Neuroscience Chapter on Neurons
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Questions and Answers

What is the primary role of microtubules in neurons?

  • They directly conduct electrical impulses.
  • They provide structural support to the neuron.
  • They are responsible for neurotransmitter synthesis.
  • They facilitate intracellular transport. (correct)

    • Which part of the neuron is primarily responsible for receiving information from neighboring cells?

  • Dendrites (correct)
  • Myelin sheath
  • Cell body
  • Axon

    • What occurs at the synapse?

  • Intracellular transport of proteins happens.
  • Neurotransmitters are released to communicate with the postsynaptic neuron. (correct)
  • Myelin sheath insulation is formed.
  • Electrical impulses are generated within the cell body.

    • Where in the neuron does the axon hillock primarily function?

    <p>To integrate incoming signals and generate output signals.</p> Signup and view all the answers

    What is NOT a function of the myelin sheath?

    <p>Facilitating neurotransmitter release.</p> Signup and view all the answers

    What is the fundamental purpose of metabolic energy in the context of neuronal function?

    <p>To maintain ionic gradients across the membrane</p> Signup and view all the answers

    What occurs during depolarization of a neuron's membrane potential?

    <p>Membrane potential becomes less negative than the resting potential</p> Signup and view all the answers

    Which equation is used to determine the equilibrium potential of an ion based on its concentration gradient?

    <p>Nernst equation</p> Signup and view all the answers

    Which of the following types of neurons is primarily responsible for transmitting signals from sensory receptors to the central nervous system?

    <p>Sensory neurons</p> Signup and view all the answers

    What distinguishes pseudounipolar neurons from other types of neurons?

    <p>They possess a single process called an axon</p> Signup and view all the answers

    What is the primary role of interneurons in the central nervous system?

    <p>Integrating information within the CNS</p> Signup and view all the answers

    According to the Goldman-Hodgkin-Katz equation, what factors determine the membrane potential of a neuron?

    <p>Permeability to K+, Na+, and Cl- and their concentrations</p> Signup and view all the answers

    What neuronal structure is primarily responsible for receiving stimuli?

    <p>Dendrites</p> Signup and view all the answers

    During repolarization, the membrane potential of a neuron returns to which state?

    <p>Resting membrane potential</p> Signup and view all the answers

    What percentage of cell body processes are typically branched in a multipolar neuron?

    <p>More than 75%</p> Signup and view all the answers

    Which structure typically conveys information to the central nervous system (CNS)?

    <p>Sensory neuron</p> Signup and view all the answers

    Which type of information does an axon transmit?

    <p>Both electrical and chemical information</p> Signup and view all the answers

    What determines the true trigger zone of a neuron?

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

    What occurs during hyperpolarization?

    <p>The membrane potential becomes more negative than the resting potential</p> Signup and view all the answers

    Which process involves the membrane potential being less negative than its resting state?

    <p>Depolarization</p> Signup and view all the answers

    What is the primary function of the axon in a neuron?

    <p>To transmit electrical signals to presynaptic axon terminals</p> Signup and view all the answers

    Which part of the neuron is primarily involved in receiving signals?

    <p>Dendrites</p> Signup and view all the answers

    What role do dendritic spines play in neurons?

    <p>They dynamically change their morphology and are associated with learning and memory</p> Signup and view all the answers

    Which structure in the neuron determines if electrical signals can proceed through the axon?

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

    What happens at the presynaptic axon terminal?

    <p>Chemical neurotransmission occurs</p> Signup and view all the answers

    Which component of axons is involved in transporting molecules like neurotransmitters?

    <p>Axonal transport</p> Signup and view all the answers

    What is contained within the presynaptic axon terminal?

    <p>Mitochondria and membrane-bound vesicles</p> Signup and view all the answers

    What is the initial segment of the axon called?

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

    Which color typically represents inhibitory synapses in diagrams?

