Topic.5.TheNeuron.powerpoint.5.1.ion.channels.and.action.potentials Flashcards
T/F A resting neuron can conduct an action potential
No
What are the 3 characteristics about a resting neuron
-voltage gated k+ and Na+ are closed
-K+ leak channels
-k+/Na+/ATPase channels 3 Na out and 2 K in
What are the four types of ion channels in neurons?
-ungated channels (leak),
-Voltage-gated channels (in axon membranes)
-Ligand-gated channels (primarily at synapses)
-Mechanically gated (in sensory receptors)
T/F At rest there are more Na+ channels open than K+
False, more ungated k+ channels open
What is an example of ligand-gated channel?
neurotransmitter bind and create a conformational change
What is an example of mechanically gated channel?
hair cell in the inner ear-involved with hearing
T/F Generally with neurons, ion channels size matters matter
Yes, even if you are smaller than the ion size channel still can’t go through
What is a voltage gated ion channel?
They are integral membrane proteins
-alpha-helical transmembrane segments that can form pores where ion can pass-through
-voltage sensing than can inactivate pore
Volted gated ion channels are sensitive to ___
membrane potential
Goldman equation predicts
membrane potential of membranes permeable to more than one ion
-depends on concentration of ions and permeability
t/F Ion channels do not always open and close independently
true
The rate of ionic flow through the channel is determined by…
-maximum channel conductance
-the electrochemical driving force for that ion
Action potential
The abrupt and transient change in membrane potential that occurs when a neuron (other electrically excitable cell) conducts an electrical impulse
hyperpolarization
membrane potential goes lower than resting membrane potential
What are the steps for action potential
- stimulus
- Depolarization occurs until a threshold potential of 10-20 mV more positive than -70mV
- Peak of action potential
- repolarization
5.hyperpolarization
.6Returns to resting membrane potential
What is all or nothing?
nonstop action potential firing, once reaches threshold regardless of stimulus strength
Write a summary of Na+/k+ channels opening in an action potential
k+ closed & Na+ open(flow in)|Action potential |Na+ inactivated and K+ open (flow out)
What are the 3 keys features of AP in neurons?
-All or none
-Maintain the size of magnitude of the action potential as it travels along the axon(voltage)
-Propagation of action on neighboring
stretches of membrane
What is a refractory period?
Sensitivity of area to further
stimulation decreases for a time
What is the difference between absolute and relative refractory period?
Absolute: Complete insensitivity exists to
another stimulus
-From beginning of action potential
until near end of repolarization.
Relative: A stronger-than-threshold stimulus can initiate another action potential
Which of the following is true
regarding the refractory period?
A. It only lasts for a few milliseconds
B. During the relative refractory period, the threshold
required for generating an action potential is much higher
than normal.
C. It keeps impulses from traveling in both directions in
neurons
D. All of the above
E. None of the above
D All of the Above
What would be the primary basis for
the absolute refractory period?
A. Not enough sodium ions left outside
B. Sodium channels closed
C. Sodium channels inactivated
D. Voltage gated potassium channels open
E. Membrane is depolarized
C. Sodium channels inactivated
D. Voltage-gated potassium channels open
In an absolute refractory period, how do we know it began, end, restart?
-Voltage-gated Na+ channels are either already open or have proceeded to the inactive stat
-once closed the channels can open to a second stimulus once the membrane is repolarized and pore is closed
What would be the basis for the
relative refractory period?
A:Not enough sodium ions left outside
B. Sodium channels closed
C. Some sodium channels still inactivated
D. Voltage-gated potassium channels open
E. Membrane hyperpolarized
C. Some sodium channels still inactivated
D. **Voltage-gated potassium channels open (contributes
most)
E. Membrane hyperpolarized
What are some trait of relative refractory period?
-some but not all Na+ are closed
-some k+ still open
During a relative refractory period, new stimulus can depolarize the membrane above threshold BUT ONLY IF.
1.The stimulus is large in magnitude
2. The stimulus outlasts the relative refractory period
If new action potenial is started during relative refractory period, we can expect the AP to be ___ than the original
smaller
-K+ is still going out
-some Na+ channels are still inactivated,
rather than closed
During relative refractory period, the threshold required for the generation of an action potential is ___. Meaning you need greater ___
higher than normal; depolarization
T/F The duration of a relative refractory period is not variable
False
Strength stimuls gradually lowers over time in relative refractory period due to
Na+ channels recover from inactivation and
as K+ permeability returns to its resting level.
the intensity of a stimulus is indicated by
the
frequency of action potentials
