Nervous+system

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==== __[|Nervous system]__ is highly connected network of tissues that allows you to think, move, sense your internal and external environment, and stimulate other organs (Nowicki 874). At the same time, it also helps the body to maintain the inner condition body of the organism known as __homeostasis__. However, to be able to function homeostasis properly, the body has to control the system of 4 different part combination. First of all is sensor, it helps to get information from outside to inside condition. Secondly is a control center where it receives sent information from the sensor and responds through sending a message to a communication system. Communication system sent hormones to the targets which include cells, tissues, and organs. At the end, the target would respond to the sent hormones. ====

====All of the system listed above would work together to released as feedback loop. __Feedback__ is “information from sensors that allows a control center to compare current conditions to a set of ideal values” (Nowicki 859). Most of the information moves along the sensors, a control center and a target. However, for most of the function from the body is working by __negative feedback loops__. This happens when body making changes that either move the condition of the body higher or lower comparing to the set points. It helps to keep the inner condition or environment stay the same. One of the example shown in the image below as in controlling blood glucose level. On the other hand, the body also uses __positive feedback__ to control the increasing rate of information comparing to the set points. Even though his kind of feedback is not as much common as the negative, but it's important when having changes quickly (Nowicki 867).==== (6)

**System**
====There are two main part of nervous system; __[|central nervous system (CNS)]__ and __peripheral nervous system (PNS)__. While the CNS receive messages from other nerves in the body to store for using it later, the PNS would be sending the message both to CNS and from CNS to the rest of the body’s organs.==== (1)

====PNS got divided as in 2 major parts which includes 4 main nerves systems. For example, __[|somatic nervous system]__ is one of the division of PNS that responsible for the movement which have voluntary control. This “connects the CNS to target organs” (Nowicki 889). On another division of PNS, the __autonomic nervous system__ is in charge of automatic functions which control involuntary muscles that work without thinking. For instance, it controls both of the cardiac muscle and smooth muscle through its autonomic system (Kimball, John W.). It helps to balance and keep the same condition of the inner body, or homeostasis.====

==== Central nervous system includes brain and the spinal cord to be able to function properly. It formed by millions of neurons (“Central Nervous System”). The brain has three main structures which are the cerebrum, the cerebellum and the brainstem. The __[|cerebrum]__ is one part of the brain that can be able to recognize the signals received from the body. It has both left and right halves, also known as hemispheres. For each individually hemisphere, its responsible is to control the other opposite half of the body. It helps to control from your movement such as walking or running to balancing the body through controlling parts of the body. While the outer layer of cerebrum is to receive sent information from sensory organs to response called as __cerebral cortex__. Different area of cerebral cortex specialized for different types of information. ====

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====The __brainstem__ is the connection between brain and spinal cord to be able to control most of the body for functionally daily activities. It has three main parts such as midbrain, pons and medulla oblongata. Midbrain is in charge of controlling the eyes which including the amount of light receive either to open bright or close slightly. Pons is to keep track of the breathing process through passing signals from the brain to the spinal cord and opposite. Medulla oblongata is the connection bridge that link brain and spinal cord together for the body to work properly. At the same time, the neurons which are motor and sensory would travel back and forth through the brainstem for signals. Most of importantly, the brainstem also “controls life supporting autonomic function of the peripheral nervous system” (Bailey, Regina).====

====Even though the movement of the body is depending on the cerebrum and cerebellum, but the brains still depend on spinal cord to be able to give out message for the muscles to function properly (Nowicki 888). In fact, all of the signals from the brain that got sent out all need to pass through the spinal cord. It also controls the “involuntary movement called reflexes” (Nowicki 888). For most of the time, they don't need to travel up back to the brain for processing which would help them to responses quicker comparing to the others ("BBC Science & Nature"). Reflex arcs is a path of nerve that crossed only two synapses in order to response (Nowicki 888).==== (7)

====Nervous system formed by a complex network of tissue, or neurons that is “highly specialized cell” (Nowicki 876). Each neuron usually has three parts. Cell body is the first part of the neuron that includes nucleus and organelles inside. Dendrites are branches of expanding cell membrane and cytoplasm in order receive signals. However, Schwann cell, synapse, and terminal are also involved in transmitting signals.====

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==== There are t hree types of neurons; sensory neurons, interneurons and motor neurons. Sensory neurons is to send signals to the spinal cord and brain. While the interneurons receive sent signal from the sensory neurons in order to “relay them within the brain and the spinal cord” (Nowicki 877). As soon the information is process to the motor neurons, it will send the message to the rest of tissue in the body. [shown in figure 8]====

====When the neuron is in __resting potential__, there wouldn’t be any signal transferring. So “the inside of its cell membrane is more negatively charged than the outside” (Nowicki 877). To be more specific, there are more of K+ inside the cell as more of NA+ outside the cell (Nowicki 877). When electrical impulse moving down the axon that started by something that caused respond, or __stimulus__, then the neuron is in __[|action potential]__. Therefore, Na+ comes inside to make it become positive while the K+ leaves. __Sodium-potassium__ pump is involved when the area of positive charge moves. Before going to the next neuron for action potential, there is a little space between the neurons needed to be close called a synapse. Then the terminal, one part of an axon would wait to receive the chemical vesicles from the impulse of the neuron. The chemical signals that received is also known as __[|neurotransmitters]__. It got released to continue the action potential at another neuron when the vesicles touch the terminal’s membrane that caused Na+ to opens.==== (4)

Picture citation
(1) [] (2) [] (3) [] (4) [] (5) http://www.infovisual.info/03/img_en/038%20Nervous%20system.jpg (6) http://adohone.wikispaces.com/file/view/EndocrineNegativeFeedback.gif/43899795/EndocrineNegativeFeedback.gif (7) http://biologyataglance.wikispaces.com/file/view/simple-reflex-action.jpg/146320909/simple-reflex-action.jpg (8) http://biologyataglance.wikispaces.com/file/view/sensory_neuron.gif/146311409/sensory_neuron.gif

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"BBC Science & Nature - Human Body and Mind - Nervous System Layer." BBC - Homepage.  Web. 15 May 2011. ======

"Central Nervous System." // Gondar Design Science //. Web. 15 May 2011. Kimball, John W. "Organization of the Nervous System." 2 Mar. 2011. Web. 15 May 2011 Nowicki, Stephen. "Human Biology." // McDougal Littell Biology //. Evanston, IL: McDougal Littell, 2008. 874+. Print.