Nervous System Physiology Essentials 2
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Questions and Answers

What distinguishes autocrine communication from intracrine communication?

  • Autocrine communication involves signals that only activate neighboring cells.
  • Autocrine signaling occurs only over long distances.
  • Intracrine communication uses receptors located on the cell surface.
  • Intracrine involves the signaling molecule staying within the cell. (correct)

    • Which type of communication involves nerve cells transmitting signals via neurotransmitters?

  • Neurocrine communication (correct)
  • Endocrine communication
  • Autocrine communication
  • Paracrine communication

    • What does specificity refer to in the context of receptor-ligand interactions?

  • The strength of the interaction between receptor and ligand.
  • The ability of a receptor to bind to multiple ligands at once.
  • The recognition of a specific ligand by a receptor. (correct)
  • The number of ligands a receptor can bind simultaneously.

    • Which type of receptor is found in the nucleus and is involved in gene transcription?

    <p>Nucleus Receptor</p> Signup and view all the answers

    What is a common characteristic of membrane receptors as opposed to intracellular receptors?

    <p>Membrane receptors react to hydrophilic signal molecules.</p> Signup and view all the answers

    Which statement accurately describes affinity in receptor-ligand interactions?

    <p>High-affinity receptors bind strongly even at low concentrations of ligands.</p> Signup and view all the answers

    What is meant by saturation in the context of receptors?

    <p>The maximum level of receptor activity attainable by a ligand.</p> Signup and view all the answers

    What is the primary function of receptors in cellular communication?

    <p>To perceive and communicate with external stimuli.</p> Signup and view all the answers

    How does competition among ligands affect receptor activity?

    <p>It determines which ligand will dominate receptor binding.</p> Signup and view all the answers

    What type of signaling sends short-distance signals to nearby cells?

    <p>Paracrine signaling</p> Signup and view all the answers

    What is hypersensitivity (up-regulation) in the context of receptors?

    <p>An increase in receptor numbers in response to decreased ligand levels.</p> Signup and view all the answers

    Which statement accurately differentiates between lipophilic and hydrophilic hormones?

    <p>Lipophilic hormones require carrier proteins in the blood; hydrophilic do not.</p> Signup and view all the answers

    How do the timing and duration of actions differ between intracellular receptors and cell surface receptors?

    <p>Intracellular receptors typically lead to longer-lasting effects than membrane receptors.</p> Signup and view all the answers

    What triggers an action potential in excitable cells?

    <p>The graded potentials reaching the threshold of stimulation.</p> Signup and view all the answers

    What characterizes the resting membrane potential in most cells?

    <p>A negative value, typically around -70 mV caused by ion concentration differences.</p> Signup and view all the answers

    What is a primary role of agonists when they interact with receptors?

    <p>Activation of the receptor to send signals within the cell.</p> Signup and view all the answers

    What occurs during the Absolute Refractory Period (ARP)?

    <p>Voltage-gated Na⁺ channels are inactive.</p> Signup and view all the answers

    During the Relative Refractory Period (RRP), what condition must be met for a new action potential to occur?

    <p>A stronger stimulus than normal is required.</p> Signup and view all the answers

    How does action potential propagation differ in myelinated nerves compared to unmyelinated nerves?

    <p>Only depolarization occurs at the nodes of Ranvier in myelinated nerves.</p> Signup and view all the answers

    What effect does the higher density of Na⁺ channels at the nodes of Ranvier have on action potential propagation?

    <p>It helps maintain the power of the action potential.</p> Signup and view all the answers

    Which statement about the Relative Refractory Period (RRP) is true?

    <p>K⁺ channels are still open during this period.</p> Signup and view all the answers

    What is the primary role of the Na⁺/K⁺ pump in maintaining the resting membrane potential?

    <p>It helps keep the intracellular environment negatively charged.</p> Signup and view all the answers

    What initiates the action potential once the threshold potential is reached?

    <p>Opening of voltage-gated Na⁺ channels.</p> Signup and view all the answers

    Which type of graded potential is responsible for sending sensory information to the spinal cord?

    <p>Receptor potential</p> Signup and view all the answers

    What characteristic of graded potentials describes their decrease in effect as they move away from the site of stimulus?

    <p>Decremental conduction</p> Signup and view all the answers

    Which of the following statements about graded potentials is TRUE?

    <p>Their magnitude is proportional to the strength of the stimulus.</p> Signup and view all the answers

    What is the resting membrane potential typically around in most cells?

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

    What role do negatively charged molecules play in the resting membrane potential?

    <p>They create a negative internal environment that aids in resting potential.</p> Signup and view all the answers

    What type of graded potential is specifically linked to the automaticity of the heart?

    <p>Pacemaker potential</p> Signup and view all the answers

    What initiates the generation of an action potential in a cell?

    <p>Sufficient stimulus raising the membrane potential to approximately -55 mV</p> Signup and view all the answers

    During which phase of an action potential does the cell interior become positively charged?

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

    Which statement correctly describes the characteristics of action potentials?

    <p>Action potentials are always generated when the threshold is reached.</p> Signup and view all the answers

    What is the role of the Na⁺/K⁺ pump after an action potential?

    <p>To transport ions back to their original locations and restore resting potential</p> Signup and view all the answers

    Which statement is true about the refractory periods following an action potential?

