{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}


NPB+112+11+membrane%2C+action+potential+lecture+notes - NPB...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
NPB 112, Jan. 4-6, 2011 OUTLINE I. The neuron (pp. 4-9) II. Resting membrane potential (Ch. 2,4) A. due mainly to K+ efflux: Nernst (Fig. 2.6.b) B. influenced by Na+ : GHK Equation C. Na+/K+ exchange pump (Fig. 4.13a) III. Action potential (Ch. 3) I. The neuron: dendrites ("antennae" to receive signals), cell body with nucleus; axon to transmit signals over sometimes long distances; presynaptic terminal to release neurotransmitter to communicate with another neuron. Fig. 1.2. II. Resting membrane potential. Ch. 2 A. Neurons have lipid bilayer which surrounds cytoplasm, intracellular organelles to isolate them from the extracellular environment. B. Neurons are electrically polarized, inside negative relative to the outside. 1. When a thin glass micropipette is inserted into a neuron one can record the electrical potential difference across the cell membrane (Fig. 2.2) 2. Voltage difference between the inside and outside is about -65 mV. This is the cell's resting membrane potential. Animation : http://www.sinauer.com/neuroscience4e/animations2.1.html 3. By convention, changes in the membrane potential toward zero are DEPOLARIZING. Changes in a more negative direction are HYPERPOLARIZING. C. Interior of cell: high concentration of K+ and organic anions, low concentrations of Na+ and Cl-. D. Extracellular fluid, like sea water, contains high Na+ and Cl-. E. Cell membrane is SELECTIVELY PERMEABLE to K+ ions, and much less permeable to other ions. F. Strong chemical driving force on K+ to DIFFUSE out of the cell into the extracellular region of lower concentration. G. As K+ ions leave the cell, the interior layer of membrane becomes progressively more negative and the exterior layer more positive.
Background image of page 1

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

View Full Document Right Arrow Icon
H. ELECTROSTATIC force develops, since negative charges accumulating inside the cell tend to pull K+ back inside (opposite charges attract). I. Chemical and electrical forces eventually balance each other to achieve a steady state- the resting potential. J. K+ ion channel: 1. 4 membrane-spanning subunits with a hole, or channel, between them through the membrane (Fig. 4.8). 2. Channel diameter is just large enough for hydrated K+ to pass, but excludes Na+ which has a larger cloud of hydration due to its stronger electric field 3. Negative charge at the mouth of K+ channel repels anions III. Nernst equation: A. Equilibrium potential. The balance between chemical and electrical forces on an ion is described by the Nernst equation: E = RT ln [K+]out This translates to 58 log [K+]out mv zF [K+] in [K+] in (R= gas constant; F= Faraday's constant; T= temperature; z= valence). 1. For [K+] in is 400 mM and [K+] out is 20 mM, we have 58 log 20/400 = 58 log 1/20 = 58 (-1.3) = -75 mV. 2.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 10

NPB+112+11+membrane%2C+action+potential+lecture+notes - NPB...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon bookmark
Ask a homework question - tutors are online