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CBNS 121 QUESTIONS AND ANSWERS, Exams of Social Sciences

United States International UniversitySocial Sciences

CBNS 121 QUESTIONS AND ANSWERS

Typology: Exams

2025/2026

Available from 01/22/2026

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CBNS 121 QUESTIONS AND ANSWERS
Noggin - Answers - - rescue ventralized embryos
- induce neural tissue in animal caps
Chordin - Answers - - expressed in the organizer
- has neural inducing activity
What happens when TGF(beta) receptors are blocked? - Answers - Mimics the effects
of Chordin/ Noggin
Follistatin - Answers - Bind to TGF(beta) secreted signals and inhibit them
Which proteins inhibit TGF(beta) signals? - Answers - - Noggin
- Chordin
- Follistatin
BMP - Answers - Bone Morphogenetic Protein
What do BMPs do? - Answers - Promote new bone growth, which is essential for
developing embryos
True/False
TGF(beta) receptors are BMPs. - Answers - True
What does the loss of Noggin and Chordin do in mice? - Answers - Causes severe
defects in the head and limits brain development
What is required for neural induction? - Answers - - Activation of FGF signaling
- Blocking of BMP signaling
When is neural tissue induced? - Answers - During Gastrulation
Where is the nervous system derived from? - Answers - Ectoderm
Where do the signals for neural induction come from? - Answers - Mesoderm
Spemann-Mangold Organizer - Answers - A tissue that secretes a mixture of growth
factor antagonists, which are able to induce embryonic cell differentiation
Wnt - Answers - - High in posterior embryo
- Wnt inhibitors in anterior mesoderm
Wnt inhibitors - Answers - - Dkk
- Cerberus
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CBNS 121 QUESTIONS AND ANSWERS

Noggin - Answers - - rescue ventralized embryos

  • induce neural tissue in animal caps Chordin - Answers - - expressed in the organizer
  • has neural inducing activity What happens when TGF(beta) receptors are blocked? - Answers - Mimics the effects of Chordin/ Noggin Follistatin - Answers - Bind to TGF(beta) secreted signals and inhibit them Which proteins inhibit TGF(beta) signals? - Answers - - Noggin
  • Chordin
  • Follistatin BMP - Answers - Bone Morphogenetic Protein What do BMPs do? - Answers - Promote new bone growth, which is essential for developing embryos True/False TGF(beta) receptors are BMPs. - Answers - True What does the loss of Noggin and Chordin do in mice? - Answers - Causes severe defects in the head and limits brain development What is required for neural induction? - Answers - - Activation of FGF signaling
  • Blocking of BMP signaling When is neural tissue induced? - Answers - During Gastrulation Where is the nervous system derived from? - Answers - Ectoderm Where do the signals for neural induction come from? - Answers - Mesoderm Spemann-Mangold Organizer - Answers - A tissue that secretes a mixture of growth factor antagonists, which are able to induce embryonic cell differentiation Wnt - Answers - - High in posterior embryo
  • Wnt inhibitors in anterior mesoderm Wnt inhibitors - Answers - - Dkk
  • Cerberus

What happens when Dkk1 is removed? - Answers - Hyperactive Wnt signaling

  • lack a forebrain and anterior head structures Retinoic Acid (RA) - Answers - - Derivative of Vitamin A (retinol)
  • Known to be powerful teratogen
  • Levels are higher in posterior than anterior
  • regulates HOX gene expression in vertebrates Is RA signaling required for development? - Answers - Yes;
  • Reduction of RA acid synthesis affects HOX expression
  • Embryos without RA die during embryonic development Activators - Answers - - BMP inhibitors
  • FGF signaling induce neural tissue with anterior characteristics Transformers - Answers - - RA
  • Wnt
  • FGF
  • Otx
  • Gbx required to transform a portion of neural tissue to more posterior structures (i.e hindbrain/spinal cord) regulate the expression of TFs that repress each other Otx2 - Answers - - /- mutants lack a forebrain and anterior head structures Pax6 - Answers - Hox gene for the development of eyes Sonic Hedgehog (Shh) - Answers - - expressed in the notochord and floorplate
  • sufficient to indicate ectopic floorplate (ventral) markers in vivo
  • induces ventral neural markers in a concentration-dependent manner
  • required for ventral fate specification
  • cause holoprosencephaly Tangential migration - Answers - refers to movement of neurons away from their site of origin along a route that is tangential to the cortical surface Permissive cues - Answers - - allow migration-regulation of adhesion
  • necessary for migration of cerebellar granule cells Attractive cues - Answers - guide a cell by "luring" it towards a particular region

Homunculus - Answers - a maplike representation of regions of the body in the brain; the depiction of the sensory system What did Sperry find? - Answers - Chemoaffinity hypothesis Chemoaffinity hypothesis - Answers - The hypothesis that growing axons are attracted to the correct targets by different chemicals released by the target sites Long-range cues - Answers - chemoattraction and chemorepulsion Chemorepulsion ligands - Answers - Semaphorins Chemoattraction ligands - Answers - Netrins Short-range cues - Answers - contact attraction and contact repulsion Contact attraction ligands - Answers - Cadherins Contact repulsion ligands - Answers - Ephrins Ephrins can signal ... - Answers - Bi-directionally Ephrins can serve as ... - Answers - Both ligands and receptors (in the growth cone) How was the neurotrophic factor discovered? - Answers - A series of experiments that isolated NGF, and confirmed that it was required for cell survival Where does NGF occur? - Answers - Nerve terminals Which receptor can initiate cell death? - Answers - P75NTR How do hormones play a role in neuron survival? - Answers - Due to sexual dimorphism, certain hormones are meant for each gender. When hormones are switched, cell death occurs for the correct hormone after the increase of the opposite hormone. How does transcription and translation play a role in cell death? - Answers - Cell death requires protein synthesis

