Excitatory and Inhibitory Neurons Overview
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Which of the following statements accurately describes the role of inhibitory neurons in a neural circuit?

  • Inhibitory neurons are predominantly responsible for transmitting sensory information to the brain, while excitatory neurons process and interpret this information.
  • Inhibitory neurons regulate the activity of excitatory neurons within a circuit, preventing excessive firing and ensuring balanced neural activity. (correct)
  • Inhibitory neurons function independently of excitatory neurons, specializing in processing specific types of information.
  • Inhibitory neurons primarily send signals to other parts of the brain, while excitatory neurons only communicate within the local circuit.

    • What is the main principle behind a feed-forward inhibitory circuit in neural networks?

  • Inhibitory interneurons create a feedback loop that modulates the activity of excitatory neurons over time.
  • Inhibitory signals from one neuron are amplified and transmitted to a larger pool of neurons, creating a cascade effect.
  • Excitatory signals in one neural column suppress signals in adjacent columns through inhibitory interneurons. (correct)
  • Excitatory signals in one column activate inhibitory interneurons, which then suppress excitatory signals in the same column.

    • How do the two types of recurrent neural networks, feed-forward inhibition and feedback inhibition, differ in their signal flow?

  • Feed-forward inhibition utilizes a single layer of neurons, while feedback inhibition involves multiple layers.
  • Feed-forward inhibition primarily functions for sensory input, while feedback inhibition handles motor output.
  • Feed-forward inhibition signals travel in a linear direction, while feedback inhibition involves looped signals within the same circuit. (correct)
  • Feedback inhibition only involves inhibitory neurons, while feed-forward inhibition relies on both excitatory and inhibitory neurons.

    • Which of the following is NOT a characteristic of excitatory neurons?

    <p>They primarily function to suppress or inhibit the activity of other neurons. (B)</p> Signup and view all the answers

    What is the primary function of a neuron's dendrites?

    <p>They receive signals from other neurons and integrate them. (B)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of unexpressed genes?

    <p>They are associated with open, unfolded chromatin. (A)</p> Signup and view all the answers

    Which of the following statements best explains how gene variants can affect neuronal function?

    <p>Gene variants can alter the structure of proteins, potentially affecting their functionality. (D)</p> Signup and view all the answers

    What is the potential implication of an imbalance between excitatory and inhibitory neurons in a neural circuit?

    <p>Development of neurological disorders characterized by uncontrolled neuronal activity, like epilepsy. (D)</p> Signup and view all the answers

    What role does the interplay between excitatory and inhibitory neurons play in learning?

    <p>It enables the brain to adapt to new situations by adjusting the strength of connections between neurons. (D)</p> Signup and view all the answers

    Based on the text, what is the primary function of beta-hexosaminidase A?

    <p>To break down specific fats that accumulate in neurons. (C)</p> Signup and view all the answers

    Which of the following statements accurately describes the relationship between gene expression and neuronal function?

    <p>Neurons can adjust the genes they express in response to environmental cues, influencing their function. (B)</p> Signup and view all the answers

    Which of the following best describes the primary function of a neuron's axon?

    <p>To generate and transmit electrical signals over long distances to other neurons, muscles, or glands. (B)</p> Signup and view all the answers

    The text suggests that our understanding of the genetic basis of brain disorders will improve in the future due to:

    <p>The ability to sequence a person's entire genome. (D)</p> Signup and view all the answers

    What is the primary function of GABA in the brain?

    <p>To inhibit the firing of neurons (C)</p> Signup and view all the answers

    How do ionotropic receptors differ from metabotropic receptors?

    <p>Ionotropic receptors directly bind to and open an ion channel, while metabotropic receptors indirectly influence channel activity. (C)</p> Signup and view all the answers

    Which of the following is NOT a role of astrocytes in synaptic transmission?

    <p>Depolarization of the postsynaptic membrane (C)</p> Signup and view all the answers

    What is the effect of NMDA receptor activation on neuronal activity?

    <p>A slower and more sustained depolarization, particularly in response to multiple action potentials (B)</p> Signup and view all the answers

    What is the primary mechanism by which steroid hormones like estradiol and cortisol influence neuronal activity?

    <p>Diffusing through the cell membrane and binding to intracellular receptors, ultimately affecting gene expression (B)</p> Signup and view all the answers

    Which of the following statements about gene expression in neurons is TRUE?

