MQ Neurobiology 3 Flashcards
True or false? Action potentials propagate distally along axons because the segment proximal to the action potential is hyperpolarized.
True
Which statement best describes the events that take place during propagation?
a.
A segment of the axon depolarizes while the following segment repolarizes.
b. A segment of the axon repolarizes while the following segment is stimulated.
c.
A segment of the axon depolarizes while the following segment returns to resting potential.
d.
A segment of the axon repolarizes while the following segment returns to resting potential.
b. A segment of the axon repolarizes while the following segment is stimulated.
Place in chronological order the steps describing propagation.
a. V-g-Na-ch close and v-gated-K-ch open in segment 15, while Na+ ions diffuse along the axon, from the 15th segment to the 16th segment of the axon.
b. K+ ions begin to rush out of segment 15 while segment 16 reaches activation threshold and V-g-Na-ch fully open.
c. Segment 15 repolarizes as segment 16 depolarizes to +30 mV.
d.Segment 15 is hyperpolarized returning to resting potential, V-g-Na-ch close and v-gated-K-ch open in segment 16, while sodium ions Na+ ions diffuse along the axon, from the 16th segment to the 17th segment of the axon.
- a
- b
- c
- d
The term “activation threshold” means:
a. potential difference which requires more stimulation to activate the neuron (-90 mV)
b. potential difference at which the voltage gated sodium channels (v-g-na-ch) open (-50 mV)
c. potential difference at which the cell has depolarized (+30 mV)
b. potential difference at which the voltage gated sodium channels (v-g-na-ch) open (-50 mV)
During the
[BLANK]
the voltage-gated ion channels are already fully open, so the maximum number of ions are already moving, such that a new or stronger event is impossible despite further stimulation.
absolute refractory period
Place in chronological order the steps describing saltatory propagation.
a. V-g-Na-ch close and v-gated-K-ch open in segment 15, while Na+ ions rush along the axon, from the 15th segment to the 16th segment of the axon.
b. K+ ions begin to rush out of segment 15 while segment 16 reaches activation threshold but few channels are present in the membrane of segment 16 because it is myelinated so half of the Na+ ions rush along the axon, from the 16th segment into the 17th segm
c. Segment 15 repolarizes as segment 17 reaches activation threshold but few channels are present in the membrane of segment 17 because it is myelinated so half of the Na+ ions move along the axon, from the 17th segment into the 18th segment of the axon.
d. Segment 15 is hyperpolarized returning to resting potential as segment 18 reaches activation threshold but few channels are present in the membrane of segment 18 because it is myelinated so half of the Na+ ions meander along the axon, from the 18th segment.
e. Segment 19 reaches activation threshold but few channels are present in the membrane of segment 19 because it is myelinated so half of the very few remaining Na+ ions trickle along the axon, from the 19th segment into the 20th segment of the axon.
f. Segment 20 reaches activation threshold and because segment 20 is unmyelinated, V-g-Na-ch open, Na+ ions rush in and segment 20 depolarizes to +30 mV.
g. V-g-Na-ch close and v-gated-K-ch open in segment 20, while sodium ions Na+ ions rush along the axon, from the 20th segment into the second 21th segment of the axon.
- a
- b
- c
- d
- e
- f
- g
True or False:
Action potentials dissipate as the ions diffuse away from the stimulation site.
False
Which statement best describes saltatory propagation?
a.
Faster frequency of action potentials due to a more intense stimulus.
b.
Stronger propagation due to a higher amplitude of action potentials because more dissociated ions from salts accumulate in the axon.
c.
Faster propagation because the diameter of the axon is wider, offering less resistance to the diffusion of ions.
d.
Faster propagation because the myelin sheaths block the channels, resulting in the generation of fewer action potentials at farther intervals.
d.
Faster propagation because the myelin sheaths block the channels, resulting in the generation of fewer action potentials at farther intervals.
True or False:
Graded potentials propagate as the ions diffuse away from the stimulation site.
False
True or False:
Action potentials propagate as the ions diffuse away from the stimulation site.
True
During propagation, how do segments of the axon reach the activation threshold?
Question 11Select one:
a.
influx of K+ ions from the previous segment
b.
influx of Na+ ions from the previous segment
c.
influx of K+ from outside the neuron
d.
influx of Na+ ions from outside the neuron
b.
influx of Na+ ions from the previous segment
True or False:
Graded potentials dissipate as the ions diffuse away from the stimulation site.
True
During the
[BLANK]
some of the voltage-gated ion channels are ready to re-open, but the cell is temporarily hyperpolarized while the Na/K pump redistributes the ions on either side of the cell membrane. It is possible to stimulate the neuron, but a stronger stimulation than usual is necessary to achieve activation threshold.
relative refractory period
