10/12 Action Potentials - Roger 2017 Flashcards
Define Polarization? 7
any deviation from the equilibrium potential from 0mv
Define depolarization? 8
Membrane potential becomes more positive
Define Hyperpolarization? 7
Membrane potential becomes more negative
Define Repolarization? 9
Membrane potential returning to resting membrane potential
What is the time interval for a motor neuron, skeletal muscle, and cardiac ventricle action potential? 10
Motor neuron —> 2 ms
Skeletal muscle —> 5 ms
Cardiac ventricle —> 200 ms
What are the key properties of action potentials? 11
PAN
P ropagated or self-reinforcing
A ll-or-none
N on-decremental
What are the characteristics of graded potentials? 12
Small/local changes in membrane potential
Dissipates with distance
What is the resting phase? 15
Phase 4
What phase is Depolarization (-90mv —> +30mv)
Phase 0
What phase is repolarization? 15
Phase 3
What else do we refer to hyperpolarization as during an action potential? 15
Refractory period
What occurs during depolarization of an action potential? 19
Increased permeability of membrane to Na+
Voltage-gated Na+ open rapidly
Channels close automatically almost as soon as they open
What are the two gates of the voltage-gated Na+ channel? 20
Activation gate
Inactivation gate
Prior to potential what is the condition of the gates of the voltage-gated Na+ channels?
Inactivation gate is open
Activation gate is closed
At the commencement of the action potential was is the condition of the gates of a voltage-gated Na+ channel? 20
Inactivation gate is open (still)
activation gate opens (previously closed)
After the initiation of the action potential was is the condition of the gates of the voltage-gated Na+ channels? 20
Inactivation gate now closes (previously open)
Activation gate remains open
Slide 20
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Slide 21
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Slide 22
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What are the key characteristics of Voltage-gated K+ channels? 23
Selectivity (an ability to close)
24
Listen to recording
25
Draw out:
Gates open/closed
What each phase is
Describe the absolute refractory period? 26
Na+ channels are either open or the inactivation gate is closed
Incapable of reopening (protects the cell)
Describe Relative refractory period? 26
Inactivation gate is open
Activation gate is closed
Action potential can be initiated but it requires a stronger stimulus
What occurs exactly at threshold potential? 28
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What occurs once threshold is reached? 31
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32- 34
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What occurs in Hypokalemic Periodic Paralysis (HypoPP)? 35
Periodic (but not always) dips in blood K+
Membrane hyperpolarized and therefore harder to reach threshold
Repolarization occurs more quickly
What occurs in Hyperkalemic Periodic Paralysis? 37
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38
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