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Biology
Neural Communication
Propagation of Action Potentials
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Created by
Alice Hadwen-Beck
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Cards (37)
What is the definition of local current in the context of nerves?
The movement of ions along the
neurone
due to
concentration differences
.
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How does local current occur in neurons?
It occurs due to an increase in
ion concentration
at one point, causing
diffusion
away from that region.
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What is saltatory conduction?
A mechanism of nerve impulse transmission in
myelinated neurons
.
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How does saltatory conduction work?
Action potential appears to
jump
from one node of
Ranvier
to the next.
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What happens when positive ions arrive at one node during saltatory conduction?
It
depolarizes
the
second
node, triggering another
action
potential.
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What are the key features of local currents and saltatory conduction?
Local currents involve
ion movement
along the neurone.
Caused by
concentration differences
leading to
diffusion
.
Saltatory conduction occurs in
myelinated neurons
.
Action potentials jump between
nodes of Ranvier
.
Positive ions
depolarize subsequent nodes.
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What is the direction of movement for an action potential along a neurone?
The action potential moves in
one
direction
until it reaches the
end
of the neurone.
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Why does the action potential not reverse direction?
Because the concentration of
sodium ions
behind the action potential is still high.
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What is the process of action potential propagation along a neurone?
Na+
channels open, allowing Na+ to
diffuse
inside the neurone.
Localized
increase
in concentration of Na+ inside the neurone occurs.
This increase causes the
action
potential.
Na+ diffuses
along
the axon.
Na+ gates that were initially closed
open
due to
Na+
movement
, allowing the action potential to move.
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How far apart are the nodes along the neurone?
The nodes are
1 - 3 mm
apart.
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What happens when Na+ channels open in a neurone?
Na+
diffuses
inside the neurone, increasing the
concentration
of Na+ inside.
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What is the role of Na+ movement in the action potential process?
Na+
movement
causes the action potential and allows it to
propagate
along the neurone.
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What is the effect of myelination on action potential conduction?
Myelination
increases
the
rate
of action potential
conduction.
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What is the term used for the conduction method in myelinated axons?
Saltatory conduction
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What is the role of the myelin sheath in neurons?
The myelin sheath insulates the
axon
to facilitate
faster
conduction.
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What happens to action potential conduction in unmyelinated axons?
It occurs at a
slower
rate compared to
myelinated
axons.
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How does the presence of nodes of Ranvier affect action potential conduction?
Nodes of Ranvier allow for
faster
conduction through
saltatory conduction
.
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What are the key differences between myelinated and unmyelinated axons in terms of action potential conduction?
Myelinated axons conduct
action potentials
faster due to
saltatory
conduction.
Unmyelinated axons conduct action potentials
slower
through
continuous
conduction.
Myelinated axons have
nodes of Ranvier
that facilitate
rapid
transmission.
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What is the resting potential of a neuron?
The resting potential is typically around
-70 mV
.
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What is the significance of action potentials in neurons?
Action potentials
are essential for transmitting
signals
along neurons.
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What ions are primarily involved in generating action potentials?
Sodium (Na+)
and
potassium (K+)
ions are primarily involved.
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What is the role of K+ ions during an action potential?
K+ ions help to repolarize the neuron after
depolarization
.
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What is the relationship between action potential conduction rates and the presence of myelination?
Myelination
increases
action potential conduction rates compared to
unmyelinated
axons.
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What is the typical resting potential of a neuron?
-60 mV
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What is the effect of action potentials on neuron signaling?
Action potentials
enable neurons to
communicate
signals effectively.
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What is the primary function of the myelin sheath?
To
insulate
axons and increase the speed of
action potential
conduction
.
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What is the state of the voltage-gated sodium channels in the resting state of a sector?
They are
closed
but in an
active
state.
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What characterizes the refractory period in a sector?
The
voltage-gated sodium ion channels
are closed and inactive.
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How does the impulse travel during the refractory period?
It only travels in one
direction
.
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What initiates an action potential in a sector?
Local depolarizations begin to open
voltage-gated sodium channels
.
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What is the composition of the myelin sheath?
It contains myelin, a
phospholipid
.
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What happens to voltage-gated sodium channels in the sector during action potential propagation?
They are opened, allowing
sodium ions
to move.
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What is the role of the myelin sheath in action potential propagation?
It does not conduct an
electric current
.
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What is the Node of Ranvier?
It is a region of
unmyelinated
nerve cell membrane.
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What occurs at the Node of Ranvier regarding ion movement?
Voltage-gated ion channels
allow
Na+
and
K+
movement across the membrane.
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How effective are depolarizations of voltage-gated sodium channels?
They are effective over
greater
distances between adjacent
Nodes of Ranvier
.
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What is saltatory conduction in myelinated neurons?
The impulse
jumps
from node to node.
It
increases
the speed of action potential
propagation.
It occurs at the
Nodes of Ranvier
.
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