What is the approximate threshold value for mammalian neurons?
-55 mV.
-80 mV.
+35 mV.
0 mV.
The Correct Answer is A
The threshold potential is the critical level to which a membrane potential must be depolarized to initiate an action potential.
Most often, the threshold potential is a membrane potential value between –50 and –55 mV.
The membrane potential of a neuron is determined by the distribution of ions across the cell membrane.
At rest, the inside of a neuron is more negative than the outside due to the presence of negatively charged proteins and other molecules.
The movement of ions across the cell membrane can change the membrane potential.
For example, when sodium ions enter the cell, they make the inside of the cell more positive (less negative), causing depolarization.
Choice B is incorrect because -80 mV is below the typical threshold value for mammalian neurons.
Choice C is incorrect because +35 mV is above the typical threshold value for mammalian neurons.
Choice D is incorrect because 0 mV is above the typical threshold value for mammalian neurons.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
In this cross, the plant heterozygous for red flowers has the genotype Rr (where R represents the dominant red allele and r represents the recessive white allele), while the plant with white flowers has the genotype rr.
The possible offspring from this cross would have the genotypes Rr (red), Rr (red), rr (white), and rr (white), resulting in a 1:1 ratio of red to white flowers.
Correct Answer is B
Explanation
The correct answer is choice B. 3’ TCGATCGCA 5’.
In DNA, the nitrogenous bases adenine (A) and thymine (T) pair together, while cytosine © and guanine (G) pair together.
Therefore, the complementary strand of the given DNA sequence “5’ AGCTAGCGT 3’” would have the nitrogenous bases T, C, G, A, T, C, G, C and A in that order.
Additionally, the 5’ to 3’ direction of the complementary strand is opposite to that of the given strand.
Choice A. 3’ AGCTAGCGT 5’ is not correct because it is not complementary to the given strand.
Choice C. 5’ UCGAUCGCA 3’ is not correct because it contains uracil (U), which is a nitrogenous base found in RNA, not DNA.
Choice D. 3’ TCGUTCGCU 3’ is not correct because it also contains uracil (U), which is a nitrogenous base found in RNA, not DNA.
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