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Lecture

NROB60-LEC05.docx


Department
Neuroscience
Course Code
NROB60H3
Professor
Janelle Leboutillier

Page:
of 27
NROB60, LEC05
- for bell-ringer, there is one person at 1 station at a time
- 2 bell-ringer exams (three pins at each station)
- content on LEC06 is not on lab bell-ringer test
- spelling counts (spelling is not a BIG issue)
>- have to pretty close to correct spelling
- print legibly
>- if not readable, then it is wrong
------------------------------------
THIS IS LAST LECTURE BEFORE MID-TERM TEST
(After this, it is all final exam material, with exception of C7 & appendix; if miss mid-
term, then get cumulative exam)
[1]
RESTING NEURONAL MEMBRANE
LECTURE OUTLINE
- SETTING THE STAGE: CAST OF CHEMICALS
- fluid composition
- phospholipid membrane
- proteins
- movemt of ions
- don't need to know Fig3.1 (Simple Reflex)
[2]
CAST OF CHEMICALS
- RESTING MEMBRANE POTENTIAL
- condition where intracellular space (inside surface of memb aka cytosol) has
slight -ve charge relative to outside (extracellular material)
- this occurs at "rest" (no electrical impulses occurring)
- UNDERSTAND THE 3 MAIN PLAYERS
- Salty fluids on either sides of memb.
- Memb
- Memb. proteins
Questions to Ponder:
- why is there change in charge across memb?
- why at rest is it -ve?
How can we ansser?
- to understand that, need to see
- fluids both inside and outside,
- memb itself, and
- groups of proteins that span across memb
[3]
CYTOSOL & EXTRACELLULAR FLUID
WATER
- [held together] by polar covalent bonds
- effective solvent for
- other polar molec's
- charged molec's or ions
- "key" for being
- the impt ingredient in intracellular & extracellular fluid
- unevenly charged
Consequence of Covalence
- if cov., then shares e-;
- O is more -ve in H2O, so has slightly more -ve charge than H
>- uneven charge => uneven sharing
[4]
CYTOSOL AND EXTRACELLULAR FLUID
IONS
- net elec. charge
- dissolve in H2O b/c charged portions of H2O have more attraction to them, then the
ions to each other
- ie. solute-solute < solute-solvent attractive F's
- SPHERES OF HYDRATION - sphere of H2O molec's surr. each ion
- insulate ions from each other
Charges
- monovalent (1+, 1-), divalent (2+, 2-) [or even higher]
- Cations => net +ve charge (ex. Na+, K+)
- Anions => net -ve charge (ex. Cl-)
Example: why does salt (NaCl) dissolve in water?
- b/c what happens w/ cov. H2O molec is that it surr. individual ions in NaCl
- have Cl- ion surr. by sphere of H2O molec's, and also for Na+
- H2O insulates the ions from each other and it turns out that ions are more attracted to
water molec's than they are to each other
(insulation occurring here for Cl-, as well as Na+; this is what is meant by them
dissolving)
[5]
WHY ARE IONS IMPORTANT?
IONS
- are MAJOR CHARGE CARRIERS involved w/ conduction of electricity in biol sys's
- this includes neurons
- particularly impt for cellular neurophysiology are the following
- Na+ (sodium; monovalent cation)
- K+ (potassium; monovalent cation)