    <p>Blue</p> Signup and view all the answers

    What are retrograde messengers in the context of neurons?

    <p>Signals that return feedback from postsynaptic dendrites to presynaptic axon terminals</p> Signup and view all the answers

    What role do motor proteins play in axonal transport?

    <p>They facilitate the transport of vesicles along microtubules.</p> Signup and view all the answers

    Which component of a motor protein is responsible for binding with microtubules?

    <p>Head</p> Signup and view all the answers

    What is the energy source required for the walking mechanism of motor proteins?

    <p>ATP</p> Signup and view all the answers

    In which direction does the anterograde transport mechanism move?

    <p>From soma to axon terminals</p> Signup and view all the answers

    What typically happens to old membrane components in neurons?

    <p>They are digested in lysosomes.</p> Signup and view all the answers

    How do electrical signals in neurons propagate after being initiated?

    <p>Unidirectionally to the presynaptic terminal</p> Signup and view all the answers

    Which statement is true regarding the cytoplasmic continuity of neurons?

    <p>Each neuron is an isolated unit with no cytoplasmic continuity.</p> Signup and view all the answers

    What characterizes the function of axons in neurons?

    <p>They are specialized to carry electrical signals unidirectionally.</p> Signup and view all the answers

    What is the primary purpose of the Na+-K+ ATPase in a neuron?

    <p>To create ionic concentration gradients</p> Signup and view all the answers

    What occurs during synaptic vesicle recycling?

    <p>Vesicles are reused and refilled with neurotransmitters.</p> Signup and view all the answers

    Which statement best describes the resting membrane potential in a typical neuron?

    <p>It results from the unequal distribution of ions across the membrane</p> Signup and view all the answers

    What is the role of K+ leak channels in maintaining the resting membrane potential?

    <p>They enable K+ to flow out of the cell, contributing to a negative potential</p> Signup and view all the answers

    What triggers the migration of the varicella zoster virus from the neuron to the skin?

    <p>Anterograde fast axonal transport</p> Signup and view all the answers

    What effect does the permeability of the membrane to ions have on resting membrane potential?

    <p>Higher permeability to K+ leads to a more negative resting potential</p> Signup and view all the answers

    The electrical and concentration gradients for K+ ions are maintained by which of the following?

    <p>Na+-K+ ATPase and K+ leakage channels</p> Signup and view all the answers

    Which ions are mainly found in extracellular fluid?

    <p>Na+ and Cl-</p> Signup and view all the answers

    How does the selective permeability of the plasma membrane contribute to the resting membrane potential?

    <p>It prevents negative ions from entering, trapping them inside</p> Signup and view all the answers

    What happens during the equilibrium potential state for K+ ions?

    <p>Counteracting forces of concentration and electric gradients are balanced</p> Signup and view all the answers

    What type of molecules can freely cross the plasma membrane?

    <p>Small uncharged polar molecules</p> Signup and view all the answers

    In which fluid are phosphate ions predominantly found?

    <p>Intracellular fluid</p> Signup and view all the answers

    The condition where the extracellular fluid is set to 0 potential is referred to as what?

    <p>Relative charge scale</p> Signup and view all the answers

    Which electrolyte is primarily responsible for generating the negative resting membrane potential?

    <p>K+</p> Signup and view all the answers

    When the membrane is described as a capacitor, what is primarily being referred to?

    <p>Its capacity to store ionic charges across the membrane</p> Signup and view all the answers

    Which of the following ions is more concentrated inside a typical neuron?

    <p>K+</p> Signup and view all the answers

    What primarily prevents the free movement of charged molecules across the plasma membrane?

    <p>The presence of phospholipids in the membrane</p> Signup and view all the answers

    Study Notes

    Nervous System - Resting Membrane Potential and Neuron

    • Objectives:
      • Understand the basic principles of resting membrane potential generation.
      • Describe the anatomy of a typical neuron and its physiological functions.

