electrical signals Flashcards
why does the body use electrical signals?
to transfer information from one part of the body to another
what are electrical signals of the cells called?
AP
what is an AP
an electrical signal produced by cells
what does the body use to transfer information from one part to another?
electrical signals/APs
what creates the electric properties of the cell membrane?
ionic concentration differences across the plasma membrane and its permeability to those ions
what does the Na+/K+ pump do?
stockpiles Na+ outside and K+ inside the plasma membrane
why do (-) cell proteins contribute to the membrane potential?
they are too big to exit the cell
what does the Na+/K+ pump require to funciton?
ATP–it is an active transport pump
at the immediate outside and inside of the cell membrane
ions concentrate to create a voltage difference
the overall charge difference between intercellular and extracellular?
there is none, voltage difference is only directly inside and outside the cell membrane
what creates the charge differential between the inside and outside of the membrane
the concentration difference of ions just across the membranes
what is the average membrane potential measurement?
-85 mV
what membrane protein helps to set up ion differences?
Na+/K+ pump
non-gated K+ channel proteins are leaky to K+, why?
they are not gated so they are just open and the concentration gradient is such that the K+ wants to go outside the cell from an area of higher to lower concentration
what type of membrane protein allows K+ to dribble out of the cell with the concentration gradient?
non-gated K+ channel protein
when the K+ diffuses out through the non-gated channel proteins, this gives the cell a ____ charge just outside the membrane and ___________ still inside the cell create a ___ charge just inside the membrane
positive
large negative proteins
negative
what would happen if v-gated K+ channels were to open?
much more K+ would diffuse out of the cell due to concentration gradient and the charge difference would increase and the membrane would be hyperpoerized
what would happen if v-gated Na+ channels were opened?
Na+ would diffuse into the cell bc of the concentration gradient and this would serve to depolarize the cell (making the inside more + when it is usually -)
how would an extracellular increase in K+ change the RMP?
a build-up of K+ on the outside of the cell would slow the release of K+ from inside the cell and would cause the interior of the cell to move more toward positive charge. The charge difference between the immediate inside and outside of the cell membrane is smaller, thus it is depolarized
define depolarization of the membrane
the membrane potential becomes more (+), it moves towards 0
when the membrane potential becomes more negative (the difference moves further away from negative) this is called
hyperpolarization
is the concentration of K+ higher inside or outside the cell?
inside
is the concentration of Na+ higher inside or outside the cell?
outside
to which ion is the plasma membrane most permeable to?
K+
what anions are trapped inside the cell?
negatively charged large proteins
gated ion channels change the _________ of the cell membrane
permeability
gated ion channels open and close because of some sort of
stimulus
ligand gated ion channels open or lose in response to
ligand binding to receptor protein
what are usually the receptor proteins on a ligand gated ion channel?
glycoproteins
voltage gated ion channels open or close in response to small voltage changes where?
across the cell membrane
most common voltage gated ion channels are
Na+ and K+
Ca++ important on cardiac and smooth muscle
what do touch receptors respond to?
mechanical stim of the skin
temperature changes in the skin trigger what kind of gated ion channel?
temperature receptor gated ion channel
the relative charge of an area of membrane changes and opens
voltage-gated ion channels
local potentials can be stimulated by
ligands binding to receptors (ligand gated) relative change in charge (v-gated) mechanical stimulation (touch) temperature changes (T receptors) spontaneous change in permeability
local potentials are called ________ potentials because the magnitude varies
graded
what are things that can have an effect the grade of a local potential?
stimulus strength
stimulus frequency
local potentials can add onto each other in a process called
summation
stimulus strength or frequency can vary the _______ of a graded local potential
magnitude
local potentials rapidly (decrease/increase) in magnitude as they spread over the surface of the plasma membrane
decrease
what do local potentials do when they summate?
add onto each other
can local potentials cause generation of an AP?
yes
local potentials are caused when a stimulus causes ______
ion channels to open
increased local permeability is caused by
opening of the ion channels by a local potential caused by a stimulus
increased permeability to Na+ results in
depolarization of the plasma membrane
increased permeability to K+ (or Cl-) has what effect on the plasma membrane?
hyperpolarizes
depolarization can be caused by increased permeability in the plasma membrane to what ion?
Na+
hyperpolarization can be caused by increased permeability in the plasma membrane with what ion?
K+ or cl-
what does it mean to say that local potentials are graded?
the size of the response is proportional to the strength of the stimulus
why is a local potential produced in response to several stimuli larger than one produced in response to one stimulus?
the local potentials summate, meaning they add together
local potentials spread and decrease in magnitude in a manor called
decremental
an AP can be caused by a depolarizing
local potential that is large enough
a large enough local potential may cause the membrane to reach
threshold
what must a stimulus or local potential reach in order to trigger an AP
threshold
what does the all-or-none principle for AP mean
no matter how strong a stimulus, as long as it reaches threshold, an AP will occur
what are the phases of an AP
depolarization (more positive)
repolarization (less positive)
what is the afterpotential?
a slight hyperpolarization “dip” after repolarization
depolarization is the result of
increased membrane permeability to Na+ and mvmt of Na+ into the cell (activation of the v-gated Na+ channels)
repolarization is the result of
decreased membrane permeability to K+
this stops the entrance of Na+ into the cell (v-gated Na+ gates close)
more K+ move out of the cell (v-gated K+ gates close)
what is produced during the absolute refractory period of the AP
nothing
what can be produced during the relative refractory period
an AP if a stronger than threshold stimulus
AP is propogated and for a given axon the magnitude of the AP is
constant
stimulus strength determines the
frequency of the AP
