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Prevention. Summary. A pathogen is any organism that causes disease. Viruses, bacteria, fungi, and parasites are all examples of pathogens. Your body is naturally full of microbes. However, these ...
You must wait at least 8 weeks between whole blood donations and 16 weeks between double red cell donations. Platelet donations can be made every 7 days, up to 24 times per year.
Neuron. Within a nervous system, a neuron, neurone, or nerve cell is an electrically excitable cell that fires electric signals called action potentials across a neural network. Neurons communicate with other cells via synapses, which are specialized connections that commonly use minute amounts of chemical neurotransmitters to pass the electric ...
Chromosomal crossover, or crossing over, is the exchange of genetic material during sexual reproduction between two homologous chromosomes ' non-sister chromatids that results in recombinant chromosomes. It is one of the final phases of genetic recombination, which occurs in the pachytene stage of prophase I of meiosis during a process called ...
coming into contact with body fluids, such as semen, vaginal fluid, blood, and breast milk. HIV is not transmitted by: breathing the same air as a person living with HIV. getting bitten by a ...
Nuclear fuel cycle. The nuclear fuel cycles describes how nuclear fuel is extracted, processed, used, and disposed of. The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end, which are the preparation of the fuel, steps in the service ...
The endomembrane system is composed of the different membranes ( endomembranes) that are suspended in the cytoplasm within a eukaryotic cell. These membranes divide the cell into functional and structural compartments, or organelles. In eukaryotes the organelles of the endomembrane system include: the nuclear membrane, the endoplasmic reticulum ...
As an action potential (nerve impulse) travels down an axon there is a change in electric polarity across the membrane of the axon. In response to a signal from another neuron, sodium- (Na +) and potassium- (K + )–gated ion channels open and close as the membrane reaches its threshold potential. Na + channels open at the beginning of the ...