.: Nervous System:.

Summary:
The nervous system is a system of cells that produce an action. It is composed of the central nervous system and the peripheral nervous system.

Central nervous system

  • - made up of brain and spinal cord

Peripheralnervous system
  • -made up of all other nerves coming off of the CNS

The peripheral nervous system is then further divided into somatic and autonomic systems. The somatic nervous system control skeletal muscle and the autonomic nervous system controls parts that are involuntary. The last division of the nervous system in the autonomic nervous system that is split into sympathetic and parasympathetic. The sympathetic system requires energy and happens when you body is in a fight or flight position, such as getting pulled over by a cop or you get scared. The parasympathetic system help keep normal up keep of the body.

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The 3 Main jobs of the nervous system are:
  1. Receive sensory input from the senses and the environment
  2. Process the information
  3. Respond to the stimulus
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How does this apply to my career?
The nervous system is very important to understand in a nurses point of view because there are multiple disorders and diseases of this complex system. cerebrovascular accidents (strokes) are one of the most common causes of disability and death in the United States. As nurse I will have to take care of these people. It may be frustrating and challenging, but having the knowledge of the nervous system would help me under stand better what is actually happening to the patient/ resident. Some of people have disorders like Alzheimer's, cerebral palsy, epilepsy, multiple sclerosis (MS) and mental illness. These are just a few of the things that can happen and people need good health care professionals to understand what is going on and try to help them as much as possible to either get their independence back or go on with life in the best way they can. Another major way I can apply this is knowing the chemical balances of the brain and how messages get passed or don't get passed to make the body work properly. This could impair people that I would work with like paralysis patients and other patient with degenerative disease.During my career as a neurs I may run into some of these problem that can go wrong in the nervous system:Disease/ disorders of the nervous system

Terms:
Action potential-
(nerve impulse) an electrical event that is produced by the electrical membrane potential of a cells rising and falling rather rapidly.

Depolarization-
This happens when the membrane potential become more negative.

Repolarzation-
This happens when the membrane potential returns to resting membrane potential (neuron is -70mV).

Hyperpoloarzation-
This happens when the membrane potential becomes more negative than the resting membrane potential.
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1. Describe how the dendrite or cell body of the postsynaptic neuron is stimulated to send an impulse from the axon hillock to the rest of the neuron.
Action potentials are conducted by the axon starting in the presynaptic neuron. In the axon terminals the voltage- gated Ca2+ channels opens. This leads to the release of excitatory neurotransmitters. The release of these neurotransmitters diffuse across the synaptic cleft and reach the the landing sight of the post-synaptic cell. When this happens its opens chemically the (ligand) gated channels of the dendrite and cell body. This will cause a inward diffusion of Na+ into the cell and the cell will depolarize (EPSP). The depolarization causes the opening of of Na+ voltage-gated channels and then K+ channels in the axon hillock. This all leads to an action potential and the message will be repeated to the next cell until it reaches its effector.


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2. Describe the sequence of events that occur to get an action potential to stimulate the release of neurotransmitters from the presynaptic axon.
The action potential starts out as the resting membrane potential at (-70mv). When the membrane has been stimulated an increase of Na+ permeability and sodium diffuses through the Na+ gates.While the Na+ rushes into the cell it causes a voltage change from -70mV to -55mV. This it called the threshold (-55mV) and now the Na+ permeability decease and no more Na+ can enter the cell. This is a sate of depolarization. Once the membrane is depolarized the repolarization starts by opening the K+ gate and a inflow of K+ enters. this causes hyperpolarization when it becomes more negative than the resting membrane potential (<-70). This is restored by the Na+ pumps and they move extra Na+ ions and bring in K+ ions and this restores the membrane potential to -70mV and action potential is achieved. The Action potential moves down to the axon terminals. This stimulates the voltage-gated Ca2+ channels to open and Ca2+ rushes into the terminals. The Ca2+ bonds with the sensor protein in the cytoplasm of the axon terminal. During this time the Ca2+ alters the protein complex that keeps the vesicles in place. After it alters the membrane of the vesicles, it releases neurotransmitters. the release of these neurotransmitters to the post synaptic cell happen through exocytosis. This is where the vesicles are brought to the synaptic cleft and the neurotransmitters are released.


3. What happens when the neuron is inhibited?
When the neuron is inhibited it means that electrical current did not meet the threshold of (-55mV) and so therefor the message was not sent on to become an impulse.


Fun Fact: If you lined up all the neurons in your body it would be around 600miles long!

Thanks to:
http://www.medindia.net/know_ur_body/nersystem.asp
Human physiology 11th edition -McGraw-Hill
Anatomy and Physiology 4th edition-Mcgraw-Hill

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookNERV.html
http://www.clarian.org/ADAM/doc/graphics/images/en/8679.jpg
http://www.healthsystem.virginia.edu/uvahealth/adult_neuro/overview.cfm

introduction to Physcology: Pearson education