cellular neurophysiology lecture 3
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Questions and Answers

Why do cells need to communicate?

  • To integrate functions (correct)
  • To synchronise events (correct)
  • Adapt to their environment (correct)
  • Turn pathways on and off (correct)

    • What is the disease associated with the degeneration of the myelin sheath called?

  • Multiple Sclerosis (correct)
  • Alzheimer's Disease
  • Parkinson's Disease
  • Amyotrophic Lateral Sclerosis

    • What is Myasthenia Gravis?

  • An autoimmune disease that affects muscle communication (correct)
  • A type of bacterial infection
  • A genetic disorder that causes bone deformities
  • A mental health condition characterized by severe anxiety

    • What is slow communication within cells called?

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

    What is slow communication between cells mediated by?

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

    What mediates fast transmission between cells?

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

    What is fast communication within cells mediated by?

    <p>Electrical signals</p> Signup and view all the answers

    What are the features of hormonal signaling? (Select all that apply)

    <p>Slower response times compared to nerve signals</p> Signup and view all the answers

    What is electrical signaling?

    <p>The transmission of signals through electrical impulses in neurons via rapid changes in membrane potential</p> Signup and view all the answers

    What are features of electrical signaling in excitable cells? (Select all that apply)

    <p>Rapid transmission of signals</p> Signup and view all the answers

    Where does electrical signaling occur in the body?

    <p>In the synapses between neurons</p> Signup and view all the answers

    What is the resting membrane potential of a typical neuron?

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

    Why is there a resting membrane potential in cells?

    <p>It is due to the difference in ion concentrations inside and outside the cell- inside negative to outside</p> Signup and view all the answers

    Which ions contribute significantly to resting membrane potential?

    <p>Sodium (Na+)</p> Signup and view all the answers

    How do ions move across the resting membrane potential?

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

    Why is the cell relatively impermeable to Na+?

    <p>Far fewer channels for Na+ making it relatively impermeable to Na+</p> Signup and view all the answers

    What pump transports Na+ and K+ in and out of the cell?

    <p>Sodium-Potassium Pump</p> Signup and view all the answers

    What does the sodium-potassium pump require to function?

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

    How many potassium ions are exchanged for sodium ions in the sodium-potassium pump?

    <p>3 sodium ions for 2 potassium ions</p> Signup and view all the answers

    What allows K+ to leak out of the cell?

    <p>Potassium leaky channels</p> Signup and view all the answers

    What is a chemical gradient?

    <p>The difference in concentration of a chemical inside and outside of a cell</p> Signup and view all the answers

    What is the electrical gradient?

    <p>The difference in ion concentration across a membrane.</p> Signup and view all the answers

    Why is there a higher concentration of Na+ ions outside the cell?

    <p>Na+ ions are actively transported out of the cell by the sodium-potassium pump.</p> Signup and view all the answers

    Why does K+ (potassium ion) want to move down its chemical gradient?

    <p>To achieve equilibrium within the cell</p> Signup and view all the answers

    What is the equilibrium potential?

    <p>The membrane potential at which there is no net movement of a particular ion across the membrane</p> Signup and view all the answers

    What equation determines the equilibrium potential of an ion?

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

    What is the equilibrium potential for potassium (K+) in millivolts (mV)?

    <p>-80 mV</p> Signup and view all the answers

    What is the equilibrium potential for sodium (Na+)?

    <p>+60 mV</p> Signup and view all the answers

    What is the equilibrium potential for chloride ions (Cl⁻)?

    <p>-65 mV</p> Signup and view all the answers

    What equation is used to calculate the resting membrane potential while taking into account the permeability of the membrane?

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

    What is an action potential?

    <p>A rapid rise and fall in membrane potential</p> Signup and view all the answers

    What do ions cross the membrane through?

    <p>Voltage -gated Ion channels</p> Signup and view all the answers

    At what threshold do sodium channels typically open during depolarization?

    <p>-55 mV</p> Signup and view all the answers

    What occurs when sodium enters a cell?

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

    What occurs during repolarization in a neuron?

    <p>Potassium ions exit the neuron</p> Signup and view all the answers

    What is hyperpolarization the result of?

    <p>Increased potassium ion permeability</p> Signup and view all the answers

    Why does hyperpolarization occur in relation to potassium channels?

    <p>Potassium channels close slowly, allowing K+ to exit the cell.</p> Signup and view all the answers

    What is the absolute refractory period?

    <p>The time period during which no new action potential can be initiated, regardless of the strength of the stimulus.</p> Signup and view all the answers

    What is a relative refractory period?

    <p>The time during which a second action potential can occur with a stronger stimulus</p> Signup and view all the answers

    What is neurotransmission?

    <p>The process of communication between neurons through chemical signals.</p> Signup and view all the answers

    What is an excitatory postsynaptic potential?

    <p>A type of electrical signal that increases the likelihood of an action potential.</p> Signup and view all the answers

    At what membrane potential do voltage-gated sodium channels (VGScs) typically open?