  • blocking either processes will delay cell death What is CED's role in cell death? - Answers - It is directly involved in PCD; causing apoptosis. When eliminated, cells survive. Apoptosis - Answers - programmed cell death (PCD) What prevents the activation of pro-capeses? - Answers - IAP

What inhibits BAX? - Answers - Bcl-x inhibits the activation of BAX, which promotes cell death. BAX also inhibits Bcl-x. What cleans the dead neurons after cell death? - Answers - Microglia How does NMDA receptors promote cell survival? - Answers - When cell depolarizes, these receptors have a high permeability to calcium. The influx of Ca2+ ions can promote survival. However, too much will kill the cell. Lateral inhibition - Answers - The pattern of interaction among neurons in which activity in one neuron inhibits adjacent neurons' responses. How does lateral inhibition determine cell fate? - Answers - The stochastic process selects one cell that expresses more Achaetescute (Asc) Achaetescute (Asc) homologs - Answers - - Mash

  • Cash
  • Xash Notch - Answers - Promotes the reduction of Asc Delta - Answers - Binds to Notch How is the isthmic organizer formed? - Answers - The boundary between Otx2 and Gbx2 expression becomes the isthmic organizer (MHB) Radial Migration - Answers - movement of cells in the developing neural tube from the ventricular zone in a straight line outward toward the tube's outer wall ionotropic receptors - Answers - receptors that are coupled to ion channels and affect the neuron by causing those channels to open Where are glutamatergic synapses found? - Answers - Postsynaptic specializations aka dendrite spines Where are GABAergic synapses found? - Answers - Cell body and proximal dendrite Reticular Theory - Answers - An early alternative to neuron theory that held that the nervous system consisted of a large network of fused nerve cells; connected by bridges and use electrical synapses Neuron Theory - Answers - the idea that the nervous system consists of distinct elements or cells and that neurons are separated; connected by chemical synapses

Agrin - Answers - - growth factor that promotes the development of a motor end plate in skeletal muscle

  • made by motoneurons and by muscle
  • clusters together & maintains ACh receptors in muscle development
  • creates an elaborate neuromuscular junction What is required for NMJ formation? - Answers - Agrin How does Agrin induce clustering? - Answers - It induces phosphorylation of AChR subunits, which cluster at synaptic contact What is the NMJ pathway for clustering? - Answers - Agrin. MuSK. Rapsyn. In that order induces AChR clustering What happens when you denervate muscle? - Answers - - Muscle becomes "super sensitive"
  • Overall AChR mRNA levels increase What happens when you artificially overstimulate intact nerve? - Answers - - AChR mRNA expression decreases Progressive events - Answers - - Neurogenesis
  • Migration
  • Lamination
  • Axon growth and guidance
  • Targeting Mainly deal with circuit building Regressive events - Answers - - Cell death
  • Synapse constraint and refinement (elimination)
  • Axon and dendrite pruning Mainly deals with refining circuits What are the three types of afferent projections? - Answers - Refinement of ...
  • topography
  • convergence
  • postsynaptic compartment Refinement of topography - Answers - Different guidances cues influence where the axon will go Refinement of convergence - Answers - Multiple axons innervate one target cell, and only one will win out

Refinement of postsynaptic compartment - Answers - Pruning of the postsynaptic cells Ocular dominance columns - Answers - Cortical columns consisting of neurons that receive signals from the left eye only or the right eye only in layer 4 of the visual cortex What happens to ocular dominance if there is binocular deprivation? - Answers - Layer 4 in the visual cortex will develop normally Is neural activity required for ODC formation? - Answers - Yes; When axons are stopped from firing completely, left and right regions terminate together; no differentiation Heterosynaptic depression - Answers - activity of one synapse decreases the strength of another What prevents heterosynaptic depression? - Answers - Injection of calcium chelators (EGTA, BAPTA) What happens if there is repeated stimulation on a nerve? - Answers - It weakens the neurons for the same target cell "Cells that fire together, wire together" - Answers - For a given postsynaptic cell, inputs that are coactive tend to be strengthened "Out of sync, lose your link" - Answers - Non co-active inputs are weakened or eliminated The Hebbian synapse - Answers - occurs when the successful stimulation of a cell by an axon leads to the enhanced ability to stimulate that cell in the future Coincidence Detection - Answers - A process by which a neuron or a neural circuit can encode information by detecting the occurrence of temporally close but spatially distributed input signals What is the sensor or coincidence detector? - Answers - NMDA receptors What makes AMPA receptors less efficient? - Answers - Ca2+ activates phosphatases that remove phosphate; weakeneing the receptors What strengthens AMPA receptors? - Answers - Phosphorylation What induces LTP? - Answers - Making multiple synapses release NTs at the same time; promoting depolarization of the the cell. high frequency stimulation How does microglia know to engulf certain cells? - Answers - Microglia tagged with C receptors help get rid of synapses tagged with C3.