Equilibrium, AP, Synapses Flashcards
Homeostatic control has 3 components:
receptor, control center, effector
what kind of solutes easily pass thru membrane
small hydrophobic
hydrophilic solutes must cross membrane thru:
channels or pores
conductance
permeability, depends on probability gate is open
diffusion potential
generated by diffusion of ions
equilibrium potential
diffusion potential that balances tendency for diffusion down [ ] grad
electrochemical equilibrium
chemical and electrical driving forces on ion are equal and opposite
membrane potential
intracellular potential relative to extracellular
nernst equation will
convert a [ ] difference for ion into voltage
inside of a cell is more +/- ?
-
driving force
what is the charge separation (mem pot) at rest? and where would they like to be if allowed to flow freely?
ionic current
movement of ions across membrane
ions move thru channels when: (2)
1) ion has a driving force
2) membrane has conductance (channels open)
resting membrane potential
about -70 mV
which are excitable cells
nerve and muscle
depolarization
process of making mem pot more positive
hyperpolarization
process of making mem pot more negative
inward current
flow of (+) charges into cell
outward current
flow of (+) charge out of cell
does inward current depol or hyperpol the cell?
depolarize
does outward current depol or hyperpol the cell?
hyperpolarizes
threshold potential
mem pot where an action potential is inevitable
value of threshold potential
-55 mV
overshoot
portion of AP where mem pot is (+)… goes above where it needs to
undershoot (hyperpolarizing afterpotential)
portion of AP where mem pot is more(-) than at rest
refractory period
period where another AP cannot occur, absolute or relative… ions are in wrong places
lidocaine blocks…
Na+ channels, no AP…no sensation
at rest, activation gate is (open/closed) and inactivation gate is (open/closed)
idk help
absolute refractory period
entire duration of AP, another AP cannot occur, VG Na channel inactivation gate is closed
relative refractory period
overlaps w period of hyperpol, begins at end of absolute RP, AP can be generated only by a greater than usual depol current
accomodation
depolarization occurs too slowly for AP, Na inact gate stay closed, not enough open Na channels
axon is (good/poor) conductor of charge?
poor, is leaky to ions… AP continuously regenerated
conduction velocity is increased by (2)
1) incr nerve diameter
2) myelination
myelin is composed of
schwann cells
bare patches on the axon
nodes of ranvier, have ion channels
saltatory conduction
AP jumps from node to node
what ion is mediator of synaptic release
Ca2+
what kind of receptor do neurotransmitters often bind to on postsynaptic cell
chemically gated ion channels
what facilitates reuptake of NT
astrocytes or axon terminals
what facilitates degradation of NT
enzymes
ACh formed from
acetyl CoA and choline via enzyme choline acetyltransferase
types of synaptic arrangements (3)
one-to-one
one-to-many (uncommon)
many-to-one (common in brain)
synaptic fatigue
repeated stimulation causes smaller than normal response in postsynaptic cell, depletion of NT storage
only NT released at neuromuscular junction
Ach
choline acetyltransferase
combines choline + acetyltransferase = Ach
acetylcholinesterase
degrades Ach
dopamine beta-hydroxylase
converts dopamine into norepi
(PMNT) phenylethanolamine-N-methyltransferase
converts norepi into epi
catechol-O-methyltransferase (COMT)
degrades biogenic amines
monoamine oxidase (MAO)
degrades biogenic amines
COMT and MAO
common targets for behavioral meds
where can histamine be found
neurons of hypothalamus and mast cells
4 subtypes of glutamate
3- ionotropic (ligand-gated ion chan)… NMDA receptor
1- metabotropic (G-protein coupled chan)
GABA A receptor
ionotropic, directly linked to Cl- channel… hyperpolarizes
targetted by benzos and barbiturates
GABA B receptor
metabotropic and coupled via G protein to K+ channel… hyperpolarizes
huntington disease
only NT that is a gas
nitric oxide
neuropeptides may function as
neuromodulator, neurohormone, neurotransmitter
2 methods of release of neuromodulators
a) co-secreted w NT
b) volume-transmission
purines
ATP and adenosine
ion channels
permit selective flow of ions across impermeable membranes
ionic disequilibrium
creates potential energy across membranes
synapses
spaces between 2 cells that allow for regulated release of substances to elicit physiologic response
neurotransmitters
diverse group of chemicals that act as chemical messengers… can stimulate APs (excitatory) or inhibit APs (inhibitory)