    <p>-55 mV</p> Signup and view all the answers

    Where do action potentials start in a neuron?

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

    How does action potential move along the neuron?

    <p>Through the opening and closing of voltage-gated ion channels</p> Signup and view all the answers

    What does the speed of movement of action potentials depend on?

    <p>The diameter of the axon</p> Signup and view all the answers

    What is the velocity of action potentials in neurons?

    <p>1-100 m/s</p> Signup and view all the answers

    Why is myelination important for nerve function?

    <p>It increases the speed of electrical impulses.</p> Signup and view all the answers

    What are the nodes of Ranvier?

    <p>Gaps in the myelin sheath of a neuron</p> Signup and view all the answers

    What is the function of the Nodes of Ranvier in a neuron?

    <p>They facilitate the rapid conduction (jumping) of nerve impulses.</p> Signup and view all the answers

    Which of the following options are types of neurotransmitters? (Select all that apply)

    <p>Amines- Dopamine</p> Signup and view all the answers

    Where are neurotransmitters synthesized?

    <p>In the cell body of neurons</p> Signup and view all the answers

    Where are neurotransmitters stored?

    <p>In synaptic vesicles</p> Signup and view all the answers

    Why are neurotransmitters stored in synaptic vesicles?

    <p>To protect them from degradation before release</p> Signup and view all the answers

    How are neurotransmitters released?

    <p>Through exocytosis upon the arrival of an action potential, opening of CA2+ which promotes fusing of vesicles</p> Signup and view all the answers

    What are SNARE proteins?

    <p>Proteins involved in vesicle fusion</p> Signup and view all the answers

    How are neurotransmitters removed from the synaptic cleft?

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

    What are the two classes of neurotransmitter receptors?

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

    What is an ionotropic receptor?

    <p>A type of receptor that directly opens ion channels in response to ligand binding</p> Signup and view all the answers

    What is a metabotropic receptor?

    <p>A receptor that activates a signaling cascade through a G-protein</p> Signup and view all the answers

    Which signaling type is slower, ionotropic or metabotropic?

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

    How does the binding of a neurotransmitter to a metabotropic receptor lead to an action potential?

    <p>G protein hydrolyses (GDP-GTP)- intracellular messengers are increased/reduced- kinases are inactivated/activated and Ca2+ is mobilised or sequestered- membrane is therefore more or less excitable</p> Signup and view all the answers

    What type of receptor is GABAa?

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

    What type of receptor is GABAB?

    <p>Metabotropic receptor</p> Signup and view all the answers

    What type of receptor does noradrenaline bind to?

    <p>Alpha-adrenergic receptor</p> Signup and view all the answers

    What is the primary function of selective serotonin reuptake inhibitors (SSRIs)?

    <p>They increase the levels of serotonin in the brain by blocking its reabsorption</p> Signup and view all the answers

    What do monoamine oxidase inhibitors do?

    <p>They increase the levels of neurotransmitters in the brain.</p> Signup and view all the answers

    What effects do amphetamines and ecstasy have on neurotransmission?

    <p>They increase the release of neurotransmitters such as dopamine and serotonin.</p> Signup and view all the answers

    Which of the following drugs cause non-impulse dependent release of dopamine?

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

    What causes the after hyperpolarization (AHP) during an action potential?

    <p>Slow closure of voltage-gated K+ channels</p> Signup and view all the answers

    What is a primary characteristic of the absolute refractory period?

    <p>Na+ channels remain inactivated for a short period post-action potential</p> Signup and view all the answers

    What primarily initiates an action potential in a neuron?

    <p>Influx of Na+ ions</p> Signup and view all the answers

    During which phase of the action potential does the membrane potential rise towards +30 mV?

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

    What is the effect of K+ moving out of the cell during the action potential?

    <p>Repolarization of the membrane</p> Signup and view all the answers

    What results from the slow closing of voltage-gated K+ channels after an action potential?

    <p>After hyperpolarization</p> Signup and view all the answers

    How does the influx of Na+ ions affect the membrane potential during an action potential?

    <p>It causes a rapid depolarization above 0 mV</p> Signup and view all the answers

    Which of the following is NOT a key feature of the action potential?

    <p>Closure of Na+ channels results in hyperpolarization</p> Signup and view all the answers

    What is the primary role of the voltage-gated Na+ channel during an action potential?

    <p>Causing depolarization of the membrane</p> Signup and view all the answers

    At what membrane potential does the voltage-gated Na+ channels typically open?

    <p>-55 mV</p> Signup and view all the answers

    What happens immediately after the rapid influx of Na+ during depolarization?

    <p>The Na+ channel enters a state of inactivation</p> Signup and view all the answers

    Which ions are primarily responsible for the repolarization phase of an action potential?

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

    What is the resting membrane potential (RMP) of a typical neuron?

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

    What causes the after hyperpolarization stage following an action potential?

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

    Which statement about voltage-gated ion channels is true?

    <p>They open at specific membrane potentials</p> Signup and view all the answers

    What occurs during the repolarization phase of an action potential?