    <p>The Relative Refractory Period occurs during the first phase of repolarization.</p> Signup and view all the answers

    What happens during hyperpolarization in an action potential?

    <p>Potassium channels close slowly, causing potential to drop below resting levels.</p> Signup and view all the answers

    What is a primary function of action potentials in excitable cells?

    <p>To transmit information quickly across the cell</p> Signup and view all the answers

    What occurs immediately after the action potential reaches its peak around +30 mV?

    <p>K⁺ channels open, beginning the repolarization phase.</p> Signup and view all the answers

    Study Notes

    Nervous System Physiology Essentials 2

    • Cellular communication is crucial for coordinating cell actions within an organism.

    Cellular Communication Types

    • Intracrine: Communication within a cell.
    • Juxtacrine: Communication via direct cell contact.
    • Autocrine: A cell responds to signals it produces itself.
    • Paracrine: Short-distance signaling to nearby cells.
    • Neurocrine: Specific signaling through synapses using neurotransmitters from neurons to muscles.
    • Endocrine (Hormonal): Long-distance signaling through hormones carried by blood to target cells.

    Autocrine vs. Intracrine

    • Autocrine: A cell secretes a signal that then binds to receptors on the same cell.
    • Intracrine: Signals are synthesized and act within the cell without leaving the cell.

    Receptor Types

    • Cells use receptors to perceive and respond to external stimuli.
    • Receptors initiate biochemical processes.
    • Membrane receptors: Respond to incoming signals and direct cellular response.
    • Intracellular receptors: Located in the cell nucleus.

    Receptor Types - Categorized by Location

    • Membrane/Intracellular Receptors Categories:
      • G-protein Coupled Receptors (in the membrane)
      • Ligand-gated Ion Channels (in the membrane)
      • Enzyme-Linked Receptors (in the membrane)
      • Nuclear Receptors (in the nucleus)

    Receptor Localization

    • Intracellular Receptors: Bind to steroid hormones, thyroid hormones, and Vitamin D. Hormone-receptor complexes influence gene transcription over hours/days.
    • Cell Surface Receptors: Recognize protein, peptide, or amino-acid derivative hormones. Hydrophilic hormones act through cell membrane receptors, initiating second messenger pathways, and influencing protein phosphorylation within seconds/minutes/hours.

    Properties of Receptors

    • Specificity: Receptors bind to specific ligands.
    • Affinity: Strength of the receptor-ligand binding.
    • Saturation: Receptors reach maximum binding sites.
    • Competition: Different molecules can compete for the same receptors.
      • Hypersensitivity (up-regulation): Increased receptor number after decreased or continuous stimuli.
      • Insensitivity (down-regulation): Decreased receptor numbers caused by constant or high stimuli.
    • Agonists: Molecules that bind to and activate a receptor.
    • Antagonists: Molecules that bind to a receptor and inhibit its signal transmission.

    Membrane Potentials and Types

    • Resting Membrane Potential: The cell's basic electrical state when not stimulated.
    • Threshold Membrane Potential: The potential required to initiate an action potential (typically about -55mV).
    • Action Potential: Rapid information transmission, especially in nerves and muscles.
    • Graded Potentials: Collect signals, initiating action potentials if they reach the threshold.

    Membrane Potential Contributors

    • Na+/K+ Pump: Maintains ion balance, crucial for negative charge.
    • K+ Leak Channels: K+ ions leak out of the cell, contributing to negative membrane potential.
    • Negatively Charged Molecules: Proteins and phosphates contribute to the cell's negative internal environment.

    Threshold Potential Definition

    • The minimum potential required for a cell to initiate an action potential.
    • Typically around -55mV.

    Graded Potentials: Key Characteristics

    • Proportional to the stimulus
    • Decrease with distance.
    • Can summate
    • Do not adhere to all-or-nothing principle

    Action Potential Characteristics

    • Requires specific voltage-gated ion channels.
    • Rapid changes in ion conductance cause them.
    • Occur in regions of excitable cell membranes.
    • Standard size and shape per cell type.
    • "All or none" response.

    Action Potential Formation

    • Resting state: -70mV.
    • Reaching threshold: Stimulus increases membrane potential to -55mV, activating voltage-gated Na⁺ channels.
    • Depolarization: Na⁺ influx makes the cell interior positive.
    • Repolarization: Na⁺ channels close, K⁺ channels open, K⁺ efflux, restoring the negative interior.
    • Hyperpolarization: K⁺ channels close slowly, potential is temporarily more negative, before returning to resting potential.

    Refractory Periods

    • Absolute Refractory Period: Na channels cannot be reopened, preventing action potential initiation.
    • Relative Refractory Period: New action potential could be initiated, though it needs a stronger stimulus than usual.

    Action Potential Propagation

    • In unmyelinated axons, depolarization spreads to adjacent areas.
    • In myelinated axons, depolarization occurs at Nodes of Ranvier. This jumping is called saltatory conduction, which makes signal propagation faster.

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    Nervous System Physiology Essentials 2 (2024-2025) PDF

    Description

    This quiz explores the essentials of nervous system physiology, focusing on cellular communication mechanisms within organisms. Different types of cellular communication, including intracrine, juxtacrine, autocrine, paracrine, neurocrine, and endocrine, are discussed. Test your understanding of these concepts and the roles of various receptor types.

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