Neuroscience: Action Potentials and RMP
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Questions and Answers

If the concentration of potassium outside a neuron increases, what is the most likely effect on the resting membrane potential (RMP)?

  • The RMP will become more positive. (correct)
  • The RMP will fluctuate erratically.
  • The RMP will remain unchanged.
  • The RMP will become more negative.

    • What type of ion channel is responsible for the rising phase of an action potential?

  • Voltage-gated sodium channels (correct)
  • Ligand-gated channels
  • Thermally-gated channels
  • Voltage-gated potassium channels

    • What is the main function of a beta-blocker medication?

  • To increase the permeability of the cell membrane to potassium.
  • To block the reuptake of neurotransmitters in the synapse.
  • To increase the release of neurotransmitters from the presynaptic neuron.
  • To reduce the strength of heart muscle contractions. (correct)

    • Why is the Nernst equation used to calculate the equilibrium potential?

    <p>To predict the direction of ion movement across the cell membrane. (A)</p> Signup and view all the answers

    How does citrate, used in blood donation, affect the threshold potential of neurons?

    <p>Citrate increases the threshold, making neurons less likely to fire action potentials. (B)</p> Signup and view all the answers

    Which of these is NOT a consequence of having too much potassium outside a neuron?

    <p>The neuron will be less likely to fire an action potential. (D)</p> Signup and view all the answers

    What is the primary reason that neurons are described as "salty bananas"?

    <p>The high concentration of salt outside the neuron and the large amount of potassium inside the neuron. (A)</p> Signup and view all the answers

    Which of these is NOT a common location for ligand-gated ion channels in neurons?

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

    What is the most common mechanism for regulating the activity of signaling proteins through membrane-bound receptors?

    <p>Inactivation of signaling protein (C)</p> Signup and view all the answers

    Which of the following statements about receptor down-regulation is TRUE?

    <p>It involves the destruction of receptors within lysosomes. (C)</p> Signup and view all the answers

    What is the primary mechanism by which lipophilic hormones exert their effects?

    <p>Modulating gene expression by binding to intracellular receptors. (A)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of intracellular receptors?

    <p>They always form dimers before binding to DNA. (B)</p> Signup and view all the answers

    How does the binding of a single extracellular molecule to a cell surface receptor lead to the activation of multiple adenylyl cyclase proteins?

    <p>The receptor activates a protein called G protein, which in turn activates multiple adenylyl cyclase molecules. (B)</p> Signup and view all the answers

    Which of the following is an example of the role of receptor sequestration in hormone signaling?

    <p>The inactivation of the insulin receptor in response to high glucose levels. (C)</p> Signup and view all the answers

    Why are steroid hormones like estrogen and testosterone considered to have low bioavailability?

    <p>They are primarily bound to plasma proteins, limiting their free concentration. (C)</p> Signup and view all the answers

    Which of the following is NOT a mechanism for regulating the activity of membrane-bound receptors?

    <p>Formation of receptor dimers. (D)</p> Signup and view all the answers

    Which of the following receptors are involved in the regulation of sympathetic output in the CNS?

    <p>Alpha-2 receptors (C)</p> Signup and view all the answers

    What is a potential side effect of using clonidine to manage hypertension?

    <p>Sedation (A)</p> Signup and view all the answers

    Which of the following is NOT a correct characteristic of α1 receptors in a sympathetic response?

    <p>They lead to vasodilation in arteriolar smooth muscle. (D)</p> Signup and view all the answers

    Which of the following statements regarding β2 receptors is FALSE?

    <p>Activation of β2 receptors leads to vasoconstriction. (B)</p> Signup and view all the answers

    Which of the following is a common misconception related to the parasympathetic nervous system?

    <p>It only affects specific organs, not the whole body. (C)</p> Signup and view all the answers

    What is the specific mechanism of the drug atropine used to block parasympathetic responses?

    <p>It acts as an antagonist, blocking acetylcholine receptors. (B)</p> Signup and view all the answers

    What is the correct order of events in the synthesis and release of polypeptide hormones?

    <p>Preprohormone -&gt; Prohormone -&gt; Hormone (D)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of membrane receptor-binding hormones?

    <p>They can enter the cell to exert their effects. (A)</p> Signup and view all the answers

    In the context of hormone secretion patterns, which of the following scenarios would most likely result in sustained secretion of cortisol?

    <p>A patient with a tumor that continuously secretes cortisol (A)</p> Signup and view all the answers

    Assuming a normal physiological state, what percentage of testosterone in circulation is readily available for biological activity?

    <p>2% (A)</p> Signup and view all the answers

    Which of the following statements accurately describes the relationship between oxytocin and estrogen during parturition (labor)?

    <p>Oxytocin increases the number of estrogen receptors in the myometrium, enhancing labor contractions. (A)</p> Signup and view all the answers

    Which of the following accurately describes the relationship between the hypothalamus and the anterior pituitary?

    <p>The hypothalamus releases hormones that directly stimulate the release of specific hormones from the anterior pituitary via a specialized vascular system known as the hypothalamic-hypophyseal portal system. (B)</p> Signup and view all the answers

    Which of the following hormones is NOT secreted by the anterior pituitary?

    <p>Vasopressin (ADH) (B)</p> Signup and view all the answers

    Which of the following pairs of hormones are derived from the same precursor molecule, pro-opiomelanocortin (POMC)?

    <p>Adrenocorticotropic hormone (ACTH) and β-endorphin (C)</p> Signup and view all the answers

    Which of the following best describes the mechanism by which suckling stimulates the release of oxytocin?