    <p>Differences in gene expression among neurons contribute significantly to their diverse structures, functions, and sensitivities to neurotransmitters and neuromodulators. (D)</p> Signup and view all the answers

    What is the role of prostaglandins in neuronal function?

    <p>To modulate the brain's response to pain and inflammation, increasing pain sensitivity (C)</p> Signup and view all the answers

    What is the primary difference between excitatory and inhibitory neurotransmitters?

    <p>Excitatory neurotransmitters increase the likelihood of a neuron firing, while inhibitory neurotransmitters decrease it. (D)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of neurotransmitter action at synapses?

    <p>Neurotransmitters remain bound to receptors indefinitely, ensuring a sustained signal. (B)</p> Signup and view all the answers

    Which of the following best describes the role of chromatin in neuronal gene expression?

    <p>Chemical modifications to chromatin play a crucial role in regulating which genes are expressed in neurons. (B)</p> Signup and view all the answers

    What is the primary role of microglia in the brain?

    <p>To act as the brain's main immune cells, protecting against infections and cellular damage. (A)</p> Signup and view all the answers

    Which statement accurately describes the role of kinesins in neurotransmission?

    <p>Kinesins transport vesicles containing neurotransmitters down the axon. (D)</p> Signup and view all the answers

    Why is it important that the synaptic cleft is wide enough to prevent the direct transmission of electrical signals between neurons?

    <p>The width of the synaptic cleft allows for the diffusion of neurotransmitters across the synapse. (A)</p> Signup and view all the answers

    What is the function of the postsynaptic density?

    <p>It contains a high concentration of neurotransmitter receptors, enabling signal reception. (C)</p> Signup and view all the answers

    How does the opening of voltage-sensitive ion channels in the axon terminal trigger neurotransmitter release?

    <p>It triggers the fusion of synaptic vesicles with the axon terminal membrane. (D)</p> Signup and view all the answers

    Which of these is a consequence of the change in the ratio of glial cells to neurons in the brains of humans and other primates?

    <p>The capacity for more complex and sophisticated brain functions. (B)</p> Signup and view all the answers

    What is the significance of the fact that the ratio of glia to neurons varies across different regions of the brain?

    <p>It implies that glial cells play a more important role in some brain regions than others. (D)</p> Signup and view all the answers

    Which of these is NOT a characteristic of a resting neuron?

    <p>The influx of calcium ions into the cell. (D)</p> Signup and view all the answers

    Why can't peptide-based neurotransmitters be synthesized in the axon terminal?

    <p>Axon terminals lack the necessary ribosomes for protein synthesis. (D)</p> Signup and view all the answers

    What is the primary difference between the function of astrocytes and oligodendrocytes?

    <p>Astrocytes regulate ion concentrations while oligodendrocytes produce myelin. (C)</p> Signup and view all the answers

    Study Notes

    Excitatory and Inhibitory Neurons

    • Majority (80%) of brain neurons are excitatory, prompting neighboring cells to fire.
    • Pyramidal cells are common excitatory neurons in the cerebral cortex, identified by their cone-shaped cell bodies and branched dendrites (apex and base).
    • Dendrites collect signals from all cortical layers.
    • Axons send signals to multiple destinations.
    • 20% of neurons are inhibitory, suppressing neighboring neuron activity and regulating circuit function.
    • Excitatory neurons typically pass signals forward in a circuit, sending outputs to other brain parts.
    • Inhibitory neurons are often local, looping responses back to the circuit's earlier segments.
    • Interplay of excitatory and inhibitory signals is crucial for learning, signal tuning, and smoothing.
    • Imbalances in excitatory/inhibitory neuron activity can contribute to seizure disorders like epilepsy.
    • Circuits can be organized in various input structures (feed-forward inhibitory, feedback inhibition).
    • Both are examples of recurrent neural networks with feedback signals between interconnected neurons.

