Studied by 0 peopletriggers voltage
Depolarization at axon terminal ________ gated Ca2+ channels (Ca2+ messenger)
Resting membrane potential difference (resting potential)
voltage difference across the cell membrane at rest
Graded potential
depolarization of soma and dendrites via influx of Na+
Membrane receptors
gated Na+ channels lining the soma and dendrites that respond to stimulus (ACh, other chemical ligand, mechanical force on cell membrane, etc.)
Summation
accumulation of Na+ from multiple graded potentials
Temporal summation
from multiple graded potentials over short period of time from the same origin (separated by time)
Spatial summation
from multiple graded potentials arriving at about the same time from different origins (separated by space)
Action potential
depolarization along length of axon
Threshold
voltage required to initate action potential
Axon hillock
connection between soma and axon
Absolute refractory period
time during which another action potential cannot be initiated
Relative refractory period
time during which it is more difficult than normal to initiate an action potential
Frequency coding
frequency or number of action potentials codes for strength of signal or strength of stimules
Axon diameter
walls cause resistance to flow, more distance from walls = faster rate; threfore larger axons allow for faster transduction (less efficient but faster)
Myelination
prevents ion leakage, if Na+ leaks back out along axon → [Na+] inside axon decreases → diffusion rate decreases → transduction rate decreases
Compound action potential
nerve segment is bundle of axons, generally not possible to separate a single one to be tested (except for squid giant axon); the sum of action potentials travelling on parallel axons at the same time, will vary in strength as number of axons depolarizing at one time changes
What is resting membrane potential difference (or resting potential)?
voltage difference across the cell membrane at rest
Is there a higher or lower concentration of K+ in ECF or ICF at rest?
higher [K+] in ICF
Is there a higher or lower concentration of Na+ in ECF or ICF at rest?
higher [Na+] ECF
What is the normal range of resting potential?
-40 to -80 mV
Stimulus --> ___ potential --> ___ potential --> exocytosis of ACh from axon terminal
graded; action
What is graded potential?
depolarization of soma and dendrites via influx of Na+
What lines the soma and dendrites that respond to a stimulus?
membrane receptors (gated Na+ channels)
What determines the strength of graded potential?
strength of stimulus
Number of membrane receptors opened, length of time membrane receptors stay open, and amount of Na+ allowed to influx affect ___.
strength of potential
What is summation?
accumulation of Na+ from multiple graded potentials
True or False: There can be multiple action potentials from a single graded potential and/or summation.
True
What is temporal summation?
multiple graded potentials over short period of time from the same origin (separated by time)
What is spatial summation?
multiple graded potentials arriving about the same time from different origins (separated by space)
What is action potential?
depolarization along length of axon
What is threshold?
voltage required to initate action potential
What is axon hillock?
connection between soma and axon
When does the activation gate of voltage gated Na+ channels open?
threshold
What does the opening of the activation gate of voltage gated Na+ channels do?
allows influx of Na+ from ECF causing depolarization
When does the inactivation gate of voltage gated Na+ channels close?
at overshoot (tip of graph)
True or False: Once the inactivation gates of voltaged gated Na+ channels close, it is ready to respond to another stimulus.
False - does not respond to voltage again after closing, takes time to reset
Voltage gated K+ channels open at ?
threshold
What does the opening of voltage gated K+ channels cause?
efflux of K+ from ICF causing repolarization and hyperpolarization
True or False: Voltage gated K+ channels have an activation and inactivation gate.
False - Only has one gate (Na+ has two gates)
Is voltage gated Na+ or K+ channels slower to open?
K+
Voltage gated K+ channels open fully when?
at overshoot (tip of graph)
What is absolute refractory period?
time during which another action potential cannot be initiated
When does the absolute refractory period occur?
between activation of the voltage gated Na+ channel and when it resets to resting state
What is relative refractory period?
time during which it is more difficult than normal to initiate an action potential
When does the relative refractory period occur?
during hyperpolarization (takes greater amound of Na+ to reach threshold)
What is frequency coding?
frequency or number of action potentials codes for strength of signal or strength of stimulus
Strength of stimulus --> strength of ___ potential --> number or frequency of ___ potentials --> amount of ___ exocytosed at axon terminal
graded; action; ACh
Smaller axon diameter cause what to occur?
resistance to flow
Larger axon diameter --> ___ transduction
faster
Myelination prevents what from occuring?
ion leakage
Why is ion leakage not good for cells?
[Na+] inside axon decreases --> diffusion rate decreases --> transduction rate decreases
Myelination is benefical because?
fewer gated channels involved, less Na+ required to be moved therefore more efficient
Fast pain is associated with myelinated or non-myelinated axon?
myelinated
Slow pain is associated with myelinated or non-myelinated axon?
non-myelinated
What is compound action potential?
the sum of action potentials travelling on parallel axons at the same time
True or False: It is possible to test a single axon.
False - nerve segment is a bundle of axons therefore not normally possible (except in squid giant axon)
What is exocytosis?
depolarization at axon terminal triggers voltage gated Ca2+ channels
Influx of Ca2+ triggers release of what?
synaptic vesicles from the cytoskeleton
Note
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