    <p>K+ ions begin to exit the cell</p> Signup and view all the answers

    What factor most significantly influences the resting membrane potential according to the Goldmann Equation?

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

    Which ion's active transport is crucial for maintaining the resting membrane potential?

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

    What is the approximate value of the resting membrane potential (RMP) in most neurons?

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

    What type of channels opens typically at depolarization during an action potential?

    <p>Sodium channels</p> Signup and view all the answers

    During which phase of the action potential does repolarization occur?

    <p>After the peak of the action potential</p> Signup and view all the answers

    In the context of a neuron, what is the role of fixed anions (A-) in maintaining resting membrane potential?

    <p>They remain inside the cell contributing to negative charge</p> Signup and view all the answers

    What is the all-or-nothing response characteristic of in excitable cells?

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

    What primarily causes the rapid change in membrane potential during the action potential?

    <p>Increased permeability to Na+ ions</p> Signup and view all the answers

    What happens to voltage-gated sodium channels (VGScs) during the action potential when the membrane potential reaches +30 mV?

    <p>They become inactivated.</p> Signup and view all the answers

    At what membrane potential do voltage-gated potassium channels (VGKCs) begin to open?

    <p>-55 mV</p> Signup and view all the answers

    Which phase of the action potential is primarily responsible for repolarization?

    <p>Repolarization phase</p> Signup and view all the answers

    What is the role of the sodium-potassium pump in maintaining resting membrane potential?

    <p>It helps establish the electrochemical gradient by moving Na+ out and K+ in.</p> Signup and view all the answers

    Which statement best describes the inactivation state of voltage-gated sodium channels?

    <p>They cannot be activated until the membrane potential returns to a certain level.</p> Signup and view all the answers

    What primarily drives repolarization during an action potential?

    <p>Potassium efflux</p> Signup and view all the answers

    What happens to the Na+ channel after it returns to its closed state?

    <p>It is then ready to reopen at the next action potential threshold.</p> Signup and view all the answers

    Which of the following best describes the function of voltage-gated ion channels?

    <p>They open and close in response to changes in membrane potential.</p> Signup and view all the answers

    What primarily determines the resting membrane potential of a neuron?

    <p>The permeability of the neuronal membrane to different ions</p> Signup and view all the answers

    What does the Goldmann equation calculate?

    <p>The resting membrane potential considering the permeability of multiple ions</p> Signup and view all the answers

    Which voltage-gated ion channel opens during the depolarization phase of an action potential?

    <p>Sodium (Na+) channels</p> Signup and view all the answers

    What occurs during the repolarization phase of an action potential?

    <p>Potassium ions exit the cell, restoring the negative membrane potential</p> Signup and view all the answers

    What is the primary function of myelination in neurons?

    <p>To insulate axons and speed up action potential conduction</p> Signup and view all the answers

    What describes the absolute refractory period in a neuron?

    <p>A time when no action potentials can be generated regardless of stimulus strength</p> Signup and view all the answers

    Which structure in a neuron primarily receives incoming signals from other neurons?

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

    What characterizes the phases of an action potential?

    <p>Rapid depolarization followed by repolarization and hyperpolarization</p> Signup and view all the answers

    Study Notes

    Voltage-Gated Ion Channels

    • Voltage-gated K+ channels close slowly, affecting membrane potential.
    • Na+ influx raises membrane potential towards +30 mV, while K+ efflux decreases it.
    • Action potentials are generated through the summation of Na+ and K+ currents.

    After Hyperpolarization (AHP)

    • K+ moves out of the cell due to concentration gradient, leading to AHP.
    • Slow closure of K+ channels allows excess positive charge to leave, causing hyperpolarization.

    Refractory Periods

    • Absolute refractory period restricts the generation of subsequent action potentials immediately after one occurs.
    • Na+ channels must return to a closed state before reopening.

    Action Potential Dynamics

    • Initiated by Na+ channel openings when membrane potential reaches -55 mV.
    • Rapid Na+ influx results in depolarization; inactivation of Na+ channels follows.
    • K+ channels open slowly for repolarization, allowing K+ to exit the cell.

    Ion Channel Function

    • Voltage-gated channels selectively permit ion passage based on size and charge.
    • K+ permeability dominates resting membrane potential (RMP) of approximately -70 mV.

    Goldmann Equation

    • RMP represents the weighted sum of the equilibrium potentials for all ions.
    • K+ has the most significant contribution to the RMP due to high permeability.

    Cellular Communication

    • Cells communicate to synchronize events, integrate functions, and adapt to environments.
    • Faulty communication can lead to neurological disorders, such as motor neuron disease or multiple sclerosis.

    Types of Signaling

    • Hormonal signaling is slower and more sustained, while electrical signaling provides rapid and precise communication in excitable cells.
    • Fast, transient changes in membrane potential are key for neuronal and muscle communication.

    Membrane Potential Overview

    • Membrane potential changes are fundamental for action potentials; these are all-or-nothing events in excitable cells.
    • Understanding action potentials is critical in neurophysiology, particularly in neurons and muscle cells.

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