    Neurons and Glia

    • Neuron is the functional unit of neural circuits and networks.
    • Neurons vary in shape and size and consist of a cell body (soma), dendrites, and an axon.
    • Cell body houses the nucleus and protein synthesis machinery.
    • Dendrites extend from the cell body, receiving signals from other neurons at synapses.
    • Axons transmit signals to other neurons, muscles, or glands; can vary in length from fractions of a centimeter to over a meter.
    • Neurons are associated with support cells called glia, previously believed to outnumber neurons 10:1, however, research suggests a closer ratio of 1:1 in some brain regions.
    • Various glial types exist in the central nervous system (astrocytes, microglia, ependymal cells, oligodendrocytes).
    • Astrocytes regulate ion concentrations, provide nutrients, and aid new connection formation between neurons.
    • Microglia are the "immune" cells, acting as phagocytes.
    • Ependymal cells produce cerebrospinal fluid.
    • Oligodendrocytes insulate axons with myelin.

    Ion Channels and Action Potentials

    • Ions cross neuron membranes through ion channels (tunnel-like proteins).
    • Membrane voltage difference in resting neurons is approximately -70 mV (more negative inside).
    • Signals from other neurons can depolarize (less negative) or hyperpolarize (more negative) the membrane by opening ion channels in dendrites.
    • If the sum of signals reaches the threshold voltage, voltage-gated ion channels open, triggering an action potential which travels down the axon.

    Synapses and Neurotransmission

    • Signals move from one neuron to the next at junctions called synapses.
    • Synapses consist of an axon terminal, the dendrite of a neighboring neuron, and the synaptic cleft (space in-between).
    • Chemical signals (neurotransmitters) cross the synaptic cleft.
    • When an action potential reaches the axon terminal, calcium ions enter the cell.
    • Calcium triggers neurotransmitter release from synaptic vesicles into the synaptic cleft.
    • Neurotransmitters include varied molecules like amino acids, gases, and small chemicals.
    • Peptide neurotransmitters are synthesized in the cell body, packaged in vesicles (bud off from Golgi) and transported down the axon along microtubules.
    • Neurotransmitters diffuse to the postsynaptic density (dendrite surface), triggering a response following binding to specific receptors.
    • Multiple neuron molecules including astrocytes are important to neurotransmitter removal preventing continuous activation.

    Receptors and Types

    • Two types of neurotransmitter receptors on the postsynaptic membrane: ionotropic and metabotropic.
    • Ionotropic receptors bind neurotransmitters directly to ion channels, opening them immediately.
    • Metabotropic receptors involve a cascade of biochemical steps before opening ion channels.
    • Neurotransmitters detach from receptors, channels return to resting states, and neurotransmitters are broken down or reabsorbed.

    Neurotransmitters and Their Roles

    • Excitatory and inhibitory actions determined by specific neurotransmitters.
    • Excitatory neurons create neurotransmitters that depolarize membranes.
    • Inhibitory neurons create neurotransmitters that hyperpolarize membranes.
    • Glutamate is the brain's primary excitatory neurotransmitter, often binding to AMPA and NMDA receptors.
    • GABA is the primary inhibitory neurotransmitter, and with ionotropic and metabotropic receptors, affects ion movement and membrane potential.

    Receptors and Molecular Signaling

    • Neurons have receptors for molecules like hormones, neuromodulators, and prostaglandins, which affect neuronal function differently.
    • Hormones carry messages about distant body conditions and activities to the brain.
    • Neuromodulators like endocannabinoids can affect release of other neurotransmitters.
    • Prostaglandins can impact the brain's pain sensitivity.
    • Intracellular changes occur following recognition of these chemical signals.
    • Hormones (ex. steroid hormones) can enter neurons directly and affect gene expression.

    Neurons, Genes, and Gene Expression

    • Neurons differ in appearance and function, producing different neurotransmitters, and possessing unique receptor types.
    • Identical genes, but cells express different subsets, creating neuronal diversity.
    • Gene expression depends on chromatin state (tightly packed, accessible).
    • Chemical changes in chromatin can either turn genes on or off, and these are reversible.
    • Allele variations can affect protein function and cause neurological conditions (e.g., Tay-Sachs disease).
    • Understanding of genetic basis of brain disorders is expected to grow with genome sequencing technology.

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    Description

    This quiz explores the roles and characteristics of excitatory and inhibitory neurons in the brain. It highlights the composition of the neuronal population, the functions of pyramidal cells, and the importance of the excitatory/inhibitory balance in neural circuits. Understanding these concepts is essential for grasping neural dynamics and their implications in disorders like epilepsy.

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