    Membrane Permeability

    • Phospholipid bilayers of cell membranes are impermeable to charged molecules (e.g., Na+, K+, Cl−, Ca²⁺).
    • These molecules are also insoluble in the hydrophobic membrane core.
    • Large water-soluble molecules (e.g., proteins, nucleic acids, sugars) also require channels to cross the cell membrane.
    • Small, uncharged, polar molecules (e.g., CO₂, O₂, NH₃, water) can freely cross the membrane, often with aquaporins.

    Electrolyte Distribution

    • Interstitial fluid: Major electrolytes are Na+, Cl−, and HCO₃⁻.
    • Intracellular fluid: Major electrolytes are K+, HPO₄²⁻ (phosphate ion), and negatively charged proteins.

    Dominant Ions

    • Extracellular fluid: Dominant cation is Na⁺, and anion is Cl⁻.
    • Intracellular fluid: Dominant cation is K⁺, and anions include phosphate ions and negatively charged proteins.

    Electrical Properties

    • Plasma membranes are ionic conductors, allowing ion currents.
    • The concentration gradient dictates the direction of ion flow.
    • The membrane's capacity to hold charges generates the transmembrane potential (electrical voltage difference).

    Generation of Membrane Potential

    • At equilibrium, the cell and solution are electrically and chemically balanced.
    • The cell membrane acts as an insulator, preventing free ion movement between compartments.
    • The Na+-K+ ATPase creates ionic concentration gradients (3 Na+ out, 2 K+ in).
    • This creates a negative intracellular potential.
    • K+ leak channels also contribute to the resting membrane potential.

    K+ Leak Channels

    • The plasma membrane has more K+ leak channels than Na+ leak channels.
    • K+ leaks out due to the concentration gradient, with other ions following.
    • The impermeability of the membrane to negatively charged ions creates a negative intracellular environment.

    Equilibrium Potential

    • Equilibrium potential (Eion) occurs when opposing forces (concentration and electrical gradients) balance the net ion movement.

    Resting Membrane Potential

    • All living cells have a resting membrane potential.
    • Chemical and electrical disequilibrium exist at rest.
    • The resting membrane potential is the measurement of electric charge inside versus outside the cell.
    • A negative resting membrane potential is typical.

    Neuron Anatomy & Functions

    • Neurons are the functional units of the nervous system, responsible for transmitting and integrating information.
    • Sensory neurons receive stimuli and carry signals to the central nervous system.
    • Interneurons integrate information within the central nervous system.
    • Motor neurons send signals from the central nervous system to muscles or glands.
    • Neurons are excitable cells whose membrane potential can change.

    Neuron Structure

    • Cell body (soma): Contains the nucleus and organelles.
    • Dendrites: Receive incoming signals.
    • Axon: Transmits signals away from the cell body. -Axon hillock: Special region of the soma. -Presynaptic axon terminal: Swelling at axon's end with mitochondria and neurotransmitter.

    Synapse

    • Synapse: The region where an axon terminal communicates with its postsynaptic target cell.
    • Neurotransmitters are released into the synaptic cleft, entering neighboring neurons.

    Dendritic Spines

    • Dendritic spines are specialized protrusions that increase contact points.
    • Protein synthesis occurs in spines and can be transferred.

    Signal Transmission and Axonal Transport

    • Information is transmitted electrically (graded potentials) to axon hillock to action potentials.
    • Signals are mostly unidirectional in the axon but bi-directional in the chemical synapses.
    • Axonal transport involves movement of vesicles along microtubules with motor proteins.

    Important Concepts

    • Electrical signals are initiated and propagated unidirectionally along the axon.
    • There is no cytoplasmic continuity between neurons.

    Additional Notes

    • The Goldman-Hodgkin-Katz (GHK) equation is used to calculate membrane potential, considering multiple ions' permeability.
    • The resting membrane potential of a mammalian neuron is −70 mV.

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