Megan+Mi.

=**__The Nervous System__**= The nervous system is made of of many different parts. It is made up of the brain, the spinal cord, the sensory organs and all the nerves that go with it to connect these organs to the body. The collection of nerves are called neurons and they transmit voluntary and involuntary actions. They transmit signals to and from the different parts of the body.

__The Nervous System__ __**Neurons-**__ the nervous system is defined by neurons. They communicate in the body by sending/transmitting electrochemical signals. These signals get sent to other cells through a thin fiber called the __//axon//__. Neurons communicate with other cells by a synapses. A synapse is a command given to the cell. There are different neurons. This is not just ONE type of neuron. There are 3 basic neurons which are, __//Afferent Neurons, Efferent Neurons and Interneurons.//__

__Neuron__

__**Afferent Neurons-**__ These are also known as the sensory neurons. They transmit sensory signals to the central nervous system from the receptors. Afferent neurons are found in the __//ganglia//__ of the peripheral nervous system. Also, in the nervous system there is a //"closed loop"// system of sensation, decision and reaction. This process is done by the activity of the afferent neurons.

__Afferent Neurons & Efferent Neurons__

__**Efferent Neurons-**__ These are also known as motor neurons. They transmit signals from the central nervous system to the effectors in the body. For example - muscles and glands. They carry nerve impulses away from the central nervous system and carry them towards the peripheral effector organs. Efferent neurons are also a part of the //"////closed loop"// system. The motor nerves are efferent nerves involved in muscular control.

__**Interneurons-**__ These are also known as connector neurons. These are like the connectors of the two other types of neurons. They create neural circuits which enables the communications between the sensory neurons (afferent neurons) and the motor neurons (efferent neurons). Interneurons are found to inhibit reflexes. They can also be broken down into smaller categories. Local interneurons and relay interneurons.

__Interneurons__

__**Here is a video clip to explain the Nervous System:**__ media type="youtube" key="x4PPZCLnVkA" width="560" height="315"

__**Sources**__ https://en.wikipedia.org/wiki/Interneuron https://en.wikipedia.org/wiki/Efferent_nerve_fiber http://www.innerbody.com/image/nervov.html#full-description https://en.wikipedia.org/wiki/Afferent_nerve_fiber https://en.wikipedia.org/wiki/Nervous_system http://www.livescience.com/22665-nervous-system.html https://www.youtube.com/

-- =**__The Evolution of a Whale__**= You believe it but whales actually come from land mammals. These mammals were around about 55 million years ago. The whale started as a //Indohyus//, then moves t o a //Pakicetus//, then to a //Ambulocetus//, then to a //Kutchicetus//, then a //Rodhocetus//, then a //Dorudon//, then a //Odontocetes//, then a //Mysticetes//. We'll be looking at every different group of the whale and learn how it went from a land mammal to a aquatic animal. __Here is a picture explain how the whale evolves__:



=__**Pakicetus**__= The //Pakicetus// is the very first member of the whale chart. Scientist believe that this mammal lived on the margins of a shallow ocean. They also believe that they were wolf size and meat eaters. __What they believe it looks like__:



= = =**__Ambulocetus__**= The name says it all. The name stands for "a walking whale that swims" so it can go walk around on land but go swim in water as well. Scientist believe that it swam by paddling and when it had to dive it would tuck in its forelimbs. They also believe it could hear sounds from its lower jaw. A sound would be made underwater and then it would travel through it's lower jaw and up into it's ears.

=__**Kutchicetus**__= This animal had a small otter-like skeleton and believed to live around 43-46 million years ago. It lived in tropical seas just like all the earlier members. Since is has small hind legs, scientist believe that it might have used it's long tail and they also believe that it didn't really "swim". They believe it did a lot more diving. __What scientist believe it looks like__:



=__Dorudon__= The skeleton of this animal showed that it represents a group of fossil whales called //Basilosaurids.// You can consider them as whales so, these whales are fully aquatic unlike the earlier group members. This animal lived between 34 to 40 million years ago. Scientist say that these animals look a lot like the whales that we have today. They had the small blowhole, square tail fluke and etc. __This is what they believe it looks like__

media type="youtube" key="8cn0kf8mhS4" width="560" height="315"
 * So usually people like to believe that whales evolved from hippos, but now we can truly see that whales and hippos have absolutely nothing in common! __Here is also a video that shows how the whale has evolved__:

=**__Sources:__**= > http://ocean.si.edu/ocean-videos/evolution-whales-animation
 * http://evolution.berkeley.edu/evolibrary/article/evograms_03
 * http://www.amnh.org/exhibitions/whales-giants-of-the-deep/whale-evolution
 * https://en.wikipedia.org/wiki/Evolution_of_cetaceans

--

Down syndrome is a genetic disorder. It is also known as Trisomy 21 or Translocation. That means that this person has a third copy of the chromosome 21. This happens when the humans body doesn't properly separate the two copies of the chromosome 21. That means when it gets to the egg and the egg fertilizes, the baby will end up with 3 copies of the chromosome 21.
 * __Down Syndrome__**
 * __Trisomy 21__**

Down syndrome affects all sorts of things. For example, your physical growth would have some delays, your characteristic's of your face would be different and your learning ability would be effected. __** Translocation **__ This is when there is extra chromosome 21 material in one of the parents. The chromosome 21 attaches itself to another chromosome then it affects the reproductive system the same way as Trisomy 21 would. The extra chromosome 21 material is given either by the mother or by the father. The parents can be in great physical and mental conditions and still give extra material out. media type="youtube" key="MLWs3h7Gf60" width="560" height="315" These problems do not affect all, some may have a lot, some may have a few and some may have none at all.
 * __Health Problems__**
 * Heart Defect
 * Intestinal Defect
 * Vision Problems
 * Hearing Loss
 * Infections
 * Thyroid Problems
 * Leukemia
 * Memory Loss
 * __Signs and Symptoms__**
 * Decreased Muscle Tone
 * Short Neck
 * Flat Face/Nose
 * Small Head/Ears/Mouth
 * Upward Slanting Eyes
 * White Spots on the Colored Part of the Eyes
 * Wide/Short Hands
 * Deep Grove Between Toes/Fingers

__**Down Syndrome Population Facts**__ http://www.globaldownsyndrome.org/about-down-syndrome/facts-about-down-syndrome/#medical https://en.wikipedia.org/wiki/Down_syndrome http://www.marchofdimes.org/baby/down-syndrome.aspx https://www.nichd.nih.gov/health/topics/down/conditioninfo/Pages/symptoms.aspx
 * 1) The Center for Disease Control estimated that down syndrome in the US is every 1 in 691 live births.
 * 2) 38% of people know someone with down syndrome
 * 3) In the US there are an estimated 281.4 million people with down syndrome
 * 4) Over the next 20 years there is expected to be an increase of down syndrome people in the world
 * __Sources__**