What is the approximate threshold value for mammalian neurons?
A. -55 mV
B. -80 mV
C. +35 mV
D. 0 mV
The approximate threshold value for mammalian neurons is -55 mV.
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.
Therefore, the Correct Answer is A.
More Questions on TEAS 7 Science
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Q #1: The cytoskeleton of a cell is comprised of which of the following macromolecules?
A. Carbohydrates
B. Nucleic acids
C. Lipids
D. Proteins
Answer Explanation
The cytoskeleton of a cell is comprised of protein fibers that provide structural support and help maintain the shape of the cell.
These protein fibers include microfilaments, intermediate filaments, and microtubules.
Choice A.
Carbohydrates is not the correct answer because carbohydrates are a type of macromolecule that provides energy to cells and are not a component of the cytoskeleton.
Choice B.
Nucleic acids is not the correct answer because nucleic acids are macromolecules that store and transmit genetic information and are not a component of the cytoskeleton.
Choice C.
Lipids is not the correct answer because lipids are a type of macromolecule that makes up cell membranes and are not a component of the cytoskeleton.
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Q #2: Which of the following is the main function of centrosomes in animal cells?
A. . Organelle trafficking.
B. Pathogen digestion.
C. Cytoplasm formation
D. Microtubule organization
Answer Explanation
Microtubule organization.
Centrosomes are organelles that serve as the main microtubule-organizing centers for animal cells.
They regulate the movement of microtubules and other cytoskeletal structures, thereby facilitating changes in the shapes of the membranes of animal cells.
Choice A, Organelle trafficking, is not the correct answer because while centrosomes do play a role in intracellular trafficking during interphase by organizing an astral ray of microtubules, their main function is microtubule organization.
Choice B, Pathogen digestion, is not the correct answer because centrosomes do not play a direct role in pathogen digestion.
Choice C, Cytoplasm formation, is not the correct answer because centrosomes do not play a direct role in cytoplasm formation.
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Q #3: Which of the following types of cells produce and release antibodies?
A. Natural killer cells
B. Cytotoxic T-cells
C. Plasma B cells
D. Helper T-cells
Answer Explanation
Plasma B cells.
Antibodies are produced by specialized white blood cells called B lymphocytes (or B cells).
When an antigen binds to the B-cell surface, it stimulates the B cell to divide and mature into a group of identical cells called a clone.
The mature B cells, called plasma cells, secrete millions of antibodies into the bloodstream and lymphatic system.
Choice A, Natural killer cells, is not the correct answer because natural killer cells are a type of white blood cell that play a major role in the host-rejection of both tumors and virally infected cells.
Choice B, Cytotoxic T-cells, is not the correct answer because cytotoxic T-cells are a type of white blood cell that kills cancer cells, cells that are infected (particularly with viruses), or cells that are damaged in other ways.
Choice D, Helper T-cells, is not the correct answer because helper T-cells are a type of white blood cell that play an important role in the immune system by helping other white blood cells fight infections.
