Answer:
The original water sample contains 830,000 cells per milliliter.
Explanation:
A sample of well water is tested for its bacterial content in a plate count assay. A one-milliliter sample of the water is diluted in a 1:10 dilution series. One milliliter of the fourth dilution tube is plated in a pour plate. After incubation, the plate has 83 colonies, indicating that the original water sample contained 830,000 cells per milliliter.
A trait that can mask another trait is known as a dominant trait.
Answer:
Neurons, as with other excitable cells in the body, have two major physiological properties: irritability and conductivity. A neuron has a positive charge on the outer surface of the cell membrane due in part to the action of an active transport system called the sodium potassium pump. This system moves sodium (Na+) out of the cell and potassium (K+) into the cell. The inside of the cell membrane is negative, not only due to the active transport system but also because of intracellular proteins, which remain negative due to the intracellular pH and keep the inside of the cell membrane negative.
Explanation:
Neurons are cells with the capacity to transmit information between one another and also with other tissues in the body. This information is transmitted thanks to the release of substances called <em>neurotransmitters</em>, and this transmission is possible due to the <em>electrical properties </em>of the neurons.
For the neurons (and other excitable cells, such as cardiac muscle cells) to be capable of conducting the changes in their membranes' voltages, they need to have a<em> resting membrane potential</em>, which consists of a specific voltage that is given because of the electrical nature of both the inside and the outside of the cell. <u>The inside of the cell is negatively charged, while the outside is positively charged</u> - this is what generates the resting membrane potential. When the membrane voltage changes because the inside of the cell is becoming less negative, the neuron is being excited and - if this excitation reaches a threshold - an action potential will be fired. But how does the voltage changes? This happens because the distribution of ions in the intracellular and extracellular fluids is very dissimilar and when the sodium channels in the cell membrane are opened (because of an external stimulus), sodium enters the cell rapidly to balance out the difference in this ion concentration. The sudden influx of this positively-charged ion is what makes the inside of the neuron become less negative. This event is called <em>depolarization of the membrane</em>.
