What is that voltage called as in most cells the

Info icon This preview shows pages 19–22. Sign up to view the full content.

View Full Document Right Arrow Icon
What is that voltage called? As in most cells, the region just outside the surface of the neuron plasma membrane has a positive electrical charge compared to the region just inside it, which is therefore negative. The normal (resting) potential difference across the neuron membrane is about –70 mV (millivolts). This voltage is called the resting potential of the neuron. The Nervous System Review - Image Diversity: neuron resting potential
Image of page 19

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
42. How sodium and potassium ions maintain the resting potential of neurons? When at rest, the plasma membrane of a neuron maintains an electric potential difference between its external and internal surfaces. This voltage is called resting potential. A resting potential around –70 mV indicates that the interior is more negative than the exterior (negative polarization). This condition is maintained by the transport of sodium and potassium ions across the plasma membrane. The membrane is permeable to potassium ions but not to sodium ions. At rest, the positive potassium ions exit the cell in favor of the concentration gradient, since within the cell the potassium concentration is higher than in the extracellular space. However, the positive sodium ions cannot enter the cell. Positive potassium ions exit the cell and not enough compensatory positive ions enter the cell, causing the intracellular space to become more negative and making the cell remain polarized. 43. How is the depolarization of the neuronal plasma membrane caused? How does the cell return to its original resting state? When the neuron receives a stimulus via the binding of neurotransmitters to specific receptors, sodium channels open and the permeability of the plasma membrane in the postsynaptic region is altered. Sodium ions then enter the cell,
Image of page 20
causing a decrease (less negative) in the potential difference of the membrane. If the reduction in the potential difference of the membrane reaches a level called the excitation threshold, or threshold potential, around –50 mV, the action potential is generated, meaning that the depolarization intensifies until reaching its maximum level. The depolarization current is then transmitted along the remaining length of the neuronal membrane. If the excitation threshold is reached, voltage-dependent sodium channels in the membrane open, allowing more sodium ions to enter the cell in favor of the concentration gradient, and an approximate level of –35 mV of positive polarization of the membrane is achieved. The voltage-dependent sodium channels then close and more voltage-dependent potassium channels open. Potassium ions then exit the cell in favor of the concentration gradient and the potential difference of the membrane decreases. This process is called repolarization. The action potential triggers the same electrical phenomenon in neighboring regions of the plasma membrane and the impulse is therefore transmitted from the dendrites to the terminal region of the axon.
Image of page 21

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 22
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern