Neurophysiology: Electrical Signals in Neurons/synapse
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Questions and Answers

What is the primary function of electrical and chemical signals in neurons?

  • To communicate information within and between neurons (correct)
  • To control the production of ion channels
  • To regulate the resting membrane potential
  • To inhibit the action of graded potentials
  • What determines the distance over which communication can occur between neurons?

  • The type of ion channels present
  • The type of potential, action or graded (correct)
  • The strength of the electrical signal
  • The quantity of charge on the neuron's membrane
  • What is the direction of ion movement through open ion channels?

  • Along the plasma membrane
  • Against their electrochemical gradient
  • Across the cell membrane, but not down a gradient
  • Down their electrochemical gradient (correct)
  • What is the net charge on the outside of a neuron's membrane at rest?

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

    What is the relationship between the quantity of charge and the electric force of attraction?

    <p>The electric force of attraction increases with the quantity of charge</p> Signup and view all the answers

    What is the primary difference between action potentials and graded potentials?

    <p>The distance over which the potential can communicate</p> Signup and view all the answers

    What is the primary function of Voltage-gated channels in the nervous system?

    <p>To give the membrane its ability to undergo an action potential propagation</p> Signup and view all the answers

    What is the main difference between myelinated and unmyelinated neurons?

    <p>Presence or absence of saltatory conduction</p> Signup and view all the answers

    How does temperature affect the speed of action potential propagation?

    <p>It decreases the speed by decreasing the rate of channel opening</p> Signup and view all the answers

    What is the purpose of gap junctions in electrical synapses?

    <p>To allow local ionic currents to flow from one cell to the next</p> Signup and view all the answers

    What determines the resting membrane potential?

    <p>All of the above</p> Signup and view all the answers

    What is the function of metabotropic receptors?

    <p>To activate second messengers in the cytosol</p> Signup and view all the answers

    What is the role of the Na+/K+ pump?

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

    What is the term for the ability of a single neuron to synapse with many other post-synaptic cells?

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

    What is the name of the structure that joins the plasma membranes of two cells in an electrical synapse?

    <p>Gap junction</p> Signup and view all the answers

    What type of ion channel is gated by a mechanical stimulus?

    <p>Mechanically gated channel</p> Signup and view all the answers

    What is the primary mechanism by which ionotropic receptors contribute to the generation of an action potential?

    <p>Influx of positively charged ions into the postsynaptic neuron</p> Signup and view all the answers

    What is the direction of the net flux of K+ and Na+ ions?

    <p>From high to low concentration</p> Signup and view all the answers

    What is the term for the delay between the time the neurotransmitter is released and the time the postsynaptic potential is produced?

    <p>Synaptic delay</p> Signup and view all the answers

    What is the term for the type of receptors that contain a neurotransmitter binding site and an ion channel?

    <p>Ionotropic receptors</p> Signup and view all the answers

    What is the effect of graded potentials on the membrane potential?

    <p>A small, localized change in the membrane potential</p> Signup and view all the answers

    Which of the following is NOT a mechanism of neurotransmitter removal from the synaptic cleft?

    <p>Synthesis of new neurotransmitters</p> Signup and view all the answers

    What is the term for the sum of the effects of multiple excitatory and inhibitory postsynaptic potentials?

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

    What is the purpose of the axon hillock?

    <p>To generate action potentials</p> Signup and view all the answers

    What is the primary effect of a neurotransmitter agonist on neurotransmission?

    <p>Mimicking the action of endogenous neurotransmitters</p> Signup and view all the answers

    What is the primary mechanism of action of neuromodulators?

    <p>Influencing the release or reuptake of neurotransmitters</p> Signup and view all the answers

    What is the threshold potential for depolarization?

    <p>Above -70mV</p> Signup and view all the answers

    Which of the following drugs is an example of a neurotransmitter antagonist?

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

    What is the sequence of events in an action potential?

    <p>Depolarization, repolarization, hyperpolarization, return to resting state</p> Signup and view all the answers

    What is the significance of the refractory period?

    <p>It's the time period during which the neuron cannot generate another action potential</p> Signup and view all the answers

    What is the primary effect of opioids on their target neurons?

    <p>Making the neurons more difficult to excite</p> Signup and view all the answers

    What is the purpose of temporal and spatial summation?

