I think Autorhythmic fibers are fibers that are self excitable or on their own for example some cardiac muscle. They repeatedly generate action potentials that trigger heart contractions.They continue to stimulate a heart to beat even when it is removed from the body. In comparison to contractile fibers, autorhythmic fibers are self excitable and do not require nervous system stimulation to trigger contractions. Contractile fibers have stable resting membrane potentials of -90mV, when a contractile fibers reaches threshold by action potential, the voltage gated fast sodium ions channels will open.
Over the past four decades, researchers have identified many types of oncogenes, including growth factor receptors, transcription factors, and intracellular signaling proteins.
<h3>What are oncogenes?</h3>
These are specific genes in an organism that can cause the formation of cancer. These genes are prone to defects that when activate, signal for a cell to become a tumor. The genes listed in the question are some examples of the types of cells that can be oncogenes.
Therefore, we can confirm that over the past four decades, researchers have identified many types of oncogenes, including growth factor receptors, transcription factors, and intracellular signaling proteins.
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D is the correct answer. Hope this helps.
The approximate LD50 of the least toxic substance will be 130 mg/Kg.
- The dose necessary to cause the death of 50% of a population under test after a predetermined test period is known as the LD50 value for a drug.
- Commonly used as a broad indicator of a substance's acute toxicity are LD50 values.
- Greater toxicity is indicated by a lower LD50. A low LD50 of 500 mg/kg or less implies severe toxicity.
- Moderate toxicity is indicated by an LD50 of 500 to 1,000 mg/kg. A modest toxicity level of 1,000 to 2,000 mg/kg is indicated.
- The species is especially vulnerable to the poison if the LD50 is low. The lethal dose (LD50) of a specific poison might change significantly between several animal species.
- Thus out of all the options, LD50 130 mg/kg will have the lowest toxicity and 20 mg/kg will be the highest.
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