physiology neurophys Flashcards
electrical potential inside a neuron is
70 millivolts more negative than the potential in the extracellular fluid on the outside of the fiber
resting membran potential of a neuron is produces by the total
ion concentration differences across the membrane
what is the reversal of potential referring to
the charges switch on the outside from negative to positive and in the inside from positive to negative
at the end of the AP what happens to the charges?
it restores itself
propagates refers to
how the AP moves along the neuron like a wave
if a charge is below the threshold stimulus what will happen?
an AP is NOT generated due to it being an “all or nothing response”
at rest is there more Na+ outside or inside of the cell at rest?
outside
there is high amounts of Na+ inside of the cell?
T/F
F
at rest inside of the membrane it is
negative
at rest there is highest amounts of this ion inside of the cell?
K+
at rest outside of the membrane is
positive
at rest the membrane is _______ to Na+
impermeable
nerve cells and muscle cells are capable of doing this because they are known as “excitable”
self-generating electrical impulses across their membrane
formation of membrane potential involves these 4 things
- selective permeability
- concentration differences of ions
- electrical potential
- separation of charge
resting membrane potential is established due to the difference
of EXCITABLE cells across the membrane at rest
how is a membrane potential created
a concentration difference of ions across a semi-permeable membrane
nernst equation is converts what to what?
concentration difference for an ion into a voltage
what is expressed at a intracellular potential relative to extracellular potential
membrane potential
resting membrane potential is established by
- diffusion potentials
- membrane permeability
- electrogenic nature of the Na+K+ pump
potassium ion will diffuse in what direction pertaining to a cell
outward
the loss of K+ inside of the cell results in what?
a negative charge inside of the cell
what is the driving force of diffusion
the equilibrium potential
what is the mv of the potential difference needed to stop further net diffusion of k+ out of a neuron?
-90
diffusion of Na+ into the cell will create a
positive charge inside of the cell
the potential difference in mv to stop further net diffusion of Na+ is
65+
neural membranes are more permeable to this ion?
K+
which of the pumps contribute most to the RMP?
potassium leak channels
which pump is responsible for maintaining the Na+ & K+ concentraion difference across the cell membrane
Na+K+ ATPase pump
what pump helps establish a Negative electrical potential inside cells?
Na+K+ATPase pump
E (equilibrium = wants to get here) of Na+ =
+65
E K+ =
-90
E ca2+ =
+120
depolarization
more positive and less negative membrane potential
repolarization/hyperpolarization
making the membrane potential more negative/ less positive
major ion contributing to depolarization
Na+
the major ion contributing to repolarization?
K+
gates of gated ion potentials are referred to as
protein/widgets that regulate the channels
when a channel is open the ions it is selective to pass by ______ diffusion
passive (no atp)
the ion pass through the gates down a (n)
electrochemical gradient
which voltage gated channels are responsible for the upstroke phase/depolarization?
voltage gated Na+ channels
threshold in mv for excitable membrane?
+ 55
why can we not get another AP when in the absolute refractory period
because ALL the Na+ gates are open
why can we get somewhat of an AP when in the relative refractory period?
because some of the Na+ gates may have closed & there is a GREATER than usual depolarizing current applied
when does the relative refractory period take place
right after the absolute refractory period
realtive refractory period overlaps with this?
hyperpolarization
voltage K+ channels are responsible for
repolarization
voltage gated K+ channels speed versus voltage Na+ channels?
K+ is slower to open
restoration
return to RMP
repolarization does not restore
resting ionic conditions
repolarization retores
resting electrical condition
restoration of resting ionic conditions is the function of
Na+ K+ ATP Pumps
why does the Na+ K+ ATPase pump require ATP?
it requires a lot energy to maintane the high [Na+] outside of the cell and high [K+] inside of the cell which is AGAINST their [] gradients
2 factors the increase the conduction velocity of the AP along a nerve
increase the size and myelination of nerve
the large the fiber the lower the
internal resistance
flow of ions occurs at what portion of cell?
nodes
myelin is white microscopically because?
it contains fat
Myelin incrases membrane ______ & decreases membrane ______
- resistance
2. capacitance
saltatory conduction referrs to ?
the jumping of an axon in myelinated axons
length of stimulus and length of depolarization have what kind of relationship?
direct ~
as length of stimulus increases the length of depolarization increases
if excitatory neurotransmitter is stimulated it causes
depolrization of postsynaptic cell - closer to threshold potential
if neurotransmitter is inhibitory is causes
hyperpolerization of the postsynaptic cell
what makes the postsynaptic neuron more likely to fire past threshold in a graded potential?
EPSP
what makes a postsynaptic neuron hyperpolarize in a graded potential
IPSP
what lead to the opening of a Na+ channel?
EPSP
what can decrease the K+ diffusion outwardly?
EPSP
what is responsible for making the inside of the cell more excitatory?
EPSP makes it more positive inside of the cell than normal
large amount of this within cell will increase the likelihood that the postsynaptic cell reaches the threshold
EPSPs
IPSPs induce
an increase of movement of k+ out of the neuron
summation of a graded potential is defined as
addition of post-synaptic potential to reach threshold
two ways that presynaptic information may be integrated in a graded potential
spatially and temporally
spatially refers to the
firing of different neurons
temporally refers to
same neuron fires at a different rate
spatial summation is when
2+ presynaptic inputs from different locations arrive at a postsynaptic cell simultaneously
do both inputs for a spatial summation need to be excitatory?
yes
if not then they will cancel each other out
temporal summation occurs when
two presynaptic inputs arrive at the post synaptic cell in RAPID SUCCESSION
what is defined as a rapidly repeated stimulation that eventually overlaps in time and causes a summation
temporal summation
with graded potential what can vary?
amplitude
graded potential can undergo
summation
do graded potential have threshold?
no
does graded potential have a refractory period?
no
in graded potential what happens to distance as the amplitude decreases
it decreases
duration may vary due to
intitiating conditions
what is the one major event in AP’s?
depolarization
graded potential has 2 major events
depolarization and hyperpolarization
an action potential can be summed?
T/F
FALSE
most synapses are
chemical
electrical synapses have what kind of junctions?
gap
gap junctions allow for
- very fast conduction
2. simultaneous activation
synaptic clefts is the
gap between the presynaptic cell membrane and the post
what is being transmitted across the synaptic cleft?
neurotransmitter
neurotransmitter binds to what?
postsynaptic terminal
NMJ also known as
cholinergic synapse
NMJ synapse between
motor neurona nd a muscle fiber
NMJ is Known is an example of a
chemical synapse
what is released at the NMJ
ACh
choline acetyltransferase is
an enzyme that forms ACh
botulins toxin blocks what?
the release of ACh
botulins health effects
parlysis of skeletal mm.
death due to respiratory failure
curare action
competes with ACh for nicotinic receptors int eh motor end plate decreasing the size of EPP
effect of curare
paralysis –> death
D-tubocurarine can be used to
relax skeletal mm.
Can one graded potential elicit an AP?
No
meaning that a graded potential is less than what?
threshold
the stimulus of a graded potential may be
chemical ot sensory
role of neurotransmitters in a graded potential
can either by excitatory or inhibitory