    <p>To increase the strength of graded potentials</p> Signup and view all the answers

    Study Notes

    Neurotransmitters and Their Effects

    • Same neurotransmitter can have different effects depending on the receptor it binds to
    • Acetylcholine (Ach) binds to ionotropic and metabotropic receptors:
      • Ionotropic receptors (e.g., nicotinic acetylcholine receptors) allow influx of positively charged ions, leading to depolarization and excitatory effects
      • Metabotropic receptors (e.g., muscarinic acetylcholine receptors) trigger intracellular signaling cascades, leading to inhibitory effects

    Neurotransmitter Removal

    • Neurotransmitters can be removed from the synaptic cleft by:
      • Diffusion
      • Enzymatic degradation
      • Uptake into cells (reuptake or uptake into neighboring neuroglia)

    Action of Drugs on the Chemical Synapse

    • Drugs can:
      • Increase leakage of neurotransmitter from vesicle to cytoplasm
      • Increase neurotransmitter release into the cleft
      • Block neurotransmitter release
      • Inhibit transmitter synthesis
      • Block neurotransmitter reuptake
      • Block cleft enzymes that metabolize neurotransmitters
      • Bind to receptors on the post-synaptic membrane
      • Inhibit or stimulate second-messenger activity in the post-synaptic cell

    Neurotransmitter Agonists and Antagonists

    • Neurotransmitter agonists:
      • Mimic the action of endogenous neurotransmitters
      • Enhance neurotransmission
      • Bind to receptors on the post-synaptic neuron, leading to an excitatory response
      • Examples: L-DOPA (levodopa) for treatment of Parkinson's disease
    • Neurotransmitter antagonists:
      • Block the action of endogenous neurotransmitters
      • Bind to receptors, preventing the neurotransmitter from exerting its usual effect
      • Result in inhibitory responses
      • Examples: Haloperidol for treatment of Schizophrenia

    Neuromodulators

    • Modulate synaptic transmission by influencing the release or reuptake of neurotransmitters
    • Examples: Opioids, which can alter the electrical properties of target neurons and induce pain relief, euphoria, and other effects

    Ion Channels

    • Types of ion channels:
      • Leak channels
      • Ligand-gated channels
      • Mechanically-gated channels
      • Voltage-gated channels
    • Ion channels open and close due to "gates" that can seal the channel pore shut or open it up
    • Ion channels allow specific ions to move across the plasma membrane down their electrochemical gradient

    Resting Membrane Potential

    • Determined by:
      • Unequal distribution of ions across the plasma membrane
      • Selective permeability of the neuron's membrane to Na+ and K+
      • Na+/K+ pump
    • Net flux of ions across membranes depends on both the concentration gradient and the electrical difference (electrochemical gradient)

    Graded Potentials

    • Small, transient changes in membrane potential confined to a small region of the plasma membrane
    • Provide signaling in short distances
    • Can be depolarizing (excitatory) or hyperpolarizing (inhibitory)
    • Magnitude of the transient changes in membrane potential can vary
    • Dependent on changes in membrane permeability to ions (ligand-gated ion channels)

    Action Potentials

    • Sequence of rapidly occurring events that decrease and eventually reverse the membrane potential (depolarization) and eventually restore it to the resting state (repolarization)
    • Large changes in membrane potential of excitable cells only
    • Membrane potential can change from -70mV to +40mV
    • Depolarization, overshoot, repolarization, hyperpolarization, and return to resting membrane potential

    Mechanism of Action of Action Potentials

    • Initiated at the axon hillock (trigger zone)
    • All-or-none event
    • Depolarization needs to exceed the threshold potential
    • CNS physiology and electrical signals in neurons

    Electrical Signals in Neurons

    • Information is carried within neurons and from neurons to their target cells by electrical and chemical signals
    • Excitable cells communicate with each other via action potentials or graded potentials
    • Action potentials allow communication over short and long distances, while graded potentials allow communication over short distances only

    Synapse

    • Anatomically specialized junction between two cells
    • One single neuron can synapse onto many other post-synaptic cells (divergence)
    • Many synapses from different presynaptic neurons can synapse with a single cell (convergence)
    • Functional anatomy of the nervous system synapse:
      • Electrical synapse (gap junction)
      • Chemical synapse (operates through the release of neurotransmitters)

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    Description

    This quiz covers the basics of electrical signals in neurons, including action potentials and graded potentials, and their role in communication within and between neurons.

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