28 public questions tagged with this topic.
Myelin acts as an insulating layer around axons, allowing faster transmission of nerve impulses through saltatory conduction. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Zoology section), Chapter: Biology - Zoology portion covering relevant system and function.
Lag phase is initial stage of growth curve lasting few hours to one day after seeding cell suspension into fresh culture vessel. During this interval, cell number remains essentially unchanged because cells are adapting to new environment, repairing membrane damage inflicted by trypsin-EDTA detachment which cleaves integrins and surface receptors, resynthesizing adhesion proteins, spreading onto substrate via integrin activation and focal adhesion kinase signaling, and re-entering cell cycle from G0 state induced by confluence. Transcriptional program activates immediate-early genes such as c-
Ref: Freshney Culture of Animal Cells Ch.13 Lag phase adaptation; Alberts MBoC Cell growth phases attachment recovery.
Glucose entry into mammalian cells is essential for glycolysis and cannot occur through lipid phase due to hydrophilicity; therefore facilitated transporters required. GLUT family SLC2A comprises fourteen members with twelve transmembrane helices organized into two six helix bundles operating by alternating access inward outward transition mechanism. Tissue distribution optimized for function: GLUT1 widely expressed in erythrocytes and endothelial cells of blood brain barrier Km about 3 millimolar providing basal uptake, GLUT2 low affinity high Km about 17 millimolar in hepatocytes and pancrea
Ref: Mueckler, Eur J Biochem, GLUT Family Tissue Distribution - GLUT3 High Affinity Neuronal Transporter.
Neuronal cytoskeleton requires robust ten nanometer filaments to stabilize long processes subjected to bending and tension during growth and circuitry formation. Neurofilament proteins comprise heteropolymers of NF-L light sixty one kDa, NF-M medium one hundred two kDa and NF-H heavy one hundred twelve kDa subunits, each with conserved central rod domain forming coiled-coil dimers and variable C-terminal tails enriched in Lys-Ser-Pro repeats heavily phosphorylated to extend as sidearms regulating interfilament spacing and axonal diameter, which directly influences conduction velocity. Alpha-in
Ref: Liem J Cell Biol; neurofilaments NF-L/M/H heteropolymers regulate axon caliber, neuron-specific IF.
Neuronal microtubules show compartment specific organization supporting unique transport needs required for polarity and synaptic plasticity. In axon nearly all microtubules oriented with plus ends distal toward growth cone forming uniform polarity highway kinesins deliver efficiently outward dynein returns inward without directional ambiguity allowing fast axonal transport of synaptic vesicles mitochondria. Uniformity maintained by selective transport of microtubules plus organized bundling via TRIM46 at axon initial segment plus patronin minus capping and augmin driven polarity sorting. In d
Ref: Baas et al., J Cell Sci 2016 – Neuron microtubule polarity mixed in dendrites vs uniform in axons.
Proliferative capacity varies markedly among differentiated tissues, with some lineages retaining ability to re-enter cycle while others become permanently postmitotic. Neurons illustrate irreversible exit: during corticogenesis, progenitor neuroepithelial cells divide, but committed neuroblasts after final mitosis migrate to cortical plate, extend axons and dendrites, and upregulate Cip/Kip inhibitors p27Kip1 and p57Kip2, maintaining retinoblastoma protein in hypophosphorylated state bound to E2F, repressing promoters of cyclins, PCNA, and MCM helicases through transcription factors REST/NRSF
Ref: Becker & Bonni, Progress in Brain Research 2004, Postmitotic Neurons. Alberts 7th ed., Chapter 22.
The sodium-potassium pump maintains the resting membrane potential by actively transporting Na⁺ out and K⁺ into the neuron.
Ref: NCERT Class 11 Biology Chapter 18: Neural Control and Coordination Sensory Organs - Ear - Structure and Physiology of Hearing and Balance
Dendrites receive signals from other neurons and transmit them to the cell body.
Ref: NCERT Class 11 Biology Chapter 18: Neural Control and Coordination Sensory Organs - Eye - Structure and Physiology of Vision
Neurons are highly specialized cells that transmit electrical and chemical signals but have a limited ability to divide.
Ref: NCERT Class 11 Biology Chapter 18: Neural Control and Coordination Sensory Organs - Eye - Structure and Physiology of Vision
Afferent neurons (sensory neurons) carry impulses from sensory receptors to the CNS.
Ref: NCERT Class 11 Biology Chapter 18: Neural Control and Coordination Sensory Organs - Eye - Structure and Physiology of Vision
Potassium ions (K⁺) play a key role in maintaining the resting membrane potential by being more permeable than sodium ions.
Ref: NCERT Class 11 Biology Chapter 18: Neural Control and Coordination Central Nervous System - Spinal Cord Reflex Action and Reflex Arc
Neurons are the structural and functional units of the nervous system responsible for transmitting electrical signals.
Ref: NCERT Class 11 Biology Chapter 18: Neural Control and Coordination Central Nervous System - Brain - Forebrain