    <p>Suckling triggers a neuronal signal that travels to the hypothalamus, which then stimulates the release of oxytocin from the posterior pituitary. (C)</p> Signup and view all the answers

    What is the primary function of SHBG (sex hormone-binding globulin)?

    <p>To bind to testosterone, reducing its free concentration in the bloodstream. (D)</p> Signup and view all the answers

    Which of the following is a characteristic of a portal system?

    <p>It is a vascular arrangement where venous blood flows directly from one capillary bed to another. (C)</p> Signup and view all the answers

    Which of the following is a TRUE statement regarding the hormones secreted by the anterior pituitary?

    <p>Most anterior pituitary hormones are trophic, meaning they stimulate the release of other hormones from different endocrine glands. (B)</p> Signup and view all the answers

    What is a primary consequence of aldosterone hypersecretion?

    <p>Hypokalemia (B)</p> Signup and view all the answers

    Which physiological role does cortisol play in response to stress?

    <p>Increases blood glucose levels (C)</p> Signup and view all the answers

    How does hyposecretion of aldosterone affect blood pressure?

    <p>Causes low blood pressure (D)</p> Signup and view all the answers

    What is the primary trigger for cortisol release?

    <p>Corticotropin-Releasing Hormone (CRH) (D)</p> Signup and view all the answers

    Which of the following is a primary action of aldosterone?

    <p>Promoting sodium retention (D)</p> Signup and view all the answers

    What condition is associated with the autoimmune destruction of the adrenal cortex?

    <p>Primary Adrenocortical Insufficiency (C)</p> Signup and view all the answers

    In which situation does cortisol exert anti-inflammatory effects?

    <p>In states of infection (A)</p> Signup and view all the answers

    What effect does cortisol have on protein metabolism?

    <p>Increases protein degradation (C)</p> Signup and view all the answers

    Which of the following signaling pathways is NOT a receptor-enzyme pathway?

    <p>Ion-gated Receptor (C)</p> Signup and view all the answers

    Which of the following statements accurately describes the role of phospholipase C (PLC) in the Gq-protein pathway?

    <p>PLC hydrolyzes PIP2 into IP3 and DAG, initiating downstream signaling events. (C)</p> Signup and view all the answers

    How many extracellular messengers are required for the activation of a Tyrosine Kinase receptor?

    <p>Two (A)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the Gs-protein pathway?

    <p>Direct phosphorylation of the receptor by an activated G-protein. (A)</p> Signup and view all the answers

    Which of the following statements is true about the JAK/STAT pathway?

    <p>Binding of one extracellular messenger activates both JAK enzymes. (B)</p> Signup and view all the answers

    What is the primary function of the Ca2+-calmodulin complex in the Gq-protein pathway?

    <p>Activating CaM kinase, which in turn activates downstream proteins. (C)</p> Signup and view all the answers

    Which of the following signaling pathways is primarily involved in regulating gene expression?

    <p>JAK/STAT (C)</p> Signup and view all the answers

    Which of the following BEST explains why the same signaling molecule can induce different responses in different target cells?

    <p>The expression of different receptors on the target cells. (C)</p> Signup and view all the answers

    Study Notes

    Action Potentials

    • Action potentials are the fundamental signals used by neurons
    • They are rapid, large changes in membrane potential that propagate down the axon
    • Strength of signal is determined by frequency of release, not amount
    • Dependent on ions like sodium, potassium and calcium, specifically their movement across the membrane
    • Muscle contraction, heartbeat, thoughts and memories depend on action potentials
    • Input zone (dendrites) receives graded potentials which may or may not initiate an action potential
    • Input zone contains different types of gated channels, leading to an action potential at the axon hillock
    • Axon hillock: Location of voltage-gated sodium and potassium channels initiating the action potential

    Resting Membrane Potential (RMP)

    • RMP is primarily dependent on potassium (K+)
    • Changes in potassium affect RMP and excitability
    • High potassium = more easily achieved threshold potential and increased excitability
    • Low potassium = reduced threshold potential and decreased excitability

    Threshold Potential

    • Threshold potential is the membrane potential at which an action potential is initiated
    • Related to calcium concentration
    • High calcium = increased threshold potential
    • Low calcium = decreased threshold potential

    Nernst Equation

    • Used to calculate the equilibrium potential for an ion
    • Reflects the balance between concentration and electrical gradients
    • Equilibrium potential changes lead to changes in the resting membrane potential

    Hyperkalemia and Hypokalemia

    • Hyperkalemia: High potassium levels in the extracellular fluid.
      • Reduced gradient between intracellular and extracellular potassium
      • Increased RMP leads to reduced excitability
    • Hypokalemia: Low potassium levels in the extracellular fluid
      • Increased gradient between intracellular and extracellular potassium
      • Reduced RMP leads to reduced excitability

    Beta-Blockers

    • Medications that block beta-1 receptors on the heart
    • Slow heart rate and decrease strength of contraction
    • Used for hypertension

    Action Potential Process

    • Input zone receives graded potentials
    • If enough positive charge is generated from signals, voltage-gated sodium channels open at the axon hillock
    • Sodium rushes into the axon, causing membrane potential to become more positive
    • At peak, sodium channels close and a slower potassium channel opens, allowing potassium to flow out, causing membrane potential to return to resting

    Neurotransmitters

    • Neurotransmitters can either excite or inhibit target cells
    • Excitatory: Causes sodium to enter the target cell
    • Inhibitory: Causes chloride to enter or potassium to leave the target cell

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    Description

    This quiz covers the essentials of action potentials and resting membrane potential (RMP) in neurons. Understand how these fundamental signals operate, the role of ions, and their implications for muscle contraction and neural function. Test your knowledge on the mechanisms that underpin neuronal excitability and transmission.

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