For organisms larger than one cell, another method of reproduction was required. Mitosis makes two cells from one. Meiosis works much faster, using one cell to create four. The usage of meiosis also allows for two parents to come together to combine DNA. This is an evolutionary advantage, as a single set of parents could pass advantages in their genes to more than two offspring. For sexual reproduction to happen, meiosis is needed to create the the sex cells. With larger and more complex organisms such as humans, reproduction requires haploids to carry the information from two separate organisms to coming and form a diploid zygote.
In this three class lesson, I learned that an action potential is when a neuron changes the charge of itself to positive from negative. It does this by using several sodium potassium pumps which allow positive ions to flow into the neuron. This changes all the way down the neuron, and continues onto the next one. A resting potential is when a neuron has a negative charge, and is waiting to change positive and carry on a signal. The action potential is carried over a synapse.
The video shows how complex neurons are and how a similar amount of pressure in a touch can set off different reactions. The video touches on a point where the central nervous system in your spinal cord is responsible for moving your body and creating quick reflexes. This happens because the neuron picks up danger, and you body instantly reacts to it without having to think about it. The video also talks about how a hair, for example, can be connected to a neuron which them can pick up a stimulus from the hair.
In this three class lesson, I learned the way that our body defends itself from invaders otherwise known as antigens. The body has external barriers, that keep unwanted germs out. Examples of these are the skin, nose hairs, and mucus. The body also has an immune response in which the body's cells consume or destroy the antigens. The most basic of this defense system are macrophages that eat up an antigen through a process called phagocytosis. The other main part of the response is the generation of antibodies. The B cells create antibodies specific to the type of antigen invading. The white blood cells carry the antibodies to the T cells, which in turn, destroy the antigens by either weighing them down with antibodies or tearing the antigens apart. The immune system is vital for keeping humans alive, as in a situation when a person does not have a fully functioning immune system such as the onset of AIDS, humans do not last long without medication.
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AuthorMichael Tellini Archives
May 2014
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