Chpt 3: Excitable Cells and Neural Communication Flashcards
Membrane potential def
refers to the difference in the electrical potential b/w icf and ecf
or
separation of opposite charges across the plasma membrane
does membrane potential occur in all human and plant cells
yes
how is membrane potential measured
millivolts (mV)
example of excitable cells
nerve and muscle cells
when do nerves and muscles rest?
during sleep, but continue to make or reserve atp
nerve and muscle cell ability
can produce rapid, transit changes in their membrane potential when excited
Resting membrane potential def
constant membrane potential present in cells of non-excitable tissues
what mV does resting potential rest at
-70mV
effects of Na-K pump in membrane potential
-contributes by its unequal transports of positive ions (3 Na and 2 K)
what restores mp and how
Na-K pump using a carrier and ATP
how is concentration measured?
millimoles/liters (mM/L)
concentration of Na+ in ecf
150mM/L
concentration of Na+ in icf
15mM/L
relative permeability of Na+
1
concentration of K+ in ecf
5mM/L
concentration of K+ in icf
150mM/L
relative permeability of K+
50-75
what ions are involved in the production of membrane potential?
Na+ and K+
what ions are present but not involved with mp
A- (carbohydrates, amino acids, proteins)
Cl-
HCO3-
what ion is the first to take charge in creating an electrical signal?
Na+
what ion is the most permeable/ leaky
K+
what ion creates the opposite concentration gradient?
K+
A- concentration in icf
65mM/L
Cl- concentration in ecf
100mM/L
what ion moves around but doesn’t create an electrical potential
Cl- and HCO3-
HCO3- concentration in ECF
30mM/L
excitable cells meaning
cells that change their resting potential to produce electrical signals when excited
Polarization
any state when mp is anywhere but at 0mV
staying at -70mV/ being negative
depolarization
- less polarized (less negative) than at rp
- moving towards 0mV after a stimulus has reached the threshold
repolarization
- membrane returns to rp (-70mV)
- becoming negative
hyperpolarization
- membrane becomes more polarized than rp
- more negative
what is the mV at hyperpolarization
below -70mV and can go down to -90mV
upward deflection =
decrease in potential (icf is less - )
downward deflection =
increase in potential (icf is more - )
what creates electrical signals
channels (many diff kinds)
voltage-gated channels
- electrical current will open them
- at rest = gate is closed
- excited = gate is open
what determines when voltage-gated channels open/close?
changes in membrane potential
chemically gated channels
open under command of chemical signals
~ neurocrines, paracrines, hormones
mechanically gated channels
- respond to stretching or mechanical deformation
- need pressure or touch to open
thermally gated channels
- respond to changes in temp
what restores resting potential?
NA-K pump
what are the two kinds of potential changes?
graded potential
action potential
where do graded potentials occur?
small, specialized region of the membrane
what type of change occurs with graded potential?
-small changes in membrane potential/ electrical state
how does graded potential progress?
dies down
which potential change goes in both directions?
graded potential
how to produce an electrical signal
-stimulus occurs, reaches threshold, depolarization ocurs
what do the magnitude and duration depend on in graded potential?
-strength and duration of triggering event (aka stimulus)
what happens with a stronger triggering event
more gated channels = more Na/ + charges in = depolarization
why does the potential in graded potential die down?
- K+ leaking out
- cytoplasm = bad conductor `
current def
any flow of electrical chargers, current follows direction of + charges
examples of graded potential
- postsynaptic
- receptor
- end-plate
- pacemakers
where does end plate graded potential occur?
- occurs in neuromuscular junction
between neuron and muscle
pace maker graded potential meaning
-set/make their own pace
where is a pacemaker graded potential found?
muscles
Action Potential location in neruon
cell membrane
ap time
brief, large, rapid
what is the magnitude of change in AP?
