Lecture 3: Action Potential Flashcards
Common structures of neutrons:
1. Input zone: _____
2. Integration zone: _____
3. Point of action potential initiation: ____
4. Conducting zone: ____
5. Out put zone: _____
Dendrite
Cell body
Axon hillock
Axon
Axon terminal
An electrical signal that travels from one end of a cell to the other very rapidly
Action potential
___ allow fast information transfer within the body
________ mediate the rapid spread of information
Neurons
Action potential
Voltage different across plasma membrane =
Membrane potential
-50 to -70mV =
Resting membrane potential
The magnitude of the potential depends on the degree of separation of _____ ____
Opposite charges
Less potential = ___
More potential = ___
Depolarized
Hyperpolarized
Lipid bilayer is a good ___
Insulator
Electrical signals in neurons depend on rapid changes in ____
Membrane potentials
____ mediate the flow of ions (currents) that underlie electrical signals in excitable cells
Ion channels
Structure of ion channels:
___ span the membrane
Form ___ -filled pore
Proteins
Water
Properties of ion Chanels:
-act as filters allowing specific ___ through the cell membrane
- have ___ states and _____ states
- transition between states = gating
- > channels gate in response to:
-changes in _______ (____ - gated channels)
- ______ binding (____-gated or ___ operated channels)
- ____ forces (______ channels)
Ions
Conducting and non conducting
Gating
Membrane potential (voltage gated)
Ligand (ligand or receptor )
Mechanical (mechanosensitive )
Structure: Functional role:
___ and ___ Synaptic potential intrinsic excitability
—— Action potential generation
___ action potential conductance
________ Transmitter release
Dendrites and cell body
Axon hillock
Axon
Axon terminal
Rapid opening of voltage gated channel triggered at ___
Threshold
Na+ channels:
___ activating and inactivating
Inactivated channels cannot ____
K+ channels:
___ activating
Persistent ___
At rest Na+ and K+ channels are ___
Fast
Reopen
Slow
Activation
Closed
A triggered event induces membrane ___
Depolarization may activate some___ channels allowing __ influx
Causing more _____
Depolarization
Na+
Depolarization
___ = start of action potential (point of no return)
Threshold
Once the threshold is reached, _____ feedback cycle of ___ channel
activation begins.
• This cannot be stopped (thus
point of no return)
• This underlies _____
nature of action potentials
Positive
Na+
All-or-none
Around the peak of action potential, two things happen that stop further____ and start____
depolarization
repolarization
___ channels cannot open while in an inactive state. Therefore action potential cannot be elicited during this time
Na+
• Membrane
____ causes
both Na+ and K+
channels to return to
closed state
• Na+ and K+ channels
are available to___ at
next stimulation
Repolarization
Open
During afterhyperpolarization (AHP), it is harder to elicit an action potential because the membrane is more ____
hyperpolarized
Strong triggering stimulus
results in ___ frequency firing
High
How do neurons fire action potentials in different patterns?
Neurons have various ion channels that can induce various firing patterns
Action potential starts at the ____
and then propagate down the ___
• While propagating, action potentials do
no wane in _____
• This is because action potential is
____
Axon hillock
Axon
Size
Regenerative
What are the Two functional roles of refractory period
- Prevent backward
propagation of action
potentials - Limit firing frequency
What ion channels underlie action potentials?
Na+ and K+ channels
Where is action potential generated?
Axon hillock
Why can an action potential travel long distance
without fail?
Because action potentials are regenerative
Why does an action potential propagate in one
direction along the axon?
Refractory period prevents backpropagation of action potential
Since action potentials are all-or-none, how are
differences in the signal intensity conveyed?
Firing frequency and pattern of action potentials
Conduction velocity is defined by:
- ____diameter
- density of ___ channels
- myelin ____
-distance between _____
Axon
Na+
Insulation
Nodes of ranvier
__________ means that action potentials jump from one node of ranvier to the next thus propagating much faster
Saltatory conduction
Action potentials jumping from one node of ranvier to the next is due to ________
Myelination of the axon
Nodes of ranvier are bare part of the ____ that support action potential conduction
Axon
Glial cells provide ___
Myelin
___ is cellular process of glial cells
Myelin
Myelin is consisted of tightly wrapped cell __
Membrane
Lipid bilayer does not pass ___
Ions
___ is mostly cell membrane = good insulation
Myelin
Electrical current propagates faster and farther along the _____ axon
Myelinated
Myelin does/does not conduct current ?
Not
Myelin is/is not part of the axon ?
Not
__ axons conduct faster
Thicker
__ nerve fibers:
- Proprioception
- contraction of skeletal muscle
Aα
___ nerve fibers
-touch
A(beta)
___nerve fibers
-acute pain
Aδ
____ nerve fibers
- chronic or dull pain
- temperature
-itch
C
Heavily _____ axons conduct faster
Myelinated
What factors determine the action potential velocity?
– Axon diameter, myelination, Na+ channel density
What is the role of nodes of Ranvier?
– Regeneration and propagation of action potential
What type of cells provide myelin?
– CNS: oligodendrocytes, PNS: Schwann cells
Action potential:
Intensity of signal is conveyed by ___
Frequency
Action potential:
______ in one direction
– Initiated at ____ (highest density of Na channels)
– _____ channel distributed along the axon supports action potential propagation
(action potential is regenerated by Na channels)
– _______ prevents action potential from going backwards
Propagates
Axon hillock
Na+
Refractory period
Conduction velocity (speed of propagation ) depends on:
– ____
–_____
Axon diameter
Myelination
