nivin sharawy_2019-01-31 14-15-00183.DOCX - Resting...

  • No School
  • AA 1
  • 3

This preview shows page 1 - 2 out of 3 pages.

Resting membrane potential Electrical potentials exist across the membranes of virtu ally all cells of the body. Some cells, such as nerve and muscle cells, generate rapidly changing electrochemical impulses at their membranes, and these impulses are used to transmit signals along the nerve or muscle membranes. In other types of cells, such as glandular cells, macro - phages, and ciliated cells, local changes in membrane potentials also activate many of the cells’ functions. Basic Physics of Membrane Potential Remember: A. K+, proteins, PO4 3- are mainly inside the membrane, while Na+, Cl+,HCO 3 _ are mainly outside the membrane B. Diffusion and Equilibrium Potentials Diffusion potential is the potential difference generated across a membrane because of a concentration difference of an ion. It can be generated only if the membranes is permeable to the ion. The size of the diffusion potential depends on the size of the concentration gradient. The sign of diffusion potential depends on whether the diffusing ion is positively or negatively charged. Equilibrium potential is the diffusion potential that exactly balances (opposes) the tendency for diffusion caused by a concentration difference. At electrochemical equilibrium, the chemical and electrical driving forces that act on an ion are equal and opposite; therefore, no net diffusion of the ions occur. The potassium concentration is great inside a nerve fiber membrane but very low outside the membrane. Let us assume that the membrane in this instance is permeable to the potassium ions but not to any other ions. Because of the large potassium concentration gradient from inside toward outside, there is a strong tendency for extra numbers of potassium ions to diffuse outward through the membrane. As they do so, they carry positive electrical charges to the outside, thus creating electropositivity outside the membrane and electronegativity inside because of negative anions that remain behind and do not diffuse outward with the potassium. Within a millisecond or so, the potential difference between the inside and outside becomes great enough to block further net potas sium diffusion to the exterior, despite the high potassium ion concentration gradient. In the normal mammalian nerve fiber, the potential difference is about 94 millivolts, with negativity inside the fiber membrane.
Image of page 1

Subscribe to view the full document.

Image of page 2
  • Fall '19

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

Ask Expert Tutors You can ask You can ask ( soon) You can ask (will expire )
Answers in as fast as 15 minutes