100mV
Action Potential description
- doesnt decrease in strength
- long-distance signals
what potential is involved with positive feedback
action potential
rising phase cause
Na+ influx which causes depolarization
peak meaning
+30 mv is reaching, K+ efflux begins
falling phase cause
- K+ efflux, repolarization occurs
threshold potential
- triggered by an increase in Na+ permeability
- minimum stimulus require to go beyond
- rests at -50mV
activation gate structure
latch like
inactivation gate structure
ball and chain
when does the inactivation gates begins to close?
at peak
undiminished movement
ensures ap will cover the entire membrane
what ensures undiminished movement?
refractory period
refractory period
- period of time followed by an ap
- marked by decreased excitabtily
- another ap will not occur
absolute period
- ap is occurring in present time, so another one cant occur
- all of depolarization and most of repolarization
- Na gates are closed
Relative period
- last part of repolarization and hyperpolarization
- Na+ gates closed, some K are open
- resting phase
can another ap occur during the relative period
yes, if the stimulus is urgent or stronger than the first
consequences of refractory period
- all or none principle
- undirectional
movement of ap propagates from ___ to ___
axon hillock to axon terminal
collaterals
side branches of axon
input zone
signals are received
dendrite/ dendrite zone
gather stimulus
cell body
contains nucleus
trigger zone location
axon hillock
trigger zone function
ap is initiated
conducting zone location
axon
conducting zone function
conducts ap in undiminishing fashion
output zone location
axon terminal
output zone structure
releases a neurotransmitter that influences other cell
how does conduction/ap propagate through nerve cells?
contigous conductions and saltatory conduction
contigous conduction location
in unmyelinated neurons
contigous conduction process
ap spreads along every portion of membrane
speed of contigous conduction
0.7m/s in digestive system neurons
energy consumption of saltatory conduction
conserves energy, since channels dont have to reset
how to increase speed of ap
- large diameter
- myelination (50x faster)
myelin function
- used to insulate
- makes saltatory conduction possible
what is myelin composed of?
lipids
which cell forms myelin in the CNS?
oligodendrocytes
where are Schwann cells found + function
PNS and make myelin
synapses
junction between 2 neurons
synaptic cleft
area between neurons
presynaptic neuron
takes message toward synapse
postsynaptic neuron
-takes message away from synapse
synaptic vesicle
-stores neurotransmitters
synaptic knob
- contains synaptic vesicles
- touches postsynaptic neuron
does contignous conduction use atp?
yes, cuz membrane resets each time
saltatory conduction location
in myelinated fibers
saltatory conduction propagation process
-impulses jump over sections of the fibers covered with insulating myelin
which conduction is faster
saltatory conduction, it is 120m/s in muscle cell
types of synapse
excitatory and inhibitory
excitatory synapse function
creates small depolarization
inhibitory synapse function
leads to small hyperpolarization
what does more negative membrane potential mean
harder to make ni
neural summation definiton
effect of 2 different potentials (inhibitory or excitatory) coming together
what does neural summation create
grand postsynaptic potential
what does grand postsynaptic potential include
temporal or spacial summation
what dictates grand postsynaptic potential
rates of presynaptic neutrons firing
temporal summation
several epsp occurring very close in time
epsp
excitatory postsynaptic potential
ipsp
inhibitory postsynaptic potential
grand postsynaptic potential depends on
sum of activity in all presynaptic inputs and determines if a neuron will undergo ap
spacial summation
-2 different excitatory or inhibitory add up in a space, 2 diff inputs from diff areas in one space
cancellation of ipsp and epsp occurs
-inhibitory and excitatory signal cancel each other
what is missing in Parkinson’s
dopamine in bASal gangli
result of Parkinson’s
muscular rigidity + involuntary tremors
cocaine use causes too much off..
dopamine in the brain
tetanus toxins prevents
release of inhibitory GABA
effects of tetanus toxins
uncontrolled muscle spasms, lock jaw, death
what is the main inhibitory neurotransmitter
GABA
most common excitatory neurotransmitter
glutamate
functions of glutamate
causes epsp
20-day embryo structures
neural crest and neural plate
neural crest
becomes the pns
neural plate
plate of cells dividing to form regions, becomes the cns
23-day embryo
pns and cons start to form
what disease demyelinates neurons?
multiple sclerosis
what causes MS
- herpes
- more in colder regions
- epstein barr virus
- genetic
- environment
- mono
symptoms of MS
- persona can’t conduct electrical signals
- extreme fatigue
- loss of vision
- muscle cramps
- difficulty walking
