Membrane Potentials and Ion Channels
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Membrane Potentials and Ion Channels

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Questions and Answers

What role does calcium play in muscle contraction?

  • Calcium prevents the binding of myosin to actin.
  • Calcium is responsible for breaking down ATP in muscle cells.
  • Calcium activates the myosin heads to contract immediately.
  • Calcium binds to the troponin complex, allowing binding sites to be exposed. (correct)

    • Which of the following best describes homeostasis?

  • The ability of an organism to change its environment.
  • The maintenance of a consistent internal environment in the body. (correct)
  • The process by which all cells in an organism become identical.
  • The development of new cells in response to environmental changes.

    • Why is maintaining homeostasis critical for organisms?

  • Unregulated internal conditions can result in cell death and organismal collapse. (correct)
  • Homeostasis enables the body to ignore changes in its environment.
  • Homeostasis allows organisms to become immune to external stimuli.
  • Uncontrolled changes in the internal environment can lead to cell growth.

    • What is the immediate effect of tropomyosin moving in muscle fibers?

    <p>It exposes the binding sites on actin for myosin.</p> Signup and view all the answers

    Which of the following is NOT a component of the cross-bridge cycle?

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

    Which internal stimulus indicates that the body is fighting an illness?

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

    What physiological response occurs when the body's temperature rises?

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

    Which type of animals are classified as ectothermal?

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

    What occurs during vasodilation?

    <p>Blood vessels expand</p> Signup and view all the answers

    What effect does piloerection have on the body in cold environments?

    <p>Conserves body heat</p> Signup and view all the answers

    Which of the following describes the body's response to dehydration?

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

    How does evaporative cooling occur in the human body?

    <p>Through the release of liquid sweat</p> Signup and view all the answers

    What body temperature do humans typically maintain?

    <p>37ºC</p> Signup and view all the answers

    What does the resting membrane potential depend on?

    <p>The concentration differences of ions across the membrane</p> Signup and view all the answers

    Which of the following describes current flow?

    <p>Flow of electrical charges from one point to another</p> Signup and view all the answers

    How is voltage measured in biological systems?

    <p>In millivolts (mV)</p> Signup and view all the answers

    What is the role of leak channels in the cell membrane?

    <p>To provide a slow leak of ions continuously</p> Signup and view all the answers

    What does Ohm's Law describe in the context of membrane potentials?

    <p>The relationship between current, potential difference, and resistance</p> Signup and view all the answers

    What happens to ions when a positive ion moves across a membrane?

    <p>A negative charge is left behind on the original side</p> Signup and view all the answers

    Which of the following statements about membrane potentials is true?

    <p>Cells can have different voltages depending on ion concentration</p> Signup and view all the answers

    Which statement best describes the body's overall electrical charge?

    <p>The body is electrically neutral as a whole</p> Signup and view all the answers

    What is the primary function of the kidneys in relation to blood?

    <p>To clean the blood of waste products</p> Signup and view all the answers

    Which substance is specifically reabsorbed by the kidneys into the capillary?

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

    What determines the amount of water reabsorbed by the kidneys?

    <p>The body's needs</p> Signup and view all the answers

    What happens to the blood components after filtration in the kidney tubule?

    <p>Glucose is reabsorbed and waste is excreted</p> Signup and view all the answers

    What is formed from the excess water and waste products left in the kidney tubule?

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

    Where is urine stored before excretion?

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

    What key element is found in urea, a waste product filtered by the kidneys?

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

    What would result in the production of very dilute urine?

    <p>Excess water in the blood</p> Signup and view all the answers

    What does an ion flux of 0 indicate about net ion movement?

    <p>There is no net ion movement.</p> Signup and view all the answers

    How does the concentration gradient affect the equilibrium potential (Nernst potential) for an ion?

    <p>The greater the concentration gradient, the greater the equilibrium potential.</p> Signup and view all the answers

    Which equation is used to determine the electrochemical potential for any ion?

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

    What is the primary determinant of the resting membrane potential in a living cell?

    <p>The net movement of all ionic currents across the membrane.</p> Signup and view all the answers

    What does the Goldman equation help calculate?

    <p>The resting membrane potential of the cell.</p> Signup and view all the answers

    Why is the resting membrane potential closer to the Nernst potential for K+ than for Na+?

    <p>K+ conductance is significantly higher than that of Na+.</p> Signup and view all the answers

    In the context of resting membrane potentials, what does the symbol 'g' typically represent?

    <p>Conductance of individual ionic species.</p> Signup and view all the answers

    What must be true for membrane potential to remain unchanged at rest?

    <p>The sum of all currents must equal zero.</p> Signup and view all the answers

    Study Notes

    Membrane Potentials

    • Body cells exhibit an electrical potential difference across their membranes known as membrane potential.
    • Electrical potential is measured in millivolts (mV) with 1 V equaling 1000 mV.
    • Current refers to the flow of electrical charges, with ions moving from higher to lower concentration areas, generating a net charge movement.
    • Ohm’s Law defines current (I) as the ratio of electrical potential (E) to resistance (R): I = E / R.
    • The resting membrane potential is closer to the Nernst potential of potassium (K+) due to its higher conductance compared to sodium (Na+).

    Membrane Ion Channels

    • Leak Channels: Are open continuously allowing slow ion leakage, notably sodium (Na+), potassium (K+), and chloride (Cl-).
    • Membrane exhibits higher permeability to K+ than to Na+, contributing to resting membrane potential.
    • When ion flux equals zero, there is no net ion movement across the membrane.

    Equilibrium Potential

    • The Nernst Equation calculates the equilibrium potential for any ion based on its concentration gradient: E(x) = RT/ZF log [x]inside/[x]outside.
    • The greater the ion concentration gradient, the larger the equilibrium potential.
    • Each ion has a unique equilibrium potential that can differ in direction and magnitude from other ions.

    Goldman Equation

    • The resting membrane potential (Em) is determined by the relative conductance of each ion: Em = [gNa+/(gNa+ + gK+ + gCl- )] ENa+ + [gK+/(gNa+ + gK+ + gCl- )] EK+ + [gCl-/(gNa+ + gK+ + gCl- )] ECl-.
    • It accounts for the weighted contributions of different ionic species to the overall membrane potential.

    Homeostasis

    • Homeostasis is the maintenance of a stable internal environment, critical for cellular function.
    • Factors such as temperature, water levels, and glucose concentration must be regulated.
    • Organisms live in variable environments but require stable internal conditions for survival.

    Mechanisms of Body Temperature Regulation

    • Sweating: Evaporation of sweat cools the body by removing heat from the skin.
    • Vasodilation: Blood vessels widen to increase blood flow to the skin, promoting heat loss.
    • Vasoconstriction: Blood vessels narrow to reduce blood flow to the skin, conserving heat.
    • Piloerection: Hair standing on end traps air, creating insulation to retain heat.

    Kidney Function in Water Regulation

    • Kidneys filter blood to control water balance and excrete waste products, including urea.
    • The process involves filtration, reabsorption of glucose and water, and excretion of urine.
    • Filtration occurs in the glomerulus; reabsorption ensures essential components like glucose and water return to circulation.

    Summary of Urine Production

    • Urea is a byproduct of protein metabolism formed in the liver.
    • Excess water and waste are processed in the kidneys and excreted as urine, which travels through the ureters to be stored in the bladder before leaving the body via the urethra.

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    Description

    This quiz covers the concepts of membrane potentials, including electrical potential differences across body cells and the roles of ion channels. Explore Ohm’s Law and the Nernst Equation as they relate to resting membrane potential and ion movement. Test your understanding of how these principles apply to cellular physiology.

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