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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Related Questions
Correct Answer is D
Explanation
Osteoporosis is caused by an imbalance between the functioning of osteoclast and osteoblast cells.
Osteoblasts are responsible for forming new bone, while osteoclasts break down old bone.
If osteoblast activity declines while osteoclast activity continues at expected levels, this means that more bone is being broken down than is being formed, leading to a loss of bone density and an increased risk of osteoporosis.
Choice A is incorrect because an increase in osteocyte activity would not result in osteoporosis.
Osteocytes are mature bone cells that maintain the mineral concentration of the bone matrix.
Choice B is incorrect because a decline in osteoclast activity would not result in osteoporosis.
Osteoclasts break down old bone, so a decline in their activity would mean that less bone is being broken down.
Choice C is incorrect because an increase in osteocyte activity would not result in osteoporosis.
As mentioned earlier, osteocytes are mature bone cells that maintain the mineral concentration of the bone matrix.
Correct Answer is C
Explanation
In an experiment, the dependent variable is the variable that is being measured and is expected to change in response to changes in the independent variable(s).
In this case, the bag mass change is being measured and is expected to change in response to changes in the independent variable (sucrose concentration).
Choice A is incorrect because duration is not a variable in this experiment.
Choice B is incorrect because temperature is not a variable in this experiment.
Choice D is incorrect because sucrose concentration is an independent variable, not a dependent variable.
An independent variable is a variable that is manipulated by the experimenter to see how it affects the dependent variable.
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