeneration shows that there is a critical period for wiring.
  • Molecular cues (ephrins, netrins, semaphorins, slits, Nrp, plexin) guide axon growth and pathfinding.

Growth Cone

  • Growth cone: Specialized structure at the tip of the growing axon from which filopodia protrude.
  • Extracellular matrix molecules (ECM): Guide axon growth, growth cones respond to favorable substrates such as collagen etc.
  • Cell surface adhesion molecules (CAMs): N-Cadherin, neural cell adhesion molecule(NCAM).

Ephrins

  • Ephrins function as both receptors and ligands (forward and reverse signaling).
  • Ephrin A gradients (high in posterior tectum, low in anterior) determine retinal ganglion cells (RGC) projection to specific tectal locations.

Semaphorins /SLITs

  • Semaphorins (repulsive) and Slit (repulsive) guide commissural axon formation.
  • Netrins and Robo receptors guide appropriate midline crossing decisions.

Morphogens

  • Morphogens are secreted signaling molecules that establish concentration gradients, directing the development of neuronal subtypes.

Modulating the Axon Guidance Response

  • Cues and Timing: Neurons respond to guidance cues in different ways depending on timing and environment (e.g. levels of cAMP, receptor expression, local protein translation, post-translational modification, receptor silencing)

Neuronal Circuits

  • Formation of complex neuronal connections.

Cell Death

  • Programmed cell death (PCD, apoptosis) removes excess neurons, sculpting the final neural circuit.
  • Trophic Factors: Proteins from target cells that support neuron survival. Nerve growth factor (NGF) is an example.

Nerve Trophic Factors (NTs)

  • NGF (Nerve Growth Factor), BDNF (Brain-Derived Neurotrophic Factor), NT3, NT4/5:
  • Promote neuron survival, growth, sprouting, modulation of transmission, differentiation.
  • Receptors (TrkA, TrkB, TrkC, p75): differentiation impacts whether cells survive or not.
  • Tyrosine Kinase (Trk) pathway: Signaling cascade for neuron survival that is activated by Neurotrophins.
  • p75: Promote/inhibit cell survival depending on NGF or other NTFs.

Apoptosis

  • Active biochemical program leading to cell death including morphological characteristics, mechanisms (caspases), and examples in neural development
  • Necrosis: Cell death from trauma or injury, leading to cell lysis.

Myelination

  • Oligodendrocytes (CNS): Produce myelin sheaths.
  • Schwann Cells (PNS): Produce myelin sheaths.
  • Myelination speeds up nerve impulses.

CNS Regeneration

  • Differences in regeneration capability between CNS and PNS.
  • Obstacles to regeneration: inhibitory molecules (e.g., NOGO), scar formation, and immune responses.
  • Regeneration strategies – PNS grafts, genetic approaches, and manipulating immune responses.

Cell Replacement Strategies

  • Stem cell therapies for remyelination, neuron replacement.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Description

Test your knowledge of the nervous system's structure and function. Questions cover neuron types, signal transmission, synapse formation, and neural development processes. This quiz assesses understanding of key components of the nervous system.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser