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44 Cards in this Set
- Front
- Back
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What part of the neuron integrates the incoming signal?
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the axon hillock (also known as initial segment)
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To open Na+ gated activation channel, the membrane potential must first be..
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depolarized to -50 mV
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To close a Na+ gated inactivation channel, the membrane potential must first...
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depolarize all the way to +30
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In the cell membrane, the trigger zone is where you find...
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a ton of voltage gated Na+ channels at the axon hillock
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When the trigger zone in the cell membrane becomes depolarized, this causes the cell to undergo an ______________, causing all other Na+ gated channels to depolarize. This process is an example of _________.
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all-or-nothing action potential
positive feedback |
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When sodium reaches the maximum depolarization membrane potential at __________, _________ have had enough time to fully open. Now that the channels are open, this ion moves (into/out) of the cell and makes the cell more (positive/negative).
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+30 mV
potassium channels -out -negative (once sodium depolarizes the cell to +30, potassium channels become fully open allowing potassium to leave the cell. As K+ leaves the cell, it becomes more negative. |
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When potassium leaves the cell AFTER depolarization, it makes the cell more (positive/negative) in a process called ______________.
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-negative
-hyperpolarization |
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Absolute refractory period?
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when a second action potential ABSOLUTELY CANNOT occur
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Relative refractory period?
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when a second action potential is possible but the threshold is elevated
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Hyperkalemic periodic paralysis is a channelopathy in which the...
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inactivation gate of Na+ voltage gated channels is altered (in muscles)--causes prolonged action potentials--> increased K+ flux--> K+ conc. after exercise -->lowering threshold--> muscle twitching and weakness, followed by paralysis
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Tetrodoxin (from blue-ringed octupuses/puffer fish), saxitoxin (dinoflagellates), muconotoxin affect the ________ channel.
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Na+ voltage gated
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If the membrane potential of the cell is -100 and you send an input that activates Cl- channels, Cl- will move (into/out) of the cell, making the cell more _________. Why?
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-out
-positive because the resting potential of Cl- is near -76. |
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What kind of cells produce the myelin sheath?
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glial
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As an action potential travels down the axon, what prevents the potential from traveling backwards?
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the refractory period (absolute--when the Na+ inactivation gate is closed, relative--when potassium hyperpolarizes cell so you need to reach a higher threshold)
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The larger the axon diameter, the (faster/slower) the action potential propagates down its length.
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faster (like a HO'S)
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What are the glial cells in the peripheral nervous system called?
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schwann cells
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What are the glial cells in the CNS called?
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oligodendrocytes
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What are the areas between adjacent patches of myelination called?
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nodes of Ranvier
(contain the voltage gated Na+ channels) |
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How does the myelin sheath speed up conduction?
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the action potential jumps from one node of Ranvier to the next because only the nodes have voltage gated sodium channels. Opening the channels takes time, so the more myelin there is=the less channels the potential has to open and the more skipping from node to node occurs = faster. Also, the areas that are covered by the sheath are safe from the current leaking.
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Action potential conduction in myelinated axons is called_____
why is it faster? |
saltatory conduction
-no current leakage in mylinated internodes, reduced capacitative current, less Na channels, less time spent opening them |
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Under a micron, it is faster to have (myelinated/unmyelinated) axons.
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unmyelinated
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Leprosy, diptheria, Guillain-Barre syndrome, hereditary and sensory neuropathy and multiple sclerosis are all...
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myelination pathologies
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Graded potentials occur in the....
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dendrites and sensory cells
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Action potentials occur in the...
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axon
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Graded potentials are (summed/all or nothing) while action potentials are (summed/all or nothing).
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-summed
-all or nothing |
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Does a graded potential require a threshold stimulus?
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no.
(amplitude depends on input signal & signal decays over time & space) |
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Sodium and potassium are ions involved in (action potentials/graded potentials) while sodium, potassium, chloride and calcium are involved in (action potentials/graded potentials)?
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-action potentials
-graded potentials |
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Action potentials occur only in _______ cells, including _______ and _____________.
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excitable
muscles and neurons |
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For ______potential, signals can be depolarizing or hyperpolarizing. For ________ potential, signals are depolarizing only.
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Graded
Action |
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(Dendrites/Axons) respond to input by changing transmembrane potentials locally, while (dendrites/axons) conduct the signal to distant locations.
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dendrites
axons |
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The _______________ is the location where graded potentials are evaluated and an action potential can be fired.
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Trigger zone
(part of axon hillock) |
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At the resting potential -70 mV, the (activation/inactivation) gate of a Voltage-gated Na+ channel is closed. When the membrane (depolarizes/hyperpolarizes), this gate opens, allowing Na+ to flow inward. When the (inactivation/activation) gate closes, Na+ entry stops.
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activation
depolarizes (to -50) inactivation (closes slowly, both gates are temporarily open) |
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When Na+ channels close, ___ channels open, allowing that ion to move (into/out) of cell, causing (depolarization/hyperpolarization). When these channels close, the cell will return to ________________.
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K+
out hyperpolarization resting membrane potential |
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Repolarization is due to the sodium potassium pump (true/false)
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false!!!
- due to opening of K channel and closing Na channel |
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(few/many) ions move across the membrane during an action potential.
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few
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The falling phase of the action potential is due to the _____ gate of the voltage gated Na+ channel and the _______ of the K + channels
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closing of the inactivation
opening |
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Wilson Disease results in (reduced/increased) conduction velocity.
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reduced
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Synthetic local anesthetics are derived from ________. They reversibly block __________, when in the open state.
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cocaine
voltage-gated Na+ channels |
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hypoparathyrodism and hyperparathyroidism reduce and increase ___________________, changing Vm and leading to neurological and neuromuscular symptoms.
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plasma Ca2+ concentration
hypoparathyroidism, decreases plasma Ca2+, increasing Vm to make it closer to -50mV thus lowering the threshold and making the cell hyperexcitable |
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Na channels open slower than K channels (true/false)
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false
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Describe the currents shaping an action potential
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1. graded potential above threshold reaches trigger zone
2. voltage gated Na channel opens, Na flows in 3. Na (+) charge flows into adjacent sections of axon by local current flow 4. local current flow causes new section of membrane to depolarize 4. refractory period prevents backward conduction. Loss of K+ from cytoplasm repolarizes membrane |
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What do the cell body and synapse terminal of neurons do?
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cell body- supports cell metabolically
synapse- transmits information to the next cell |
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In a prototypical cell, how long does it take for each phase:
depolarization: repolarization: hyperpolarization: |
depolarization: 0.5 ms
repolarization: 0.75 ms hyperpolarization: 2.5 ms |
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what factors cause refractory periods?
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takes time to reset Na+ voltage-gated channels, all Na channels have been opened, K+ channel is also open allowing current from graded potential to leak through membrane
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