Lecture 2: Membrane potential (voltage) Flashcards
What is or are the advantages to having a membrane?
allows cell to maintain concentration differences
why a phospholipid bilayer? what are the advantages?
we can separate out particles to keep an aqueous solution on both sides of bilayer
- lipid membrane gives opportunity to separate ions
- lipid means ions will have difficult time crossing from one side to the other
structure of a cell membrane
- phospholipid bilayer
- cholesterol
- variety of molecules imbedded
- physical properties
variety of molecules embedded in the cell membrane
- extrinsic- only on outtre or inner surface
- intrinsic (transmembrane) spans glycol (glycosylated) proteins
physical properties of cell membrane
liquid at body temperature
why are the differences between extra and intra cellular concentration of ions
- intracellular anions (proteins) are unable to migrate
- membrane semipermeable to K+ and Cl- but not to Na+
two types of gradients or driving forces
chemical or concentration gradient
-electrical gradient
the electoral gradient is _______________ to the concentration gradient
equal to and opposite in direction
Na+/K+ pump
- 2 subunits
- binding sites
- requires ATP to go against concentration gradient
- 3Na+ moved out of the cell and 2 K+ are moved into the cell
calculated Em from GHK eq
-90mV
actually measured Em
-85 mV
contribution to Em by Na+/K+ pump
-5 mV
what are the unique features of neural muscle tissue
threshold, overshoot, hyperpolarizing afterpotential
what did the Hodgkin and Huxley experiment with the giant squid axon suggest:
there was a change in membrane permeability to Na+ and K+
-too fast to be a carrier process; suggested channel or pore
Na+ channel
- multiple subunits
- selectivity filter (lets Na+ through)
- voltage sensor
- inactivity gate
- domains or alpha subunit
- function during depolarization
inactivation after ____ms depolarization clases the h gate
1-2
K+ channel
- 1 domain x 4 subunits
- 30 types similar in muscle and nerve
- stabilizes membrane counteracts Na+
why is the fact that depolarization spreading in all directions from the initial depol a problem?
in the nerve: want unidirectional depolarization
in the muscle: NMJ in middle of length of fiber
are all nerve fibers myelinated?
no not c-fibers-pain (motorneurons are all myelinated though)
salutatory conduction
depolarization from node to node
what is the advantage of salutatory conduction? (depol from node to node)
less energy required to pump ions across membrane following depolarization
Action potentials propagate more slowly in ______ fibers than along _____ axons
action potentials propagate more slowly in muscle fibers than they do along nerve axons (myelination makes it faster)
